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.

The present invention relates to a method for producing a hexafluoromanganate(IV), said method being characterized by comprising: inserting an anode and a cathode into a reaction solution that contains a compound containing manganese having an atomic valence of less than 4 and/or manganese having an atomic valence of more than 4 and hydrogen fluoride; and then applying an electric current having an electric current density of 100 to 1000 A/m.sup.2 between the anode and the cathode. According to the present invention, it becomes possible to produce a hexafluoromanganate(IV) in which the content ratio of manganese having an atomic valence of 4 is high and the contamination with oxygen is reduced and which has high purity. When a complex fluoride red phosphor is produced using the hexafluoromanganate(IV) as a raw material, the phosphor produced has high luminescence properties, particularly high internal quantum efficiency.

Preparation of semiconductor nanocrystals and their dispersions in solvents and other media is described. The nanocrystals described herein have small (1-10 nm) particle size with minimal aggregation and can be synthesized with high yield. The capping agents on the as-synthesized nanocrystals as well as nanocrystals which have undergone cap exchange reactions result in the formation of stable suspensions in polar and nonpolar solvents which may then result in the formation of high quality nanocomposite films.

Provided is a method for producing a phosphor having a s chemical composition represented by formula (I), A.sub.2MF.sub.6:Mn (I) (A is one type or more of an alkali metal selected from Li, Na, K, Rb, and Cs, and includes at least Na and/or K, and M is one type or more of a tetravalent element selected from Si, Ti, Zr, Hf, Ge, and Sn.), the method comprising preparing a first hydrofluoric acid solution containing M and a second hydrofluoric acid solution containing A as well as either dissolving a compound containing Mn in either the first hydrofluoric acid solution or the second hydrofluoric acid solution or preparing a separate solution in which the compound containing Mn is dissolved. When the solutions are mixed to precipitate the phosphor of the formula (I), the solutions are mixed so that the concentration of M is 0.1 to 0.5 mol/liter when all the solutions are mixed. According to the present invention, a complex fluoride phosphor having excellent luminescence properties can be produced stably with high yield.

Provided is a method for forming a ferroelectric film of a metal oxide having a fluorite-type structure at a low temperature of lower than 300 C., and a ferroelectric film obtained at a low temperature. The present invention provides a production method of a ferroelectric film comprising a crystalline metal oxide having a fluorite-type structure of an orthorhombic crystal phase, which comprises using a film sputtering method comprising sputtering a target at a substrate temperature of lower than 300 C., to deposit on the substrate a film of a metal oxide which is capable of having a fluorite-type structure of an orthorhombic crystal phase, and having a subsequent thermal history of said film of lower than 300 C.; or applying an electric field to said film after said deposition or after said thermal history of lower than 300 C. Also provided are the ferroelectric film, which is formed on an organic substrate, glass, or metal substrate, which can be used only at low temperatures, and a ferroelectric element and a ferroelectric functional element or device using the ferroelectric film.

An embodiment may solve the problem of low sinterability of electrolytes of existing high entropy perovskite oxide materials through an electrolyte with improved structural stability of a matter at high temperatures without unnecessary enthalpy change, and provide a bidirectional proton conductive fuel cell with improved proton conductivity and electrochemical performance by using such an electrolyte.

A chalcogenide perovskite having an average particle size of less than 1 m and a composition other than BaZrS.sub.3.