Luminescence properties of solid solutions $\mathrm{Lu_xY_{1-x}PO_4:Eu^{3+}}$

Solid solutions Lu$_x$Y$_{1-x}$PO$_4$ doped with Eu$^{3+}$ were synthesized by the sol-gel method. Luminescence spectra under UV and X-ray excitation and luminescence excitation spectra in the UV-VUV energy range are presented. Observed variations of the structure of 4f-4f Eu3+ lines with the composition of the solid solution are explained by the fluctuations in the distribution of substitutional cations. The role of electronic structure modification in the fundamental absorption region with changing Y/Lu ratio is discussed and is suggested as the origin of different efficiency of energy transfer to Eu$^{3+}$ in this region. Temperature dependence of the luminescence yield is related to the competition between emission centers and traps