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Large magnetocaloric effect (MCE) and magnetic properties in R3Ni6Al2 (R = Dy, Ho and Er) compounds were systematically investigated. Large magnetic moment and low magnetic transition temperature play a decisive role in the magnetocaloric performance for R3Ni6Al2 (R = Dy, Ho and Er) compounds. Ho3Ni6Al2 compound shows the largest magnetic entropy change with the value of 19.7 J/kg K at ~20 K under field change of 0–5 T because of the large magnetic moment and moderate transition temperature. For Dy3Ni6Al2 compound, it exhibits the largest refrigeration capacity with the value of 394.5 J/kg due to the successive magnetic transitions. The Er3Ni6Al2 compound has a large MCE at ultra-low temperatures around 4 K. Furthermore, the second-order phase transition in R3Ni6Al2 (R = Dy, Ho, Er) compounds were confirmed according to Arrott plots, rescaled universal magnetic entropy change curves and mean field theory with negligible thermal and magnetic hysteresis. The large reversible MCE with low working temperatures indicates that R3Ni6Al2 compounds are potential excellent MCE materials for low-temperature magnetic refrigeration.

In this work, we develop a two-step sintering technology special for porous ceramics to resolve the contradiction between porosity and mechanical strength. It contains a first long-time sintering at the relatively low temperature (T1) and a second fast sintering at higher temperature (T2). Porous ceramics of aluminum titanate-strontium feldspar-mullite (ASM) ternary composite were prepared by this method, and exhibit both high porosity and high mechanical strength. The effects of T1 and T2 on the phase composition, microstructure, porosity, pore size distribution, mechanical strength and thermal expansion coefficient (TEC) of ASM porous ceramics are systematically studied. The sample sintered at T1 = 1400 °C & T2 = 1500 °C shows optimum performance: the porosity, bulk density, and mean pore diameter (D50) are 63.48%, 1.20 g/cm3 and 15.94 μm, respectively; while the flexural strength reaches 9.22 MPa and the TEC is 2.9 × 10−6/K. The two-step sintering technology provides a powerful tool to develop porous ceramics with excellent comprehensive properties.