To unambiguously clarify the long-debated crystal structure of the low-temperature orthoborate π-YBO₃, single-crystals of the europium-doped π-YBO₃:Eu³⁺ were prepared via a high-pressure/high-temperature route at 7.5 GPa and 1400 °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) Å, and β=113.08(2)°. This structure determination was corroborated by powder X-ray diffraction and vibrational spectroscopy. ¹¹B as well as ⁸⁹Y MAS NMR spectroscopy was used to verify that our results are also accurate for the undoped π-YBO₃ and samples with varying europium content prepared under ambient pressure conditions. Additionally, the luminescence properties of the Eu³⁺ doped π-orthoborate were determined in comparison with these ambient-pressure samples.

中文翻译：

---

π-YBO3:Eu3+的晶体结构重测定、光谱和光致发光

为了明确阐明低温原硼酸盐π -YBO ₃的长期争论的晶体结构，铕掺杂的π -YBO ₃ :Eu ³⁺单晶通过高压/高温路线在 7.5 GPa 和 1400 °C。结构在拟硅灰石结构类型的单斜空间群C 2/ c (no. 15)中解析细化，晶格参数a =11.3407(5), b =6.5501(3), c =9.5798(4) Å，β =113.08(2)°。这种结构测定得到了粉末 X 射线衍射和振动光谱的证实。¹¹ B 和⁸⁹ Y MAS NMR 光谱用于验证我们的结果对于未掺杂的π -YBO ₃和在环境压力条件下制备的具有不同铕含量的样品也是准确的。此外，与这些环境压力样品相比，确定了 Eu ³⁺掺杂的π -原硼酸盐的发光特性。