Single crystals of LaB6 were prepared by the RF-heated floating zone method. CaB6 was used as an additive of boron because calcium violently evaporates during melting and boron remains. When 6 wt% of CaB6 was added to the feed rod, the molten zone had almost the congruent composition. The single crystals without inclusions were obtained at a rate of 2 cm/h, twice as fast as that in conventional growth. The Ca content was 100 ppm in the crystals. (C) 2002 Published by Elsevier Science B.V.