Thermal and structural characterization of the Bi_2‐xSm_xSr₂Ca₂Cu₃O_10+δ glass‐ceramic system

Abstract

In this work, investigations on the crystallization and oxidization kinetics of the Sm substituted BiSrCaCuO glass-ceramic system were performed. It has been shown that the Sm ions changed the glassification properties of the BiSrCaCuO system.While fully glass samples were obtained for low Sm-substitution levels (x=0.2 and x=0.4), the Sm containing particles on the surface have grown especially at high Sm-substitution levels (x>0.6) and glassification problem increased. Nonisothermal crystallization kinetics including activation energy for crystallization, E a , and Avrami parameter, n, of the samples prepared was investigated using differential thermal analysis (DTA) at four different uniform heating rates. The values of glass transition temperature and crystallization temperature exhibited compositional and heating rate dependence. E a value of the samples showed an increase with increasing the Sm concentration. The Avrami parameter, n, was found approximately 4.5, suggesting the growth of small particles with an increasing nucleation rate. The calculated values of the oxidization rates and the activation energy for oxygen out-diffusion process, E, indicated that the oxygen deficiencies by the Sm substitution in the unit cell of BiSrCaCuO were formed and more oxygen atoms were absorbed to fill the oxygen deficiencies in the system. K E Y W O R D Sglass-ceramics, activation energy, Avrami parameter, oxygen out-diffusion process

Thermal and structural investigations of xLi2O‐(1−x)Bi2O3 (0.25 ≤ x ≤ 0.35) glasses

“…Here, E Oc and E Kc are the activation energies of crystallization determined, using Ozawa and Kissinger methods, respectively. Some authors have applied the Johnson‐Mehl‐Avrami (JMA) equation for the nonisothermal crystallization to estimate the nature of crystallization. However, JMA equation is derived for the isothermal crystallization (see Section 3.2 below).…”

“…However, in nonisothermal crystallization glass is heated at a fixed rate and the change in enthalpy is recorded as a function of temperature . Various theoretical models have been suggested to obtain the kinetic parameters and the activation energies of crystallization from the isothermal and nonisothermal thermograms. These theoretical models also explain their applicability at different stages of crystallization of glasses .…”