Effects of A-Site Ions on the Phase Transition Temperatures and Dielectric Properties of ($1-x$)(Na0.5K0.5)NbO3--$x$AZrO3 Solid Solutions

概要

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($1-x$)(Na0.5K0.5)NbO3--$x$AZrO3 (A = Sr, Ca) solid solutions have been prepared to study the effcts of A-site ions on the successive phase transition temperatures. It is found that the phase diagram for the solid solutions are very similar: with increasing $x$, the cubic--tetragonal phase transition temperature $T_{\text{C{\mbox{--}}T}}$ and the tetragonal--orthorhombic phase transition temperature $T_{\text{T{\mbox{--}}O}}$ shift to the lower-temperature region, while the orthorombic--rhombohedral phase transition temperature $T_{\text{O{\mbox{--}}R}}$ shifts to the higher temperature region. When $x$ is between 8 and ${\sim}15$ molar percentage, the orthorhombic--rhombohedral phase transition temperature is higher than room temperature and the ($1-x$)(Na0.5K0.5)NbO3--$x$AZrO3 solid solutions exhibit rhombohedral symmetry at room temperature. It is found that $T_{\text{C{\mbox{--}}T}}$ is affected by A-site ions; while $T_{\text{T{\mbox{--}}O}}$ and $T_{\text{O{\mbox{--}}R}}$ are almost independent of A-site ions.
2011-09-25