Microstructure and properties of AlN-BN composites prepared by sparking plasma sintering method

•Dense AlN-BN composites can be prepared by SPS technique.•Suitable sintering additive help to improve thermal and dielectric properties of composite.•Sintering additive, BN grains, secondary phases and structural defects have impact on dielectric loss of composites.

Spark plasma sintering (SPS) method was applied to prepare aluminum nitride/boron nitride (AlN-BN) composites using Sm2O3–CaF2 as sintering additives. Effects of sintering additive and BN content on microstructure, thermal conductivity and dielectric properties of AlN-BN composites were investigated. The results reveal that dense AlN-BN composites with uniform microstructure can be successfully fabricated by SPS method. Suitable sintering additive not only promotes sintering densification process but also improves thermal and dielectric properties of AlN-BN composites through liquid phase sintering. AlN-BN composites containing 8 wt.% sintering additives exhibit higher thermal conductivity and lower dielectric loss. BN content, sintering additive, impurity elements, secondary phases, dislocation, and pores have influence on dielectric loss of AlN-BN composites. The main polarization mechanism of AlN-BN composites might be the space charge polarization.

Graphical abstractSpark Plasma Sintering (SPS) technique was used to fabricate AlN-BN composites. Effects of sintering additive and BN content on thermal conductivity and dielectric properties of composites were investigated. The flaky BN, sintering additive, secondary phases, microstructures and defects have important effect on the thermal conductivity and dielectric properties of AlN-BN composites.Figure optionsDownload full-size imageDownload as PowerPoint slide