Unusual effects of manual grinding and subsequent annealing process observed in Gd5.09Ge2.03Si1.88 compound

TL;DR

This study investigates how manual grinding and annealing processes alter the structural and magnetic transition behaviors of Gd5.09Ge2.03Si1.88, revealing significant effects on phase transitions relevant for magnetic refrigeration.

Contribution

It demonstrates that annealing and pressing modify phase transitions and structural parameters in Gd-based magnetocaloric materials, which is crucial for their application optimization.

Findings

Annealing removes the monoclinic phase and first-order transition.

Pressing shifts the second-order magnetic transition to lower temperatures.

Cell parameter c directly influences the Curie temperature (TC).

Abstract

The Gd5.09Ge2.03Si1.88 compound, as well as other magnetocaloric materials, certainly will not be used in their un-manufactured as-cast condition in future magnetic refrigeration applications or other devices. In this work, we have studied the Gd5.09Ge2.03Si1.88 compound processed in different ways, mainly, the as-cast powder, the annealed powder and the pressed and sintered powder. The annealed powder (1370 K / 20 hours) does not present the monoclinic phase and the first-order-magneto-structural transition observed in the as-cast powder. The pressed and sintered powder also do not present the first-order transition. Furthermore, the compacting pressure shifts the second-order-magnetic transition to lower temperatures. The behavior of cell parameters as a function of the compacting pressure indicates that TC is directly affected by parameter c change.