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CeAl is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Ce is bonded in a body-centered cubic geometry to eight equivalent Al atoms. All Ce–Al bond lengths are 3.18 Å. Al is bonded in a body-centered cubic geometry to eight equivalent Ce atoms.
CeAl crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Ce is bonded in a 10-coordinate geometry to two equivalent Ce and eight Al atoms. Both Ce–Ce bond lengths are 3.10 Å. There are a spread of Ce–Al bond distances ranging from 3.10–3.45 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 10-coordinate geometry to eight equivalent Ce and two equivalent Al atoms. Both Al–Al bond lengths are 2.79 Å. In the second Al site, Al is bonded to eight equivalent Ce and four Al atoms to form a mixture of face, edge, and corner-sharing AlCe8Al4 cuboctahedra. Both Al–Al bond lengths are 2.69 Å.
CeAl(NiCu)2 crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. Ce is bonded in a 6-coordinate geometry to six equivalent Ni, eight equivalent Cu, and four equivalent Al atoms. There are two shorter (2.85 Å) and four longer (2.90 Å) Ce–Ni bond lengths. All Ce–Cu bond lengths are 3.21 Å. All Ce–Al bond lengths are 3.27 Å. Ni is bonded in a 12-coordinate geometry to three equivalent Ce, four equivalent Cu, and two equivalent Al atoms. All Ni–Cu bond lengths are 2.52 Å. Both Ni–Al bond lengths are 2.48 Å. Cu is bonded to four equivalent Ce, four equivalent Ni, two equivalent Cu, and two equivalent Al atoms to form a mixture of distorted edge, corner, and face-sharing CuCe4Al2Cu2Ni4 cuboctahedra. Both Cu–Cu bond lengths are 2.55 Å. Both Cu–Al bond lengths are 2.47 Å. Al is bonded in a 12-coordinate geometry to four equivalent Ce, four equivalent Ni, and four equivalent Cu atoms.
CeAl(NiCu)2 crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. Ce is bonded in a 6-coordinate geometry to eight equivalent Ni, seven Cu, and three equivalent Al atoms. There are four shorter (3.22 Å) and four longer (3.28 Å) Ce–Ni bond lengths. There are a spread of Ce–Cu bond distances ranging from 2.94–3.26 Å. There are one shorter (2.95 Å) and two longer (3.00 Å) Ce–Al bond lengths. Ni is bonded to four equivalent Ce, two equivalent Ni, four Cu, and two equivalent Al atoms to form distorted NiCe4Al2Cu4Ni2 cuboctahedra that share corners with eight CuCe3Al3Cu2Ni4 cuboctahedra, corners with twelve equivalent NiCe4Al2Cu4Ni2 cuboctahedra, edges with four equivalent CuCe4Al2Cu2Ni4 cuboctahedra, edges with six equivalent NiCe4Al2Cu4Ni2 cuboctahedra, faces with six equivalent NiCe4Al2Cu4Ni2 cuboctahedra, and faces with ten CuCe3Al3Cu2Ni4 cuboctahedra. There are one shorter (2.58 Å) and one longer (2.60 Å) Ni–Ni bond lengths. There are a spread of Ni–Cu bond distances ranging from 2.48–2.58 Å. Both Ni–Al bond lengths are 2.47 Å. There are two inequivalent Cu sites. In the first Cu site, Cu is bonded to three equivalent Ce, four equivalent Ni, two equivalent Cu, and three equivalent Al atoms to form distorted CuCe3Al3Cu2Ni4 cuboctahedra that share corners with four equivalent CuCe4Al2Cu2Ni4 cuboctahedra, corners with eight equivalent NiCe4Al2Cu4Ni2 cuboctahedra, edges with six equivalent CuCe3Al3Cu2Ni4 cuboctahedra, faces with eight CuCe3Al3Cu2Ni4 cuboctahedra, and faces with twelve equivalent NiCe4Al2Cu4Ni2 cuboctahedra. Both Cu–Cu bond lengths are 2.47 Å. There are two shorter (2.96 Å) and one longer (3.03 Å) Cu–Al bond lengths. In the second Cu site, Cu is bonded to four equivalent Ce, four equivalent Ni, two equivalent Cu, and two equivalent Al atoms to form distorted CuCe4Al2Cu2Ni4 cuboctahedra that share corners with eight equivalent NiCe4Al2Cu4Ni2 cuboctahedra, corners with twelve CuCe3Al3Cu2Ni4 cuboctahedra, edges with two equivalent CuCe4Al2Cu2Ni4 cuboctahedra, edges with eight equivalent NiCe4Al2Cu4Ni2 cuboctahedra, faces with eight equivalent NiCe4Al2Cu4Ni2 cuboctahedra, and faces with eight CuCe3Al3Cu2Ni4 cuboctahedra. Both Cu–Al bond lengths are 2.52 Å. Al is bonded in a 12-coordinate geometry to three equivalent Ce, four equivalent Ni, and five Cu atoms.
Dy-free sintered magnets were fabricated by blending Neo powder with different grain boundary diffusion alloy powders. Cu, CeAl and CeAlCu have a negative effect on H cj of magnets, while PrAlCu and AlCuGa have a positive effect. The PrAlCu-added magnet achieves the best magnetic properties among all magnets with the additions of different diffusion alloys. With increasing PrAlCu from 0-10 wt.%, H cj of the magnets gradually increases from the original 14.5 kOe to 19.2 kOe. The magnet with 7.5 wt.% PrAlCu obtains a H cj of 18 kOe and (BH) max of 39.1 MGOe. It is found that Pr and Cu in PrAlCu alloy is mainly distributed at grain boundary and triple junctions, leading to a reduced coupling among grains, thus an enhanced H cj . Here, the grain boundary engineering by adding an appropriate alloy is an effective method to improve H cj of Dy-free NdFeB magnets.