Rietveld refinements, impedance spectroscopy and phase transition of the polycrystalline ZnMoO4 ceramics

International audienceThe triclinic phase of zinc molybdate ?-ZnMoO 4 (ZMO) was synthesized by a simple co-precipitation method at 600°C. The crystal structure of the obtained polycrystalline sample of ZMO was characterized by X-ray diffraction (XRD) and Rietveld calculations using the space group P-1. The electrical properties of ?-ZnMoO 4 compacted pellets were determined at room temperature from Electrical Impedance Spectrometry (EIS), in the temperature range of 400°C to 700°C. Nyquist representations were interpreted in terms of two types of electrical circuits, involving a high frequency bulk component and a low frequency Warburg component. Analyses of the frequency dependence of the real and imaginary impedance show a non-debye type relaxation. A phase transition corresponding to the allotropic transformation triclinic-monoclinic (α?β) of ZnMoO 4 was observed in the temperature range of 450 to 500°C, with a variation of activation energies. The Warburg component is discussed in terms of electrode surface reactions