The effect of pH on the luminescence properties of Y2O3:Bi phosphor powders synthesised using co-precipitation

Abstract

This article focuses on studying how the pH, during the synthesis procedure, effects the luminescence properties of Y2O3:Bi2.0 mol% phosphor material. The x-ray diffraction pattern showed that the phosphor material crystallised as a single phase cubic structure with a Ia-3 space group. The photoluminescence spectrum revealed two Bi3+ emission bands, a narrow band centred at 409 nm and a broad band centred at 490 nm originating from S6 and C2 sites that Bi3+ ions may occupy with in the Y2O3 host lattice. The emission at 409 nm showed two excitation bands one centred at 330 nm and another at 390 nm. For the 490 nm emission two excitation bands were also observed centred at 330 nm and 345 nm. X-ray photoelectron spectroscopy showed that the Y 3 d spectrum consisted of ten sub peaks, two peaks for each of the two different sites that both Y3+and Bi3+ occupy within the Y2O3 lattice and last two peaks for the Y-OH bond. The O 1s spectrum consisted of eight peaks, one peak for each of the two different sites that O2− ions occupy within the Y2O3 and Bi2O3 lattice and the remaining four peaks relates to the hydroxy and carbon oxygen bonds. Energy dispersive x-ray spectroscopy confirmed qualitatively the presence of Y, O and Bi ions and indicated that it was not a change in Bi concentration that was responsible for the PL intensity changes.