Fabrication of Grain‐Oriented Bi2WO6 Ceramics

Abstract

Grain‐oriented Bi2WO6 ceramics were fabricated by normal sintering techniques. Platelike crystallites were initially synthesized by a fused salt process using an NaCl‐KCI melt. When calcined at <800°C, the Bi2WO6 crystallites are 3∼5 μm in size and, at >850°C, =100 μm. After dissolving away the salt matrix, the Bi2WO6 particles were mixed with an organic binder and tapecast to align the platelike crystallites. Large particles were easily oriented by tapecasting but the sinterability of the tape was poor. Preferred orientation of small particles was increased by tapecasting and grain growth during sintering further improves the degree of orientation. Sintering above the 950°C phase transition, however, results in discontinuous grain growth and low densities. Optimum conditions for obtaining highly oriented ceramics with high density occur at sintering temperatures of 900°C using fine‐grained powders which yield orientation factors of =0.88 and densities of 94% theoretical.