Materials Science Findings to Trigger some Industrial Applications

Often newer practical materials and devices, with huge economic gains, have resulted from commercialization of suitable selections of latest research on materials and their applications. Spread of laboratory discoveries of semiconductors and their properties to practical applications in every sphere of life and industry is the easiest example. Present work will focus on a few random examples of newer materials science research topics that is, or may possibly be, commercially exploited. Piezoelectric (PE) materials including High Temperature (HT) PE materials will be outlined for industry to explore novel applications ranging from ultrafine manipulation to heavy duty drilling and making PE sensors, actuators and ultrasonic devices. Higher electrical conductivity of a defect form of II=VI oxides (Cd-O in particular) is highlighted for possible practical exploitations. For 2 nd generation Electromagnetic Interference (EMI) Shielding, polymeric composites with either newer absorbing agents or newer reflecting agents or their mixtures will be outlined. Novel Fe-or Ni-based HTSCs (high temperature superconductors) are less anisotropic and rather metallic in contrast to Cu-oxide HTSCs. So, these offer added advantage for making superconducting electrical cables. A balanced presentation of these potentially usable materials and their basic physics will be attempted.


Introduction
Materials and Device manufacture at industrial level is low in some countries like India, compared to their basic research achievement and such commercialization level in few other countries like Japan and China. This results in huge imports of critical items (like sensors & actuators, chips and special polymers) and common commodities (like ink cartridges, piezoelectric generators in gadgets and fun-shoes for children, for example). A communication gap between the industry and basic research in science & technology, except a few recent developments, appears to be the main cause of this low contribution of indigenous research to industry. The industries, till very recently, felt that import of "proven" knowhow from advanced countries to be the easier and supposedly safer option. However, materials and technologies "proved" attractive in western countries may be somewhat inappropriate for hot and humid countries like India. A simple example is that the widely used rubber bands soften in hot summer months. This softening temperature should be raised by suitable blending or other procedure. Here, we will outline a few materials development areas that have potential for applications but not yet fully developed into specific applications. Few less discussed but promising materials or topics, rather than well-known materials, have been arbitrarily chosen -mainly from or related to our work: (i) Newer piezoelectric materials for sensors, actuators & imaging applicationsparticularly for high temperature (HT) applications, 1,2 (ii) utilizing the higher electrical conductivity, due to non-stoichiometric defects, in some II-VI compounds (cadmium oxide etc.), 3,4 (iii) novel Electromagnetic Interference (EMI) shielding by rubber-like flexible sheets of composites of a polymeric binder with either newer absorbing agents or newer reflecting agents or their mixtures, 5,6 and (iv) novel Fe-based HTSCs (high temperature superconductors) for making superconducting electrical cables. 7,8 Electronic control and operation in most of the modern devices or machines involve use of various sensors and actuators, many of which are based on piezoelectric (PE) effect. Ferroelectric (FE) materials forming a sub-group of piezoelectric materials have additional applications. 2 Subject to success in materials and related developments, PE and FE devices perform competitively better than alternative devices (like electro-magnetic devices) but usually at lower cost. There is increasing commercial and technical interest for PE actuators (ranging from electronic muscles, fuel injectors and inkjet printers to various vibrators and drilling machines), PE sensors (pressure and other sensors, heart beat monitors and motion detection to energy recovery applications), and ultrasonic imaging devices. So, business houses can pay more attention to production of latest and newer PE materials and devices, to be reviewed under point (i), mentioned above.
Cadmium oxide (Cd-O), a II-VI semiconductor, appears to be a promising electromagnetic material. 3,9 It is almost entirely transparent in the optical part of the electromagnetic spectrum, and can have high electrical conductivity on firing at temperatures like 800°C, as detailed later. 10 There has been interest for more than two decades in Cd-O and other transparent conducting oxides (TCOs) for optoelectronic devices of short wavelengths, thinfilm photo-voltaic devices and flat panel displays. Now, current decade finds potential applications of these oxide semiconductors (widely studied ZnO, and Cd-O & Mg-O) in optoelectronics and high-performance electronic device applications. 3,10 While ZnO, with 3.3 eV room-temperature band gap (E g ) and large exciton binding energy of 60 meV, is playing the main role in many II-VI optoelectronic devices, their spectral range is being extended into the visible and deep ultraviolet ranges by alloying ZnO with the smaller band-gap compound CdO, having room-temperature E g of ~2.2eV at the Brillouin-zone center, and with larger band-gap compound MgO with E g of 7.7eV, respectively. 3 We find non-stoichiometry in differently heat treated "CdO" and, hence, widely varying electrical conductivity for Cd-O, referred in point (ii).
