Anti-thermal-quenching and colour-tuneable Tb3+/Ce3+-doped phosphor from natural wollastonite

Abstract

Series of doped natural wollastonite phosphors (xTb3+/xLi+, yCe3+/yLi+ and xTb3+/0.06Ce3+/xLi+ co-doped wollastonite) were synthesized by high temperature solid state thermal diffusion method in vacuum furnace. The powders mainly consisted of low temperature α-CaSiO3 phase corresponding to the triclinic crystal structure, and according to ionic radii differences it was proposed that Tb3+ and Ce3+ had tendency to be incorporated at the Ca2+ position. The natural wollastonite powder has primarily needle-like particles with small amount of finer spherical aggregates, whereas the portion of finer particles increases significantly after the doping with Tb3+/Ce3+ ions. Under 352 nm light excitation, the Tb3+/Li+ co-doped wollastonite phosphors with Tb3+/Li+ content between x = 0.08-0.18 achieved tuneable luminescence from green to yellow through energy transfer from Tb3+ to minor impurity Mn2+ existing in the matrix. All of the Ce3+/Li+ co-doped wollastonite phosphors with Ce3+/Li+ content between y = 0.02-0.10 emitted intense purple-blue light centred at 382 nm. In the xTb3+/0.06Ce3+/xLi+ (0.01 ≤ x ≤ 0.09) co-doped wollastonite phosphors, Ce3+ acted as a sensitizer and the energy transfer efficiency from Ce3+ to Tb3+ reached 62.5%. Temperature dependent photoluminescence within 298-498K suggested an excellent thermal stability of the 0.06Ce3+/0.06Li+ co-doped wollastonite phosphor, of which the intensity at 498 K retained 96.2% of that at room temperature. Importantly, anti-thermal-quenching phenomenon was observed in the 0.12Tb3+/0.12Li+ co-doped wollastonite phosphor, and the 545 nm emission intensity at 498 K reached 120.3%of that at 298K. The regulation of thermal luminescence behaviour for Tb3+ was achieved by incorporating Ce3+ ions in the 0.12Tb3+/0.12Li+ co-doped wollastonite phosphor. Based on the observations, the above materials display good thermal stability and can be developed as phosphors for application in display devices and LEDs above room temperature.

Keywords

• tb3+/ce3+-doped wollastonite
• optical properties
• energy transfer
• thermal stability