[Luminescence properties of thenardite activated with Cu]

Na2SO4:Cu phosphors were prepared by heating pure natural thenardite with Cu at 1100 degrees C for 20 min in air. Their photoluminescence spectra were investigated at room temperature. The shapes of emission spectra depend on the excitation wavelengths, The emission spectrum under 260 nm excitation consists of a broad band with a peak at 430 nm, which can be attributed to the 3d 94s --> 3d10 transition within Cu+. The emission spectrum under 300 nm excitation consists of two broad bands with peaks at 430 and 550 nm respectively, which can be attributed to the 3d 94s --> 3d10 transition within Cu+ and transition from the conduction band of Na2 SO4 to the level of excited Cu2+ (d9) in the Na2SO4 band gap, respectively. With the increase in Cu contents, concentration quenching did not occur in the luminescence at 430 nm, but occured at 550 nm.