Uniform high crystallinity short belt-like Ca2B2O5 center dot H2O nanostructures (nanobelts) were facilely synthesized through a room temperature coprecipitation of CaCl2, H3BO3, and NaOH solutions, followed by a mild hydrothermal treatment (180 degrees C, 12.0 h). By a preferential growth parallel to the (1 0 0) planes, Ca2B2O5 center dot H2O nanobelts with a length of 1-5 mu m, a width of 100-400 nm, and a thickness of 55-90 nm were obtained. The calcination of the nanobelts at 500 degrees C for 2.0 h led to short Ca2B2O5 nanobelts with well preserved 1D morphology. Calcination at 800 degrees C led to a mixture of Ca2B2O5 and Ca3B2O6. The products were with belt-like and quasi-polyhedron morphology, while they turned into pore-free micro-rod like and polyhedron morphology when the calcination was taken in the presence of NaCl. NaCl assisted high temperature calcination at 900 degrees C promoted the formation of Ca3B2O6 in the products. When dispersed in deionized water or absolute ethanol, the Ca2B2O5 center dot H2O nanobelts and Ca2B2O5 nanobelts showed good transparency from the ultraviolet to the visible region. The as-synthesized Ca2B2O5 center dot H2O and Ca2B2O5 nanobelts can be employed as novel metal borate nanomaterials for further potential applications in the area of glass fibers, antiwear additive, ceramic coatings. and so on. (C) 2011 Elsevier B.V. All rights reserved.