Magnetocaloric Properties of ${\hbox {La}}({\hbox {Fe}},{\hbox {Co}},{\hbox {Si}})_{13}$ Bulk Material Prepared by Powder Metallurgy

Bulk samples of La(Fe,Co,Si)₁₃ have been prepared by powder metallurgy starting from elemental powders and cast master alloys. After sintering at about 1400 K for a few hours, the samples achieve densities of about 7.2 g/cm³. For ternary La(Fe_0.893Si_0.107)₁₃ the magnetic entropy change for a field variation of 16 kOe and the adiabatic temperature change for a field variation of 17 kOe amounts to 21.9 J/kgK and 4.2 K at a temperature of 193 K, respectively. For this composition, the thermal and the field hysteresis were determined to be 2.5 K and 2.2 kOe, respectively. With increasing Si content the hysteresis as well as the entropy change decreases. By increasing the Co content from La(Fe_0.865Co_0.05Si_0.085)₁₃ to La(Fe_0.803Co_0.112Si_0.085)₁₃ the peak temperature of the magnetic entropy change was tailored to the commercial relevant range of 254 K-336 K. The Co-containing samples hardly showed any hysteresis at all. Such powders were pressed in a die and sintered to fully dense blocks of about 23times19times12 mm . The blocks can be machined by conventional techniques to the shapes required in magnetic refrigeration prototypes.