Many of the modern electrical and electronic gadgets (including mobile towers) generate electromagnetic (EM) radiation that can be harmful or disturbing to other instruments and living beings to the extent of causing carcinogenic damage to body cells. EM radiation from such radiation-emitting equipment is minimized to the legally required electromagnetic compatibility (EMC) by wrapping it up, without any gap, by an efficient electromagnetic shielding material. Alternatively, one shields the object (like sensitive measuring instruments) that is to be electromagnetically protected. This is the only way if the EM source cannot be shielded (e.g. mobile towers that must emit). We will overview, as mentioned in point (iii), 2 nd generation EM Shields based on a polymer. Superconductivity discovered in 1911, has shown some new surprises since the recent and surprising discovery of Cu-O based High Temperature Superconductors. 8,[11][12][13] Latest surprise is superconductivity including HT superconductivity in Fe-As or Fe-Te/Se materials containing magnetic ions like Fe or often Ni as a major component. Shattering the textbook idea that magnetic impurities destroy electron pairing and hence superconductivity, the new Fe pnictides (Pn) and chalcogenides (Ch) superconduct at high temperature up to T c = 56 K.

Overview of Basics & Background Outline of The Physics of Piezoelectricity
Generation of an electrical signal due to an applied stress (Figures 1 & 2) is called Direct Piezoelectric (PE) Effect. Converse or Inverse PE effect is the generation of motion / force from applied voltage (Figures 1 & 3).  As shown in Figure 2, Curie brothers measured surface charges appearing on specially prepared PE crystals, on hanging a small weight from the crystal. Generated charge was measured by opening up of attached leaves of an electrometer. Tourmaline, quartz, topaz, cane sugar and Rochelle salt were used as their PE samples. For detecting the inverse PE effect (Figure 3), a thin and long quartz plate, QQ, was sandwiched between two tin foils. By applying a voltage to the tin foils, the quartz plate elongates or contracts according to the polarity of the applied voltage. To measure the very small displacement, they used a lever ABD. The displacement of the tip (A) of the long arm of the lever was measured with an optical microscope.  Using the example of piezoelectric effect in BaTiO 3 (BT) in its tetragonal (orthorhombic) structure below T(Curie) ~120°C, and no PE effect in its cubic perovskite structure above T(Curie) ~120°C, Figure 4(a) & 4(b), one can confirm that noncentro-symmetry in crystal structure generates piezoelectricity.
Centers of positive and negative charges being different at T < T(Curie), an applied electrical voltage will change their separation leading to dimension change or generation of force if the dimension change is externally resisted. This is inverse or converse effect. Direct effect can be similarly understood. In Figure 4(b), an applied force (causing dimension change) will move the centers of positive and negative charges, causing electrical charging of the sample faces (equivalent to generation of voltage). A sample may be a single crystal (SXL) or polycrystalline, consisting of crystallites or grains. A piezoelectric grain or SXL usually consists of many PE domains. 1,14,15 Domain is a region in which all unit cells are polarized in the same direction ( Figure 5). So, each domain has its own polarization direction, as shown in LHS picture of Figure 6 (and in Figure 5 for only a few domains). Random orientation of these polar domains results in zero net polarization for the sample as depicted in RHS part of Figure 5, so that piezoelectricity does not show up. "Poling" or orienting all the domains to practically same polarization direction turns such a non-PE sample PE. In "poling", a constant electric field (often at mediumly high temperature) is applied to "force" all the dipole moments to align in one direction (middle picture in Figure 6). Remanent polarization (RHS picture in Figure 6) after withdrawal of the applied field appears enough to keep the sample practically unidirectionally polarized and piezoelectric. Synthetic PE materials (like polycrystalline FE ceramics) with a much improved piezoelectric response are nowadays manufactured commercially for specific actuating or sensing applications. These are always "poled" samples. This has been a big step, from naturally occurring PE materials, for moving towards applications.
