N ELSEVIER Journal of Crystal Growth 177 (1997) 74 78 ........ CRYSTAL GROWTH Growth of vanadium garnet fiber crystals and variations of lattice parameter Young Moon Yu 1, Valery I. Chani*, Kiyoshi Shimamura, Katsuhiko Inaba, Tsuguo Fukuda lnstitute lbr Materials Research. Tohoku UnieersiO,, 2-1-I Katahira, Aoba-ku, Sendai 980-77, Japan Received 6 June 1996: accepted 6 November 1996 Abstract Crack-free, transparent and colorless fiber single crystals with the size of 0.8 1.2 mm in diameter and 2(~80 mm in length were grown from the melts ofNaxCaz.5 .,./xMg2V3OI2 where x = 0.0 1.0 by the micro-pulling-down method. The crystals grown from stoichiometric, NaCa2Mg2V3012, and Na+-rich (x < 1.0) melt in air were transparent and gray colored. It was found that lower the x value, higher is the uniformity of lattice parameters of the solidified fraction. Maximal uniformity was achieved for the Caz.sMg2V30~2 crystals of less than _+ 0.001 A. PACS. 81.10.Fq; 81.05.L; 61.50.Nw; 85.70.G Kevwords. Garnet: Fiber; Stoichiometric; Pulling; Vanadate 1. Introduction There are many reports I1 6] concerning the synthesis of vanadates {A3}[B2](V3)O12 with the garnet structure, where the cations which occupy the c, a, and d positions with coordination numbers 8, 6, and 4 are enclosed in braces, brackets, and parentheses, respectively. About 100 of vanadium garnets with V 5 + cations located in fourfold sites 1present address: Korea Research Institute of Chemical Technology, Taejon, Yuseung-ku, Jang-dong 100. South Korea. *Corresponding author. Fax: +81 22 215 2104: e-mail: chani(aivostok.imr.tohoku.ac.jp. were sintered by solid-state reaction with different combinations of cations in [A}- and [B]-positions. But there are very few reports concerning the crys- tal growth of vanadium garnets. Although it was reported that NaCa2Mg2V3012 compound has garnet structure and melts congruently at temper- ature about 1165'C [4], the details of crystal growth from stoichiometric melt were not found in literature. There is another report that the cation- defective garnet of Nao.86Ca2.07Mg2V3Oz2 single crystal was grown up to 1 mm of crystal dimensions by spontaneous crystallization from solution in molten sodium vanadates [5]. Moreover, many ceramics of vanadium garnets with a defective structure were also reported [6]. 0022-0248/97/$17.00 Copyright c 1997 Elsevier Science B.V. All rights reserved PII S0022-0248[97)01070-6