Molten Salt Flux Synthesis, Structure determination, Optical, Impedance and Modulus Spectroscopy Characterization of perovskite compound

The chemical Molten Salt Flux process was used for the synthesis of Ba_0.97La_0.02Ti_1-xNb_4x/5O₃ polycrystalline sample (well-known as BLTi_0.93Nb_0.056). Doping with Niobium caused significant alterations in the physical properties of BLT ceramic. The XRD analysis revealed that Nb introduction forms a pure perovskite phase and crystallize in the P4/mmm-tetragonal symmetry. The average crystallite size was proven to decrease with the increase in Nb concentration. TEM image showed the formation of particles, where the average grain size decreased with Nb doping. The Nb incorporation into the BLT host lattice was also confirmed by the optical band gap (Eg) value. The optical properties were strongly influenced by Nb doping. The dielectric parameters were subsequently investigated as a function of frequency and d.c bias voltage. The observed dielectric dispersion was interpreted on the basis of Maxwell-Wagner interfacial model and Koop's phenomenological theory. Overall, Nyquist plot shows both bulk and grain boundary effect. The electrical relaxation process occurring in the material has been found to be d.c bias voltage dependent. Modulus analysis has established the possibility of hopping mechanism for electrical transport processes in the system.