Since, the electrical-to-mechanical and mechanicalto-electrical energy transfer in a PE material takes place in a complex 3-dimensional way, tensor equations govern these processes. 1,2,14,15 It involves electric field and polarization, which are vectors, and elastic stress and strain which are second-order tensors. Piezoelectric coefficients in the equations link the variables, and provide quantitative measure of the performance of the PE material, as detailed in above references and many texts. For example, d mh are the piezoelectric strain coefficients representing strain in h-direction due to an electric field applied in m-direction. Jbaily and Yeung have explained that unlike in elastic compliances and dielectric permittivities, d mh is different from d hm . 15 It is noted that d mh also gives the electrical displacement created in m-direction by a stress, applied in h-direction. Generation of electricity (electrical displacement) from a stress obtained from vibration or ocean waves generally use either d 31 or d 33 mode. 15 Here, d 31 means 3-1 or (z-axis)-(x-axis) coupling mode, implying application of the stress in a direction perpendicular to that of poling, along which PE voltage will be generated. Similarly, in d 33 or 3-3 coupling mode, the applied stress and the poling of the piezoelectric material have the same direction. 16 Ocean energy recovery by PE effect is still in the developing stage. Nations with vast ocean or sea front can investigate its commercial viability.

Defect Form of Cadmium Oxide with High Electrical Conductivity
We observe cadmium oxide to assume different colors with different room temperature electrical conductivities on firing it (for 36 h in present tests) at different temperatures ( Figure 7). A series of characterizations, proved thermally created nonstoichiometry defect. 3,4,17,18 This must generate charge-carriers (found by us to be electrons for the samples subjected to Hall measurements), and, hence, extra electrical conductivity. Fig. 7: Room temperature Electrical Resistivity 3 of 4 samples of differently non-stoichiometric cadmium oxide, obtained by 36h firing at the temperatures specified in the graph. Resistivity reduces to almost 1/9 or so, for the fired cadmium oxides. Since, heat treatment at 800°C turns it into a good electrical conductor, we wanted to see whether it can shield EM waves like a metal Newer Polymeric Composites for Electromagnetic Shielding Electromagnetic Interference (EMI) shields should better be flexible for easier and gapless coverage and also light. Metallic shields, the best for EMI shielding, loose on both counts to the 2 nd generation EMI shielding materials based on polymers. 6,19 On using a conducting polymer in pure or composite form, one still needs the addition of a binder polymer to get a flexible sheet. So, we tried a Si-based polymeric binder that is initially a liquid. It could be mixed with potential shielding powder/s and cured overnight to any desired shape.

Fe-superconducting Compounds
The 1111 family of Fe-superconductors (RFeAsO with substitution, R = rare earth element), having tetragonal P4/nmm, ZrCuSiAs type structure, shows the maximum T c ~ 56 K for Gd (1-x) Th x FeAsO at x = 0.20. 20 Here, we have chosen 122 family Fe-superconductors like Ba(Fe (1-x) Co x ) 2 As 2 , x = 0.102 having Tc = 22.5 K. 8 Fe/Ni -based HTSCs being metallic, their fabrication into superconducting wires will be easier, with potential use in all high field magnets as needed in modern developments like fusion devices and accelerators. Our current work, mainly on radiation damage in Fe-superconductors, involves thin single crystal 122 samples to eliminate extra properties inevitable in polycrystalline and thin film samples. 21

Experimental Results & Discussions HT and Other Applications of Piezoelectric Materials
Piezoelectric imaging (using piezoelectric actuator/ generator and sensor materials) find innumerable applications ranging from ultrasonography, fishing and underwater viewing (for navigation and warfare) to viewing, through high pressure molten metal coolant in Fast Breeder Reactors, of control and radioactive fuel rods. 2,22 It is simple in principle. In Figure 8, reflected ultrasonic waves image the man. We have taken the freedom of showing the ultrasonic image itself as the Object (the man). Imaging by transmitted wave is also widely used. Common items like cell phones, diesel fuel injectors, acoustic guitar pickups, grill igniters, ultrasonic transducers, vibration sensors, certain printers, musical greeting cards and host of specialized and common applications utilize piezoelectric devices -often at lower cost and with better efficiency than other devices like eletro-magnetic devices.
Applications discussed by us in 2015 will be largely skipped, but without affecting the completeness of present work. 2 It will be useful to quote from the webpage of APC International about different applications of PE sensors, actuators and imaging devices. 23 (a) "PE Engine Knock Sensors" detects detonation in petrol engines, and prevents explosion by a feed-back mechanism. This has reduced the safety margin of older cars without such sensors.
