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Improvement of Physical Properties for KNN ‐based Ceramics by Modified Two‐Step Sintering
Author(s) -
Zhang Jialiang,
Qin Yalin,
Gao Yong,
Yao Weizeng,
Zhao Minglei
Publication year - 2014
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.12794
Subject(s) - natural bond orbital , ceramic , microstructure , materials science , sintering , grain size , relative density , piezoelectricity , mineralogy , analytical chemistry (journal) , composite material , density functional theory , chemistry , chromatography , computational chemistry
A modified two‐step sintering (MTSS) technique was attempted to fabricate dense (K,Na)NbO 3 ‐based lead‐free ceramics through the solid‐state reaction route. (K 0.50 Na 0.50 ) 0.98 Li 0.02 (Nb 0.795 Ta 0.18 Sb 0.025 )O 3 and (K 0.45 Na 0.55 ) 0.98 Li 0.02 Nb 0.77 Ta 0.18 Sb 0.05 O 3 were chosen as the test chemical compositions, and high relative density values over 97.5% were successfully obtained in their corresponding ceramics. Consequently, the d 33 values were enhanced considerably and reached 353 and 436 pC/N, respectively. The latter d 33 value is a record one ever achieved in the (K,Na)NbO 3 ‐based ceramic materials so far. Furthermore, observation analyses of microstructure and domain patterns were carried out and showed that partial depoling occurs more easily in large grains than in small ones. In particular, it was found that the (K 0.50 Na 0.50 ) 0.98 Li 0.02 (Nb 0.795 Ta 0.18 Sb 0.025 )O 3 ceramic densified by MTSS has a quite uniform grain‐size distribution with comparatively small grains and exhibits the very excellent time‐aging stability. The study results suggest that microstructure with high relative density and suitably suppressed grain sizes is desirable for further acquiring the superior KNN‐based ceramics of both excellent piezoelectric properties and good depoling stabilities.