A sintered ferrite magnet represented by the general formula of Ca.sub.1-xLa.sub.xFe.sub.2n-y-zCo.sub.yZn.sub.z expressing the atomic ratios of metal elements of Ca, La, Fe, Co and Zn, wherein x, y, z, and n [2n is a molar ratio represented by 2n=(Fe+Co+Zn)/(Ca+La)] meet 0.4<x<0.75, 0.15≤y<0.4, 0.11≤z<0.4, 0.26≤(y+z)<0.65, and 3≤n≤6.

An ultra low density film and an ultra low density solid material are produced by the steps of providing a vessel, introducing two immiscible fluids into the vessel, adding nanocrystals to at least one of the two immiscible fluids, applying a shear force to the two immiscible fluids and the nanocrystals in a manner that causes the nanocrystals to self-assemble and form colloidosomes. The colloidosomes amass and evaporation of the two fluids produces dried colloidosomes. The ultra low density self-assembled colloidosomes are hollow self-assembled colloidosomes, which are formed into the ultra-low density film and the ultra-low density solid.

Disclosed are air electrode materials suitable for use in solid oxide electrochemical cells (SOCs). The disclosed cells can operate in a dual function modes, i.e., as a fuel cell and as an electrolysis cell. In both cases, chemical energy and electrical energy can be directly convert from one mode to the other; thereby providing a highly efficient energy conversion process that can be used as a sustainable energy source.

An electromagnetic wave absorbing particle has a composition, which is represented by Formula 1 of Sr.sub.1-xR.sub.xFe.sub.y-2zM.sub.2zO.sub.a and contains M-type hexaferrite as a main phase. In Formula 1, R is one or more substances selected from among Ba, Ca, and La, M is one or more substances selected from among Co, Ti, and Zr, 0<x≤0.8, 8≤y≤14, 0<z≤1.5, and a is equal to 19.

A cathode configured to use oxygen as a cathode active material includes: a porous film including a metal oxide, where a porosity of the porous film is about 50 volume percent to about 95 volume percent, based on a total volume of the porous film, and an amount of an organic component in the porous film is 0 to about 2 weight percent, based on a total weight of the porous film.

A ferrite sintered magnet including ferrite grains having a hexagonal crystal structure. The ferrite grains satisfy 0.56≤W≤0.68 where W is an average value of circularities of the ferrite grains in a cross section parallel to an axis of easy magnetization.

To provide a ferrite sintered magnet having a high residual magnetic flux density (Br), a high coercive force (HcJ), a good production stability, and also able to produce at a low cost. The ferrite sintered magnet includes a hexagonal M-type ferrite including A, R, Fe, and Co in an atomic ratio of A.sub.1-xR.sub.x(Fe.sub.12-yCo.sub.y).sub.zO.sub.19. A is at least one selected from Sr, Ba, and Pb. R is La only or La and at least one selected from rare earth elements. 0.14≤x≤0.22, 11.60≤(12-y)z≤11.99, and 0.13≤yz≤0.17 are satisfied. 0.30≤Mc≤0.63 is satisfied in which Mc is CaO content (mass %) converted from a content of Ca included in the ferrite sintered magnet.

To provide a ferrite sintered magnet having a high residual magnetic flux density (Br) and a high coercive force (HcJ), and also able to produce at a low cost. The ferrite sintered magnet includes a hexagonal M-type ferrite including A, R, Fe, and Co in an atomic ratio of A.sub.1-xR.sub.x(Fe.sub.12-yCo.sub.y).sub.zO.sub.19. A is at least one selected from Sr, Ba, and Pb. R is La only or La and at least one selected from rare earth elements. 0.13≤x≤0.23, 10.80≤(12−y)z≤12.10, and 0.13≤yz≤0.20 are satisfied.

A thermoelectric material, having a formula Tb.sub.xM1.sub.y-xM2.sub.zO.sub.w where M1 is one of Ca, Mg, Sr, Ba and Ra, M2 is at least one of Co, Fe, Ni, and Mn, x ranges from 0.01 to 5; y is 1, 2, 3, or 5; z is 1, 2, 3, or 4; and w is 1, 2, 3, 4, 5, 7, 8, 9, or 14. The thermoelectric material is chemically stable within 5% for one year and is also non-toxic. The thermoelectric material can also be incorporated into a thermoelectric system which can be used to generate electricity from waste heat sources or to cool an adjacent region.

A positive electrode active material includes secondary particles. The secondary particles include a plurality of primary particles. The primary particles include a lithium-containing composite metal oxide. Inside the secondary particles, an electron conducting oxide is disposed at at least a part of a grain boundary between the primary particles. The electron conducting oxide has a perovskite structure.