"PE Pressure Sensors" is replacing strain gauges or displacement sensors. (c) "Depth sounders and similar Sonar Equipments" rely extensively on piezoelectric sensors. It transmits and receives ultrasonic "pings" usually in 50-200k Hz range, with the advantage of high power density ~500 W, in a compact ~10 cm transducer. (d) Replacement of older Diesel Fuel Injectors by "PE Diesel Fuel Injectors" mainly in last one decade or so. It now controls, with precise timing, the high pressure (~1800 bar) fuel at high rapidity rate (several times during a single power stroke) -reducing emission and noise, while increasing power and efficiency. (e) "Solenoid Replacement" by PE Actuator, implying replacement of electromagnetic solenoids by "PE Solenoids" is a big step towards faster response, lower power consumption and fewer moving parts. (f) "PE Micro Manipulators", a kind of Solid State Motion, for fine movement in certain advanced investigations, correcting disturbances to mirrors / diffraction gratings or to earth-based telescope arrays or to spacecraft optics. (g) "Ultrasonic Cleaning" (h) "Ultrasonic Bonding" or "Ultrasonic Welding" (i) "Piezoelectric Motors", providing Solid State Motion, are more precise, compact and predictable. Unlike conventional motors, these can be designed to work in adverse environments with strong magnetic fields or at cryogenic temperatures. (j) "PE Hammer" or "PE Drill" for heavy duty work. (k) Deflection can be achieved in "Stripe Actuators". 2 A Stripe Actuator is made by sandwiching together two strips of PE material in such a configuration (similar to a bimetallic strip) that an electric input causes one strip to expand while the other strip simultaneously contracts, causing a deflection. "Piezoelectric Linear Actuators" and "PE Bending Actuators" can now generate huge forces up to several kilo Newtons and large displacements up to several mm. 24 (l) In line with the last entries, there are "Stack Actuators" or multiple piezoelectric elements may stacked to multiply the displacement achieved for a given voltage. These are used in proportioning valves, electrical relays, optical modulation, vibration dampening, and other applications demanding fast and/ or precise control of movement. (m) "Ultrasound Imaging" -"Medical" and "Industrial". In addition to various medical detection it is facilitating minimally invasive surgical procedures. (n) "Medical Ultrasonic Procedures" include use of focused ultrasonic waves to break up kidney stones or destroy malignant tissue. Also, the harmonic scalpel has allowed surgeons to simultaneously incise and coagulate tissue during a surgical procedure without the need for cauterization. This leads to less tissue damage, less blood loss, and faster healing.
Inkjet-printer and dot-matrix-printer. 2,23 (p) "Piezoelectric Speakers" found in cell phones, ear buds, sound-producing toys, musical greeting cards, musical balloons. (q) "Piezoelectric Buzzers", with lower fidelity than piezoelectric speakers, are louder. But they have a narrower frequency range. (r) "Musical Instrument Pickups" -Many acoustic-electric stringed instruments have PE pickups to convert acoustic vibrations to electric signals. 23 Typically, a strip of PE material is placed between the instrument body and the structure that supports the strings. For instance, an acoustic-electric guitar usually houses its piezoelectric strip beneath the bridge and within the saddle. As the strings vibrate, the strip is agitated to generate an electric signal. Electrical pickups on violins, violas, and cellos use the same concept, but the PE pickup may be clamped to the bridge or integrated within the bridgeinstead of being located between the bridge and the instrument body. (s) "Microphones" -Various microphones (such as contact microphones for percussion instruments) use PE materials to convert sound to an electricity. These microphones generally possess high output impedances that must be matched when designing their respective pre-amplifiers. 23 (t) "Piezoelectric Igniter". (u) "Electricity Generation through Piezoelectric Effect" is done by converting deflections or displacements (due to water waves, wind, dancing floor or engine vibrations) into electricity. Waste energy recovery will also cool the vibrating machine.
