Structural and electrical characteristics of nanocrystalline La2Sn2O7 pyrochlore

Abstract

Nanocrystalline La2Sn2O7 ceramic with pyrochlore structural phase was prepared by the chemical co-precipitation method followed by conventional sintering. Structural analysis by X-ray diffraction, transmission electron microscopy, and Raman spectroscopy revealed the pyrochlore phase formation. The Nyquist impedance plots measured at different temperatures (550–700 °C) exhibited a single semicircular arc and the relaxation times corresponding to grain interior and grain boundary were found to lie close to each other. The dielectric relaxation behavior in La2Sn2O7 was found to be of non-Debye type. The activation energy for conduction of oxygen ions was determined to be 0.87 eV. Frequency and temperature-dependent ac conductivity spectra were analyzed based on the Universal dielectric response model given by Jonschers’ power law. The conduction mechanism in La2Sn2O7 was discussed by employing the jump relaxation model and correlated barrier hopping (CBH) model. The maximum barrier height for the mobile ions to overcome for hopping was found to be 0.62 eV. The insights into the frequency and temperature dependence of the dielectric permittivity and dielectric loss in La2Sn2O7 were discussed using the Maxwell–Wagner model. The electric modulus spectra of La2Sn2O7 were manifested by the Kohlrausch-Williams-Watts (KWW) function. Further, the non-Debye type of relaxation was explicitly confirmed by the β values. Additionally, the universal scaling behavior was also demonstrated in La2Sn2O7 by the electrical modulus and impedance characteristics.