Effect of Zr substitution on structural, dielectric and electrical properties of Sr5SmTi3Nb7O30 ceramics

The polycrystalline samples of Sr5SmTi3-xZrxNb7O30 (x = 0-3) (SSTZN) were prepared by a high-temperature solid-state reaction technique. The formation of the compounds was checked by an X-ray diffraction (XRD) technique. The quality and grains distribution over the surface of the samples were checked by scanning electron microscopy (SEM). Detailed dielectric and electrical properties of the compounds as a function of frequency (1-100 kHz) and temperature (150-650 K) show that the compound with x= 0-2 undergoes ferroelectric-paraelectric phase transition of diffuse nature. The variation of pyroelectric coefficient with temperature strongly supports the diffuse phase transition of the material. The ferroelectric nature of the studied compounds was confirmed by the hysteresis loop traced at room temperature. The detailed electrical properties studied with the help of complex impedance spectroscopy study confirm the existence of grains and grain boundaries and the absence of electrode material interface. The conductivity study over a wide temperature range suggests that the compounds have negative temperature coefficient of resistance (NTCR). (c) 2005 Elsevier B.V. All rights reserved.