A phosphor material is a substance that emits light through the process of luminescence. Inorganic solids may show luminescence when a host material is doped with impurities, referred to as activators. These activators are essentially a light emitting center within the host material, and can be stimulated with a variety of sources, such as light, heat, electric current and mechanical pressure. One of the most common types of activators are inner transition metal ions, which utilize high energy electromagnetic radiation to achieve luminescence. Currently, there is a large drive to utilize these materials for solid state lighting which have many advantages over ubiquitous incandescent and fluorescent sources. Here we report on novel light emitting materials based on a recently reported oxide system, CaYGaO4. The system belongs to the olivine family and crystallizes in the orthorhombic Pmna space group. CaYGaO4 exhibits full cationic ordering, which is a different structural feature from all reported silicate and germanate olivines. The host lattice contains three independent cationic positions, each of which gives rise to a different coordination environment. While the edge shared CaO610- octahedra form infinite chains along the b crystallographic axis, corner shared YO69- octahedra form puckered layers, perpendicular to the a-axis and discrete GaO45- tetrahedra fill in the empty spaces between the octahedra. The parent compound was doped with various lanthanide ions in the yttrium position. Conventional high temperature method was employed to synthesize the target phases from stoichiometric mixtures of CaCO3, Y2O3, Ga2O3 and M2O3 (M=Eu, Gd, Nd, and Tb). The completion of reactions and phase homogeneities were monitored using powder X-ray diffraction technique. Absorption and emission spectra were measured by diffuse reflectance and fluorescence techniques. Europium, gadolinium, neodymium, and terbium were all successfully doped into the yttrium position in system at varying amounts from two to ten percent. All excitation spectra were found to lie within the UV range and emission colors varied from blue to yellow, depending on the activator. Furthermore, the lanthanide doped samples were subject to co-doping with 3d ions in the gallium position towards more control of the resultant emitted light.

Novel light emitting phosphors based on olivine structure type oxide, CaYGaO4

253rd National Meeting (2017)

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