Cold sintering of hexagonal boron nitride micro flakes

Hexagonal boron nitride (hBN) is electrically insulating and has a high in-plane thermal conductivity, therefore it is expected to have wide applications at high temperatures as both a structural and functional material. However, its flake-like microstructure and inherent refractory nature typically necessitate high sintering temperatures (at least 1800 °C) and significant uniaxial pressure (tens of megapascals) to achieve dense bulk hBN ceramics. The cold sintering process, a low-temperature and energy-efficient technique utilizing uniaxial pressure on a powder mixed with a solvent under moderate heat, has attracted attention. This paper presents an example of fabricating a dense bulk hBN ceramic and an hBN multilayer with Ag internal electrodes using cold sintering. The process employs deionized water as a transient liquid, facilitating high-density compaction through shear and particle rearrangement.