ReviewGrain growth and piezoelectric property of KNN-based lead-free ceramics
Highlights
► In this review, recent progress on the piezoelectric properties and grain growth of KNN-based systems were presented. ► The process of self-ripening from sub-grain to super-grain showed a new option for grain orientation, which based on the cluster phenomena of super fine powders and intrinsic polarization of materials. ► The microstructures on domain and domain wall of KNN-based ceramics showed a substantial relations with piezoelectric constant d33. ► KNN based lead-free piezoelectric systems with improved properties will be obtained by grain engineering.
Introduction
Lead-based piezoelectric materials with high piezoelectric and electromechanical properties, such as Pb(Zr,Ti)O3 (PZT) [1], Pb(Mg,Nb)O3 (PMN) [2], have been used extensively for transducer applications. But their high concentrations of lead (Pb), e.g. for PZT up to 63 wt%, are hazardous to human health and environment. These concerns have induced considerable momentum for lead-free ceramic research in recent years. Especially, high piezoelectric properties were reported by Y. Saito et al in 2004 [3], for (K,Na,Li)(Nb,Sb,Ta)O3 (KNLNST) system which were modified simultaneously by A-site and B-site substitutions of perovskite structure ABO3.
For such a complex system, it is not simple binary even or ternary system [4], but based on (K,Na)NbO3 (KNN) which is essentially a binary solid solution of potassium niobate KNbO3 (KN) and sodium niobate NaNbO3 (NN). From the phase diagram of KNN [5], the phase transitions from rhombohedral to orthorhombic and from orthorhombic to tetragonal of KN occur near −10 °C and 225 °C, respectively. At room temperature, NaNbO3 shows antiferroelectric-liked behaviors and orthorhombic symmetry with space group of Pbcm determined by X-ray diffractionary (XRD) [6], but its competing antiferroelectric phase Pbcm and ferroelectric phase R3c interactions was obtained by the theoretical analysis of neutron diffraction data [6]. Compared with KN and NN, unclear phase transitions of alkali antimonates or tantalates still need further study. Near the morphotropic phase boundary (MPB) of Na+ and K+ molar ratio 1:1, relatively high piezoelectric properties of KNN were obtained [1]. And their higher piezoelectric properties were realized by hot-pressing or hot forging than pressureless sintering [7] without obvious grain orientation. But as the result of asymmetrical polarization P, piezoelectric constant d33 follows the formula of d33 = 2ɛ33P3Q11 [8,9], where ɛ33 is the longitudinal dielectric constant and Q11 is the horizontal electrostrictive coefficients, thereby being affected by the orientation of grains which possess polarization P. The grain growth technologies can texture ceramic grains growing along specified direction which show optimization properties, such as reactive-templated grain growth (RTGG) used by Y. Saito et al. [3] and screen-printing multi-layer grain growth techniques (MLGG) invented by our group [10]. All technologies of grain growth, orientations and their enhancement of polarization may be called by “Grain Engineering” of piezoelectric ceramics.
To improve the piezoelectric properties, it is very effective to find structure regions of morphotropic phase boundary (MPB) by changing various compositions, and is the aim to composite new systems. For the inside physical mechanism, the polymorphic phase transition (PPT) between orthorhombic and tetragonal phases near room temperature is proposed which plays a very important role for higher piezoelectric properties [11], [12], [13]. For details, orthorhombic phase mm2 should result in 12-fold degenerate domain variants, and 6-fold degenerate domain variants should been resulted in from tetragonal phase mm4. So that their phase transition should at least induce 18-fold degenerate domain variants in total, which suggests the extrinsic contribution to d33 should be substantial [14], [15]. The total contribution of each phase to Ps (and d33) would be governed by the lever rule on the coexistence of different domains with various phases in grains [9]. For the crystal structures of grains is equal to those of domains, therefore, the objects of the research of phases and phase transitions are various domains contained in grains. Except single crystal grain with single domain, lots of domains are exist in one grain for piezoelectric ceramics, as piezoelectric grains also contain domain walls and other defects like faults in addition to domains. Evidently, domains and domain walls in grains have direct relationships with piezoelectric properties [16], [17], [18], and further research indicated that the grain size [19], [20], and defects [21], [22], have effective actions on domain density. So far, the properties of alkali niobate based piezoelectric should be very processing sensitive, especially in regard to building-in process of domains.
