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Effect of antimony substitution for niobium on the crystal structure, piezoelectric and dielectric properties of (K0.5Na0.5)NbO3 ceramics
Citation Link: https://doi.org/10.15480/882.808
Publikationstyp
Working Paper
Date Issued
2010
Sprache
English
TORE-DOI
Citation
Functional materials letters ; Vol. 3.2010, no.1, pp. 25-30
The effect of antimony substitution for niobium on potassium sodium niobate (KNN) ceramic was investigated with respect to the densification behaviour at different sintering temperatures, microstructure and electrical properties. Sb5+ was slightly added while simultaneously lowering the amount of Nb5+and in this study of the (K0.5Na0.5)(Nb1-xSbx)O3 system, x content was varied from 0 to 14 mol.%
Our results show that Sb5+ slightly increased the optimum sintering temperature for KNN but above 8 mol %, its resistivity and piezoelectric properties decreased. As the amount of Sb5+ substituted is increased, the structure of the ceramic transformed from orthorhombic to pseudocubic which led to slight shrinkage in the unit cell volume. Microstructural examination revealed that above 10 mol %, a second phase (K2NaSb3O9) was formed which segregated mainly to the grain boundary while the quantitative EDX analysis showed that there was A-site vacancy due to loss of the alkali elements. The two phase transitions points, Curie temperature (TC) and the tetragonal to orthorhombic (TT-O)
shifted to lower temperature with increasing Sb5+ content and above 10 mol %, the TT-O shifted to below room temperature. The dielectric loss slightly increases with increasing Sb5+ content up to 200°C. There was an improvement in the piezoelectric properties with ≤ 6 mol % Sb content while optimum properties were obtained with 4 mol % (KP = 0.46, Qm= 6.2, NP = 2296).
Our results show that Sb5+ slightly increased the optimum sintering temperature for KNN but above 8 mol %, its resistivity and piezoelectric properties decreased. As the amount of Sb5+ substituted is increased, the structure of the ceramic transformed from orthorhombic to pseudocubic which led to slight shrinkage in the unit cell volume. Microstructural examination revealed that above 10 mol %, a second phase (K2NaSb3O9) was formed which segregated mainly to the grain boundary while the quantitative EDX analysis showed that there was A-site vacancy due to loss of the alkali elements. The two phase transitions points, Curie temperature (TC) and the tetragonal to orthorhombic (TT-O)
shifted to lower temperature with increasing Sb5+ content and above 10 mol %, the TT-O shifted to below room temperature. The dielectric loss slightly increases with increasing Sb5+ content up to 200°C. There was an improvement in the piezoelectric properties with ≤ 6 mol % Sb content while optimum properties were obtained with 4 mol % (KP = 0.46, Qm= 6.2, NP = 2296).
Subjects
Lead-free piezoelectrics
ceramics
potassium sodium niobate
DDC Class
620:Engineering and allied operations
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