Method for preparing alkaline beta alumina parts

Claim 1

Method for preparing beta sodium alumina parts, suitable for use as solid electrolytes, in which the following successive steps are carried out: A. an intimate mixture of alumina powder and sodium carbonate powder is formed in respective quantities such that a predetermined ratio of A1 2 0 3 /Na 2 0 of between 5 and 11 is obtained; B. the said intimate mixture is heated in an open crucible at 1150° to 1300° C for 1 to 5 hours; C. the said mixture is allowed to cool freely; D. the beta sodium alumina powder thus obtained is crushed; E. the shaping of said powder into the said parts is effected; F. the sintering of said parts is effected by arranging the said parts in a sintering enclosure, suitable for creating, during the sintering operation and in the immediate vicinity of the parts, an atmosphere which is rich in sodium, the said enclosure being heated to a temperature comprised between 160° and 1700° C, maintained for 30 minutes to 4 hours, then being cooled freely down to ambient temperature, wherein said sintering enclosure comprises a body suitable for accomodating the said parts, said body being closed at its ends by means of a top plate and a bottom plate, each of said plates comprising a hollowed out portion filled with sodium carbonate, the said bottom plate resting on a bottom, the said top plate being covered by means of a cover, and wherein at least one of said hollowed out portions is in communication with the interior of said body, and wherein the body of the sintering enclosure is made entirely of beta sodium alumina or said parts are arranged inside the body on chocks made of beta sodium alumina.