Provided is an alumina ceramic with a low secondary electron emission coefficient and suitable for components of a high frequency generator, a plasma generator and so on. The alumina ceramic contains alumina as a main component, and at least two kinds of elements selected from an alkaline earth metal and from an element belonging to period 3, 4 or 5. The alkaline earth metal and the element belonging to period 3, 4 or 5 have a higher first ionization energy than aluminum. An electronegativity difference between the alkaline earth metal and the element belonging to period 3, 4 or 5 is 0 or more and 0.6 or less. A ratio (x/y) of the grain boundary area (x) to the grain area (y) in the alumina ceramic is 0.0001 to 0.001.

Ceramics and glass-ceramics have low and/or negative coefficients of thermal expansion. Crystalline phases of the formula AM.sub.2Si.sub.2-yGe.sub.yO.sub.7 (A=Sr and Ba and M=Zn, Mg, Ni, Co, Fe, Cu, Mn, with Sr, Ba and Zn necessarily having to be present) can be produced by conventional ceramic processes or by crystallization from glasses. The compositions form solid solutions, where the elements indicated as component M can be replaced by one another in virtually any concentration but the concentration of Zn must always be at least 50% of the sum of all components indicated under M. The stoichiometry of these silicates and also their structure can differ to a greater or lesser extent.

A method of forming a solid, dense, hermetic lithium-ion electrolyte membrane comprises combing an amorphous, glassy, or low melting temperature solid reactant with a refractory oxide reactant to form a mixture, casting the mixture to form a green body, and sintering the green body to form a solid membrane. The resulting electrolyte membranes can be incorporated into lithium-ion batteries.

A green tape composition includes at least one Li-garnet ceramic powder; at least one excess lithium source; at least one dispersant; at least one binder; and at least one plasticizer, such that a porosity of the green tape composition is <10 vol. %. A method includes dispersing at least one lithium garnet powder and at least one excess lithium source in a predetermined ratio in an organic solvent to form a garnet suspension; adding at least one dispersant, at least one binder, and at least one plasticizer to the garnet suspension; milling the garnet suspension; and de-airing under vacuum, such that a porosity of the green tape composition is <10 vol. %.

A hexagonal ferrite material includes a Y phase hexagonal ferrite material having the composition Sr.sub.2Co.sub.2Fe.sub.12O.sub.22 or Sr.sub.2-xNa.sub.xCo.sub.2-xSc.sub.xFe.sub.12O.sub.22, 0<x<2, doped with a trivalent element, a tetravalent element, and/or a transition metal.

There is provided a platy Mg-containing zinc oxide sintered compact containing 1 to 10 wt % Mg as a first dopant element and 0.005 wt % or more at least one second dopant element selected from the group consisting of Al, Ga and In, the balance consisting essentially of ZnO and optionally at least one third dopant element selected from the group consisting of Br, Cl, F, Sn, Y, Pr, Ge, B, Sc, Si, Ti, Zr, Hf, Mn, Ta, W, Cu, Ni, Cr, La, Gd, Bi, Ce, Sr and Ba, wherein the (002)-plane or (100)-plane orientation in the plate surface is 60% or more. The Mg-containing zinc oxide sintered compact of the present invention has excellent properties such as high orientation despite solid dissolution of Mg.

A piezoelectric composition including copper, germanium and a complex oxide represented by a compositional formula K.sub.mNbO.sub.3 and having a perovskite structure, in which m in the compositional formula satisfies 0.970 m0.999, and with respect to 1 mol of the complex oxide, x mol % of copper in terms of a copper element and y mol % of germanium in terms of a germanium element are contained, wherein x satisfies 0.100 x1.000 and y satisfies 0.000<y1.500.

A refractory object may include a zircon body that may include at least about 0.1 wt. % and not greater than about 5.5 wt. % of an Al.sub.2O.sub.3 containing component for a total weight of the zircon body. The zircon body may further include at least about 25 wt. % and not greater than about 35 wt. % of a SiO.sub.2 component for a total weight of the zircon body.

A method of forming a solid, dense, hermetic lithium-ion electrolyte membrane comprises combing an amorphous, glassy, or low melting temperature solid reactant with a refractory oxide reactant to form a mixture, casting the mixture to form a green body, and sintering the green body to form a solid membrane. The resulting electrolyte membranes can be incorporated into lithium-ion batteries.

Disclosed herein are embodiments of an enhanced resonant frequency hexagonal ferrite material and methods of manufacturing. The hexagonal ferrite material can be Y-phase hexagonal ferrite material, such as those including strontium. In some embodiments, oxides consistent with the stoichiometry of Sr.sub.3Co.sub.2Fe.sub.24O.sub.41, SrFe.sub.12O.sub.19 or CoFe.sub.2O.sub.4 can be used form an enhanced hexagonal ferrite material.