Cold sintering of α‐alumina using functionalized boehmite: A cost‐effective approach to reduce sintering temperature

Abstract A novel cold‐assisted sintering process using a combination of functionalized boehmite and α‐alumina particles is demonstrated. Functionalized boehmite and α‐alumina composites were initially densified using a cold sintering process at <300°C followed by heat treatment at 1400°C‒1450°C (∼200°C‒300°C lower than conventionally sintered α‐alumina). Highest relative densities (99%) were achieved using meso‐scale α‐alumina (D50 = 720 nm) in a 50:50 wt% mixture with boehmite, functionalized in 2 M acetic acid. The high densities at low temperature were attributed to easy propagation of the transformation to α phase within the dense boehmite matrix, accompanied by enhanced nucleation on the surface of the alumina particles. Critical aspects of the transformation sequence from functionalized boehmite to α‐alumina were characterized using Raman and Fourier transform infrared spectroscopy. Preliminary hardness measurements were comparable with conventional alumina sintered at ∼1650°C and initial microwave measurements showed promise for the fabrication of high‐temperature co‐fired ceramic substrates in electronics.