Influence of synthetic temperature and heating time on the luminescence behavior of M5PO43Cl：Eu2＋,Mn2＋（M=Ca, Sr） phosphors

To further understand the energy loss mechanism of the ＂charge transfer process＂ that was proposed in our previous work on Eu^2＋-Mn^2＋ co-doped phosphors, the influence of synthetic temperature and heating time on the photoluminescence（PL） behavior of M5（PO4）3Cl：Eu^2＋,Mn^2＋（M=Ca, Sr） phosphors was investigated by analyzing their PL spectra and decay curves. For the Ca phase, an increase in the synthetic temperature resulted in an increase in the loss from the ＂charge transfer process＂ since more Eu^2＋ ions were involved in the Eu^2＋-Mn^2＋ clusters. This was contrary to the thermodynamic expectation. To solve this contradiction, we proposed that the formation of Eu^2＋-Mn^2＋ clusters was kinetically blocked at lower synthetic temperatures. With an increase in heating time for the phosphors synthesized at lower temperature（such as 1100 ℃） the PL intensity decreased, which supported the above assertion.