Dielectric characteristics of Mn-doped LaTiO$_{\mathrm{3+\delta }}$ ceramics.

A series of ceramic composites of Mn-doped La$_{\mathrm{1-}}_{x}$Mn$_{x}$TiO$_{\mathrm{3+}}_{\delta }$ and LaMn$_{x}$Ti$_{\mathrm{1-}}_{x}$O$_{\mathrm{3+}}_{\delta }$ ($x \quad =$ 0.1, 0.2) were synthesized by conventional solid-state reaction method. The low-frequency complex dielectric properties of the composites were investigated as functions of temperature (77 K $\le \quad T \le $ 360 K) and frequency (100 Hz $\le \quad f \le $ 1 MHz), respectively. The dielectric constant of $A$-site doped samples is higher than that of $B$-site doped samples. The loss tangent of low doped samples is much less than that of high doped samples. The $A$-site doped composites exhibit intrinsic dielectric response with a dielectric constant of \textasciitilde 40 in the temperature below 250 K. Interestingly, the dielectric constants of $B$-site doped ceramics increase slightly in the temperature range from 77 to 360 K. And it is clearly observed that extraordinarily high dielectric loss tangent (\textasciitilde 6) appear at low frequency (100 Hz) in LaMn$_{\mathrm{0.2}}$Ti$_{\mathrm{0.8}}$O$_{\mathrm{3+}}_{\delta }$, which is \textasciitilde 8 times larger than that of LaMn$_{\mathrm{0.1}}$Ti$_{\mathrm{0.9}}$O$_{\mathrm{3+}}_{\delta }$, which indicates that the doped content can affect the intrinsic dielectric characteristics significantly.