The effect of Al doping on the crystal structure and magnetocaloric behavior of Mn1.2Fe0.8P1−xGex compounds
The effect of Al doping on the crystal structure and magnetocaloric behavior of Mn1.2Fe0.8P1−xGex compounds
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DOI：
10.1016/j.jallcom.2015.01.141
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发表时间：
2015-06
影响因子：
6.2
通讯作者：
Dong Liu;H. Zhang;Sai Wang;W. Xiao;Z. L. Zhang;N. Tian;Chengpeng Liu;M. Yue;Qingzhen Huang;J. Zhang;J. Lynn
中科院分区：
文献类型：
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作者：
Dong Liu;H. Zhang;Sai Wang;W. Xiao;Z. L. Zhang;N. Tian;Chengpeng Liu;M. Yue;Qingzhen Huang;J. Zhang;J. Lynn
研究了在x= 0.24、0.25、0.26和y= 0、0.004、0.008、0.010、0.12条件下，Al掺杂对放电等离子烧结制备Mn 1.2 Fe 0.8 p1−x Ge x Al y化合物晶体结构和磁热性能的影响。这些化合物具有与未掺杂体系相同的fe2p - P型结构（空间群p6¯2m），我们发现Al的加入对化合物的六方晶胞及其物理性能有显著影响。随着y的增大，晶格参数a和胞体体积增大，晶格参数c减小，热滞后（ΔT hys）减小，居里温度（T c）明显高于y= 0时。tc和ΔT hys的变化与c/a比的变化几乎呈线性相关，表明Al掺杂可以增加tc。此外，Al掺杂对其他磁热学性质，如熵变、绝热温度变化、顺磁相和铁磁相共存的温度范围等均无不利影响。我们还发现Mn 1.2 Fe 0.8 p1−x Ge x Al y化合物的磁热性能可以通过均匀退火得到改善。特殊成分Mn 1.2 Fe 0.8 P 0.74 Ge 0.26 Al 0.010表现出接近室温的温度（292.2 K），迟滞为ΔT hys 2.1 K，使其成为非常有前途的室温磁制冷材料。
We studied the influence of Al doping on the crystal structure and magnetocaloric properties of Mn 1.2 Fe 0.8 P 1− x Ge x Al y compounds prepared by spark plasma sintering, with x= 0.24, 0.25, 0.26 and y= 0, 0.004, 0.008, 0.010 or 0.12. These compounds have the same Fe 2 P-type structure (space group P 6¯ 2m) as the undoped system, and we found that the addition of Al had significant effects on the hexagonal unit cell of the compound and its physical properties. As y increased, the lattice parameter a and cell volume increased, the lattice parameter c decreased, the thermal hysteresis (ΔT hys) decreased, and the Curie temperature (T c) became significantly higher than at y= 0. The variations of T c and ΔT hys correlated almost linearly with variation in the c/a ratio, indicating that T c can be increased with Al doping. In addition, Al doping did not have any adverse effects on other magnetocaloric properties, such as the entropy change, adiabatic temperature change, and the temperature range of the coexistence of the paramagnetic and ferromagnetic phases. We also found that the magnetocaloric properties of Mn 1.2 Fe 0.8 P 1− x Ge x Al y compounds could be improved by homogenous annealing. The particular composition Mn 1.2 Fe 0.8 P 0.74 Ge 0.26 Al 0.010 exhibited a T c close to room temperature (292.2 K) with a hysteresis of ΔT hys 2.1 K, making it a very promising material for magnetic refrigeration around room temperature.