Disclosed are a grain boundary- and surface-doped lithium-lanthanum-zirconium composite oxide solid electrolyte, a preparation method therefor, and an application thereof. Part of doping elements are step-doped at the grain boundary and the surface of the lithium-lanthanum-zirconium composite oxide solid electrolyte to improve the distribution state of the doping elements at the grain boundaries, reduce the number of grain boundaries, lower the grain boundary resistance of the lithium-lanthanum-zirconium composite oxide, thereby obtaining high ionic conductivity. The doping method has the advantages of being simple and convenient in process, low in cost and high in universality, can meet the requirements of different solid electrolytes on doping elements, and is suitable for large-scale application. The solid electrolyte obtained from the technical solution of the present application can be used in fields such as all-solid-state lithium or lithium ion batteries, semi-solid lithium ion batteries, lithium air batteries and the like.

A membrane electrode assembly includes an electrode consisting of at least one compound selected from the group consisting of lanthanum strontium cobalt complex oxide, lanthanum strontium cobalt iron complex oxide, and lanthanum strontium iron complex oxide, or consisting of a composite of the at least one compound and an electrolyte material, and a first solid electrolyte membrane represented by a composition formula of BaZr.sub.1xLu.sub.xO.sub.3 (0<x<1). The electrode is in contact with the first solid electrolyte membrane.

A gas sensor including a conductive oxide sintered body, the sintered body including a crystal phase having a perovskite-type oxide crystal structure represented by a compositional formula: RE.sub.aCu.sub.bFe.sub.cNi.sub.dO.sub.x wherein RE represents a rare earth element, wherein the following conditions: a+b+c+d=1 and 1.25x1.75 are satisfied, and wherein a, b, c, and d satisfy the following conditions: 0.375a0.524; 0.050<b0.200; 0.025c0.250; and 0.150d0.350. Also disclosed is a conductive oxide sintered body, a wiring board including a conductor layer formed of the conductive oxide sintered body and a gas sensor including an electrode formed of the conductive oxide sintered body.

Provided is a method of making a composite ceramic material for a fuel cell. The composite ceramic material for the fuel cell forms a cored structure where perovskite ceramic particles having a small particle diameter surround lanthanum cobaltite particles having a large particle diameter. Lanthanum cobaltite is added as a starting material in a process of synthesizing the perovskite ceramic particles. The composite ceramic material for the fuel cell made according to this method improves an electric connection characteristic between a separation plate and a polar plate of the fuel cell, and is chemically and mechanically stable.

A method for forming a LaNiO.sub.3 thin film is provided, the method including: a step of forming a coating film by coating a substrate surface which is coated with a Pt electrode with a LaNiO.sub.3 thin film-forming liquid composition and drying the LaNiO.sub.3 thin film-forming liquid composition in a state where amounts of H.sub.2, H.sub.2O, and CO adsorbed on the substrate surface per 1 cm.sup.2 are 1.010.sup.10 g or less, 2.710.sup.10 g or less, and 4.210.sup.10 g or less, respectively; a step of pre-baking the coating film; and a step of forming a LaNiO.sub.3 thin film by baking the pre-baked coating film.

A composition includes a compound of the formula A.sub.xM.sub.yO.sub.z, wherein A is an A-site element and includes Ba, Ca, Cu, Dy, Er, Gd, La, Nd, Pr, Sm, Sr, Y, or Yb, or a combination thereof, M is an M-site element and includes Co, Cu, Fe, Mn, Ni, Ti, Sc, or P, or a combination thereof, and 0<x1, 0<y2, (3)z(4), and 1<<1. Use of the composition as a catalyst composition, for example an oxygen reduction reaction catalyst composition, in gas diffusion electrodes, and in metal-air batteries is also described.

An oxide-based aerogel having cerium and nickel may be used as a water-gas shift reaction catalyst without producing methane as a byproduct. It may be made by forming a gel from a cerium salt and a nickel salt solution and converting the gel to an aerogel.

An oxide-based aerogel having cerium and nickel may be used as a water-gas shift reaction catalyst without producing methane as a byproduct. It may be made by forming a gel from a cerium salt and a nickel salt solution and converting the gel to an aerogel.

An oxide-based aerogel having cerium and nickel may be used as a water-gas shift reaction catalyst without producing methane as a byproduct. It may be made by forming a gel from a cerium salt and a nickel salt solution and converting the gel to an aerogel.

An electrochemical half-cell includes an electrical terminal lead in contact with a solid electrolyte, wherein the solid electrolyte includes a doped high-entropy oxide. The electrochemical half-cell can be used as either a reference half-cell or a measuring half-cell. Methods of manufacturing the solid electrolyte and the electrochemical half-cell are further disclosed.