Chemistry of inorganic compounds – Treating mixture to obtain metal containing compound – Rare earth metal
Patent
1981-12-28
1983-03-01
Carter, Herbert T.
Chemistry of inorganic compounds
Treating mixture to obtain metal containing compound
Rare earth metal
423111, 423122, 423132, 423263, 423624, C01G 1500, C01F 1700
Patent
active
043754538
ABSTRACT:
Gd.sub.2 O.sub.3 and Ga.sub.2 O.sub.3 are currently used for the fabrication of Gd.sub.3 Ga.sub.5 O.sub.12 (GGG) wafers which are employed as substrates for bubble domain memory devices. In the processing, in the order of 25% of the starting material ends up as process "saw kerf" contaminated with variable amounts of iron, nickel, magnesium, aluminum, zirconium, iridium and silicon. A process is described whereby the "saw kerf" can be reprocessed in sufficient purity to be re-used in the process, thereby improving the economics of production of GGG wafers significantly. Gadolinium and gallium oxides are recovered and separated from transition metal impurities introduced during fabrication of GGG wafers. The process "saw kerf" produced from slicing the crystal boule is dissolved in HCl, treated with H.sub.2 SO.sub.4, and the resulting sulfates separated. Metathesis with (NH.sub.4).sub.2 C.sub.2 O.sub.4 results in conversion of the sulfates to the ammonium oxalates which were calcined at 850.degree. C. to form Ga.sub.2 O.sub.3 and Gd.sub.2 O.sub.3 of purity >99.99%. The process can be extended to include purification and re-use of by-products generated in other grinding and polishing operations which may result in the recycling of the order of 80% of the generated by-products.
REFERENCES:
patent: 4198231 (1980-04-01), Gusset
Eibeck Richard E.
Nalewajek David
Recla Eugene B.
Wiles Robert A.
Allied Corporation
Carter Herbert T.
Friedenson Jay P.
Plantamura Arthur J.
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