First brittle material particles; and second brittle material particles having smaller size than the first brittle material particles, wherein a void formed between the first brittle material particles is filled with at least one of the second brittle material particles, at a porosity of less than 20%.

First brittle material particles; and second brittle material particles having smaller size than the first brittle material particles, wherein a void formed between the first brittle material particles is filled with at least one of the second brittle material particles, at a porosity of less than 20%.

A piezoelectric ceramic containing a perovskite-type compound containing at least Pb, Zr, Ti, Mn, and Nb, in which in an X-ray crystal structure analysis chart of the perovskite-type compound, there is no X-ray diffraction peak branching between a (101) plane of a main peak of a PZT tetra phase in a range of 2θ=30.5° to 31.5° and a (110) plane on which an X-ray diffraction peak is in a range of 2θ=30.8° to 31.8°, and a number of X-ray diffraction peaks based on the (101) plane and the (110) plane is one.

A piezoelectric ceramic containing a perovskite-type compound containing at least Pb, Zr, Ti, Mn, and Nb, in which in an X-ray crystal structure analysis chart of the perovskite-type compound, there is no X-ray diffraction peak branching between a (101) plane of a main peak of a PZT tetra phase in a range of 2θ=30.5° to 31.5° and a (110) plane on which an X-ray diffraction peak is in a range of 2θ=30.8° to 31.8°, and a number of X-ray diffraction peaks based on the (101) plane and the (110) plane is one.

A transparent optical element may include a layer of an electroactive ceramic disposed between transparent electrodes, such that the electrodes are each oriented perpendicular to a non-polar direction of the ceramic layer. Optical properties of the optical element, including transmissivity, haze, and clarity may be improved by the application of a voltage to the electroactive ceramic, and an associated phase transformation.

An electroactive ceramic may be incorporated into a transparent optical element and may characterized by an average grain size of less than 200 nm, a relative density of at least 99%, and a transmissivity within the visible spectrum of at least 50%, while maintaining a d.sub.33 value of at least 20 pC/N. Optical properties of the electroactive ceramic, including transmissivity, haze, and clarity may be substantially unchanged during actuation of the optical element and the attendant application of a voltage to a layer of the electroactive ceramic.

The invention relates to a process for producing a structured shaped body or a layer of this type from a precursor of a metal oxide or mixed oxide selected from compounds of metals selected from among magnesium, strontium, barium, aluminum, gallium, indium, silicon, tin, lead and the transition metals. The process includes at least the following steps: (a) dissolving at least one compound of the at least one metal in an organic solvent and/or exchanging a ligand of the one or more dissolved metallic compounds for a stabilizing ligand, (b) adding a ligand that has at least one photochemically polymerizable group and at least one such group that allows a stable complex formation to the solution and forming a sol with or from the product of this reaction (precursor), (c) applying the sol on a substrate, and (d) exposing the sol anisotropically in such a way that a polymerization of the photochemically polymerizable groups takes place in the exposed areas.

The invention relates to a process for producing a structured shaped body or a layer of this type from a precursor of a metal oxide or mixed oxide selected from compounds of metals selected from among magnesium, strontium, barium, aluminum, gallium, indium, silicon, tin, lead and the transition metals. The process includes at least the following steps: (a) dissolving at least one compound of the at least one metal in an organic solvent and/or exchanging a ligand of the one or more dissolved metallic compounds for a stabilizing ligand, (b) adding a ligand that has at least one photochemically polymerizable group and at least one such group that allows a stable complex formation to the solution and forming a sol with or from the product of this reaction (precursor), (c) applying the sol on a substrate, and (d) exposing the sol anisotropically in such a way that a polymerization of the photochemically polymerizable groups takes place in the exposed areas.

An electroactive ceramic may be incorporated into a transparent optical element and may characterized by an average grain size of less than 200 nm, a relative density of at least 99%, and a transmissivity within the visible spectrum of at least 50%, while maintaining a d.sub.33 value of at least 20 pC/N. Optical properties of the electroactive ceramic, including transmissivity, haze, and clarity may be substantially unchanged during actuation of the optical element and the attendant application of a voltage to a layer of the electroactive ceramic.

An electroactive ceramic may be incorporated into a transparent optical element between transparent electrodes and may characterized by a preferred crystallographic orientation. The preferred crystallographic orientation may be aligned along a polar axis of the electroactive ceramic and substantially parallel to each of the electrodes. Optical properties of the optical element, including transmissivity, haze, and clarity may be substantially unchanged during actuation thereof and the attendant application of a voltage to the electroactive ceramic.