对La_0.9Ce_0.1Fe_11.44Si_1.56合金进行饱和吸氢, 之后在不同放氢温度(T_d=200~250 ℃)下进行3 h放氢处理, 得到H含量不同即具有不同Curie温度(T_C)的氢化物, 对其相结构和磁热效应进行测试分析. 结果表明, 合金在吸氢前后有相同的相结构, 主相为NaZn₁₃型立方结构, 同时含有少量a-Fe杂相; 随着放氢温度的提高, T_C近似线性的降低; 由于H原子的引入消弱了一级巡游电子变磁(IEM)转变, 等温磁熵变较母合金有所降低, 当T_d>230 ℃时, 磁熵变随着放氢温度的升高明显降低, 磁滞减小, 当T_d=250 ℃时, 磁熵变曲线宽化, 一级相变特性弱化. 饱和吸氢后的La_0.9Ce_0.1Fe_11.44Si_1.56H_y粉末经固化后得到的粘结样品在0~1.5 T的磁场下, 绝热温变和等温磁熵变的最大值分别达到2.7 K和7.5 J/(kgK).

Recently, La(Fe, Si)₁₃-based magnetic refrigeration materials have been widely explored due to the advantages of giant magnetocaloric effect (MCE), tunable Curie temperature (T_C), low cost of raw materials and excluding deleterious elements compared to other room-temperature giant MCE materials such as Gd₅(Ge_1-xSi_x)₄, MnFeP_0.45As_0.55 and MnAs based compounds. In this work, in order to shift the T_C to around room temperature and maintain the large MCE, the method of absorbing hydrogen was employed. La_0.9Ce_0.1Fe_11.44Si_1.56 hydride was prepared by saturated hydrogen absorption and then hydrogen contents and T_C of the hydrides were controlled by subsequent dehydrogenation at different temperatures (T_d=200~250 ℃ for 3 h). The phase structure and magnetocaloric effect were investigated. The results show that the samples possess the cubic NaZn₁₃-type structure with a small amount of a-Fe as impurity phase. T_C exhibits an approximately linear decrease with increasing the dehydrogenation temperature. The isothermal magnetic entropy change (ΔS_m) of the hydrides decreases compared with the parent compound, which is mainly attributed to the fact that the field-induced itinerant-electron metamagnetic transition has been weakened upon hydrogen absorption. For the sample desorbed hydrogen at temperatures above 230 ℃, ΔS_m is remarkably decreased and favorably the magnetic hysteresis loss has been reduced simultaneously. With further increasing the temperature to 250 ℃, ΔS_m curve is broadened, weakening the characteristic of the first-order phase transition. Due to the intrinsic brittleness of hydrides, the preparation of a certain shape is of great importance for practical application. For a magnetic field change of 1.5 T, the maximum adiabatic temperature change (ΔT_ad) and ΔS_m for the bonded block of fully hydrogen absorption La_0.9Ce_0.1Fe_11.44Si_1.56 hydride are about 2.7 K and 7.5 J/(kgK), respectively, which are larger than those of La(Fe, Co, Si)₁₃ materials in the same magnetic field change range. In conclusion, the bonded La_0.9Ce_0.1Fe_11.44Si_1.56 hydrides with good MCE and different T_C have been successfully prepared and will be very useful for the practical application of layered magnetic refrigerants at ambient temperature under low field change in magnetic refrigerators.