Sol-gel method of making ceramics
AssigneeAlcan International Limited
InventorsJames L. Woodhead, Paul Groves
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Abstract
The invention concerns sol-gel techniques for making PZT-type ceramics having a perovskite-type structure and ferrite ceramics having a spinel-type structure. Colloidal hydrated oxide sols are mixed with metal salt solutions in the required concentration and the mixed sols dehydrated to form homogeneous gels which are fired at 250.degree. C.-650.degree. C., pressed and sintered at 900.degree.-1300.degree. C. The resulting ceramics include PZT4, PZT5 and lithium ferrites. These have excellent homogeneity, small grain size, high density and improved electrical properties, particularly low dielectric loss, compared with known ceramics of similar composition.
Claims21
A method of making a titanate ceramic material having a perovskite structure comprising mixing a first sol selected from the group consisting of hydrated titanium oxide sol and hydrated zirconium oxide sol with at least one second sol selected from the group consisting of hydrated oxide sols of zirconium (IV), indium (III), gallium (III), iron (III), aluminium (III), chromium (III), cerium (IV), silicon (IV) and titanium (IV), with the proviso that the first and second sols are not the same, wherein the first and second sols are mixed in proportions to form a mixed sol having a composition corresponding to that of the desired ceramic material, and then dehydrating the mixed sol to form a homogeneous gel, and heating the gel to form the desired ceramic material.
A method of making a ferrite ceramic material having a spinel structure comprising mixing a first sol which is hydrated ferric oxide sol with at least one second sol selected from the group consisting of hydrated oxide sols of zirconium (IV), indium (III), gallium (III), aluminum (III), chromium (III), cerium (IV), silicon (IV) and titanium (IV), and with a solution of a salt of at least one metal selected from the group consisting of Li, Mg, Mn, Zn, Cu, Ni, Co, Cr, Ba, Sr, Pb, Al, Si, Na, K, Sc, Ti, V, Ga, Ge, As, Rb, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Cs, La, Hf, Ta, W, Pt, Au, Hg, Tl, Bi or a rare earth, wherein the first and second sols and the metal salt solution are mixed in proportions to form a mixed sol having a composition corresponding to that of the desired ceramic material, and then dehydrating the mixed sol to form a homogeneous gel, and heating the gel to form the desired ceramic material.
A method of making a ferrite ceramic material having a spinel structure comprising mixing a first sol which is a hydrated ferric oxide sol with at least one second sol selected from the group consisting of hydrated oxide sols of zirconium (IV), indium (III), gallium (III), aluminum (III), chromium (III), cerium (IV), silicon (IV) and titanium (IV), wherein the first and second sols are mixed in proportions to form a mixed sol having a composition corresponding to that of the desired ceramic material, and then dehydrating the mixed sol to form a homogeneous gel, and heating the gel to form the desired ceramic material.
Dependencies are inferred from the claim text.