Effect of simultaneous Ti and Nb doping on structure and ionic conductivity of Bi2V1-xTix/2Nbx/2O5.5- (0.1x0.25) ceramics

Solid solution of general formula Bi2V1-xTix/2Nbx/2O5.5- (0.1x0.25) were synthesized and characterized by XRD, SEM, FTIR spectroscopy, and AC impedance spectroscopy. The detail XRD analysis reveals coexistence of two phases, i.e., -orthorhombic and tetragonal at room temperature in these compounds. For lower x (?0.15), -orthorhombic phase dominates while at higher doping concentration tetragonal phase dominates with the optimum concentration of tetragonal phase for x=0.15 composition. FTIR studies are in conformity with the observation of XRD results. SEM studies show decrease in average grain size with increase in dopants' concentration. The impedance spectroscopy data were fitted with suitable equivalent circuit and circuit parameters were obtained. A correlation among crystal structure, surface morphology, and ionic conductivity was found. At low and intermediate temperature regime, highest conductivity was obtained for x=0.15 and at high temperature region, it was for x=0.1. The measured conductivity values are higher as compared to single doped Ti/Nb and parent compounds.