Effect of the Y : B ratio on phase purity and development of thermally stable nano-sized Eu+3-doped YBO3 red phosphor using sodium borohydride

Abstract

This research focuses on the effect of the Y : B ratio on phase purity and the development of thermally stable 10 mol% Eu³⁺-doped YBO₃ red phosphor nanomaterial using a novel sodium borohydride based solution precursor route. An equimolar concentration of Y and B leads to the development of chemically and thermally stable un-doped and Eu³⁺-doped YBO₃ up to 1300 °C. An impurity phase, Y₃BO₆, was observed at a higher temperature of around 1400 °C. FESEM micrographs indicate that the particles of Eu³⁺-doped YBO₃ are agglomerated with peanut-like morphology having an average size of ∼50 nm at 800 °C, whereas the average agglomerated size was in between ∼200 nm and 1.5 μm, at 1200 °C. The particles of Eu³⁺-doped YBO₃ are nearly spherical having size ∼8–10 nm at 800 °C and the size increases in the range of ∼30–100 nm at 1200 °C, as observed from TEM micrographs. In addition, the borohydride synthesized Eu³⁺-doped YBO₃ phosphor calcined at 800 °C showed comparatively better colour purity (denoted as R/O ratio, i.e. the integral ratio of red to orange emission = 1.25) than the high temperature (1200 °C) calcined sample (R/O ratio = 0.97). Both the calcined powders indicated nearly reddish-orange colour based on calculated Commission Internationale de I'Eclairage (CIE) coordinates. The synthesis strategy followed in the current research work emphasizes the feasibility of synthesizing thermally stable Eu³⁺-doped YBO₃ red phosphor materials by a borohydride route, which may be suitable for lighting applications.