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Abnormal grain growth in (K, Na)NbO 3 ‐based lead‐free piezoceramic powders
Author(s) -
Thong HaoCheng,
Xu Ze,
Zhao Chunlin,
Lou LuYao,
Chen Shi,
Zuo SiQing,
Li JingFeng,
Wang Ke
Publication year - 2019
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/jace.16070
Subject(s) - calcination , nucleation , materials science , sintering , grain growth , abnormal grain growth , natural bond orbital , mineralogy , ternary operation , ball mill , grain boundary , ceramic , grain size , chemical engineering , metallurgy , crystallography , thermodynamics , microstructure , chemistry , density functional theory , biochemistry , physics , computational chemistry , computer science , engineering , programming language , catalysis
Abnormal grain growth ( AGG ) is frequently observed in sintered (K, Na)NbO 3 ( KNN )‐based piezoceramics. However, in the present study, abnormal grain growth was unexpectedly discovered in calcined KNN ‐based powders. To explain the phenomenon, three well‐established models that account for the AGG in sintered ceramics were discussed, including (a) liquid‐phase‐assisted grain growth, (b) two‐dimensional nucleation grain growth, and (c) complexion coexistence. However, the AGG in calcined powders was concluded to be none of them, but a consequence of the A‐site compositional inhomogeneity in the K 2 CO 3 ‐Na 2 CO 3 ‐Nb 2 O 5 ternary system. Since repeated calcination and ball milling have low efficiency on solving AGG and the accompanied compositional inhomogeneity, abnormal grains were found to coexist with normal grains at a very high calcination temperature, that is, 1000°C. The compositional inhomogeneity is believed to be remaining even after sintering and consequently deteriorate the comprehensive performances, which might be a determinant for the unstable reproduction of KNN ‐based piezoceramics.