Abstract Two new tellurite-phosphates NaTePO5, SrTeP2O8 and the previously reported Ba2TeP2O9 were synthesized successfully via high-temperature solid-state reactions and their structures were determined by single-crystal X-ray diffraction. The structures of NaTePO5 and SrTeP2O8 feature two-dimensional (2D) [TePO5]- and [TeP2O8]2- anionic layers interleaved with Na+ and Sr2+ cations, respectively. The 31P NMR spectra show that electron density around phosphorus atoms in SrTeP2O8 is slightly larger than that in Ba2TeP2O9, owing to the connection modes of [TeO5] and [PO4] units and counter-ion effects. The calculated electric field strength (Z/a2) based on the 31P chemical shift indicate as the chemical shift increases the Z/a2 also increases, as evidenced by the binding energy of P 2p determined by the X-ray photoelectron spectroscopy. Further, first-principle calculations show that the NaTePO5, SrTeP2O8 and Ba2TeP2O9 exhibit large birefringence of 0.212, 0.133 and 0.126 at 1064 nm, respectively, compared to other phosphates.

中文翻译：

---

NaTePO5、SrTeP2O8 和 Ba2TeP2O9：三种具有大双折射的亚碲酸盐磷酸盐

摘要 通过高温固相反应成功合成了两种新的亚碲酸盐-磷酸盐NaTePO5、SrTeP2O8和先前报道的Ba2TeP2O9，并通过单晶X射线衍射确定了它们的结构。NaTePO5 和 SrTeP2O8 的结构具有二维 (2D) [TePO5]- 和 [TeP2O8]2- 阴离子层，分别与 Na+ 和 Sr2+ 阳离子交错。31P NMR谱表明，由于[TeO5]和[PO4]单元的连接方式和反离子效应，SrTeP2O8中磷原子周围的电子密度略大于Ba2TeP2O9中的电子密度。根据 31P 化学位移计算的电场强度 (Z/a2) 表明，随着化学位移的增加，Z/a2 也增加，这由 X 射线光电子能谱测定的 P 2p 的结合能证明。更多，