Synthesis, Structure and Luminescence of Mn4+- Doped ATiO3 (A=Ca, Mg, Zn) Deep Red Phosphors

Abstract

Red emission of the Mn4+ ions incorporated in different materials is used in various applications, such as lighting and holographic recording. Mn4+ emission can improve color-rendering-index of phosphor-converted white-light-emitting diodes, and it is a promising candidate to replace the well-established rare-earth Eu activator in red phosphors. Here, synthesis, structure, morphology, and detailed spectroscopic and crystal field analysis of Mn4+ doped metal titanates ATiO3 (A = Ca, Mg, Zn) are presented. Materials were prepared by combining sol-gel and molten salt methods. In the first step a typical sol-gel procedure is applied in which acetic acid, absolute ethanol, tetrabutyl titanate and metal compound were mixed at the molar ratio of 3:16:1:1 with appropriate amount of manganeze nitrate hexahydrate. In the second step, obtained dry gels were mixed with eutectic salt NaCl/KCl = 1:1 at molar ratio of 1:10, and then calcined at 750oC. Structural analysis was done by X-ray diffraction for all samples. Optical characterization included measurements of photoluminescence excitation and emission spectra, emission decay analyses and diffuse reflection measurements. Optical spectra showed emission and absorption bands originating from d–d electronic transitions (a d3 configuration). The energy levels of the Mn4+ ions in the crystal field of ATiO3 are calculated using the exchange charge model and showed nice matching with the experimental photoluminescence excitation and emission spectra.