Effects of Ca Substitution for Sr on Ferroelectric Properties and Crystal Structure of (Sr1-xCax)Bi3Ti2NbO12

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The effects of substituting Ca for Sr in (Sr1-xCax)Bi3Ti2NbO12 compounds on the ferroelectric properties and the weight fraction of the orthorhombic phase were investigated in this study. Mixtures of orthorhombic and tetragonal phases of (Sr1-xCax)Bi3Ti2NbO12 compounds were obtained in the composition ratio range of $x=0--0.4$. The weight fraction of the orthorhombic phase calculated by Rietveld analysis increased from 89.66 to 92.83 wt % as the composition ratio $x$ increased from 0 to 0.25. The remanent polarization ($P_{\text{r}}$) of the samples in the composition ratio range of 0–0.25 was greatly improved by the substitution of Ca for Sr, and the maximum value of $P_{\text{r}}$ was 9.31 μC/cm2 at $x=0.25$. These results suggest that the $P_{\text{r}}$ values of (Sr1-xCax)Bi3Ti2NbO12 compounds are related to the weight fraction of the orthorhombic phase, because the variation in remanent polarization showed the same tendency as the variation in the weight fraction of the orthorhombic phase. Moreover, the Curie temperature ($T_{\text{c}}$) increased as the tolerance factor ($t$) of the pseudo-perovskite block (SrBiTi2NbO10)2- decreased; it is suggested that the increase in $T_{\text{c}}$ is connected to the structural distortion of the pseudo-perovskite block.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2005-09-15