Temperature-induced phase transition, luminescence and magnetic properties of Eu2(MoO4)3 microcrystal red phosphors

Abstract

A series of Eu2(MoO4)3 crystals with different crystal structures have been successfully fabricated via a conventional ceramics process under different sintering temperatures. Using X-ray diffraction (XRD), Rietveld refinement, Fourier transform infrared (FT-IR) spectra, scanning electron microscope (SEM), differential thermal analysis (DTA), photoluminescence (PL) and vibrating sample magnetometer (VSM), the microstructures, luminescent and magnetic properties of the as-fabricated Eu2(MoO4)3 crystals have been investigated in detail. XRD, FT-IR and Rietveld refinement results show that the crystal structure of the final Eu2(MoO4)3 crystals can be remarkably influenced by the sintering temperature, exhibiting the phase transformation from tetragonal to monoclinic and then orthorhombic in the region of 600–1000 °C. SEM images manifest the sintering temperature has significantly influence on grain size and dispersity of the samples, although it has negligible effect on their morphology. DTA results confirm that the phase transition temperature for tetragonal to monoclinic and monoclinic to orthorhombic is 624 and 887 °C, respectively. PL results reveal that the excitation and emission intensities of the Eu2(MoO4)3 crystals initially increase and then decrease with increasing sintering temperature, given the maximum at 900 °C. VSM results indicate that all the as-fabricated Eu2(MoO4)3 crystals exhibit paramagnetic property. Our work can offer a simple and effective strategy to adjust the crystal structure of Eu2(MoO4)3 crystals.