High dielectric constant and tunability of strontium titanate ceramics modified by chromium doping

The incorporation of chromium on the strontium site of the perovskite lattice of SrTiO₃ ceramics and its influence on the structural, microstructural and low-frequency dielectric properties is studied in this work. Dense Sr_1-1.5xCr_xTiO₃ (x = 0, 0.0005, 0.0010, 0.0015) ceramics are prepared from powders obtained by a sol-gel method. The lattice parameter ∼3.906 Å and average grain size ∼2.5 μm are almost identical for all the ceramic samples under study. On the other hand, the dielectric constant increases from approximately 7000 for x = 0 to >16 000 for x = 0.0005. Detailed investigations of the low-temperature dielectric properties show a remarkable increase of the tunability and nonlinearity of the dielectric constant as a function of dc bias field in strontium titanate ceramics modified by chromium doping but no ferroelectric or relaxor-like behaviour. These results imply the possible incorporation of small Cr amounts on the Sr site of strontium titanate ceramics and expand the tunable applications of SrTiO3-based materials.