Studies On Magnetocaloric Properties Of（La, R）（Fe, Mn, Si）₁3H_x Alloys And Their Powder Bonded Samples

La(Fe1-xSix)13 series compounds with Na Zn13-type cubic structure are widely concerned because of their low costs of raw material, non-toxic cinstituting, continuously adjustable Curie temperature(Tc) and good magnetocaloric effects(MCEs) compared with other magnetic refrigeration compounds, which is one of the most promising candidates for magnetic refrigerantion. In this paper, the MCEs of hydrides and their bonded samples of La(Fe1-xSix)13 series compounds are investigated.The La0.9Ce0.1Fe11.7Si1.3H1.8 and La0.9Ce0.1Fe11.41Mn0.29Si1.3H1.8 alloys were prepared, and the two kinds of powder bonded samples of hydrides were obtained by bonding technology. The samples has the same major phase of Na Zn13-type cubic structure before and after bonding, and there is a small amount of α-Fe as impurity phase in their hydride and powder bonded samples. The two bonded samples show a very good compressive strength of 320 and 332 MPa, which are about 10 % and 14 % higher than that of bulk La Fe10.99Co0.91Si1.1B0.2 compound. By partial substitution of Mn for Fe, the Tc of bonded La0.9Ce0.1Fe11.7Si1.3H1.8 decreases remarkably from 325 to 279 K. The magnetic entropy change(?Sm) for bonded La0.9Ce0.1Fe11.7Si1.3H1.8 and La0.9Ce0.1Fe11.41Mn0.29Si1.3H1.8 slightly reduces comparing with hydride alloys, while large values of 8.8 and 7.9 J/kg K are maintained. The two bonded samples exhibit the same adiabatic temperature change(?Tad) of about 2.6 K under a field change from 0 to 1.5 T. The bonded La0.9Ce0.1(Fe,Mn)11.7Si1.3 hydrides samples with good magnetocaloric effects and better mechanical properties are promising as high performance magnetic refrigerants materials.The alloys and powder bonded samples of La1-yCeyFe11.41Mn0.29Si1.3Hx(y = 0.0, 0.1, 0.2, 0.3, 0.4) and La0.9Ce0.1Fe11.7-zMnzSi1.3H1.8(z = 0.27, 0.29, 0.31, 0.33, 0.35) were prepared by hydrogen absorption and bonding technology, respectively. When y ≤ 0.3, with increasing Ce content, the lattice constant decreases with decreasing the Tc due to a smaller atomic radius of Ce comparing with that of La, but the ?Sm for the samples enhances, because the Ce atom can enhance the itinerant-electron metamagnetic transition of samples above Tc; when y ≥ 0.3, the MCEs of sample reduces, due to the excessive amounts of Ce in the sample which leads to separating out a large number of α-Fe in the sample after heat treatment. When the Ce contents in the sample are determined, with increasing Mn content, the Tc of samples presents a linear decrease, which means the Tc for samples can be effectively adjusted near the room temperature by adjusting the Mn comtent in the sample; and the MCEs for the samples present a decreasing trend but very small. Compared with hdride alloys, the MCEs of bonded samples slightly reduce, but compared with other magnetic refrigeration materials, the bonded samples still remain relatively high MCEs. So, this series samples is a very promising magnetic refrigeration materials near the room temperature.The major phase of La0.9Ce0.1Fe11.44Si1.56 and its hydride alloys are the Na Zn13-type cubic structure. After hydrogen absorption, the lattice constant enhances with the Tc increases. The hydride alloy remains a fine stability after staying in air a period of time at room temperature. In the process of heating the hydride alloy has been in a condition of weightlessness from ～483 K to ～708 K, by the calculation the weightlessness percentage of hydride is about 0.19 %. By improving the insulation temperature, the interstitial H in the alloy overflows, which leads to the decrease of Tc, insulation temperature increases 10 K and the Tc of hydride alloy decreased 10 K, and the ?Sm of the hydride alloy slightly decreases, the difference for samples between the maximum and minimum of ?Sm is only 0.616 J/kg K. So by hydrogen desorption the Tc of hydride alloy can be effectively adjusted near the room temperature, and a good MCEs can be also remained.