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Fabrication of Grain‐Oriented Bi 2 WO 6 Ceramics
Author(s) -
KIMURA T.,
HOLMES M. H.,
NEWNHAM R. E.
Publication year - 1982
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.1151-2916.1982.tb10410.x
Subject(s) - sintering , crystallite , materials science , fabrication , ceramic , calcination , grain growth , grain size , mineralogy , dissolution , chemical engineering , composite material , grain boundary , microstructure , metallurgy , chemistry , medicine , biochemistry , alternative medicine , pathology , engineering , catalysis
Grain‐oriented Bi 2 WO 6 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 Bi 2 WO 6 crystallites are 3∼5 μ m in size and, at >850°C, =100 μm. After dissolving away the salt matrix, the Bi 2 WO 6 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.