Disclosed herein are embodiments of an enhanced resonant frequency hexagonal ferrite material and methods of manufacturing. The hexagonal ferrite material can be Y-phase strontium hexagonal ferrite material. In some embodiments, sodium can be added into the crystal structure of the hexagonal ferrite material in order to achieve high resonance frequencies while maintaining high permeability.

A composite ceramic including: a lithium garnet major phase; and a grain growth inhibitor minor phase, as defined herein. Also disclosed is a method of making composite ceramic, pellets and tapes thereof, a solid electrolyte, and an electrochemical device including the solid electrolyte, as defined herein.

A zirconia sintered body that includes a transparent zirconia portion and an opaque zirconia portion has a biaxial bending strength of 300 MPa or more. In addition, the opaque zirconia portion is configured by an opaque zirconia sintered body that is any one of a dark-colored zirconia sintered body, a medium-light-colored zirconia sintered body, and a light-colored zirconia sintered body.

A sintered composite ceramic, including: a lithium-garnet major phase; and a grain growth inhibitor minor phase, such that the grain growth inhibitor minor phase has a metal oxide in a range of 0.1 wt. % to 10 wt. % based on the total weight of the sintered composite ceramic.

A magnesium-based thermoelectric conversion material made of a sintered compact of a magnesium compound, in which, in a cross section of the sintered compact, a Si-rich metallic phase having a higher Si concentration than in magnesium compound grains is unevenly distributed in a crystal grain boundary between the magnesium compound grains, an area ratio of the Si-rich metallic phase is in a range of 2.5% or more and 10% or less, and a number density of the Si-rich metallic phase having an area of 1 μm.sup.2 or more is in a range of 1,800/mm.sup.2 or more and 14,000/mm.sup.2 or less.

A solid electrolyte layer includes a solid electrolyte and a compound represented by a composition formula M.sub.xZr.sub.2(PO.sub.4).sub.y. In the composition formula, M represents at least one selected from the group consisting of Na, K, Mg, Ca, Sr, Ba, Cu, Zn, and Ni, x satisfies 0<x≤2.5, and y satisfies 2.7≤y≤3.5.

There is provided a raw material for a zirconia sintered body formed by pressureless sintering and having a high fracture toughness value measured by an SEPB method, a sintered body formed from the raw material, and a method for producing at least one of the raw material and the sintered body.

Also provided is a sintered body that includes zirconia that contains a stabilizer and having a monoclinic fraction of 0.5% or more. Such a sintered body is produced by a method including using a powder that contains a stabilizer and zirconia with a monoclinic fraction of more than 70%, wherein monoclinic zirconia has a crystallite size of more than 23 nm and 80 nm or less.

A thermoelectric conversion material consists of a non-doped sintered body of a magnesium-based compound, in which an electric resistance value is 1.0×10.sup.−4 Ω.Math.m or less. The magnesium-based compound is preferably one or more selected from a MgSi-based compound, a MgSn-based compound, a MgSiSn-based compound, and a MgSiGe-based compound.

A composite ceramic including: a lithium garnet major phase; and a grain growth inhibitor minor phase, as defined herein. Also disclosed is a method of making composite ceramic, pellets and tapes thereof, a solid electrolyte, and an electrochemical device including the solid electrolyte, as defined herein.

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.