Synthesis of (Ca_1-xSr_x)₄Si₂O₇F₂oxyfluoride solid solutions and their photoluminescence properties activated by Eu²⁺ions

The synthesis of oxyfluoride solid solutions with the composition (Ca_1-xSr_x)₄Si₂O₇F₂is reported in this study. (Ca_1-xSr_x)₄Si₂O₇F₂is found to form a solid solution within the entire composition range. Synthesis of Sr₄Si₂O₇F₂, which is the first compound in the SrSiOF system, can be regarded as one of the interesting results of this study. The Eu²⁺-activated (Ca_1-xSr_x)₄Si₂O₇F₂solid solutions, except for Sr₄Si₂O₇F₂exhibited photoluminescence under excitation at 300450nm at room temperature. The samples with x = 0.250.75 showed a broad red emission band with a peak around 630 nm, whereas the Ca₄Si₂O₇F₂:Eu²⁺(x = 0) showed blue emission with a peak at 470 nm. Thus, the substitution of Sr for Ca in Ca₄SiO₇F₂:Eu²⁺changed the photoluminescence properties remarkably.