Synthesis, crystal structure and characterization of iron pyroborate (Fe2B2O5) single crystals

Single crystals of iron(II) pyroborate, Fe2B2O5, were prepared at 1000-1050 degrees C under an argon atmosphere. The crystals were transparent, yellowish in color and needle-like or columnar. The crystal structure of Fe2B2O5 was analyzed by single-crystal X-ray diffraction. Refined triclinic unit cell parameters were a = 3.2388(2), b = 6.1684(5), c = 9.3866(8)angstrom, alpha = 104.613(3)degrees, beta = 90.799(2)degrees and gamma = 91.731(2)degrees. The final reliability factors of refinement were R1 = 0.020 and wR2 = 0.059 [1 > 2 sigma(1)]. Transmittance over 50% in the visible light region from 500 to 750 rum was observed for a single crystal of Fe2B2O5 with a thickness of about 0.3 mm. The light absorption edge estimated from a diffuse reflectance spectrum was at around 350 nm (3.6 eV). Magnetic susceptibility was measured for single crystals at 4-300 K. Fe2B2O5 showed antiferromagnetic behavior below the Neel temperature, T-N approximate to 70 K, and the Weiss temperature was T-W = 36 K. The effective magnetic moment of Fe was 5.3 mu(B). (C) 2009 Elsevier Inc. All rights reserved.