"Under Liquid Sodium PE Viewing" of radioactive-fuel and control rods in a Fast Breeder Reactor (FBR) has been mentioned earlier, and detailed in our 2015 review. 2 Point (v) above needs PE imaging and attention to keep FBR type nuclear reactors safe. U-235 from mined uranium is the most common fuel for nuclear power reactors that deliver green energy without any carbon footprint, while coal and oil fired power stations produce huge pollution and large C-footprint. Safe storing of Spent Fuel of the nuclear reactors is another problem, as the spent fuel still contains a lot of radio nuclides like U-238. Fast Breeder Reactor (FBR) can breed U-233 fuel from thorium (available worldwide and abundant in monazite sand in India) as well as fissile Pu-239 from U-238 in spent fuel (called nuclear waste), while producing electrical power. 2 So, FBR helps solve three problems (i) nuclear waste disposal through re-cycling of U-238, (ii) overcoming U-shortage by producing nuclear fuels and (iii) producing electricity. FBRs will continue to be strategically important to energy-starved India -till fusion energy is commercially viable.  We will show here only three characterizations of these PE materials in Figures 9, 10 and 11. One is measurement of ε(i) = ε(imaginary) and ε(r) = ε(real), the imaginary and real parts of complex dielectric constant of the shielding material. Dielectric loss or loss tangent of present samples is defined as tan δ = ε(i) / ε(r  So, there is no significant Pb-loss on heating up to 1065°C. 2 This is a relief till Pb-free substitutes are ready flow rate and monitoring of exhaust composition to check pollution. A particular chemical coating that absorbs a particular gas, is given on a quartz crystal oscillator. Gas absorption increases the oscillator mass causing a detectable change of the oscillation frequency. This way gases like SO 2 , CO, CO 2 , O 2 and hydrocarbons in the exhaust can be identified and concentration estimated. Compared to commercial strain gauges and optical fibre sensors, PE sensors already reach higher temperature (>600°C), higher accuracy, faster response and ease of integration. 40 Advantages of PE injection of diesel in automobile engines has already been discussed.   6 has been utilized here. By measuring:

Fig. 12:The main panel summarizes the types of composites fabricated and the expected mechanisms (absorption and reflection) of shielding. Two panels below schematically explain Vector Network Analyzer measurement of EM wave transmission and reflection 6
• P in , EM power incident on the shield, • P reflec , EM power reflected by the shield, and • P out , EM power transmitted through the shield, in the VNA, one can know, P absorb = EM power absorbed in the shield.
The 2-port network parameters S 12 = S 21 (for transmission) and S 11 (for reflection) are related to transmittance and reflectance: T = Transmittance = P out / P in = |S 12 | 2 and R = Reflectance = P refl / P in = |S 11 | 2 .
Since R = reflected fraction of EM wave intensity and T = transmitted fraction, A = absorbed fraction, can be found from the equality: R+A+T = 1.
Absorbed power = (P in -P out -P refl ).
For quantitative estimate of total shielding one defines: SE = Shielding Effectiveness in dB unit = 10 log (P out / P in ).
Since P out < P in , SE will be a negative quantity. A large negative value of Shielding Effectiveness will, therefore, indicate high shielding. To avoid dealing with this negative quantity, many authors 4 define a new parameter: Shielding Efficiency = -10 log (P out / P in ) in dB = 10 log (P in /P out ) in dB, which has higher positive value (larger P in /P out ), for materials that shield more.
Similarly, 10 log (P refl / P in ) in dB = Reflection Effectiveness = RE, is a negative quantity, and Shielding Efficiency = -10 log (Prefl / Pin) in dB. These arise from reflection. However, the terminology in certain treatise is often different from what we present here.
Three main types of polymer-solid composites indicated in Figure 12 have been extended to their mixtures in search of better results. A full list of our composite samples is given in Table 3 of reference. 6 Weighed amounts of this sealant (PB) and components have been mechanically mixed for 20 to 40 minutes into a dough-like mixture, and then pressed between a Teflon plate and a glass plate into a sheet of approximately the desired thickness. An important reason for choosing the Dow Corning Silicone sealant is that the composite sheet cured overnight into a flexible cloth-like rubber-sheet. Chemical inertness is another advantage of this polymeric binder. Unexpected shielding activity of the sealant has been noticed in sheets without any additive(s).
For situations 30 with negligible magnetic interaction and low internal multiple reflections correction term, the decibel value of EM Shielding Effectiveness (SE or SE total ) is simplified to:

SE = SE total = SE reflection + SE absorption
For 700 MHz to 3 GHz VNA measurements, based on coaxial holder, annular samples (or circular samples with central hole) have been prepared by a newly devised Double Plunger [6]. Rectangular wave guide system is used in VNA frequency ranges covering 8 to 40 GHz. This needs rectangular samples -in four specified sizes for the four above-mentioned frequency ranges. Present VNA gives the variations of 10 log (P out / P in ) = Shielding Effectiveness in dB unit = SE, related to S 12 , and 10log (P refl / P in ) in dB = Reflection Effectiveness = RE, related to S 11 , with frequency graphically, with digital data for selected representative points.

