Luminescence in Manganese (II)-Doped SrZn₂S₂O Crystals From Multiple Energy Conversion

Under the excitation of ultraviolet, X-ray, and mechanical stress, intense orange luminescence (Mn²⁺, ⁴T₁ → ⁶A₁) can be generated in Mn²⁺-doped SrZn₂S₂O crystal in orthorhombic space group of Pmn2₁. Herein, the multiple energy conversion in SrZn₂S₂O:Mn²⁺, that is, photoluminescence (PL), X-ray-induced luminescence, and mechanoluminescence, is investigated. Insight in luminescence mechanisms is gained by evaluating the Mn²⁺ concentration effects. Under the excitation of metal-to-ligand charge-transfer transition, the most intense PL is obtained. X-ray-induced luminescence shows similar features with PL excited by band edge UV absorption due to the same valence band to conduction band transition nature. Benefiting much from trap levels introduced by Mn²⁺ impurities, the quenching behavior mechanoluminescence is more like the directly excited PL from Mn²⁺ d-d transitions. Interestingly, this concentration preference leads to varying degrees of spectral redshift in each mode luminescence. Further, SrZn₂S₂O:Mn²⁺ exhibits a good linear response to the excitation power, which makes it potential candidates for applications in X-ray radiation detection and mechanical stress sensing.