Enhancement of luminescence properties and the role of ZnO in Tb3+ ions doped zinc aluminum phosphate glasses

Terbium ion doped zinc aluminum phosphate (ZAP) glasses with composition (90−x)((90−y)P2O5–10Al2O3–yZnO)–xTb2O3 (x=0.5–9 in mol% and y=30, 35, 40 in mol%) have been prepared by melt quenching method, and the effects of the Tb2O3 and ZnO content on the luminescence properties have been studied by photoluminescence spectroscopies. It was found that the green emission peaked at 544 nm is significantly enhanced under higher Tb2O3 content, meanwhile the sensitization effect of ZnO content is confirmed from the enhanced main emission. The quenching effect attributed to the resonant energy transfer through the cross-relaxation mechanism is observed when Tb2O3 concentration is beyond 2.5 mol% due to the fact that more Tb3+ ions enhance the 4f→5d and 4f→4f electronic transitions through the dipole–dipole (d–d) interaction. Also, ZnO plays a role of the disperser to prevent non-radiative de-excitation process. A characteristic luminescence image of the (100−x)(60P2O5–10Al2O3–30ZnO)·xTb2O3 series glasses under UV excitation at 366 nm is presented for the first time, and the transition of luminescence suggests that the Tb3+-doped ZAP glasses are suitable for green and dual-color blue/green LED applications by modulation of Tb and ZnO composition.