Insight into energy transfer, color tuning, and white emission in Tm3+ and Dy3+ codoped Ca8ZnLa(PO4)7 phosphors

A series of Ca8ZnLa(PO4)7: 0.01 Tm3+, xDy3+ (x = 0–0.15) and Ca8ZnLa(PO4)7: 0.1Dy3+ phosphors were obtained via the high temperature solid state reaction method. The crystal structure, photoluminescence properties, and energy transfer from Tm3+ to Dy3+ were investigated. The prepared phosphors possess the β-Ca3(PO4)2 structure and belong to the R3c (161) space group. The luminescent colors of Ca8ZnLa(PO4)7: 0.01 Tm3+, xDy3+ phosphors can be modulated from blue to yellow and white light emission of a single matrix was realized. In the Ca8ZnLa(PO4)7 (abbreviated as: CZLPO) matrix, the Tm3+→Dy3+ energy transfer process proceeds due to electric dipole-quadrupole interaction, and the energy transfer mechanism is explored in detail according to Dexter's energy transfer theory and Reisfeld's equation. Moreover, the CZLPO: 0.01 Tm3+, xDy3+ phosphors exhibit good thermal stability. These characteristics indicate that a single matrix CZLPO: 0.01 Tm3+, xDy3+ phosphor has a potential for applications in white LEDs.