Optimized conditions for the growth of good quality double-perovskite transition metal oxide Ca2FeMoO6 crystals by a floating zone technique have been investigated. It was verified that the formation of single phase Ca2FeMoO6 in a large volume of as-grown crystals was found to occur only when isostatic inert atmosphere (ultrapure N-2) at a specific pressure range (0.25-0.50atm) and unreacted starting reagents are used. A secondary phase was evidenced and identified as CaMoO4 from structural refinement data. It is present mainly far from the middle region of 30 mm length crystals grown under more adequate conditions and represents not more than 6.5% in mass percentage. Thermal analysis measurements in air and N-2 reveal that the best as-grown crystal is stable from room temperature to about 1395degreesC, where main and secondary endothermic reactions are evidenced. (C) 2003 Elsevier Science B.V. All rights reserved.