Structural and optical characterization of RbLaP₄O₁₂:Ln³⁺ (Ln³⁺ = Ce³⁺, Nd³⁺, Tm³⁺, or Yb³⁺)

In this work, for the first time, detailed structural and optical characterization of RbLaP₄O₁₂ doped with different concentrations of Ce³⁺, Nd³⁺, Tm³⁺, or Yb³⁺ ions is reported. The samples were obtained via a precipitation technique. Their structural characterization was performed using X-ray diffraction (XRD), and infrared and Raman spectroscopies. Following XRD data, the unit cell parameters of host lattices were calculated using Rietveld refinement. It was found that an increase in the dopant content leads to a decrease in the unit cell volume. The optical characterization of RbLaP₄O₁₂:Ln³⁺ was carried out by collecting absorption and emission spectra, as well as luminescence decay profiles. Following absorption spectra, the energy band gap of the studied matrix was determined. It was found that the broad absorption band located in the ultra-violet range, in most cases ascribed to charge transfer or f-d transitions, is in fact related to the absorption of the host lattice. The analysis of luminescence properties allowed us to investigate possible ways of depopulation emission levels of impurities.