Premium
Crystallization Kinetics and Electrical Relaxation of BaO–0.5Li 2 O–4.5B 2 O 3 Glasses
Author(s) -
Vaish Rahul,
Varma K.B.R.
Publication year - 2009
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2009.03152.x
Subject(s) - materials science , crystallization , differential scanning calorimetry , amorphous solid , dielectric , activation energy , thermodynamics , electrical resistivity and conductivity , analytical chemistry (journal) , relaxation (psychology) , glass transition , mineralogy , composite material , chemistry , crystallography , polymer , psychology , social psychology , physics , optoelectronics , chromatography , electrical engineering , engineering
Transparent glasses in the composition BaO–0.5Li 2 O–4.5B 2 O 3 (BLBO) were fabricated via the conventional melt‐quenching technique. X‐ray powder diffraction combined with differential scanning calorimetric (DSC) studies carried out on the as‐quenched samples confirmed their amorphous and glassy nature, respectively. The crystallization behavior of these glasses has been studied by isothermal and nonisothermal methods using DSC. Crystallization kinetic parameters were evaluated from the Johnson–Mehl–Avrami equation. The value of the Avrami exponent ( n ) was found to be 3.6±0.1, suggesting that the process involves three‐dimensional bulk crystallization. The average value of activation energy associated with the crystallization of BLBO glasses was 317±10 kJ/mol. Transparent glass–ceramics were fabricated by controlled heat‐treatment of the as‐quenched glasses at 845 K/40 min. The dielectric constants for BLBO glasses and glass–ceramics in the 100 Hz–10 MHz frequency range were measured as a function of the temperature (300–925 K). The electrical relaxation and dc conductivity characteristics were rationalized using electric modulus formalism. The imaginary part of the electric modulus spectra was modeled using an approximate solution of the Kohlrausch–Williams–Watts relation. The temperature‐dependent behavior of stretched exponent (β) was discussed for the as‐quenched and heat‐treated BLBO glasses.