Thermally stable double-perovskite Ca3TeO6: Eu3+ red-emitting phosphors with high color purity

A series of novel Eu3+-activated tellurate Ca(3-2x)EuxNaxTeO6 (x= 0.01-0.25) red-emitting phosphors were synthesized through a high-temperature solid-state route at 1220 degrees C. The phosphors were well crystallized in the space group P2(1)/c (No. 14). Their photoluminescence emission and excitation spectra were investigated. The results indicate that the Ca3TeO6:Eu3+ phosphor can be effectively excited under 394 nm irradiation, which is suitable for UV LED chip. Upon 394 nm excitation, the Ca3TeO6:Eu3+ phosphor shows five peaks, corresponding to the D-5(0)-F-7(J) (J= 0, 1, 2, 3 and 4) transitions of Eu3+. The optimal doping concentration of Eu3+ in Ca3TeO6:Eu3+ was determined at 20 mol%. By temperature dependent emission spectra, the quenching temperature for Ca3TeO6:0.20Eu(3+) was found to be over 500 K. The CIE chromaticity coordinates of Ca3TeO6: 0.20Eu(3+) are very close to the National Television System Committee (NTSC) standard red.