Photoluminescence properties of γ-Ca3(PO4)2:Sm3+ prepared under high-pressure and high-temperature conditions

Abstract

γ-Ca3(PO4)2:Sm3+ samples were synthesized under high-pressure and high-temperature conditions. The samples were characterized by X-ray diffraction measurements. The excitation and emission spectra and fluorescence decay curves of synthesized samples were collected to study the photoluminescence properties. The excitation spectra of γ-Ca3(PO4)2:Sm3+ exhibit a series of narrow peaks attributed to the typical f–f transition of Sm3+. The emission spectra of γ-Ca3(PO4)2:Sm3+ compose of four bands attributed to transitions from 4G5/2 excited state to 6HJ/2 (J=5, 7, 9 and 11) ground states of Sm3+. The average decay lifetimes were obtained by fitting the decay curves for 6H7/2 level of Sm3+ emission using a double exponential function. The photoluminescent spectra of γ-Ca3(PO4)2:Sm3+ show that the samples belong to a red-emitting phosphor and can be pumped in the near ultraviolet light region, which can easily be applied for NUV LED chips and thus in WLEDs. There exists a concentration quenching of Sm3+ in γ-Ca3(PO4)2:Sm3+ samples. The critical concentration of Sm3+ in γ-Ca3(PO4)2 is about 1.0mol%.