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Grain Growth of ZnO in ZnO‐Bi 2 O 3 Ceramics with TiO 2 Additions
Author(s) -
Suzuki Hironori,
Bradt Richard C.
Publication year - 1995
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.1151-2916.1995.tb08494.x
Subject(s) - grain growth , spinel , materials science , activation energy , phase (matter) , liquid phase , ceramic , grain size , diffusion , mineralogy , analytical chemistry (journal) , metallurgy , chemistry , physics , organic chemistry , chromatography , thermodynamics
Grain growth of ZnO in liquid‐phase‐sintered ZnO‐Bi 2 O 3 ceramics containing systematic additions of TiO 2 to the 0.55 wt% level has been studied for flring in air from 900° to 1400°C. The Bi 2 O 3 melts during flring, and then the TiO 2 dissolves into the Bi 2 O 3 ‐rich liquid. The TiO 2 initially reacts with the Bi 2 O 3 to form the compound Bi 4 Ti 3 Oi 2 . Above ∼1050°C, the Bi 4 Ti 3 O 12 reacts with ZnO to form the Zn 2 TiO 4 spinel phase. This results in two distinct regions of ZnO grain growth in this System; one below 1050°C, where the Bi 4 Ti 3 O 12 affects the process, and the other above 1050°C, where the Zn 2 TiO 4 spinel dominates. The exponent for ZnO grain growth decreases from 5 for TiO 2 ‐free ZnO‐Bi 2 O 3 to 3 for ZnO‐Bi 2 O 3 ‐TiO 2 at temperatures below 1050°C, but increases to 6 at temperatures above 1050°C. The exponents are related to the presence of Bi 4 Ti 3 O 12 in the Bi 2 O 3 ‐rich liquid phase below 1050°C and the Zn 2 TiO 4 particles that are present above 1050°C. The activation energy for grain growth of the ZnO is ∼300 kJ/mol below 1050°C, but 360 kj/mol above 1050°C. It is suggested that diffusion of ZnO through the Bi 2 O 3 ‐rich liquid phase is the rate‐controlling mechanisrn for ZnO grain growth below 1050°C and that grain‐boundary drag by the pores and Zn 2 TiO 4 spinel particles is the rate‐controlling mechanism above 1050°C.