At least partial substitution of zirconium by hafnium in ion-conducting zirconium-based ceramics provides enhanced chemical stability in alkaline and acid environments.

An inorganic oxide has a composition represented by General formula: M.sub.2LnX.sub.2(AlO.sub.4).sub.3 (where M includes Ca, Ln includes Eu, and X includes at least either one of Zr and Hf). Then, a crystal structure of the inorganic oxide is a garnet-type structure. Eu.sup.3+ in the inorganic oxide emits a plurality of bright line-like fluorescent components, and a principal bright line of the fluorescent component is present within a wavelength range of 600 nm or more to less than 628 nm. Moreover, a maximum height of the bright line present within a wavelength range of 700 nm or more to less than 720 nm is less than 60% of a maximum height of the principal bright line. A phosphor composed of the inorganic oxide can emit narrowband red light with good color purity.

The present invention provides for a composition comprising an inorganic scintillator comprising an alkali metal hafnate, optionally cerium-doped, having the formula A.sub.2HfO.sub.3:Ce; wherein A is an alkali metal having a valence of 1, such as Li or Na; and the molar percent of cerium is 0% to 100%. The alkali metal hafnate are scintillators and produce a bright luminescence upon irradiation by a suitable radiation.

The present invention provides for a composition comprising an inorganic scintillator comprising an alkali metal hafnate, optionally cerium-doped, having the formula A.sub.2HfO.sub.3:Ce; wherein A is an alkali metal having a valence of 1, such as Li or Na; and the molar percent of cerium is 0% to 100%. The alkali metal hafnate are scintillators and produce a bright luminescence upon irradiation by a suitable radiation.

Provided, as a transparent magneto-optical material which does not absorb fiber laser light within a wavelength range of 0.9-1.1 m and is thus suitable for constituting a magneto-optical device such as an optical isolator wherein the formation of a thermal lens is suppressed, is a magneto-optical material which is composed of a transparent ceramic that contains a complex oxide represented by formula (1) as a main component, or which is composed of a single crystal of a complex oxide represented by formula (1).

Tb.sub.2xR.sub.2(2-x)O.sub.8-x(1)

(In the formula, 0.800<x<1.00, and R represents at least one element selected from the group consisting of silicon, germanium, titanium, tantalum tin, hafinum and zirconium (excluding the cases where R represents only silicon, germanium or tantalum).)

A method may produce a perovskite-type ceramic compact including a perovskite-type ceramic having an alkaline earth metal element, at least one element selected from Ti, Zr, and Hf, and O. Such a method may include a contact reaction process in which a precursor compact including singly a gel including water and an oxide of at least one element selected from Ti, Zr, and Hf, and a liquid containing a hydroxide of the alkaline earth metal element are brought into contact with each other.

A semiconductor device according to an embodiment includes a first conductive layer, a second conductive layer, and a dielectric film provided between the first and the second conductive layers. The dielectric film including a fluorite-type crystal and a positive ion site includes Hf and/or Zr, and a negative ion site includes O. In the dielectric film, parameters a, b, c, p, x, y, z, u, v and w satisfy a predetermined relation. The axis length of the a-axis, b-axis and c-axis of the original unit cell is a, b, and c, respectively. An axis in a direction with no reversal symmetry is c-axis, a stacking direction of atomic planes of two kinds formed by negative ions disposed at different positions is a-axis, the remainder is b-axis. The parameters x, y, z, u, v and w are values represented using the parameter p.

A semiconductor device according to an embodiment includes a first conductive layer, a second conductive layer, and a dielectric film provided between the first and the second conductive layers. The dielectric film including a fluorite-type crystal and a positive ion site includes Hf and/or Zr, and a negative ion site includes O. In the dielectric film, parameters a, b, c, p, x, y, z, u, v and w satisfy a predetermined relation. The axis length of the a-axis, b-axis and c-axis of the original unit cell is a, b, and c, respectively. An axis in a direction with no reversal symmetry is c-axis, a stacking direction of atomic planes of two kinds formed by negative ions disposed at different positions is a-axis, the remainder is b-axis. The parameters x, y, z, u, v and w are values represented using the parameter p.

The present invention provides a production method that can produce a garnet-type compound containing zirconium and lithium, the compound being in the form of fine particles, with high productivity. The method produces a garnet-type compound containing Zr, Li, and element M.sup.1 (wherein M.sup.1 is at least one element selected from the group consisting of La, Sc, Y, and Ce) as constituent elements. The method includes a first step of (1) mixing a first raw material and a second raw material to obtain a precipitate, the first raw material being a solution containing a zirconium carbonate complex and having a pH of at least 7.0 and not more than 9.5, and the second raw material containing a compound containing the above element M.sup.1 as a constituent element; and (2) a second step of mixing the precipitate and a third raw material containing Li as a constituent element to obtain a mixture, and then firing the mixture at a temperature of less than 1,000 C. to obtain a fired product. The first raw material is prepared by mixing, at a prescribed molar ratio, at least a compound that contains a carbonate species and a compound that contains a zirconium species.

The present invention provides a production method that can produce a garnet-type compound containing zirconium and lithium, the compound being in the form of fine particles, with high productivity. The method produces a garnet-type compound containing Zr, Li, and element M.sup.1 (wherein M.sup.1 is at least one element selected from the group consisting of La, Sc, Y, and Ce) as constituent elements. The method includes a first step of (1) mixing a first raw material and a second raw material to obtain a precipitate, the first raw material being a solution containing a zirconium carbonate complex and having a pH of at least 7.0 and not more than 9.5, and the second raw material containing a compound containing the above element M.sup.1 as a constituent element; and (2) a second step of mixing the precipitate and a third raw material containing Li as a constituent element to obtain a mixture, and then firing the mixture at a temperature of less than 1,000 C. to obtain a fired product. The first raw material is prepared by mixing, at a prescribed molar ratio, at least a compound that contains a carbonate species and a compound that contains a zirconium species.