Concentration and temperature dependence of Pr3+ f-f emissions in La(PO3)3

La(PO3)3 activated with different concentrations of Pr3+ was synthesized by a solid-state process. The obtained powder was composed of chunks of several microns in size, typical for this type of synthesis. X-ray diffraction confirmed an orthorhombic crystal structure with the C2221 space group. The electronic band structures and density of states of La(PO3)3 and La(PO3)3:Pr3+ are calculated and presented. The visible and near-infrared emissions from Pr3+ [Xe]4f2 [Xe]4f2 electronic transitions were detected under 442 nm excitation. The red emission from the 1D2 state dominates visible spectra while emissions from the 3P0,1,2 states have smaller intensities. The 1D2 emission centered around 1020 nm is detected in the near-infrared spectral range. Intensities of 3P0 emissions increased with an increase in Pr concentration, while 1D2 emissions decreased in intensity. We found that the main process responsible for the 1D2 state decay is the Pr(1D2) + Pr(3H4) Pr(1G4) + Pr(3F3,4) cross-relaxation between two Pr ions of electric dipole-dipole character. This finding is supported by 1D2 emission decay measurements, which revealed a reduction of average decay constants from 242 μs for a 0.5 mol% doped sample to 11 μs for a 10 mol% doped sample and an increasingly stronger non-exponential behavior of emission decay patterns with an increase in Pr3+ concentration

Analysis of site symmetries of Er3+ doped CaF2 and BaF2 crystals by high resolution photoluminescence spectroscopy

The understanding of complex relationships between luminescent properties, local symmetry of an emitting center, and the host crystal structure provides a better insight into optical properties of materials. In this work, the alkaline earths CaF2 and BaF2 fluoride crystals doped with 0.1 mol% ErF3 were investigated. The crystals structure has been studied using a synchrotron and laboratory X-ray diffraction. The C3v and C4v sites symmetry were determined using erbium probed high resolution emission spectroscopy (HRPL) at low temperature (LT) of 10 K. The considerable difference in room temperature (RT) optical properties for CaF2 compared to BaF2 crystals was observed. Such difference in absorption intensity of 4.7 times of erbium 4G11/2 manifold in UV, and 7.5 times in green emission from 4S3/2 manifold, could be due to the distinction in the host crystals cationic radius (ΔrCa,Ba) and the dopant-host ionic radius (ΔrCa-Er, ΔrBa-Er). Those Δr differences influence the structure and lead to the following symmetry formation: In CaF2, the C4v and C3v isolated centers were identified, with the determined Er3+- F−i bond lengths of 2.734 Å and 4.735 Å respectively; In BaF2, only C3v isolated centers were identified with the determined Er3+- F−i bond lengths of 5.380 Å. The present work is the first study that takes into account correlations of optical properties, the local symmetry and the structure in mentioned fluorides crystals, and it could be a step forward in the lanthanide doped optical materials systematics