Effect of simultaneous substitution of La and Mn on dielectric behavior of barium titanate ceramic

A few compositions in the valence compensated system Ba1–xLaxTi1–xMnxO3 were synthesized by solid-state ceramic method to study the effect of co-doping lanthanum and manganese in equimolar amounts on dielectric behavior of BaTiO3. Compositions with x £ 0.10 have shown solid solution formation. Compositions with x £ 0.05 are found to have tetragonal structure at room temperature while composition with x = 0.10 is cubic. Plots of relative dielectric constant, er versus temperature for composition with x = 0.01 show dielectric anomalies around 376 ± 2, 264 ± 2 and 179 ± 2 K which correspond to cubic to tetragonal (TC–T), tetragonal to orthorhombic (TT–O) and orthorhombic to rhombohedral (TO–R) transition, respectively, similar to BaTiO3. Curie temperature has been found to decrease with increasing concentration of lanthanum and manganese simultaneously in barium titanate. The broadening in the dielectric peak at cubic to tetragonal (TC–T) transition temperature increases with increasing x. For x = 0.10, only one anomaly at 100 K is observed in its er versus T plots. The observation of this single anomaly may be due to pinching effect of the substitutions on the three phase transitions.