Low temperature synthesis of SrS:Ce phosphor by carbothermal reduction method: Influence of sulfur and charge compensator on the luminescent properties

We report here on an ecologically friendly carbothermal reduction method to realize SrS:Ce phosphor. The method effectively reduces the preparation temperature by 100 °C. The effect of sulfur and charge compensator were studied separately and in combination, on the luminescent properties of SrS:Ce phosphor prepared from SrSO₄:Ce(SO₄)₂·4H₂O using this method without inert gas or hazardous gas (H₂S) environment. To analyze the role of charge compensator on the luminescent emission property of SrS:Ce, various fluxes, viz., NH₄Cl, NaCl were used. The synthesized products were characterized by XRD, photoluminescence emission and excitation spectroscopy (PLE). SrS:Ce showed a bright blue-green emission at 480 and 540 nm corresponding to energy bands originating from ²T_2g (5d) to ²F_7/2, ²F_5/2 (4f) of Ce³⁺ transitions. The characterization results showed the formation of SrS calcined at 900 °C for 5 h with an increase in blue-green luminescence intensity after the addition of sulfur and charge compensator, separately. When the sulfur and NH₄Cl were jointly added, the intensity of blue emission was enhanced, whereas, that of green emission was suppressed. The excitation spectrum showed a fundamental absorption of SrS host crystal lattice at 283 nm and Ce³⁺ absorption at 430 nm respectively. The CIE (Commission International de’Eclairge) chromaticity coordinates of the phosphor are also reported.