Structural, dielectric and electrical properties of pyrochlore-type Gd2Zr2O7 ceramic

This work reports on the dielectric and electrical properties of a single-phase polycrystalline pyrochlore structured Gd2Zr2O7 ceramics with a highly dense and compact microstructure. X-ray diffraction along with Raman spectroscopic studies confirmed the formation of the pyrochlore phase; while the electron microscopy investigations showed the uniformly distributed and densely packed micrometer-sized grains. The relaxation phenomena and conduction processes in Gd2Zr2O7 analyzed using complex impedance spectroscopy which showed the appearance of low-frequency dielectric dispersion suggesting the dominance of conduction by oxygen ions. Observation of double semi-circular arcs in the Nyquist plots confirms that both grains and grain boundaries contribute to the electrical impedance of Gd2Zr2O7. The temperature-dependent ac conductivity studies on Gd2Zr2O7 followed the Jonscher's power law exhibited a strong dispersive behavior at the low temperature (< 300 degrees C) over the whole frequency region; whereas a weak dispersive nature observed at the higher temperature in the higher frequency region. An enhanced conductivity with relaxation phenomenon at elevated temperature is attributed to the transition from prolonged hopping to short-range ionic transportation. The increase in the ac conductivity with temperature reveals that Gd2Zr2O7 pyrochlore has a negative coefficient of resistance. Because of the good control of the electrical transport properties of Gd2Zr2O7 ceramic on its structure, it could be further exploited for the development of advanced solid-electrolytes for solid oxide fuel cells.