Structure and dielectric properties of high-pressure perovskite-type oxyfluorides $xKTiO2F–(1−x)BaTiO3$ Available to Purchase

We synthesized $xKTiO2F–(1−x)BaTiO3$ solid solution by the high pressure and temperature method. With regard to the temperature dependence of the dielectric permittivity, the three anomalies corresponding to the three phase transitions of $BaTiO3$ merged with the increase in $x$⁠, and only one peak was observed for $0.12≤x≤0.20$⁠. The variation in $TC$ with the composition, $dTC/dx$⁠, of $xKTiO2F–(1−x)BaTiO3$ was approximately $−14K/mol%$ for $x≥0.12$⁠, which is almost the same as and larger than that of the $1/3xBaLiF3−(1−1/3x)BaTiO3$ and $Ba(Ti1−xMx)O3$ (⁠$B=Zr$⁠, Sn, Hf, and Ce) solid solutions, respectively. This result indicates that the phase transition temperature is significantly affected by the substitution with F ion. Furthermore, it was found that the $0.15KTiO2F−0.85BaTiO3$ is an ideal relaxor and that the remnant polarization is $5.6μC/cm2$ at 70 K, which is comparable to that of $Ba(Ti0.7Zr0.3)O3$⁠. However, the $εm$ of $0.15KTiO2F−0.85BaTiO3$ (⁠$≈5000$ at 100 kHz) was smaller than that of the $B$-site ion-substituted relaxors: $Ba(Ti0.7Zr0.3)O3$ and $Ba(Ti0.82Sn0.18)O3$⁠. Since the remnant polarization of $0.15KTiO2F−0.85BaTiO3$ at 70 K was comparable to that of $Ba(Ti0.7Zr0.3)O3$ at 175 K, the small $εm$ of $0.15KTiO2F−0.85BaTiO3$ is found to be due to the decrease in the dielectric permittivity in the paraelectric region.