Innovative Borohydride Synthesis Strategy to Fabricate Red (YBO3:Eu3+) and Green (YBO3:Tb3+) Nanophosphor with Improved Photoluminescence Characteristics

Abstract

The research endeavour on lanthanide ions doped YBO3 nanophosphors is escalating with the availability of these borate hosts, which present incentives such as excellent UV absorbance, high thermal stability and exceptional optical damage threshold [Appl. Phys. Lett., 80, 1447 (2002)]. However, for preparation of this host, the use of boric acid (H3BO3) as a boron source is rampant [Small, 3, 438 (2007)]. Literature gives a plethora of evidences for use of excess H3BO3 in addition to difficulties encountered in formation of high temperature stable YBO3 [J. Am. Ceram. Soc., 2008, 91, 591]. Different syntheses employed for YBO3 fabrication aim towards improving colour purity and chromaticity. Our approach allows accomplishing this goal by means of a unique synthesis strategy for producing high temperature phase pure phosphors with better photoluminescence properties. In this context, for the first time, innovative borohydride synthesis strategy using sodium borohydride (NaBH4) has been explored to fabricate red (YBO3: 5 mol % Eu3+) as well as green (YBO3: 5 mol % Tb3+) phosphor. Moreover, phase-stability, microstructure and photoluminescence properties of these phosphors were studied in detail. The colour purity [R/O ratio: area under the curve of red (5D0→7F2 transition) to orange (5D0→7F1) emission] of red phosphor and CIE coordinates of both red and green phosphor are strongly dependent on the excitation wavelengths. The colour tuning from pink to reddish-orange for YBO3:Eu3+ and bluish-green to green for YBO3:Tb3+ is achieved by adjusting excitation wavelengths from near-VUV to UV. The findings of the study suggest that this borohydride method is better than the conventional boric acid based solid-state method. The follow up of the properties unanimously depicts that the use of NaBH4 is virtuous for synthesizing nanophosphors and could be put to use in light emitting diodes and flat display technology