Since the asymmetrical character of polarization, macroscopical piezoelectric properties are not only based on domain density and the amplitudes of their inherent polarization, but also based on the uniform orientation of grains and arrangement of domains inside grains, which are achieved usually through polarizing procedure. For a remarkable increase of d33, it should be attribute to the MPB in the system and to grain texturing, which essentially are polarizations of domains with various phases and their performance, respectively.
In this review article, a concise overview of the recent progress in KNN-based piezoelectric ceramics will be provided. The grain growth and formation of domains and domain walls will be elaborated with special emphasis on KNLNST system which is the most available lead-free system up to date. This review article draws heavily on our research results, while also includes major data published by other researchers. The pointed message in this article is that the lead-free piezoelectric study will begin a new research stage based on the integration of grain growth and properties improvement after the last four decades since the basic research of KNbO3 and NaNbO3 in the 1960’s.
Section snippets
Experimental
As follows, the detailed stages of grain growth crystallization and the formation in crystallography of domains and domain walls which are related with piezoelectric properties are described from a phenomenological perspective. The experimental methodologies herein can be traced by comparing different works cited as references in this review.
KNLNST ceramics with chemical formula of (K0.44Na0.56-xLix)(Nb0.95-xSbxTa0.05)O3 (KNLNST1-4 for x = 0.035, 0.040, 0.045, 0.050) were synthesized by
Overview of KNN-based piezoelectric ceramics
Most piezoelectric ceramics principally contain lead which based on PZT solid solutions. After new systems with the compositions of (K0.5Na0.5)(1-x)(Nb1-yTay)O3 and (K0.44Na0.52Li0.04)(Nb0.86Sb0.04Ta0.10)O3 were reported [3], a worldwide effort is underway to remove lead from some commercial products by adopting alkali niobate based materials. In those systems, Li+, Sb5+, Ta5+ ions were tried to replace partial alkali metal elements and/or niobium to form MPB solid solutions. Only with the
Conclusions
In this review, recent progress on the piezoelectric properties and grain growth of KNN-based systems has been presented. It was shown that the endeavor for seeking advanced lead-free materials attained the impressive new results of KNLNST system which showed excellent piezoelectric properties. It was also shown that grain texturing can be realized by reactive-templated grain growth method, template grain growth method, even Cu-doping method. Eventually, the entire stages of self-ripening from
Acknowledgements
We thank Dr. Adrian Trinchi of CSIRO Materials Science & Engineering, Clayton VIC, Australia, for his kind help. This work was supported by the Ministry of Sciences and Technology of China through 973-Project (2009CB613305), The Major Program of the National Natural Science Foundation of China (50932007), and The Science & Technology Commission of Shanghai Municipality (08JC1420500, 10XD1404700).
References (61)
- et al.
Phase formation and electrical properties of lead-free bismuth sodium titanate-potassium niobate ceramics
Curr. Appl. Phys.
(2008) - et al.
Lead-free piezoceramics based on alkali niobates
J. Eur. Ceram. Soc.
(2005) - et al.
(Na0.5K0.5)NbO3-LiTaO3 lead-free piezoelectric ceramics
Mater. Lett.
(2005) - et al.
Piezoelectric and ferroelectric properties of 0.96(Na, K)(Nb0.9Ta0.1)O3–0.04LiSbO3 ceramics synthesized by molten salt method
J. Alloy Compd.
(2009) - et al.
Structural aspects and thermal behavior of the proton-exchanged layered niobate K4Nb6O17
Mater. Res. Bull.
(2004) - et al.
Nano-structuration of CoO film by misfit dislocations
Surf. Sci.
(2007) - et al.
Piezoelectric Ceramics
(1971) A Study of Electromechanical Properties of PMN-PT Ceramics and Analysis of the Effects of Loss on Frequency Response of Piezoelectric Ceramics
(1998)- et al.
