Production method of high strength polycrystalline ceramic spheres

1. A method for making hollow spheres of alumina or aluminate comprising:

a) coating polymeric beads with an aqueous solution of an alumoxane;

b) drying the beads so as to form an alumoxane coating on the beads;

c) heating the beads to a first temperature, wherein the first temperature is sufficient to convert the alumoxane coating to an amorphous alumina or aluminate coating and is not sufficient to decompose the polymeric beads;

d) dissolving the polymeric bead in a solvent;

e) removing the dissolved polymer from the amorphous alumina or aluminate coating; and

f) heating the amorphous alumina or aluminate coating to a second temperature that is sufficient to form a hollow ceramic sphere of desired porosity and strength.

2. The method of claim 1 wherein the alumoxane comprises acetate-alumoxane.

3. The method of claim 1 wherein the average diameter of the polymeric beads is approximately 3 μm.

4. The method of claim 1 wherein the first temperature is between 180° C. and 230° C.

5. The method of claim 1 wherein the second temperature is above 600° C.

6. The method of claim 1 , further comprising:

g) covering the ceramic sphere with a solution of a metal-doped alumoxane so as to form a metal-doped alumoxane coating on the ceramic sphere; and

h) heating the coated sphere to a temperature sufficient to convert the metal-doped alumoxane coating to a mixed metal oxide phase.

7. The method of claim 6 wherein the metal-doped alumoxane comprises methoxy(ethoxyethoxy)acetic acid alumoxane.

8. The method of claim 6 wherein the metal-doped alumoxane comprises elements La, Ca, Er, Mg, Ti, or Y.