Borohydride synthesis strategy to fabricate YBO3:Eu3+ nanophosphor with improved photoluminescence characteristics

Abstract

This paper investigates for the first time the use of sodium borohydride (NaBH₄) as a boron source as well as a precipitating agent for successfully preparing high temperature stable YBO₃:Eu³⁺ nanophosphor. Moreover, the potential of this unique borohydride synthesis strategy is compared with the conventional boric acid based solid-state route in terms of phase stability, morphology and photoluminescence characteristics. The novel synthesis approach adopted here renders a high temperature stable phase pure YBO₃:Eu³⁺ nanophosphor at 1200 °C with nearly spherical dumb-bell shaped particles in the range of ∼200 nm to 700 nm and exhibits improved color purity when compared to the irregular polyhedral shaped (size ∼5 μm) YBO₃:Eu³⁺ phosphor prepared by the conventional solid-state method. Color purity, determined in terms of R/O ratio, of borohydride YBO₃:Eu³⁺ nanophosphor was found to be 1.72 for the near vacuum ultra-violet (VUV is characterized with wavelength shorter than 200 nm) wavelength of 205 nm, which gradually decreases with increase in excitation wavelength. It has never been reported that the color of YBO₃:Eu³⁺ phosphors can be tuned from pink to reddish-orange. The chromaticity coordinates revealed evidently that the YBO₃:Eu³⁺ phosphor emission is tunable by simply adjusting the excitation wavelengths. In addition to providing spectroscopic data the reason for better color purity and tunability of chromaticity coordinates are also accredited in this work.