Pr3+-doped Y2O3 nanocrystals (NCs) have been obtained via five wet-chemistry synthesis methods which were optimized in order to achieve superior optical properties. To this end, a systematic study on the influence of different reaction parameters was performed for each procedure. Specifically, precursor concentration, reaction temperature, calcination temperature, and time, among others, were analyzed. The synthesized Y2O3: Pr3+ NCs were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), and reflectance and Raman spectroscopy. In addition, the optical properties of such NCs were investigated by excitation, emission, and luminescence decay measurements. Concretely, emission from the 1D2 level was detected in all samples, while emission from 3PJ was absent. Finally, the effect of the synthesis methods and the reaction conditions on the luminescence decay has been discussed, and a comparative study of the different methods using the fluorescence lifetime of so-obtained Y2O3: Pr3+ NCs as a figure of merit has been carried out.

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An experimental correlation study between the low-symmetry 3d orbital splitting pattern, Δe and Δt, determined by optical spectroscopy, and the local distortion ρ, determined by X-ray diffraction, for different Cu2+ and Mn3+ fluorides and chlorides is presented. Single crystals of different dimensionalities were explored, some of them studied under high-pressure conditions. The collection of structural and spectroscopic data provides structural correlations relating ρ and Δe and Δt in Cu2+ and Mn3+ systems, showing that Δe (and Δt) scales with ρ. Such correlations can be used to estimate local distortions of Cu2+ (or Mn3+) introduced as impurities in different chloride and fluoride host lattices from spectroscopic data. The results can be interpreted in the framework of the Jahn–Teller theory and provide support for the proposed structural scenario. The influence of the crystal anisotropy in the local structure is analyzed as well and compared with transition metal ion systems having E⊗e Jahn–Teller (Cu2+, Mn3+) and singly orbital (Ni2+, Mn2+, Fe3+) ground states in octahedral symmetry.