Europium-doped nanocrystalline Y2O3−La2O3 solid solutions with bixbyite structure

• Nanoparticles of cubic Y2O3–La2O3 are prepared for La2O3 content of up to 50 mol%.
• Energy levels of Eu3+ in (Y1−xLax)2O3 are derived from photoluminescence spectra.
• Second-order crystal field parameters and crystal field strength are calculated.
• Stark splitting of 7F1 manifold (ΔE) linearly varies with the crystal field strength.
• Semi-empirical equation relating the unit cell parameter with the ΔE is derived.

Nanocrystals of Y2O3 and La2O3 solid solutions were synthesized with a cubic bixbyite structure containing La2O3 content of up to 50 mol%. This is comparatively higher than that in bulk materials of the same structure, where La2O3 content of only 20 mol% can be obtained. A set of europium-doped (Y1−xLax)2O3 (x=0.1, 0.2, 0.3, 0.4) cubic bixbyite solid solutions with crystallites of approximately 10 nm in size was prepared using the polymer complex solution method. Structural analysis was performed using X-ray diffraction measurements, Rietveld full profile refinement, and from Eu3+ luminescence emission. The energy levels of the Eu3+ ion, second order crystal field parameters, and crystal field strength were obtained for all compositions of solid solutions. We show that the crystal field parameters linearly depend on unit cell parameter and that these dependencies may be considered as part of an overall dependence for the entire sesquioxide family.