Effect of pressure on the luminescence of zinc sulphide phosphors

Abstract

The effect of hydrostatic pressure of up to about 52 kb has been investigated on the six representative luminescence bands in zinc sulphide phosphors. The Cu-blue and -green, Ag-blue and self-activated blue emissions show blue shifts, while the Mn 2+-orange emission exhibits a red shift. The green emission in ZnS: Pb is rather insensitive to pressure. From the observed pressure shift of the self-activated luminescence in ZnS: Cl, the one dimensional configuration coordinate diagram has been constructed for this centre with the aid of the other data on the luminescence. Peak shifts found in the Cu-blue and -green and Ag-blue emissions are nearly parallel to the pressure change of the band gap energy of ZnS. These behaviours under isothermal compression are interpreted with the existing models of the centres in connection with their characteristics under isobar temperature change. The red shift observed in the orange emission of ZnS: Mn is explained in terms of the crystal field theory for the Mn 2+ ion. The effect of pressure has also been investigated on the excitation spectrum for the Mn 2+ emission to examine the pressure shifts of the higher energy transitions. The results were analysed by using the crystal field theory for the Mn 2+ ion in cubic ZnS, and the crystal field strength was estimated to be Dq = 410±10 cm −1.