Crystal structure re-determination, spectroscopy, and photoluminescence of -YBO₃:Eu³⁺

To unambiguously clarify the long-debated crystal structure of the low-temperature orthoborate pi-YBO3, single-crystals of the europium-doped pi-YBO3:Eu3+ were prepared via a high-pressure/high-temperature route at 7.5 GPa and 1400 degrees C. The structure was solved and refined in the monoclinic space group C2/c (no. 15) in the pseudowollastonite structure type, with the lattice parameters a=11.3407(5), b=6.5501(3), c=9.5798(4) angstrom, and beta=113.08(2)degrees. This structure determination was corroborated by powder X-ray diffraction and vibrational spectroscopy. B-11 as well as Y-89 MAS NMR spectroscopy was used to verify that our results are also accurate for the undoped pi-YBO3 and samples with varying europium content prepared under ambient pressure conditions. Additionally, the luminescence properties of the Eu3+ doped pi-orthoborate were determined in comparison with these ambient-pressure samples.