Structure of Yttrium Aluminium Garnet Obtained by the Glycothermal Method

Abstract

The reaction of a stoichiometric mixture of aluminium isopropoxide and yttrium acetate in 1,4-butanediol (1,4-BG) at 300 °C directly yielded crystalline yttrium aluminium garnet (YAG), while the reaction in ethylene glycol (EG) afforded an amorphous product in which a large amount of EG moieties remained. The latter product exhibited an exothermic peak due to the crystallization of YAG at around 900 °C and single-phase YAG was obtained by calcination at 1000 °C. The YAG sample directly obatained in 1,4-BG had a large unit cell parameter (12.144 Å), whereas the YAG sample obtained by the latter method had a unit cell parameter (12.015 Å) essentially identical with the value (12.01 Å) reported in the JCPDS card. Rietveld analysis indicates that the former crystals had Al vacancies at 24d sites and oxygen vacancies while the latter was essentially free from these vacancies.