Effects of YH2 addition on pressureless sintered AlN ceramics

Abstract

A new type of non-oxide sintering additive of YH2 was introduced for the fabrication of AlN ceramics with high thermal conductivity and flexural strength. The effects of YH2 addition (0–5 wt%) on the phase composition, densification, microstructure, thermal conductivity and flexural strength of pressureless sintered AlN ceramics were investigated and compared with those Y2O3-added samples (1–5 wt%). The addition of 1 wt% YH2 led to an in-situ reduction reaction with oxygen impurities, the formation of Y2O3 and finally the formation of yttrium aluminate, which in turn improved densification and microstructure. A high flexural strength (408.69 ± 28.23 MPa) was achieved. The addition of 3 wt% YH2 increased the average grain size and purified the lattice. All these effects are believed to help achieve a high thermal conductivity of 184.82 ± 1.75 W·m−1·K−1. Although the thermal conductivity was close to the value of 3 wt% Y2O3-added sample, its strength was much increased to 381.53 ± 43.41 MPa. Meanwhile, it demonstrated a good combination of the thermal conductivity and flexural strength than the values reported in some literature. However, further increasing the YH2 addition to 5 wt% resulted in a high N/O ratio that inhibited the densification behavior of AlN ceramics. The current study showed that AlN ceramics with excellent thermal and mechanical properties could be obtained by the introduction of a suitable YH2 additive.