Influence of ceramic substrate porosity and glass phase content on the microstructure and mechanical properties of metallized ceramics via an activated Mo-Mn method

With the development of power electronics, metallizing of ceramics has been developed and employed in many industrial applications. This paper describes the effect of porosity, mean pore size and glass phase content of Al₂O₃ substrate on the microstructure evolution and mechanical properties of metallized ceramics obtained by an activated Mo–Mn method. The interface reaction as well as the joining strength between Al₂O₃ ceramic and Mo–Mn layer were investigated systematically using X-ray diffraction, SEM, energy dispersive X-ray analysis et al. The overall porosity affects the ‘absorptivity’ of the substrate towards the glass phase in the metallized layer, while the glass phase content affects the diffusion depth of the Mn-containing phase. The results show that the distribution of the Mn-containing glass phase in the alumina substrate determined the failure characteristics of specimens under bending and tension conditions. The mean pore size determines the magnitude of capillary force responsible for the diffusion of Mn-containing glass phase into the ceramic substrate. The thickness of the Mo–Mn layer reduced and the thickness of the transition region increased at high alumina porosity. This resulted in a decrease of tensile strength, and an increase of flexural strength growth rate GR for specimens after metallization. The tensile strength of metallized specimens monotonously increased with the glass phase content, while the flexural strength first increased and then decreased. A tensile strength of 1990 ± 75 N, a flexural strength of 9499 ± 346 N and a He leakage rate of 3.5 × 10⁻¹¹ Pa m³ s⁻¹ were obtained in the optimized specimens after metallization.