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A series of LaFe11.8Si1.2/La65Co35 bulk composites were fabricated by spark plasma sintering (SPS) followed by diffusion annealing. The effect of sintering temperature (1073–1223 K) on the magnetocaloric and other properties of LaFe11.8Si1.2/La65Co35 bulk composites were investigated. The 1:13 phase content in all the annealed samples was ∼90 wt%. The mechanical and magnetocaloric properties of these annealed bulk composites could be improved by tuning the sintering temperature. The Curie temperature (TC) and maximum magnetic entropy change (−ΔSM)max of the annealed samples varied in the range of 211–228 K and 5.56–9.33 J kg−1 K−1, respectively. Selected samples exhibited excellent mechanical and magnetocaloric properties. The (−ΔSM)max value was 9.33 J kg−1 K−1 at TC of 217.8 K. Its maximum compressive strength (σbc)max value was 540 MPa at a strain of 3.48%, which exceeded the mechanical properties of most La–Fe–Si based bulk composites prepared by hot-pressing sintering (HPS). Thus, La–Fe–Si based bulk composites with good comprehensive properties could be obtained by combining SPS and diffusion annealing.

There is a growing demand for high coercivity of NdFeB magnets with low heavy rare earth in the emerging applications. In this work, dip-coating 0.02 g and 0.09 g TbH3 on the Tb-containing NdFeB magnet enhance coercivity at room temperature，respectively. The highest coercivity achieve about 30 kOe at room temperature after diffusion, which can apply to traction motors of electric vehicles. The magnetic field intensity distribution of magnet was analyzed by finite element method. Microstructures show TbH3 coat contents and original composition of NdFeB magnet influences the formation of Tb-rich shell and grain boundary phase, and determine finally diffusion depth and Tb concentration. The Tb atoms diffuse into the interior of the magnet, forming a network Tb-rich shell existed around Nd2Fe14B grains, resulting in the coercivity enhancement.