The UV-phosphor strontium fluorooxoborate Sr[B5O7F3]:Eu

The fluorooxoborates Sr[B5O7F3] (Ccm21 (no. 36), Z = 4, a = 864.777(3) pm, b = 1001.037(4) pm, c = 810.110(5) pm, 630 refl., 68 param., R F = 0.061, R Bragg = 0.051) and Sr[B5O7F3]:Eu2+ were synthesized via solid-state reactions from Sr(BF4)2 and B2O3. Doping was achieved by adding EuF3, which was reduced to its divalent state during the synthesis. Sr[B5O7F3] was investigated by infrared spectroscopy. Photoluminescence spectra of the doped compound revealed an Eu2+ 5d-4f emission in the UV regime peaking at 371 nm with a full width at half maximum (FWHM) of 21 nm upon excitation at 239 nm, which proves a weak coordination of europium by the anionic fluorooxoborate network.

Synthesis of the first nickel borate nitrate K7Ni[B18O24(OH)9](NO3)6· (H3BO3)

The novel potassium nickel borate nitrate K7Ni[B18O24(OH)9](NO3)6 ·(H3BO3) was obtained from a simple hydrothermal synthesis in a stainless-steel autoclave at T = 513 K starting with nickel dichloride hexahydrate, and boric and nitric acid with the pH adjusted to 8 by KOH. Single-crystal X-ray diffraction data provided the basis for the structure analysis and refinement. The compound crystallizes in the trigonal space group R3̅ (no. 148) with the lattice parameters a = 1222.29(8) and c = 5478.4(4) pm. Generally, K7Ni[B18O24(OH)9](NO3)6 ·(H3BO3) is comprised of nitrate layers and complex nickel borate layers surrounded by boric acid, nitrate anions, and potassium cations.

Ni6B22O39·H2O – extending the field of nickel borates

Ni6B22O39·H2O was synthesized in a high-pressure/high-temperature reaction at 5 GPa/900°C. It crystallizes in the orthorhombic space group Pmn21 (no. 31) with the lattice parameters a=7.664(2), b=8.121(2) and c=17.402(2) Å. The crystal structure is discussed with regard to the isotypic compounds M 6B22O39·H2O (M=Fe, Co) and the structurally related phase Cd6B22O39·H2O. Furthermore, the characterization of Ni6B22O39·H2O via X-ray powder diffraction and vibrational spectroscopy is reported.

High-Pressure Synthesis and Characterization of the Ammonium Yttrium Borate (NH4)YB8O14

The first high-pressure yttrium borate (NH₄)YB₈O₁₄ was synthesized at 12.8 GPa/1300 °C using a Walker-type multianvil module. The compound crystallizes in the orthorhombic space group Pnma (no. 62) with the lattice parameters a = 17.6375(9), b = 10.7160(5), and c = 4.2191(2) Å. (NH₄)YB₈O₁₄ constitutes a novel structure type but exhibits similarities to the crystal structure of β-BaB₄O₇. X-ray single-crystal and powder diffraction, EDX, vibrational spectroscopy as well as quantum chemical calculations were used to characterize (NH₄)YB₈O₁₄.