This ferrite magnet has a magnetoplumbite structure and is characterized in that, when representing the composition ratios of the total of each metal element A, R, Fe and Me with expression (1) A.sub.1-xR.sub.x(Fe.sub.12-yMe.sub.y).sub.z, the Fe.sup.2+ content (m) in the ferrite magnet is greater than 0.1 mass % and less than 5.4 mass % (in expression (1), A is at least one element selected from Sr, Ba, Ca and Pb; R is at least one element selected from the rare-earth elements (including Y) and Bi, and includes at least La, and Me is Co, or Co and Zn). The invention makes it possible to achieve a ferrite magnet with increased Br.

Disclosed herein are embodiments of composite hexagonal ferrite materials formed from a combination of Y phase and Z phase hexagonal ferrite materials. Advantageously, embodiments of the material can have a high resonant frequency as well as a high permeability. In some embodiments, the materials can be useful for magnetodielectric antennas.

The present invention provides a ferrite sintered magnet comprising ferrite crystal grains having a hexagonal structure, wherein the ferrite sintered magnet comprises metallic elements at an atomic ratio represented by formula (1). In formula (1), R is at least one element selected from the group consisting of Bi and rare-earth elements, and R comprises at least La. In formula (1), w, x, z and m satisfy formulae (2) to (5). The above-mentioned ferrite sintered magnet further has a coefficient of variation of a size of the crystal grains in a section parallel to a c axis of less than 45%.
Ca.sub.1-w-xR.sub.wSr.sub.xFe.sub.zCo.sub.m  (1)
0.360≤w≤0.420  (2)
0.110≤x≤0.173  (3)
8.51≤z≤9.71  (4)
0.208≤m≤0.269  (5)

A method for ammonia decomposition to produce hydrogen, the method comprising the steps of introducing an ammonia stream to a reactor, wherein the ammonia stream comprises ammonia, wherein the reactor comprises a cobalt-based catalyst, the cobalt-based catalyst comprising 15 wt % and 70 wt % of cobalt, 5 wt % and 45 wt % of cerium, and 0.4 wt % and 0.5 wt % barium, wherein a remainder of weight of the cobalt-based catalyst is oxygen; contacting the ammonia in the ammonia stream with the cobalt-based catalyst, wherein the cobalt-based catalyst is operable to catalyze an ammonia decomposition reaction; catalyzing the ammonia decomposition reaction to cause the ammonia decomposition in the presence of the cobalt-based catalyst to produce hydrogen; and withdrawing a product stream from the reactor, the product stream comprising hydrogen.

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.

This ferrite sintered magnet comprises ferrite phases having a magnetoplumbite type crystal structure. This magnet comprises an element R, an element M, Fe, Co, B, Mn and Cr, the element R is at least one element selected from rare earth elements including Y, the element M is at least one element selected from the group consisting of Ca, Sr and Ba, with Ca being an essential element, and when an atomic composition of metallic elements is represented by R.sub.1-xM.sub.xFe.sub.m-yCo.sub.y, x, y and m satisfy formulae:
0.2≤x≤0.8  (1)
0.1≤y≤0.65  (2)
3≤m<14  (3). Additionally, a content of B is 0.1 to 0.4% by mass in terms of B.sub.2O.sub.3, a content of Mn is 0.15 to 1.02% by mass in terms of MnO, and a content of Cr is 0.02 to 2.01% by mass in terms of Cr.sub.2O.sub.3.

A composite oxide powder including a composition formula (1), wherein the ratio α/β of a surface area value α(m.sup.2/g) calculated by a BET one-point method to a surface area value β(m.sup.2/g) calculated from a formula (2) is greater than 1.0 and equal to or less than 1.5 and the surface area value α is equal to or less than 20 m.sup.2/g. ABO.sub.3-δ (1) (wherein A is one or more types of elements (La, Sr, Sm, Ca and Ba), B is one or more types of elements (Fe, Co, Ni and Mn) and 0≤δ<1); and surface area value β(m.sup.2/g)=specific surface area value γ- surface area value ε(2) (the specific surface area value γ(m.sup.2/g) is a value in a total pore size range measured by a mercury intrusion method.The specific surface area value ε(m.sup.2/g) is a value in a range of pore sizes that are larger than a 50% cumulative particle size.

A sintered ferrite magnet comprising (a) a ferrite phase having a hexagonal M-type magnetoplumbite structure comprising Ca, an element R which is at least one of rare earth elements and indispensably includes La, an element A which is Ba and/or Sr, Fe, and Co as indispensable elements, the composition of metal elements of Ca, R, A, Fe and Co being represented by the general formula of Ca.sub.1-x-yR.sub.xA.sub.yFe.sub.2n-zCo.sub.z, wherein the atomic ratios (1-x-y), x, y and z of these elements and the molar ratio n meet the relations of 0.3≦(1-x-y)≦0.65, 0.2≦x≦0.65, 0≦y≦0.2, 0.03≦z≦0.65, and 4≦n≦7, and (b) a grain boundary phase indispensably containing Si, the amount of Si being more than 1% by mass and 1.8% or less by mass (calculated as SiO.sub.2) based on the entire sintered ferrite magnet, and its production method.

Thermochemical storage materials having the general formula A.sub.xA′.sub.1-xB.sub.yB′.sub.1-yO.sub.3-δ, where A=La, Sr, K, Ca, Ba, Y and B=Mn, Fe, Co, Ti, Ni, Cu, Zr, Al, Y, Cr, V, Nb, Mo, are disclosed. These materials have improved thermal storage energy density and reaction kinetics compared to previous materials. Concentrating solar power thermochemical systems and methods capable of storing heat energy by using these thermochemical storage materials are also disclosed.

A ferrite sintered magnet has a ferrite phase having a magnetoplumbite-type crystal structure, and contains at least a metal element A, a metal element R, Fe, Co, Zn, and B. The element A is at least one kind of element selected from the group consisting of Sr, Ba, Ca, and Pb, and essentially includes Ca. The element R is at least one kind of element selected from the group consisting of Bi and rare-earth elements including Y, and essentially includes La. Atomic ratios of the metal elements satisfy the following expressions.

A.sub.1-rR.sub.rFe.sub.xCo.sub.yZn.sub.z  (1)

0.40≤r≤0.70  (2)

8.20≤x≤9.34  (3)

0.05<y≤0.50  (4)

0<z≤0.20  (5)

The content of Si is 0 to 0.60% by mass in terms of SiO.sub.2, and the content of B is 0.01 to 0.70% by mass in terms of B.sub.2O.sub.3.