Tuning emission spectrum of KSrPO$_4$:Eu$^{2+}$ phosphor by co-doping with Y$^{3+}$

A series of co-doped KSrPO$_4$:Eu$^{2+}$ , Y$^{3+}$ phosphors have been prepared through a high-temperature solid-state reaction at various temperatures. Luminescence spectroscopic characterization allowed to demonstrate that emission spectrum of original KSrPO$_4$:Eu$^{2+}$ phosphor that is typically dominated by Eu$^{2+}4f^65d^1\to4f^7$ emission can be significantly modified by co-doping with Y$^{3+}$ ions, which results in appearance of a broad defect emission. The latter makes the phosphor potential for WLED application. The Y$^{3+}$ co-doping related defect emission was found to get enhanced with the increase of Y$^{3+}$ content and synthesis temperature. The nature and peculiarities of the new defect emission are discussed.