Dielectric properties of ${\mathrm{Sr}}_{1-x}{\mathrm{Mn}}_x{\mathrm{TiO}}_3$ ceramics ($x=0–0.15$ and 1) prepared by conventional mixed oxide method were investigated in radio frequency, high frequency, terahertz, and infrared ranges. It is shown that the real and imaginary parts of the dielectric permittivity between $100\mathrm{Hz}$ and $1\mathrm{MHz}$ exhibit a relaxation in the temperature range of $30\text{–}80\mathrm{K}$, shifting to higher temperatures with increasing Mn content. The dielectric relaxation is also observed at higher frequencies (around $100\mathrm{K}$ for high frequencies and up to room temperature for terahertz frequencies) in ${\mathrm{Sr}}_{0.95}{\mathrm{Mn}}_{0.05}{\mathrm{TiO}}_3$ ceramics. Activation energy $U\sim$$52\text{–}78\mathrm{meV}$ and relaxation time pre-exponent ${\tau }_0\sim \left(1\text{–}12\right)\times {10}^{-14}\mathrm{s}$ are obtained using Arrhenius and Vogel-Fulcher relations. Such dielectric behavior is attributed to Mn off-center relaxation at Sr site of highly polarizable ${\mathrm{SrTiO}}_3$ lattice. Moreover, a reduction of the phonon contribution to the dielectric constant with Mn doping accompanying a stiffening of the soft lattice mode is found in infrared reflectivity spectra and could be related to the interaction of the soft mode with off-centered Mn ions and polar clusters.

• Received 23 October 2005

DOI:https://doi.org/10.1103/PhysRevB.73.104113