Lead-free piezoceramics
Nature
(2004) - et al.
Competing antiferroelectric and ferroelectric interactions in NaNbO3: neutron diffraction and theoretical studies
Phys. Rev. B.
(2007)
Hot pressing of ptassium-sodium niobates
J. Am. Ceram. Soc.
Thermodynamic theory of PbTiO3
J. Appl. Phys.
Origin of high piezoelectric activity in ferroelectric (K0.44Na0.52Li0.04)-(Nb0.84Ta0.1Sb0.06)O3 ceramics
Appl. Phys. Lett.
Application of texture techniques to enhanced lead-free piezoceramics
J. Inorg. Mater.
Raman spectroscopy of (K, Na)NbO3 and (K, Na)(1-x)LixNbO3
Appl. Phys. Lett.
A study of the phase diagram of (K, Na, Li)NbO3 determined by dielectric and piezoelectric measurements, and Raman spectroscopy
J. Appl. Phys.
Phase transitional behavior in K0.5Na0.5NbO3-LiTaO3 ceramics
Appl. Phys. Lett.
Piezoelectric properties in perovskite 0.948(K0.5Na0.5)NbO3-0.052LiSbO3 lead-free ceramics
J. Appl. Phys.
Theory of Structural Transformations in Solids
Dielectric properties of fine-grained barium titanate ceramics
J. Appl. Phys.
90o domain reversal in Pb (ZrxTi1-x) O3 ceramics
J. Mater. Sci.
Domain-wall contribution to the piezoelectric response of epitaxial ferroelectric thin films
Appl. Phys. Lett.
Grain-size effects on the ferroelectric behavior of dense nanocrystalline BaTiO3 ceramics
Phys. Rev. B.
High piezoelectric properties and domain configuration in BaTiO3 ceramics obtained through the solid-state reaction route
J. Phys. D
Large electric-field-induced strain in ferroelectric crystals by point-defect-mediated reversible domain switching
Nat. Mater.
Role of defects in the ferroelectric relaxer lead scandium tantalate
J. Am. Ceram. Soc.
Effect of Li on the microstructure and electrical properties of (K0.17Na0.83)NbO3 lead-free piezoceramics
Curr. Appl. Phys.
Piezoelectric properties of Li- and Ta-modified (K0.5Na0.5)NbO3 ceramics
Appl. Phys. Lett.
Phase transitional behavior and piezoelectric properties of (Na0.5K0.5)NbO3-LiNbO3 ceramics
Appl. Phys. Lett.
Perovskite (Na0.5K0.5)(1-x)(LiSb)(x)Nb1-xO3 lead-free piezoceramics
Appl. Phys. Lett.
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Improving non-sensitivity of sintering behavior in KNN-based ceramics via Fe<inf>2</inf>O<inf>3</inf> doping
2023, Journal of Alloys and CompoundsLead-free NaNbO<inf>3</inf>-based ferroelectric perovskites and their polar polymer-ceramic composites: Fundamentals and potentials for electronic and biomedical applications
2022, Ceramics InternationalCitation Excerpt :These high d33 values were related to the influence of the tetragonality factor at x ∼0.5 [115]. The maximum real dielectric constants (ε′m) extracted from different works are shown in Fig. 5(b) [23,111–114,116]. Similarly, to the d33 behavior, the higher ε′m were obtained for the sample with x = 0.5, reaching up to 7000, as reported by Cheng et al. [111].
Progress and challenges of 3D-printing technologies in the manufacturing of piezoceramics
2021, Ceramics InternationalProgress in high-strain perovskite piezoelectric ceramics
2019, Materials Science and Engineering R: ReportsCitation Excerpt :It should be noted as well, that texturing is quite effective for strain enhancement, although very challenging for lead-free perovskite type ceramics. Much research work has been conducted to develop textured, lead-free ceramics through the design of new compositions using (R)TGG process [202,334–346,477–485,569,571–579]. All the textured samples exhibited an obviously improved strain response when compared to random ceramics, which was detailed in Section 2 of this review.