Regulating the photoluminescence and energy transfer process of Sr5(PO4)3Cl:Eu2+, Mn2+ via pressure-induced phase transition

Abstract

Single-phase phosphors with emissions covering the whole visible spectra are a superior strategy for efficient generation of white light, in which the color rendering index/correlated color temperature indices can be conveniently regulated by means of the energy transfer process between sensitizer/activator ions. In this paper, we report pressure regulation of the photoluminescence performance and energy transfer process between Eu²⁺–Mn²⁺ ions in Sr₅(PO₄)₃Cl:0.02Eu²⁺, xMn²⁺ phosphors under high pressure. The Raman spectra under pressure show signs of local symmetry phase transitions around 7 GPa. Along with this phase transition, significant divergence arises between Sr₅(PO₄)₃Cl:0.02Eu²⁺, 0.04Mn²⁺ and its counterpart without Mn²⁺ ions, with regard to features such as redshift of the emission spectra, luminescence intensity and lifetime decay. The efficiency of the energy transfer exhibts an interestingly inverse tendency with respect to the pressure, before and after the phase transition. Pressure manipulation generally results in steerable luminescence color, and can produce emission of white light. Our study offers insights into the photophysical properties of energy transfer under pressure, and also provides more understanding of controlled regulation of luminescence.