High thermal conductivity versus robust mechanical properties: exploring synergistic effects and pathways in AlN-ZrN ceramics

Two-step sintering of ball-milled AlN-based powders removes surface Al 2 O 3 nanolayers and forms in situ ZrN/YAG grain boundary phases, enabling concurrent high bending strength (406 MPa) and thermal conductivity (184 W/(m·K)). • The novel conclusion of our work can be shortly summarized as follows: • Two-step sintering process successfully broadened the densification temperature window • Multi-cation synergistic regulation established the AlN-YAG-ZrN composite structure. • Enhanced the strain energy density of ceramic, achieving a balance between thermal conductivity and mechanical strength. AlN ceramics demonstrate exceptional potential in the protection and thermal management of high-power, highly integrated electronic devices. However, its inherent insufficient strength and high brittleness remain critical factors limiting the widespread application. This study employed Y-Ca-Mg-Li as sintering aids and incorporated YSZ (3 mol% Yttria-Stabilized Zirconia) doping to fabricate AlN multiphase ceramics via pressureless sintering. The research results indicate that the coexistence of multiple cations promotes the formation and flow of the high-temperature liquid phases during sintering, while the coexistence of multiple phases appropriately enhances the overall strain absorption capacity of the material. Under dynamic loading, stress dispersion occurs through the pores collapse and micro-deformation of grains. Moreover, the in-situ generated ZrN and YSZ, through particle size distribution effects, achieve fine-grain strengthening while maintaining the continuity of the AlN matrix. Thereby improving the ceramic’s strength and fracture toughness to 406 MPa and 2.5 MPa·m 1/2 , respectively. The thermal conductivity is 184 W/(m·K). This energy-centered design approach, without pursuing maximization of individual property enhancement, coordinates collective energy absorption and dissipation processes from a multi-property perspective to ultimately construct ideal materials, thereby providing theoretical support for ceramic material development.