Fabrication of (Y0.95Eu0.05)2O3 phosphors with enhanced properties by co-precipitation of layered rare-earth hydroxide

Abstract

This work is devoted to a simple method for synthesizing phosphors based on layered rare earth hydroxonitrates (LRH). Layered precursors of (Y0.95Eu0.05)2(OH)5(NO3)·xH2O with different morphologies were obtained via co-precipitation at a constant pH and hydrothermal methods. It was established that LRHs co-precipitated at pH 7 are highly ordered close-packed micron-sized plates with low porosity. With an increase in the pH of co-precipitation to 9.5, the phase composition is retained, but the isotropy and porosity of the particles increases sharply: the morphology changes from micron flat plates to curved nanosheets and nanoflakes. Co-precipitated LRHs crystallize more intensively into cubic (Y0.95Eu0.05)2O3 during heat treatment compared to precursors obtained under mild hydrothermal conditions (120 °C, 24 h). The structural characteristics of the material laid at the stage of synthesis directly determine its optical properties and the fundamental parameters of photoluminescence. The phosphors that co-precipitate at pH 7 demonstrate the highest yield of luminescence due to a more ordered structure, larger crystallite size, lower asymmetry factor and surface to volume ratio. The proposed co-precipitation method with a constant pH value of 7 allows one to obtain (Y0.95Eu0.05)2O3 phosphor with enhanced structural and optical properties compared to materials synthesized in hydrothermal conditions. The LRHs co-precipitated in this work are a promising precursor for the preparation of crystal-oriented and highly-efficient luminescent coatings and nanofilms.