Simultaneously tuning emission color and realizing optical thermometry via efficient Tb3+→Eu3+ energy transfer in whitlockite-type phosphate multifunctional phosphors

A series of Ca8ZnLa(PO4)7 (CZLPO) phosphors doped with Tb3+ and Tb3+, Eu3+ have been synthesized using a high-temperature solid-state method. The XRD pattern verifies that all prepared samples are attributed to whitlockite-type structure of β-Ca3(PO4)2 with R3c (161) space group. Under 366 nm excitation, the CZLPO: Tb3+, Eu3+ phosphors exhibit a tunable multi-color emission owing to energy transfer from Tb3+ to Eu3+ via a quadrupole-quadrupole interaction mechanism. The emission colors of the phosphors could be modulated from green to red under NUV (366 nm) excitation due to efficient Tb3+→Eu3+ energy transfer. The fluorescence intensity ratio (I542nm/I611nm) for the Tb3+→Eu3+ of this material displayed excellent temperature sensing properties between 298 and 498 K. Moreover, it was found that the intensity ratio was unchanged when the temperature was cycled between 298 and 498 K, thus demonstrating the recyclability of this system. These results show that CZLPO: Tb3+, Eu3+ phosphors have potential as high performance multifunctional materials for solid state lighting and temperature sensing applications.