Synthesis, Crystal Structure Refinement, and Nonlinear-Optical Properties of CaB3O5(OH): Comparative Crystal Chemistry of Calcium Triborates

Calcium triborate CaB3O5(OH) obtained by hydrothermal synthesis in the Ca(OH)(2)-H3BO3-Na2CO3-KCl system is studied by single-crystal X-ray diffraction. The parameters of the orthorhombic unit cell are as follows: a = 13.490(1), b = 6.9576(3), and c = 4.3930(2) angstrom ; V = 412.32(3) angstrom(3) and space group Pna2(1). The structure is refined in the anisotropic approximation of the atomic displacement parameters to R = 4.28% using 972 vertical bar F vertical bar > 4 sigma(F). It is confirmed that the crystal structure of Ca triborate CaB3O5(OH) is identical to that described earlier. The hydrogen atom is localized. An SHG signal stronger than that of the quartz standard is registered. The phase transition of calcium triborate into calciborite is found on heating. The comparative crystal-chemical analysis of a series of borates with the general chemical formula 2CaD center dot 3B(2)D(3) center dot nH(2)O (n = 0-13) with the constant CaO : B2O3= 2 : 3 ratio and variable content of water is performed.