Apatite-type gadolinium-based dense MGd4Si3O13 (M = Mg, Ca, and Sr) ceramics: An emerging class of sub-liquid helium temperature magnetic refrigerant

Abstract

Low-temperature magnetic refrigeration (MR), based on the magnetocaloric (MC) effect of magnetic materials, is recognized as a distinct and powerful cooling technology. We herein introduce a class of promising low-temperature magnetic refrigerants: the apatite-type gadolinium-based dense MGd₄Si₃O₁₃ (M = Mg, Ca, and Sr) ceramics. These ceramics exhibit giant MC effects and prominent performance in the sub-liquid helium temperature range. The maximum magnetic entropy change values of these ceramics are 59.5 and 32.2 J/kgK under magnetic fields of 0–7 and 0–2 T, respectively. These results surpass those of the commercial magnetic refrigerant gadolinium gallium garnet (GGG, ∼32.8 and 14.6 J/kgK) and are superior to most known benchmarked low-temperature magnetic refrigerants. Furthermore, these apatite-type gadolinium-based ceramics possess relatively high density (6.277∼6.562 g/cm³) and exhibit good environmental stability. These characteristics make these apatite-type MGd₄Si₃O₁₃ ceramics highly suitable for practical sub-liquid helium temperature MR applications.