Optimization of boric acid content in developing efficient blue emitting, long persistent phosphor

The active role of boric acid (H3BO3) in enhancing the Eu2+ photoluminescence; varying persistence times and formation of several crystalline phases of calcium aluminate system is presented. The luminescence characteristics of CaAl2O4: Eu2+, Nd3+ (CA) phosphor took an immense leap forward with the addition of very small quantities of H3BO3 (as low as 1-2 mol%) to the initial oxide mixture. The maximum PL augmentation is observed for an H3BO3 content of similar to10 mol%, and for higher concentrations PL decreased. The persistence of the Eu2+ afterglow is in the range of 10-12 h, which is relatively high compared with the value reported so far. Based on the results, we identified two major roles for H3BO3 in tailoring efficient blue phosphorescence of CA phosphors suitable for many practical display applications. In the lower (< 10 mol%) concentration range, H3BO3 acted as a better fluxing agent in promoting formation of the required crystalline phase for producing efficient luminescent characteristics, whereas in the higher (greater than or equal to 20 mol%) range it behaved as one of the precursor materials for formation of aluminoborate complexes, which in turn cloaked the luminescence. Finally, a correlation has been drawn between the amount of H3BO3 and the energy conversion efficiency and the energy conversion efficiency of Eu2+ in tailoring an efficient blue emitting, long persistent phosphor.