An abnormal yellow emission and temperature-sensitive properties for perovskite-type Ca2MgWO6 phosphor via cation substitution and energy transfer

A series of Ca2MgWO6:Bi-3(+), Eu3+ phosphors were prepared via a high temperature solid-state reaction method. The crystal structure of Ca2MgWO6:Bi3+, Eu3+ phosphors adopt the double perovskite structure. Different from previous study, a yellow-emitting was observed in the Ca2MgWO6 matrix. Roman spectrum indicated that the yellow emission is a result of the existence of oxygen vacancies during the preparation process. By co-doping Bi3+ into Ca2MgWO6 matrix, the yellow emission was enhanced due to the more defect concentration and the P-3(1)-S-1(0) transition of Bi3+. Two strategies containing cation substitution and energy transfer in single Ca2MgWO6 compound were used to tune photoluminescence properties. Bi3+ and Eu3+ as substitution ions were co-doped into Ca2MgWO6 matrix and the energy transfer from Bi3+ to Eu3+ caused the tunable emission color from yellow to deep red. The energy transfer mechanism from Bi3+ to Eu3+ ions has been defined to be a quadrupole-quadrupole interaction in our work. Notably, the Bi3+ and Eu3+ in this system showed excellent temperature sensing properties owing to different luminescent thermal quenching behaviors of Bi3+ and Eu3+ in the range of 298-523 K. In addition, the maximum values for absolute (S-a) and relative (S-r) sensitivities were calculated to be 0.961 K-1 (523 K) and 8.52% K-1 (323 K), respectively, which validates the possibility of optical thermometric applications of Ca2MgWO6:Bi3+ Eu3+ phosphors.