NASICON-type Na3.6Y1.8-xScx(PO4)3 solid solutions: structure and luminescence

Abstract

The structural and luminescent properties of single-phase Na_3.6Y_1.8-xSc_x(PO₄)₃ (0 ≤ x ≤ 0.7, x = 1.8) phosphors have been studied for the first time. X-ray diffraction revealed the formation of a homogeneous solid solution with a NASICON-type structure. No phase transitions were observed by Raman spectroscopy within the 88-873 K temperature range. The bandgap of Na_3.6Y_1.8-xSc_x(PO₄)₃ solid solutions was estimated to be E_g ~ 8 eV, showing no significant dependence on composition.Luminescence properties were examined under VUV, synchrotron, and electron beam irradiation. An intense UV emission was observed under VUV and synchrotron excitation, attributed to 2pO-3dSc self-trapped excitons. The enhanced intensity and thermal stability of exciton emission is detected for solid solutions and related to the effect of structural disorder.