Some Selected Highlights of Polymeric Composites for Emi Shielding
Success has been achieved for the newly used self-curing polymeric binder to prepare a variety of flexible cloth-like composites (numbering 52), and measure SE and RE over the wide range 700 MHz to 40 GHz (Figures 13 & 14 for example).
Brass and copper turnings, which can be obtained practically free from mechanical workshops, were cleaned and sieved through a 1mm X 1mm net, before making brass and copper composites ( Figure  14). Its success paves the way for reducing cost. Figure 13 shows the new but welcome feature of two transmission minima 6   Reflection effectiveness, 10 log (P refl / P in ), of polymeric composites involving PN, BT and metal turnings (over ~26 to 40 GHz), is depicted in Figure 15.   Figure 9) and similar or lower transmission down to ~ 8.4 GHz ( Figure   9). 2  More work remains to be done than what have been done, for understanding and fruitful applications.

Characterization of Non-Stoichiometry In Ii-Vi (Cd-O) Samples and their Novel Properties
It has been known for decades and even recorded in standard chemistry texts (F.A. Cotton and G. Wilkinson (Wiley), and H. Remy (Elsevier)) that cadmium oxide, prepared by different techniques, show different colors ranging from black to gray and golden. But it was never seriously investigated before we started this work around 1996. 3,4,17,31,32 We wanted to investigate in more details, also because CdO is a II-VI compound, potentially important as a semiconducting material. Next, we found that prolonged heat treatment (decided to be 36 h) at different temperatures give at room DE & BHATTACHARYA, Mat. Sci. Res. India, Vol. 17(2), pg. 90-116(2020) temperature -different colors, and more importantly, different electrical conductivity. Firing at 800°C or so produced black Cd-O. Clearest indication of the real difference of the differently fired samples came from our Rutherford backscattering experiment using 3.05 MeV alpha-beam at the pelletron facility of IOP, Bhubaneswar, India ( Figure 16). 4 Measured energy of the backscattered projectile (here, alpha-particle) gives the mass of the target (sample) atom that backscattered it (say Cd). The intensity of the backscattered alphas at that energy corresponds to atomic percent of the scattering atom (here, Cd, giving Cd step in the intensity vs. energy plot, Figure 17). 3,4 The energy of 3.05 MeV of the projectile alpha beam was chosen to give the resonant scattering peak of O-atoms in the samples, in addition to the step for Cd. Larger RBS step for Cd will imply more Cd in the sample (Figure 17). In these characterizations, relative compositions rather than absolute compositions have been determined as no standard Cd-O have been available for calibration.
Our RBS also showed that 700°C firing of ZnO_400 increased relative Zn% implying O-loss.  Figure 19 are not the absolute values.
Exact composition could not be obtained by any of the techniques. Atomic Absorption Spectroscopy (AAS) determines bulk composition. 3,17 Other techniques probe down to the depth reached by the probing fast particle or ray. Still, composition approximately estimated by AAS and X-ray Photoelectron Spectroscopy (XPS), are quoted below. Apparent fall or near constancy of "estimated" Cd-content on moderate heating and rise in Cd-content or O-loss at higher temperatures towards 800°C appear to be suggested by all the techniques, although details differ due inherent special factors of different techniques and compromises in our data analysis. These pellet samples contain a lot of absorbed and adsorbed moisture, different gases and dirt. These are removed by heat up to moderate temperatures increasing fraction of detected Cd in the sample. By not taking this partly known factor into consideration one can wrongly conclude fall of Cd fraction in "CdO compound" up to moderate temperatures. Real fall of Cd-fraction in "CdO compound" would have to involve O-intake by the O-rich sample at this low temperature, while O-loss is confirmed, at least at higher temperatures. heat absorbed by the sample (endothermic process) or heat evolved by the sample (exothermic process) for upward or downward temperature scanning of the sample. 3 Here, taking out atoms must be endothermic, the two dips or minima in our DSC. These endothermic dips are at the 2 major steps of mass loss in TGA -a satisfying agreement.
