Diffuse ferroelectric phase transition in Na2Pb2Nd2W2Ti4Nb4O30 ceramic

The polycrystalline sample of Na2Pb2Nd2W2Ti4Nb4O30 was prepared by a high-temperature solid-state reaction technique. Preliminary Xray diffraction (XRD) studies of the compound showed the formation of single-phase compound in an orthorhombic crystal structure at room temperature. Studies of dielectric properties (epsilon, tan delta) of the above compound as a function of temperature (273-700 K) at frequencies 10, 100 and 1000 kHz exhibit a ferroelectric phase transition of diffuse type. Detailed studies of impedance parameters provide a better understanding of the electrical properties and type of relaxation processes in the material. Temperature variation of dc conductivity shows that this compound exhibits negative temperature coefficient of resistance (NTCR) in high temperature region. (c) 2006 Elsevier B.V. All rights reserved.