| 摘要 |
969,448. Ceramic monocrystals. CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE. March 22, 1963 [March 29, 1962], No. 11476/63. Heading B1G. A ceramic monocrystal is produced by passing a hot non-molten zone or front through a polycrystalline agglomerate containing 0À1-1 mol per cent of a substance which enters into solid solution during the heating. The temperature of heating (which embraces the temperature of solid solution) is between the temperatures of agglomeration and fusion. The substance is such as to retard crystal growth below solid solution temperature and accelerate crystal growth above solid solution temperature. It may be added before or after formation of the material of the polycrystalline agglomerate. The material may be a ferrite, perovskite, garnet, or ruby. The ferrite may be manganese-zinc or nickel-zinc ferrite. The additive may be silica, lanthanum oxide, neodymium oxide, palladium oxide, scandium oxide, aluminium oxide, chromium oxide, gadolinium oxide, thorium oxide, hafnium oxide, zirconium oxide, titanium oxide, tantalum oxide, or niobium oxide ; or ferric oxide calcined at 1000 ‹C. It may have a particle size of less than 1000 Angstrom Units. Growth of the monocrystal may be initiated by passing a hot zone through a restriction 8 near one end of the rod, Fig. 3, forming an initial hot point, Figs. 4 and 5, or the use of a preformed seed orientated in a desired manner, Figs. 7 and 8. Heating may be by a single resistance or induction heating coil 4 or a pair of outwardly moving coils 5 and 6 and cooling may be aided by a cooling ring 7 which precedes the heating coil. A hot front may be passed through the material by means of heat passed from a furnace 19 through a slit 17, Fig. 6. A bicrystal may be produced by passing two hot zones towards one another. The material may be in the form of a solid or hollow rod or ring or square frame. |
