Microstructure formation and magnetocaloric effect of the Fe2P-type phase in (Mn,Fe)2(P, Si, B) alloys
Jiawei Lai (South China University of Technology)
Z. G. Zheng (South China University of Technology)
B. Huang (TU Delft - QRD/Kouwenhoven Lab, South China University of Technology)
H. Y. Yu (South China University of Technology)
Z. G. Qiu (South China University of Technology)
Y. L. Mao (South China University of Technology)
S. Zhang (South China University of Technology)
F. M. Xiao (Guangdong Province Key Laboratory of Rare Earth Development and Application)
D. C. Zeng (South China University of Technology)
K Goubitz (TU Delft - RST/Fundamental Aspects of Materials and Energy)
E.H. Brück (TU Delft - RST/Fundamental Aspects of Materials and Energy)
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Abstract
The relation between the microstructure and the magnetic properties of Fe2P-type (Mn,Fe)2(P,Si,B) based materials has been systematically investigated by changing the annealing temperature and time. X-ray diffraction, Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy measurements show that the alloys contain the main Fe2P-type phase and two impurity phases of (Fe,Mn)5Si3-type and Fe2MnSi-type. Boron appears to facilitate the formation of the Fe2P-type phase during the arc-melting progress. Upon increasing the annealing temperatures from 1123 to 1423 K, the Curie temperature (TC) decreases from 302.0 to 270.5 K in the Mn1.15Fe0.85P0.55Si0.45 alloys and the magnetic-entropy change (ΔSM) increases linearly with annealing temperature. For the Mn1.15Fe0.85P0.52Si0.45B0.03 alloys annealed at 1423 K for different times, TC decreases from 263.8 and 232.8 K with increasing annealing time and ΔSM reaches a maximum value after annealing for 48 h. The differences in the annealing temperature and time influence the Si content in the Fe2P-type phase of the alloys and determine TC, the thermal hysteresis and the magneto-elastic transition.
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