Structure and dielectric properties of 0.70 Ba 1-x La2x/3TiO3-0.30 Bi (Mg0.5 Ti0.5) O3 ceramics

Abstract

In the present work, we synthesized La-doped 0.70 Ba _1-x La_2x/3TiO₃-0.30 Bi (Mg_0.5 Ti_0.5) O₃ ceramics (where x-0.02, 0.04, 0.06, 0.08) hereby designated as BLT-BMT by conventional solid-state sintering method. The emphasis was to evaluate the structure and dielectric properties of BLT-BMT as a function of La concentration. Reitveld refinement of the structure confirmed single-phase perovskite structure with pseudo-cubic symmetry. Incorporation of La₂O₃ into the ceramic matrix resulted in the decrease of lattice parameters and cell volumes, this infers that long-range ordering has been destroyed in the samples. This statement is further supported by Raman measurements. Shift in the dielectric peaks was observed towards higher-temperature side with increasing frequency, and this may be attributed to the effects induced by La³⁺ incorporation. This also improves the temperature stability of dielectric permittivity which in turn supports the relaxation behavior present in all the compositions. Dielectric diffusivity of the samples was found to lie between 1.52 and 1.67, while the activation energy was found to increase from 0.25 to 0.42 eV with increase in La concentration. All the samples exhibit Negative temperature Coefficient of Resistance (NTCR) behavior. Conductivity increases with increasing temperature for all the compositions.