Journal
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
Volume 107, Issue 1, Pages 355-366Publisher
WILEY
DOI: 10.1111/jace.19465
Keywords
K/Na ratio; lead-free piezoelectric; local heterogeneity; multiphase coexistence; potassium sodium niobate
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This study investigates the effect of K/Na ratio on the phase structure, ferroelectric domains, and piezoelectric properties of potassium sodium niobate (KNN)-based ceramics. It reveals that high Na+ content leads to large ferroelectric domains, while high K+ content results in local polarity heterogeneity and distinct dielectric relaxational behavior. The balanced local polarity and stress heterogeneities contribute to improved piezoelectricity.
Although certain efforts were paid to the effect of K/Na ratio on the phase structure and piezoelectric properties of potassium sodium niobate {(K, Na)NbO3, KNN}-based ceramics, insufficient attention was given to the local structure and ferroelectric domains, hindering the further understanding of physical mechanisms. Herein, we studied the effect of the K/Na ratio on KNN-based ceramics with multi-phase coexistence from multiscale structure. High Na+ content leads to local stress heterogeneity and retains large ferroelectric domains, while high K+ content rotates the NbO6 octahedron and results in local polarity heterogeneity and distinct dielectric relaxational behavior, consequently fragmenting ferroelectric domains. The improved piezoelectricity is obtained at the equal K/Na ratio and originates from the balanced local polarity and stress heterogeneities. Therefore, an appropriate K/Na ratio should be fully considered when designing compositions with the purpose of improving performance of KNN-based ceramics in the future.
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