The Influence of Heat Treatment on the Phase Transformation Behavior and Magnetocaloric Effect of Gd_5Si_2Ge_2

摘要

In this thesis, a study was conducted on the magnetic phase transformation behavior and magnetocaloric effect (MCE) under a low magnetic field ranging from 0-1.5 T for the casted and annealed Gd_5Si_2Ge_2 alloys. The result shows that high-heat treatment significantly influences the structural and magnetocaloric properties of Gd_5Si_2Ge_2 alloy. High-heat treatment at 1573 K is beneficial to increasing Gd_5Si_2Ge_2-type monoclinic structure which benefits the first-order transition. The MCE of annealed Gd_5Si_2Ge_2 alloy drastically increases and the highest value of ?S_M~18.12 J/kg·K at 282 K upon ?H=1.5 T which is obviously larger than that of as-casted Gd_5Si_2Ge_2 (?S_M~5.03 kg·K at 276 K upon ?H=1.5 T). The giant magnetocaloric effect is obtained for Gd_5Si_2Ge_2 alloy by high-heat treatment.