A ceramic composition in one embodiment contains, relative to 100 parts by mass of diopside crystal powder, 0.3 to 1.5 parts by mass of a Li component in terms of an oxide thereof and 0.1 to 1 part by mass of a B component in terms of an oxide thereof. In this embodiment, the content of the Li component in terms of an oxide thereof is larger than the content of the B component in terms of an oxide thereof. In this embodiment, a total content of the Li component and the B component is 2.25 parts by mass or less in terms of oxides thereof.

A ceramic composition in one embodiment contains, relative to 100 parts by mass of diopside crystal powder, 0.3 to 1.5 parts by mass of a Li component in terms of an oxide thereof and 0.1 to 1 part by mass of a B component in terms of an oxide thereof. In this embodiment, the content of the Li component in terms of an oxide thereof is larger than the content of the B component in terms of an oxide thereof. In this embodiment, a total content of the Li component and the B component is 2.25 parts by mass or less in terms of oxides thereof.

A method of producing polycrystalline Y.sub.3Ba.sub.5Cu.sub.8O.sub.y (Y-358) whereby powders of yttrium (III) oxide, a barium (II) salt, and copper (II) oxide are pelletized, calcined at 850 to 950° C. for 8 to 16 hours, ball milled under controlled conditions, pelletized again and sintered in an oxygen atmosphere at 900 to 1000° C. for up to 72 hours. The polycrystalline Y.sub.3Ba.sub.5Cu.sub.8O.sub.y thus produced is in the form of elongated crystals having an average length of 2 to 10 μm and an average width of 1 to 2 μm, and embedded with spherical nanoparticles of yttrium deficient Y.sub.3Ba.sub.5Cu.sub.8O.sub.y having an average diameter of 5 to 20 nm. The spherical nanoparticles are present as agglomerates having flower-like morphology with an average particles size of 30 to 60 nm. The ball milled polycrystalline Y.sub.3Ba.sub.5Cu.sub.8O.sub.y prepared under controlled conditions shows significant enhancement of superconducting and flux pinning properties.

A method of providing an article having a set of directional channels, including a first directional channel, therein is described. The method comprises preparing a mixture including particles comprising a first material and a first binding agent. The method comprises providing an article precursor by surrounding a pattern comprising a second material with the mixture. The method comprises heating the article precursor thereby coalescing the particles to provide the article. The method comprises removing the pattern by reacting the second material to form a gaseous product, thereby providing the set of directional channels in the article, wherein the set of directional channels corresponds with the removed pattern. Such an article is also described.

A method of providing an article having a set of directional channels, including a first directional channel, therein is described. The method comprises preparing a mixture including particles comprising a first material and a first binding agent. The method comprises providing an article precursor by surrounding a pattern comprising a second material with the mixture. The method comprises heating the article precursor thereby coalescing the particles to provide the article. The method comprises removing the pattern by reacting the second material to form a gaseous product, thereby providing the set of directional channels in the article, wherein the set of directional channels corresponds with the removed pattern. Such an article is also described.

An oxide superconductor according to an embodiment includes an oxide superconducting layer includes a single crystal having a continuous perovskite structure containing at least one rare earth element selected from the group consisting of yttrium, lanthanum, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, barium, and copper, containing praseodymium in a part of the site of the rare earth element in the perovskite structure, and having a molar ratio of praseodymium of 0.00000001 or more and 0.2 or less with respect to the sum of the at least one rare earth element and praseodymium; fluorine in an amount of 2.0×10.sup.15 atoms/cc or more and 5.0×10.sup.19 atoms/cc or less; and carbon in an amount of 1.0×10.sup.17 atoms/cc or more and 5.0×10.sup.20 atoms/cc or less.

A method for producing a solid composition according to the present disclosure is a method for producing a solid composition that is used for forming a functional ceramic having a first crystal phase. The method for producing a solid composition includes: producing an oxide composed of a second crystal phase different from the first crystal phase; and mixing the oxide and an oxo acid compound.

An oxide superconductor according to an embodiment includes an oxide superconducting layer includes a single crystal having a continuous perovskite structure containing at least one rare earth element selected from the group consisting of yttrium, lanthanum, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, barium, and copper, containing praseodymium is a part of the site of the rare earth element in the perovskite structure, and having a molar ratio of praseodymium of 0.00000001 or more and 0.2 or less with respect to the sum of the at least one rare earth element and praseodymium; fluorine in an amount of 2.010.sup.15 atoms/cc or more and 5.010.sup.19 atoms/cc or less; and carbon in an amount of 1.010.sup.17 atoms/cc or more and 5.010.sup.20 atoms/cc or less.

An oxygen sensor element made of a ceramic sintered body detects oxygen concentration based on an electric current value measured when a voltage is applied. The ceramic sintered body has a composition formula LnBa.sub.2-xSr.sub.xCu.sub.3O.sub.7- generated by substituting any element selected from group 2 elements in the periodic table, such as strontium (Sr), for a part of a composition formula LnBa.sub.2Cu.sub.3O.sub.7- (Ln denotes rare earth element and is 0 to 1). Sr substitution quantity x should satisfy an inequality constraint 0<x1.5. This allows provision of an oxygen sensor element that improves durability etc. without losing sensor characteristics.

A method of producing polycrystalline Y.sub.3Ba.sub.5Cu.sub.8O.sub.y (Y-358) whereby powders of yttrium (III) oxide, a barium (II) salt, and copper (II) oxide are pelletized, calcined at 850 to 950 C. for 8 to 16 hours, ball milled under controlled conditions, pelletized again and sintered in an oxygen atmosphere at 900 to 1000 C. for up to 72 hours. The polycrystalline Y.sub.3Ba.sub.5Cu.sub.8O.sub.y thus produced is in the form of elongated crystals having an average length of 2 to 10 m and an average width of 1 to 2 m, and embedded with spherical nanoparticles of yttrium deficient Y.sub.3Ba.sub.5Cu.sub.8O.sub.y having an average diameter of 5 to 20 nm. The spherical nanoparticles are present as agglomerates having flower-like morphology with an average particles size of 30 to 60 nm. The ball milled polycrystalline Y.sub.3Ba.sub.5Cu.sub.8O.sub.y prepared under controlled conditions shows significant enhancement of superconducting and flux pinning properties.