foerfarande foer framstaellning av i polykristallin granat innehaollande aluminium och / eller indium and aotminstone i metall ur gruppen saellsynta jordmetaller och yttrium motsvarande monokristallina granater

摘要

A process for the manufacture of a polycrystalline garnet containing aluminium and/or gallium and/or indium and at least one element taken from the group comprising the rare earths and yttrium, and to the corresponding monocrystal. The process comprises the following steps: (1) a solution containing the salts of the constituent cations of the garnet, in the proportions corresponding to the composition of the latter, is prepared; (2) corresponding hydroxides are co-precipitated by means of a base in order to obtain a co-hydroxide, the solution of salts and the base being added simultaneously at a temperature between ambient temperature and the boiling point of the solution of salts, in such a way that the pH of the medium is between about 5 and 10 and that, within these limits, it is kept at a constant value throughout the co-precipitation; (3) if appropriate, the co-hydroxide is left to age; (4) it is filtered off; (5) it is washed; (6) it is dried; and (7) it is then calcined at a temperature above the temperature for the formation of the desired garnet structure. The monocrystals obtained by Czochralski drawing of the polycrystalline garnets of the invention can be used, in particular, as substrates in magnetic bubble memory devices.