CHEMICAL SYNTHESIS ROUTE TO MAGNETOCALORIC MATERIALS OF TRANSITION METAL-BASED PNICTIDES AND METALLOIDS

摘要

Giant magnetocaloric materials of transition-metal pnictides/metalloids have been prepared by a facile synthetic route, solid-state metathesis reaction. Single phase materials could be obtained in a simpler and faster way compared to the conventional metallurgical method, which is attributed to a lowered atomic diffusion barrier and large negative reaction enthalpies. In this synthetic design, transition metal-chlorides were used as metal sources and a reductive metal was adopted as reaction-mediating agent. This could also provide a bottom-up approach for size- and morphology-controlled particles of magnetocaloric materials. In addition, it was possible to combine elements of high melting point and volatile pnictogen elements (P, As, Sb) in a lattice system. An interstitial doping of boron into the transition metal pnictide MnFePAs lead to an increase of Curie temperature (T_c) without substantial modification of magnetic entropy change, which can be a useful tool for fine-tuning of magnetocaloric properties. Solid-state metathesis synthesis route to transition metal pnictides or metalloids may be a speedy way to explore new magnetocaloric compounds because of its simple synthetic route and scalability to mass production for magnetic refrigeration application.