P. Becker, P. Held, L. Bohatý: Crystal Growth and Optical Properties of the Polar Hydrated Pentaborates Rb[B5O6(OH)4] . 2H2O and NH4[B5O6(OH)4] . 2H2O and Structure Redetermination of the Ammonium Compound

Crystal Research and Technology

Cryst. Res. Technol. 35 (2000) 1251 - Abstract -

P. Becker, P. Held, L. Bohatý

Institut für Kristallographie der Universität zu Köln, Köln, Germany

Crystal Growth and Optical Properties of the Polar Hydrated Pentaborates Rb[B₅O₆(OH)₄] . 2H₂O and NH₄[B₅O₆(OH)₄] . 2H₂O and Structure Redetermination of the Ammonium Compound

Large single crystals of the polar, hydrated pentaborates Me[B₅O₆(OH)₄]·2H₂O (Me = Rb, NH₄) were grown from aqueous solutions. The structure of NH₄[B₅O₆(OH)₄] . 2H₂O was redetermined and proved to be orthorhombic (space group Aba2 (No. 41) with a = 11.3192(7) Å, b = 11.0261(8) Å, c = 9.2316(5) Å, V = 1152.2(1) Å³, D_x = 1.569 Mgm^-3, Z = 4, M = 272.15 gmol^-1, R(F) = 0.0369 for 1266 unique reflections (I >= 4 σ (I)), isomorphous with the potassium and rubidium compounds. Refractive indices between 365 nm and 1100 nm as well as unpolarized absorption spectra of [B₅O₆(OH)₄] . 2H₂O and NH₄[B₅O₆(OH)₄] . 2H₂O were determined and phase-matching curves for second-harmonic generation were calculated. Both compounds allow type I and type II phase-matching at wavelengths from about 450 nm to the near infrared region.

Keywords: hydrated pentaborates, Rb[B5O6(OH)4] . 2H2O, NH4[B5O6(OH)4] . 2H2O, optical properties, crystal structure

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