YVO4 single crystals doped with CaO are grown by the floating zone method in nitrogen atmosphere. The crystal is colorless and transparent after annealing in oxygen atmosphere. The effects of CaO addition are discussed. The Ca2+ ions can substitute for Y3+ at Y-sites in the YVO4 structure to form oxygen vacancies via which oxide ions can easily diffuse and, consequently, yield transparent crystals. (C) 2002 Elsevier Science B.V. All rights reserved.