The study reveals opportunity of using the emission of Eu ³⁺ , together with X-ray diffraction, and dielectric spectroscopy, for sensitive determination of the symmetry β-TCP related structures.

The structural and luminescence properties of undoped Y_1−xSc_xPO₄ solid solutions have been studied. An intense thermally stable emission with fast decay (τ_1/e ~ 10⁻⁷ s) and a band position varying from 5.21 to 5.94 eV depending on the Sc/Y ratio is detected and ascribed to the 2p O-3d Sc self-trapped excitons. The quantum yield of the UV-C emission, also depending on the Sc/Y ratio, reaches 34% for the solid solution with x = 0.5 at 300 K. It is shown by a combined analysis of theoretical and experimental data that the formation of Sc clusters occurs in the solid solutions studied. The clusters facilitate the creation of energy wells at the conduction band bottom, which enables deep localization of electronic excitations and the creation of luminescence centers characterized by high quantum yield and thermal stability of the UV-C emission.