Samarium doped apatite-type orange-red emitting phosphor Ca5(PO4)2SiO4 with satisfactory thermal properties for n-UV w-LEDs

Abstract

A novel single-phase Sm3+ activated Ca5(PO4)2SiO4 phosphor was successfully fabricated via a conventional solid-state method, which can be efficiently excited by near ultraviolet (n-UV) light-emitting chips. The crystal structure and luminescence properties were characterized and analyzed systematically by using relevant instruments. The Ca5(PO4)2SiO4:Sm3+ phosphor shows an orange-red emission peaking at 600 nm under the excitation of 403 nm and the optimal doping concentration of Sm3+ is determined to be 0.08. The critical distance of Ca5(PO4)2SiO4:0.08Sm3+ is calculated to be 1.849 nm and concentration quenching mechanism of the Sm3+ in Ca5(PO4)2SiO4 host is ascribed to energy transfer between nearest-neighbor activators. The decay time of Ca5(PO4)2SiO4: 0.08Sm3+ is determined to be 1.1957 ms. In addition, the effect of temperature on the emission intensity was also studied, 72.4% of the initial intensity is still preserved at 250 °C, better thermal stability compared to commercial phosphor YAG:Ce3+ indicates that Ca5(PO4)2SiO4:0.08Sm3+ has excellent thermal stability and active energy is deduced to be 0.130 eV. All the results demonstrate that orange-red emitting Ca5(PO4)2SiO4:0.08Sm3+ phosphor exhibits good luminescent properties. Owing to the excellent thermal quenching luminescence property, Ca5(PO4)2SiO4:0.08Sm3+ phosphor can be applied in n-UV white light emitting diodes and serve as the warm part of white light.