Synthesis, thermo physical and electrical properties of Nd2-xLixTi2O7-δ

Nd2-xLixTi2O7-δ (x = 0, 0.1 and 0.15) (NDT) was synthesised by Gel Entrapment Technique. These ceramics were structurally characterized by analysis of X-ray diffraction (XRD) patterns, indicates that NDT ceramics present a monoclinic structure. Proton Induced Gamma Emission (PIGE) technique was used to determine the Li content in the as synthesised and sintered samples. Dielectric relaxations of these compounds were investigated in the temperature range 250 °C–900 °C. Using the Cole–Cole model, an analysis of the dielectric loss with frequency was performed, assuming a distribution of relaxation time. The observed loss tangent was very low for the base material and by doping with Li the dielectric loss found to increase. The presence of the peaks in temperature dependent dielectric loss indicated that the hoping of charge carriers is responsible for the relaxation. The Nyquist plot shows overlapping semicircles, for grain and grain boundary of NDT ceramics. The variation of dc conductivity confirmed that the NDT's exhibit negative temperature coefficient of resistance behavior in high temperature. Studies indicated onset of the grain boundary conduction process occurs even at lower temperatures in these systems with increase in the Li content.

Research highlights►Gel Entrapment Technique has been used to synthesize Li doped Nd2Ti2O7 powders. ►Particle Induced Gamma Emission used for Li analysis showed that sintering at 1500 °C for 3 h led to ~ 18 % loss for samples that contained 5% Li originally where as for samples that contained 7.5% Li in the as synthesised samples was reduced by 27%. ►Li has been found to enhance the grain boundary conduction even at lower temperatures. ►The permittivity of the system found to be improved with increase in the dopant ion concentration. ►Significant changes in the activation energies could be visualized due to the effect of Li doping in the Nd sites.