Investigations of structure-improper ferroelectricity relationships to enhance the multifunctional applications of the ß0-Y2(MoO4)3 phase

Abstract

Polycrystalline samples of the compound Y2(MoO4)3 have been synthesized by solid-state reaction starting from the corresponding yttrium and molybdenum oxides, and the pure ferroelectric phase has been successfully isolated. Both β’ (ferroelectric) and β (paraelectric) phases were studied by conventional X-ray diffraction at different temperatures, performing the corresponding Rietveld refinements before and after the phase transition. An analysis of the displacive symmetry modes involved was carry out. The thermal dependence of the crystal structure was also studied, confirming that it is an improper ferroelectric with a primary order parameter that does not correspond to the spontaneous polarization. To corroborate the purity of the β′-phase, TG and SEM-EDX analyses were performed, demonstrating the absence of the γ-phase. Moreover, DSC analysis and impedance spectroscopy confirmed the Curie temperature of the β′-β phase transition (Tc around 378 ​K). Ferroelectric hysteresis cycles were recorded as a function of temperature and at different maximum applied electric fields. The values of the maximal and remanent polarization were correlated with the structural study. Finally, anomalies in the electrical permittivity and conductivity were observed between 600 and 877 ​K, which may be associated with the evolution of the lattice parameter c at high temperatures. With this ferroelectric characterization we want to highlight this still unexploited crystal matrix in comparison to other rare earth molybdates with the β′-phase and other yttrium molybdate compounds.