Magnetocaloric effect of compositionally partitioned Mn5-xGe3Nix alloys produced by solid state sintering

Abstract

Mn5-xGe3Nix (x = 0, 0.05, 0.1) alloy powders were synthesized to evaluate the effect of the Ni substitution on the magnetocaloric effect (MCE) of Mn5Ge3. Equi-molar mixture of the three powder samples was consolidated into a mechanically sturdy form through solid state sintering. By controlling the sintering period, compositional non-uniformity was intentionally introduced into the sintered sample to form a quasi-steady state composite-like structure. The compositionally partitioned structure enabled combining Delta S-M - T curves from the alloys with the three different compositions, hence, providing a means to optimize the shape of the Delta S-M T curve and the refrigeration capacity. The sintered Mn5-xGe3Nix alloy produced a refrigeration capacity of 43 J kg(-1), peak entropy change at 282 K, and operating temperature range of 32 K under Delta H = 1 T which are possibly suitable for room-temperature magnetic refrigeration. It was demonstrated that sintering powders of brittle samples with different compositions while minimizing compositional homogenization can be used to engineer the magneto caloric properties of the refrigerant and, at the same time, to obtain desired physical shapes.