Method of making sodium beta-alumina powder and sintered articles

A method of forming a sodium beta-alumina article comprising

• adding a water dispersible alpha-alumina monohydrate to an acidic aqueous solution to form a colloidal solution (sol) of the alumina,
• adding an aqueous solution containing an inorganic oxygen-containing sodium salt to said sol to form a uniform mixture, the sodium salt being added in an amount to provide an Al.sub.2 O.sub.3 /Na.sub.2 O molar ratio in the range of 5 to 11,
• drying the mixture to form a powder,
• pressing a quantity of the powder into a porous article of predetermined configuration,
• heating the pressed article as necessary to drive off volatile material,
• and then sintering the article at an elevated temperature to densify it and to form the desired sodium beta-alumina.

A method of forming a sodium beta-alumina article comprising

• adding a water dispersible alpha-alumina monohydrate to an acidic aqueous solution to form a colloidal solution (sol) of the alumina,
• adding an aqueous solution containing an inorganic oxygen-containing sodium salt and an inorganic oxygen-containing salt of an element taken from the group consisting of lithium and magnesium to said sol to form a uniform mixture of the alumina and the salts, the respective salts being added in an amount to provide an (Al.sub.2 O.sub.3 + Li.sub.2 O + MgO)/Na.sub.2 O molar ratio in the range of 5 to 11,
• drying the mixture to form a powder,
• pressing a quantity of the powder into a porous article of predetermined configuration,
• heating the pressed article as necessary to drive off volatile material,
• and then sintering the article at an elevated temperature to densify it and to form the desired sodium beta-alumina.

A method of forming a sodium beta-alumina article comprising

• adding a water dispersible alpha-alumina monohydrate to an aqueous solution of an inorganic acid to form a colloidal solution (sol) of the alumina,
• adding an aqueous solution containing an inorganic oxygen-containing sodium salt and optionally an inorganic oxygen-containing salt of an element taken from the group consisting of lithium and magnesium to said sol to form a uniform mixture,
• spray drying the mixture to form a powder of free flowing microspheres,
• blending the powder, if necessary, with one or more other powder compositions prepared by the same process steps to obtain a blended powder composition having an (Al.sub.2 O.sub.3 + Li.sub.2 O + MgO)/Na.sub.2 O molar ratio in the range of about 5 to 11,
• pressing a quantity of the powder composition into a porous article of predetermined configuration,
• and sintering the article at an elevated temperature to densify it and to form the desired sodium beta-alumina.