Onset of spontaneous electrostrictive strain below 520 K in Pr-doped SrTiO3

$Sr_{0.95}Pr_{0.05}TiO_{3}$ ceramic is shown to exhibit anomalous value of cubic lattice parameter at room temperature. A combination of temperature dependent dielectric and synchrotron x-ray powder-diffraction study has revealed that the anomalous lattice parameter has contribution from spontaneous electrostrictive strain that sets in below 520 K. In analogy with the lead-based classical relaxor ferroelectrics, it is suggested that Pr-doped $SrTiO_{3}$ is a new class of high-temperature lead-free relaxor ferroelectric system