The lithium tantalate single crystal substrate is a rotated Y-cut LiTaO.sub.3 single crystal substrate having a crystal orientation of 36 Y-49 Y cut characterized in that: the substrate is diffused with Li from its surface into its depth such that it has a Li concentration profile showing a difference in the Li concentration between the substrate surface and the depth of the substrate; and the substrate is treated with single polarization treatment so that the Li concentration is substantially uniform from the substrate surface to a depth which is equivalent to 5-15 times the wavelength of either a surface acoustic wave or a leaky surface acoustic wave propagating in the LiTaO.sub.3 substrate surface.

A piezoelectric PTZT film is formed of a metal oxide having a perovskite structure including Pb, Ta, Zr, and Ti, in which the metal oxide further includes carbon, and a content of the carbon is 80 to 800 ppm by mass. In a process for producing a liquid composition for forming a piezoelectric film, a Ta alkoxide, a Zr alkoxide, -diketones, and a diol are refluxed, a Ti alkoxide is added into a first synthesis solution obtained by the refluxing, and then refluxing is performed again, a Pb compound is added into a second synthesis solution obtained by performing the additional refluxing, and then refluxing is performed again, a solvent is removed from a third synthesis solution obtained by performing the additional refluxing, and then, dilution with alcohol is performed, to produce the liquid composition for forming a piezoelectric PTZT film.

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 dielectric composition containing a complex oxide represented by the formula of A.sub.B.sub.C.sub.2O.sub.++5 as the main component, wherein A represents Ba, B represents at least one element selected from the group consisting of Ca and Sr, C represents at least one element selected from the group consisting of Ta and Nb, and , and meet the following conditions, i.e., ++=1.000, 0.000<0.375, 0.625<1.000, 0.0000.375.

An electrode formulation including a polymer, which can be ion-conducting or non-conducting; an ion-conducting inorganic material; a lithium salt; and optionally an additive salt.

A solid-state electrolyte including a polymer, which can be ion-conducting or non-conducting; an ion-conducting inorganic material; a lithium salt; an additive salt and optionally a coupling agent.

A solid electrolyte material includes a solid electrolyte and an oxide material. The solid electrolyte includes Li, M, O, and X. M is at least one selected from the group consisting of Nb, Ta, and Zr. X is at least one selected from the group consisting of F, Cl, Br, and I. The oxide material includes at least one selected from the group consisting of oxides of divalent metal elements and oxides of trivalent metal elements. The mass proportion of the oxide material to the solid electrolyte is 1% or more and 50% or less. A battery includes a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode, and at least one selected from the group consisting of the positive electrode, the negative electrode, and the electrolyte layer contains the above solid electrolyte material.

A solid electrolyte material of the present disclosure comprises Li, M, O, and X, wherein M is at least one selected from the group consisting of Nb and Ta, and X is at least one selected from the group consisting of F, Cl, Br, and I. The solid electrolyte material contains columnar crystals. The average of aspect ratios (L/W) of the length (L) and the width (W) of the columnar crystals is 5 or more, and the average length is 20 m or less. A battery of the present disclosure includes a positive electrode, a negative electrode, and an electrolyte layer disposed between the positive electrode and the negative electrode. At least one selected from the group consisting of the positive electrode, the negative electrode, and the electrolyte layer contains the solid electrolyte material according to the present disclosure.

A lithium-lanthanum-titanium oxide sintered material has a lithium ion conductivity 3.010.sup.4 Scm.sup.1 or more at a measuring temperature of 27 C., the material is described by one of general formulas (1a)La.sub.xLi.sub.2-3xTiO.sub.3-aSrTiO.sub.3, (1a)La.sub.xLi.sub.2-3xTiO.sub.3-aLa.sub.0.5K.sub.0.5TiO.sub.3, La.sub.xLi.sub.2-3xTi.sub.1-aM.sub.aO.sub.3-a, Sr.sub.x-1.5aLa.sub.aLi.sub.1.5-2xTi.sub.0.5Ta.sub.0.5O.sub.3 (0.55x0.59, 0a0.2, M=at least one of Fe or Ga), amount of Al contained is 0.35 mass % or less as Al.sub.2O.sub.3, amount of Si contained is 0.1 mass % or less as SiO.sub.2, and average particle diameter is 18 m or more.

According to one embodiment, a negative electrode active material includes particles and a carbon material. The particles is represented by Li.sub.2+aA.sub.dTi.sub.6bB.sub.bO.sub.14c, where A is at least one element selected from the group consisting of Na, K, Mg, Ca, Ba, and Sr; B is a metal element other than Ti; and a, b, c, and d respectively satisfy 0a5, 0b6, 0c0.6, and 0d3. The carbon material covers at least a part of surfaces of the particles.