A new study on the energy transfer in the color-tunable phosphor CaWO4:Bi

In this article, the scheelite-structured phosphors of CaWO4 and Bi(3+) doped CaWO4 were successfully synthesized by the high temperature solid state reaction, and the photoluminescence (PL) properties and decay curves of the samples were investigated between 10 and 300 K. The results have shown clearly that the sample emission is tunable via tailoring the energy transfer between the Bi(3+) and WO4(2-) anion groups by the selection of either proper bismuth content or excitation scheme. Depending on the excitation scheme, energy transfer does happen from Bi(3+) to WO4(2-) or in the reverse, which, however, has never been noticed. Direct spectroscopic evidences as well as the mechanism have been presented for these processes in this work.