Nonisothermal Crystallization Kinetics of Bi_xY_3−xFe₅O₁₂ (0.25≤x≤1.00) Prepared from Coprecipitation Process

Abstract

The nonisothermal crystallization kinetic of BixY3−xFe5O12 (0.25≤x≤1.00) powders prepared by coprecipitation process has been investigated. The activation energy of crystallization was calculated by differential scanning calorimetry at different heating rates. The activation energies of crystallization of BixY3−xFe5O12 system are 492, 447, 377, and 353 kJ/mol and the Avrami constant n are 3.49, 2.25, 2.48, and 2.33 for x=0.25, 0.50, 0.75, and 1.00, respectively. The Avrami exponent values (1<n<3) were consistent with surface and internal crystallizations occurring simultaneously for 0.50≤x≤1.00, the value (n>3) for the Avrami exponent was consistent with bulk crystallization domination in BixY3−xFe5O12 system. The results reveal that increasing the substitution amount of bismuth for yttrium would significantly decrease activation energy in BixY3−xFe5O12 system.

Comparison of Precursor Preparation Routes on Final Density of Y3Fe5O12 Garnets Prepared via Reactive Sintering

“…In this method, it is very difficult to achieve an ideal homogenization of the system. In addition, as a result of roasting at high temperatures, there is significant grain growth and the formation of mechanically durable agglomerates [13,14].…”