The High‐Pressure Borate HP‐(NH₄)B₃O₅

Abstract

Abstract The high‐pressure ammonium triborate HP‐(NH 4 )B 3 O 5 was synthesized in a high‐pressure/high‐temperature experiment at 3 GPa and 600 °C. It crystalizes in the monoclinic space group C 2/ c (No. 15) with the parameters a = 981.0(2), b = 880.2(2), c = 922.2(2) pm, β = 103.8(1)°, V = 0.7735(3) nm 3 , Z = 8, R 1 = 0.0436, and wR 2 = 0.1059 (all data). The compound is built up from ribbons of interconnected corner‐ and edge‐sharing BO 4 tetrahedra that are linked by planar BO 3 groups to form a three‐dimensional structure. The ammonium ions are situated in channels, forming four hydrogen bonds to oxygen of the boron oxygen network. The structure is a substitutional variant of the compounds HP‐ M B 3 O 5 , ( M = K, Rb) and HP‐Cs 1– x (H 3 O) x B 3 O 5 ( x = 0.5–0.7). The collected IR and Raman spectra of HP‐(NH 4 )B 3 O 5 show great similarities to the spectra of the analogous phases.