Heating of cadmium oxide should, therefore, involve more and more O-loss, basically at the indicated temperatures. Midway between these endothermic dips, one sees a large exothermic peak that needs to be explained. The O-loss from random positions at the lower temperature endotherm must have left the sample rather disordered. So, on further increase of temperature a re-arrangement of Cd and O atoms into a lower potential energy structure may have taken place as supported by evolution of heat. So, higher temperature of the higher temperature endotherm is needed to eject more atoms, as evidenced from TGA, from the structure.
Knowing and understanding non-stoichiometry in II-VI compounds like CdO, ZnO and MgO is essential before undertaking their doping to make p type or n type semiconductors.

Fe-HTSC -Characterization and Application Potentials
The Fe-based HTSCs fall in following 4 families, identified by their general formulae and the high temperature crystallographic structures: • the 1111 family (RFeAsO with substitution, R = rare earth element), having tetragonal P4/nmm, ZrCuSiAs type structure, showing maximum T c ~ 56 K for Gd (1-x)  On lowering the temperature below a certain temperature (T s ), the metallic parent compound shows a tetragonal-to-orthorhombic structural change: to Cmma for the 1111 family, to Fmmm for the 122 family, to Cmma for the 111 family, and to structures like Pnmm for the 11 family. 20,21,[37][38][39] Various mechanisms of superconductivity involving magnetic interactions have been suggested for these Fe-based superconductors. 13 Now we note that the high temperature structure for all the 4 families is tetragonal. More important is the fact that they all contain Fe-As or Fe-Te/Se layers in tetrahedral coordination, and superconductivity originates from these layers. For these reasons, doped BeFe 2 As 2 or 122 superconductors can roughly represent all the four families. It has the relative ease of making its SXL, as our advantage for working on Ba(Fe (1-x) Co x ) 2 As 2 . Still, above outline is included to introduce all the Fe-HTSCs. 8,21,40 A 5th structure with FePn-planes,where Pn= Pnictide, to join this superconducting set of materials is the so-called 21311 (sometimes called the 42622) structure. 43 27,55 Suitable irradiation induced defects can also increase critical current density, as discussed next from a recent publication. 44 In type II practical superconductors like Cu-O HTSCs, critical current density (loss-less electrical current density), is increased by increasing vortex pinning centers in the superconductor so that the flux lattice is pinned by these centers. 15 44 That brings many benefits ( Figure 24). They incorporated a low density of columnar defects into pristine SmFeAsO 0.8 F 0.15 crystals by using high-energy, heavy-ion irradiation along the c-axis. The induced columnar defects produce very high critical current density, as shown in Figure 24(c), without degradation of the transition temperature, vide Figure 23(e). The enhanced critical current of J c (5 K, 0 T) ≈ 20 MA.cm −2 corresponds to ~20% of the depairing current density. Interestingly, the radiation also reduced the superconducting anisotropy from 8 to 4. This can be qualitatively explained in the framework of anisotropic electron scattering by columnar defects.
A reduction of the anisotropy after heavy-ion irradiation with virtually unchanged Tc was also observed in 122-compounds. The anisotropy of Ba 0.6 K 0.4 Fe 2 As 2 is reduced from 2.5 to 2.1 after 1.4 GeV Pb-ion irradiation to a dose of BΦ=21 T; heavy-ion-irradiated SrFe 2 (As 1−x P x ) 2 shows an anisotropy change from 1.6-1.5 to 1.2-1.3. The comparatively small reduction of anisotropy in the FeAs-122 materials can be attributed to the initial low anisotropy and the discontinuous morphology of the damage tracks. Similar phenomena is expected in high-T c cuprates, MgB 2 and other anisotropic superconductors. Very limited attention has been paid to the reduction of the superconducting anisotropy due to correlated defects in these materials. In the case of cuprates, any change of H c2 is convoluted with a reduction of T c , whereas the high conductivity of MgB 2 and of most conventional superconductors has prevented the creation of columnar defects with heavy-ion irradiation. For Fe-based superconductors, their semimetal property and weak gap anisotropy enable one to tune the anisotropy via heavy-ion irradiation. Other poor-metallic and fully gapped type II superconductors can be expected to follow present predictions and demonstrate tailored anisotropy. This general phenomenon is important for the application of new superconducting materials.
