Synergistic Improvement in Mechanical and Thermal Properties of VPP‐Printed AlN via Mg(H ₂ PO ₄ ) ₂ Bonding Densification

ABSTRACT Digital light processing shows significant potential for fabricating AlN ceramics with complex geometries. However, porosity formed during the debinding stage remains the primary factor limiting the relative density of the material. This work uses magnesium dihydrogen phosphate (Mg(H 2 PO 4 ) 2 ) as an additive to solve densification problem of DLP printed AlN ceramics. We found Mg(H 2 PO 4 ) 2 can shorten the distance between AlN particles to promote densification during the printing and debinding stages. And Mg(H 2 PO 4 ) 2 can further react with residual alumina to form a small amount of magnesium aluminum spinel (MgAl 2 O 4 ) and reduce the content of oxygen impurities during the sintering stage. With the addition of 7% Mg(H 2 PO 4 ) 2 , the mechanical and thermal properties of the AlN ceramics were significantly enhanced. The sample achieved a curing depth of 94 µm when printed with a slurry of 55% solid loading. The bending strength is 387.9 MPa, the thermal conductivity is 183.9 W/(m × K), the relative density is 99.5 ± 0.1% and the porosity is 0.5% ± 0.1% when sintered at 1850°C. Moreover, after 20 thermal cycles (400°C), the printed sample retained a high bending strength of 334.0 MPa. This work solved the problem of relatively low density by adding Mg(H 2 PO 4 ) 2 , laying the foundation for further improvement of its mechanical and thermal properties.