Structural and electrical properties of Na1/2Gd1/2TiO3 nanoceramics

The polycrystalline fine (i.e., 38 nm) powder of Na1/2Gd1/2TiO3 was prepared by a high-temperature solid-state reaction technique. The formation of single phase compound was confirmed by an X-ray diffraction technique. A preliminary structural analysis exhibited the orthogonal crystal structure of the compound. The surface morphology was studied by scanning electron microscopy. The dielectric permittivity and the loss tangent of the pellet sample were obtained in a wide frequency range (1 kHz-1 MHz) at different temperatures (28-500 degrees C). A dielectric anomaly was observed at 73 degrees C which may be related to ferroelectric-paraelectric phase transition. The ferroelectric transition was confirmed by observation of hysteresis loop at room temperature. Electrical properties of the pellet sample were studied using an AC impedance spectroscopic technique. Detailed analysis of impedance spectra indicated the bulk contribution to electrical properties below 375 degrees C, and the grain boundary above 375 degrees C. The negative temperature coefficient of resistance (NTCR) effect and the temperature dependant electrical relaxation phenomenon in the sample were also observed. Studies of DC conductivity exhibited that the material has a thermally activated process. AC conductivity spectrum obeys Jonscher's universal power law. (C) 2007 Elsevier B.V. All rights reserved.