The low anisotropy, high J c and high T c of optimaldoped SmFeAsO 1−x F x indicated that it was then the best Fe-based superconductor for practical applications. SmFeAsO1−x Fx thin film synthesis has progressed well. Further improvement of the performance of these films can be expected on introducing columnar-type defects. Self-assembled columnar defects, possible in Cu-O HTSCs can be tried in Fe-HTSC films.
Having discussed few of yet the best Fe-HTSCs for making high current superconducting films and wires, an outline of making such wires will be appropriate. 45 Techniques like pulsed laser deposition (PLD) onto room temperature LaAlO 3

Concluding Summary
As outlined elaborately, continuing development of specialized piezoelectric materials and intelligently designed devices have led to • varied, precise, fast and economical detection or sensing, of pressure or movement through direct piezoelectric effect -with control through added feed-back mechanism, • varied, precise, fast and economical generation of force or motion (from micromanipulator to hammer) through inverse or converse piezoelectric effect, and • varied, precise and fast imaging -through different ultrasonography scanning -either inside human body and liquid-metal-filled fast breeder reactor or outside under the sea of fish shoals or submarines Items in (i) and (ii) are, in most aspects, superior to electro-magnetic or similar devices, justifying their nicknames: electronic muscle and solenoid replacement. These are usually more economical than electromagnetic devices, that often involve bulky moving parts. Latter consumes more electricity and require more frequent replacements. Industries need to notice latest of successful applications of piezoelectricity, and more importantly potential applications that can be profitably exploited. Here, earlier discussion of piezoelectric sensing of fuel and exhaust gases in automobiles, aircrafts, rockets and missiles and necessary control may be recalled. Even chemicals in the exhaust are detected by frequency change due mass change of an implanted piezoelectric oscillator due absorption of the targeted gas by the target-specific coating given on the piezoelectric oscillator. These advances have led to great improvements in automobile engine performance.
There is harmful Electromagnetic Interference (EMI) to humans and sensitive instruments in certain range of the Electromagnetic Spectrum (Table 1 of Reference 42) like the microwave range. EMI Shielding of either the source or to-be-protected item is best done by a suitable gapless metal sheet shielding. Difficulty of making the metal shield gapless and its higher weight with respect to a flexible polymer-based shield have moved the world towards 2 nd generation EMI Shielding by Polymeric Materials. Others using conducing polymer with solid particle inclusion, have to usually add a binder-polymer or adhesive material. Here, composites of a polymeric binder only with EM wave reflecting particles (of a metal or a conducting oxide) or with EM wave absorbing particles (ferroelectric or dielectric) or their mixture have been developed as flexible sheets and their EM Shielding Effectiveness (SE or SEtotal) and Reflection Effectiveness have been measured from 700 MHz to 40 GHz measured by a Vector Network Analyser. Polymeric composites fabricated by the present group include EMI Shielding materials and Radar Absorption Materials (RAMs). 6,42 Non-stoichiometry in II-VI compounds, and CdO in particular, has been shown to be significant, although it is not fully know and not discussed well in the literature. Since this non-stoichiometry has to generate free charge carriers, this can interfere with p-type or n-type doping efforts. 800°C fired cadmium oxide has fairly high electricl conductivity (Figure 7). Optical transparency of cadmium oxide allows its use as TCO or Transparent Conducting Oxide in solar cells. Different techniques for characterization of composition (like Cd:O) as well as electrical and thermal properties of differently fired "CdO" have been outlined.
Fe pnictides, like Ba(Fe (1-x) Co x ) 2 As 2 and Fe chalcogenides superconduct defying the dictum arising from observations in conventional superconductors that magnetic ions like Fe, even in traces, destroys superconductivity. Here, newer pairing mechanism involves Fe magnetism. These Fe pnictide and chalcogenide superconductors have Fe electrons at the Fermi surface, and an unusual Fermiology that can change rapidly with doping, leading to normal and superconducting state properties very different from those in standard electron-phonon coupled ''conventional'' superconductors. As already indicated, superconductivity and magnetism or magnetic fluctuations are here intimately related and even coexist in some instances. Most importantly, these Fe-HTSCs are metals and less anisotropic than Cu-O based HTSCs, helping fabrication of superconducting wires for high current high field applications. This has been reviewed rather extensively in view of emerging potential for commercial exploitation.
This review touches only few topics from materials science research that is fruitfully extending into industry to make life more comfortable by inventing newer devices and techniques.

Funding
There has been no specific funding for this work, although general office facilities of the authors allowed execution of the work.