High-pressure/high-temperature Synthesis of the First Walstromite-Analogue Borate Tm2CrB3O9

Tm2CrB3O9 was obtained by high-pressure/high-temperature syntheses at 7.5 GPa and 850 degrees C. The compound crystallizes homeotypically to walstromite in the triclinic space group P 1 (no. 2) with the unit cell parameters a = 5.9118(4) & Aring;, b = 5.9148(4) & Aring;, c = 8.3575(6) & Aring;, alpha = 83.64(1)degrees, beta = 71.19(1)degrees, and gamma = 79.93(1)degrees, and two formula units per cell. Single-crystal and powder diffraction data are accompanied by an infrared spectroscopic investigation and the structural features of this new compound are discussed in detail.