Magnetocaloric Properties of La(Fe,Co,Si)₁₃ Bulk Material Prepared by Powder Metallurgy

Bulk samples of La(Fe,Co,Si)13have 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(Fe0.893Si0.107)13the 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(Fe0.865Co0.05Si0.085)13to La(Fe0.803Co0.112Si0.085)13the 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.