Crystallization kinetic studies on Bi_1.75Pb_0.25Sr₂Ca₂Cu_3-xSnxO_δ glass-ceramic by using non-isothermal technique

Abstract

The Sn substituted Bi_1.75Pb_0.25Sr₂Ca₂Cu_3-xSnxO_δ glass ceramic (where x = 0, 0.1, 0.3, and 0.5) samples were prepared by the melt-quenching method. Crystallization kinetic studies of the samples were conducted using the differential thermal analysis (DTA). The oxidation behavior of the samples was also analyzed using the thermogravimetry analysis (TG). The DTA curves were registered with different heating rates (5, 10, 15, and 20 Kmin^− 1) up to 1200 ± 0.5 K. The crystallization results were analyzed, and activation energy of crystallization process as well as the crystallization mechanisms and the effect of Sn substitution on powder glass ceramic were characterized. The glass transition temperature (T_g), the first crystallization peak temperature (T_x1) and the second crystallization peak temperature (T_x2) values were obtained as 713.0 ± 0.5–746.6 ± 0.5, 731.0 ± 0.5–760.8 ± 0.5 and 789.0 ± 0.5–820.1 ± 0.5 K, respectively. The activation energy (E_a) of crystallization was estimated from DTA results to be about 332.8 ± 0.1, 358.0 ± 0.1, 353.1 ± 0.1 and 348.9 ± 0.1 kJ/mol for x = 0, 0.1, 0.3 and 0.5, respectively, by using the Kissinger method. The Avrami parameter (n) values calculated at different Sn ratio from DTA results were found to be between 1.70 ± 0.01 and 2.57 ± 0.01, results reflect the growth of small particle with a decreasing nucleation rate.

Introduction

Since the first report on new high T_c superconducting BiSrCaCuO ceramics by Maeda et al. [1], many attempts have been done on the effect of the doping or substitution by different rare earth elements on the electrical properties, magnetic properties and thermal characterizations for the high-T_c superconductors [1], [2], [3], [4], [5], [6], [7], [8], [9]. Study of the thermal and structural properties [5], [6], [7], [8], [9], [10], [11], [12], [13], [14] of BiSrCaCuO (BSCCO) glass ceramics is important to understand the nucleation and crystal growth mechanism which is essential to obtain high quality glasses for technological applications. Many works have reported the glass thermal properties studied by isothermal and non-isothermal methods [10], [11], [12], [13], [14]. The non-isothermal method offers some advantages when compared to isothermal method. One of them is that the non-isothermal experiments can be performed in shorter time period and in a wider temperature range. In addition, most phase transformations occur too rapidly to be measured under isothermal conditions because of the inherent transients associated with the experimental apparatus [15], [16].

Glasses are useful model materials in which to study phase development and kinetics in variety of systems can be studied. Various mechanisms of superconducting phase development have been reported in the literature [17], [18], [19], [20], [21]. The crystallization kinetics of BSCCO systems have been investigated by using DTA, differential scanning calorimeter (DSC) and TG methods and the crystallization activation energies, Avrami parameters, and the average oxidation rates of these systems have been calculated [11], [12], [13], [14], [22], [23], [24].

Apart from our study, and to best of our knowledge, no other information on effects of tin substitution for copper sites on the crystallization kinetic parameters of Bi_1.75Pb_0.25Sr₂Ca₂Cu_3-xSn_xO_δ glasses have been reported in any study in the literature. The present work is focused to study the effect of replacement of the tin by copper in the chemical composition of the Bi_1.75Pb_0.25Sr₂Ca₂Cu_3-xSn_xO_δ glasses with various x values of 0, 0.1, 0.3 and 0.5 on their crystallization characteristics. The samples were fabricated by conventional glass ceramic technique. In order to determine the crystallization kinetic of the investigated samples, DTA and TG analysis were employed. Four different heating rates were used during the kinetic studies. The activation energy, nucleation and growth like curves, and finally the crystallized fraction have been determined and compared as a function of x (x = 0, 0.1, 0.3, and 0.5).