Synthesis, Crystal Structure, and Properties of Bi 3 TeBO 9 or Bi 3 (TeO 6 )(BO 3 ): A Non‐Centrosymmetric Borate–Tellurate(VI) of Bismuth

Pale‐yellow single crystals of the new borate tellurate(VI) Bi 3 TeBO 9 were obtained by reaction of stoichiometric amounts of Bi 2 O 3 , B 2 O 3 , and Te(OH) 6 at 780 °C. The non‐centrosymmetric crystal structure ( P 6 3 , Z =2, a =8.7454(16), c =5.8911(11) Å, 738 refl., 43 param, R 1=0.037, wR 2=0.093) contains isolated trigonal‐planar BO 3 units and nearly undistorted TeO 6 octahedra. The Bi 3+ cations are located in between in octahedral voids. The BiO 6 octahedra are significantly distorted to a [3+3] pattern (2.25/2.50 Å) due to the n s 2 configuration. According to the structural features, the formula can be written as Bi 3 (TeO 6 )(BO 3 ). Alternatively, the structure can also be described as hcp of oxygen with Te VI and Bi III in octahedral voids and B III in trigonal‐ planar voids. The vibrational spectra show the typical features of BO 3 and TeO 6 units with a significant 10 B/ 11 B isotopic splitting of the IR‐active B−O valence mode (1248 and 1282 cm −1 ). The UV/Vis spectrum shows an optical band edge with an onset around 480 nm (2.6 eV). MAS‐NMR spectra of 11 B show an anisotropic signal with a quadrupole coupling constant of C Q =2.55 MHz. and a very small deviation from rotational symmetry ( η =0.2). The isotropic chemical shift is 20.1 ppm. The second harmonic generation (SHG) test was positive with an activity comparable to potassium dihydrogen phosphate (KDP). Bi 3 TeBO 9 decomposes in air at 825 °C to Bi 2 TeO 5 .