Optical and electronic detection of chemicals, and particularly strong electron-donors, by 2H to 1T phase-based transition metal dichalcogenide (TMD) films, detection apparatus incorporating the TMD films, methods for forming the detection apparatus, and detection systems and methods based on the TMD films are provided. The detection apparatus includes a 2H phase TMD film that transitions to the 1T phase under exposure to strong electron donors. After exposure, the phase state can be determined to assess whether all or a portion of the TMD has undergone a transition from the 2H phase to the 1T phase. Following detection, TMD films in the 1T phase can be converted back to the 2H phase, resulting in a reusable chemical sensor that is selective for strong electron donors.

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.

To provide a lithium ion conductive crystal body having a high density and a large length and an all-solid state lithium ion secondary battery containing the lithium ion conductive crystal body. A Li.sub.5La.sub.3Ta.sub.2O.sub.12 crystal body, which is one example of the lithium ion conductive crystal body, has a relative density of 99% or more, belongs to a cubic system, has a garnet-related type structure, and has a length of 2 cm or more. The Li.sub.5La.sub.3Ta.sub.2O.sub.12 crystal body is grown by a melting method employing a Li.sub.5La.sub.3Ta.sub.2O.sub.12 polycrystal body as a raw material. With the growing method, a Li.sub.5La.sub.3Ta.sub.2O.sub.12 crystal body having a relative density of 100% can also be obtained. In addition, the all-solid state lithium ion secondary battery has a positive electrode, a negative electrode, and a solid electrolyte, in which the solid electrolyte contains the lithium ion conductive crystal body.

To provide a lithium ion conductive crystal body having a high density and a large length and an all-solid state lithium ion secondary battery containing the lithium ion conductive crystal body. A Li.sub.5La.sub.3Ta.sub.2O.sub.12 crystal body, which is one example of the lithium ion conductive crystal body, has a relative density of 99% or more, belongs to a cubic system, has a garnet-related type structure, and has a length of 2 cm or more. The Li.sub.5La.sub.3Ta.sub.2O.sub.12 crystal body is grown by a melting method employing a Li.sub.5La.sub.3Ta.sub.2O.sub.12 polycrystal body as a raw material. With the growing method, a Li.sub.5La.sub.3Ta.sub.2O.sub.12 crystal body having a relative density of 100% can also be obtained. In addition, the all-solid state lithium ion secondary battery has a positive electrode, a negative electrode, and a solid electrolyte, in which the solid electrolyte contains the lithium ion conductive crystal body.

A solid electrolyte capable of securing grain boundary resistance even when firing is performed at a relatively low temperature and a battery using the solid electrolyte are provided. The solid electrolyte includes a first electrolyte which contains a lithium composite metal compound, and a second electrolyte which contains Li and at least two kinds of metal elements selected from group 5 elements in period 5 or higher or group 15 elements in period 5 or higher.

According to one embodiment, provided is an active material including monoclinic niobium titanium composite oxide particles, and carbon fibers with which at least a part of surfaces of the monoclinic niobium titanium composite oxide particles is covered. The monoclinic niobium titanium composite oxide particles satisfy 1.5(/)2.5. The monoclinic niobium titanium composite oxide particles have an average primary particle size of 0.05 m to 2 m. The carbon fibers contain one or more metal elements selected from the group consisting of Fe, Co and Ni, and satisfy 1/10000(/)1/100. The carbon fibers have an average fiber diameter in the range of 5 nm to 100 nm.

A solid electrolyte material having high ion conductivity and a all-solid-state lithium-ion secondary battery using this solid electrolyte material are provided. The solid electrolyte material has a garnet-related structure crystal represented by the chemical composition Li.sub.7xyLa.sub.3Zr.sub.2xyTa.sub.xNb.sub.yO.sub.12 (0.05x+y0.2, x0, y0), which belongs to an orthorhombic system and a space group belonging to Ibca. The solid electrolyte material has lithium-ion conductivity at 25 C. of at least 1.010.sup.4 S/cm. Also, in this solid electrolyte material, the lattice constants are 1.29 nma1.32 nm, 1.26 nmb1.29 nm, and 1.29 nmc1.32 nm, and three 16f sites and one 8d site in the crystal structure are occupied by lithium-ions. The all-solid-state lithium-ion secondary battery has a positive electrode, a negative electrode, and a solid electrolyte, the solid electrolyte comprising this solid electrolyte material.

A solid electrolyte material having high ion conductivity and a all-solid-state lithium-ion secondary battery using this solid electrolyte material are provided. The solid electrolyte material has a garnet-related structure crystal represented by the chemical composition Li.sub.7xyLa.sub.3Zr.sub.2xyTa.sub.xNb.sub.yO.sub.12 (0.05x+y0.2, x0, y0), which belongs to an orthorhombic system and a space group belonging to Ibca. The solid electrolyte material has lithium-ion conductivity at 25 C. of at least 1.010.sup.4 S/cm. Also, in this solid electrolyte material, the lattice constants are 1.29 nma1.32 nm, 1.26 nmb1.29 nm, and 1.29 nmc1.32 nm, and three 16f sites and one 8d site in the crystal structure are occupied by lithium-ions. The all-solid-state lithium-ion secondary battery has a positive electrode, a negative electrode, and a solid electrolyte, the solid electrolyte comprising this solid electrolyte material.

Disclosed is a synthesis method for preparing tantalum pentoxide colloid including the steps of: a. Providing a transparent solution of amorphous tantalum pentoxide, b. Subjecting the solution to solvothermal conditions in order to form tantalum pentoxide nanocrystals, c. Dispersing the tantalum pentoxide nanocrystals in a solvent so as to form a tantalum pentoxide colloid.

Disclosed is a synthesis method for preparing tantalum pentoxide colloid including the steps of: a. Providing a transparent solution of amorphous tantalum pentoxide, b. Subjecting the solution to solvothermal conditions in order to form tantalum pentoxide nanocrystals, c. Dispersing the tantalum pentoxide nanocrystals in a solvent so as to form a tantalum pentoxide colloid.