Dielectric behavior of paraelectric ${\mathrm{KTaO}}_3,$ ${\mathrm{CaTiO}}_3,$ and ${(Ln}_{1/2}{\mathrm{Na}}_{1/2}){\mathrm{TiO}}_3$ under a dc electric field

The dc electric-field dependence of dielectric constant in the paraelectrics, ${\mathrm{KTaO}}_3$ single crystals, ${\mathrm{CaTiO}}_3$ and ${(Ln}_{1/2}{\mathrm{Na}}_{1/2}){\mathrm{TiO}}_3$ $(Ln=\mathrm{La}$ and Nd) ceramics is studied at cryogenic temperatures in the dc electric-field range 0–60 kV/cm. The results indicate that ${\mathrm{KTaO}}_3$ possesses a high tunability $K\{=\left[\epsilon {(E}_0\right)-\epsilon \mathrm{}\left(E\right)\mathrm{}]/\epsilon {(E}_0)=\sim 50\%\}$ at 20 kV/cm, and low dielectric loss $\tan \delta$ $(\sim 0.003);$ while ${\mathrm{CaTiO}}_3$ and ${(Ln}_{1/2}{\mathrm{Na}}_{1/2}){\mathrm{TiO}}_3$ $(Ln=\mathrm{La}$ and Nd) show low tunability of $\sim 1\%$ and $\sim 0.1\%,$ respectively, at 20 kV/cm; however, the dielectric loss $\tan \delta$ is very small $(\sim 0.0004–0.003).$ The possible physical mechanism of the behavior observed is discussed.