Orthorhombic bismuth triborate (delta-BiB3O6) Single crystals were grown via the top-seeded method at atmospheric pressure. delta-BiB3O6 is shown to be a stable polymorph at temperatures close to the melting point while alpha-BiB3O6 is a metastable one. Optical, acoustic and electromechanical properties of delta-BiB3O6 are measured. Possibility of doping delta-BiB3O6 with large amounts of rare earths is demonstrated. (C) 2008 Published by Elsevier B.V.