Thermodynamics-driven prediction of sintering temperatures for high-entropy diboride ceramics

High-entropy diboride (HEB) ceramics exhibit exceptional potential for ultrahigh-temperature applications, yet their extensive compositional diversity poses challenges in determining optimal sintering parameters. This study introduces a thermodynamics-guided strategy to predict sintering parameters by linking calculated melting behavior with densification performance. Through thermodynamic analysis, equilibrium phase compositions were evaluated for five HEB systems: (Ti, Zr, Hf, Nb, Ta)B2 and (Ti, Zr, Hf, Nb, Ta, Me)B2 (Me = V, Cr, Mo, W). Experimental results revealed an inverse relationship between predicted liquid-phase formation temperatures and relative densities of samples sintered via spark plasma sintering at 2173 K. Systems with lower predicted liquid formation temperatures, (Ti, Zr, Hf, Nb, Ta, W)B2 and (Ti, Zr, Hf, Nb, Ta, Mo)B2, achieved near-full densification (98.2% and 97.3%, respectively). In contrast, (Ti, Zr, Hf, Nb, Ta)B2 and (Ti, Zr, Hf, Nb, Ta, V)B2 with higher liquid formation temperatures only reached 90.4% and 85.8% relative densities, necessitating higher densification temperatures. By bridging thermodynamic predictions with experimental validations, this work provides a rational pathway to seek suitable sintering parameters for diverse HEB compositions, enabling efficient fabrication of high-performance diboride ceramics with complex compositions for extreme environments.