Demonstration of the cold sintering process study for the densification and grain growth of ZnO ceramics

TLDR

ZnO is frequently used as a model ceramic system for fundamental sintering studies. The cold sintering process (CSP) was characterized by a kinetic grain‑growth exponent of N = 3 and an activation energy of 43 kJ mol⁻¹, markedly lower than conventional sintering. Adding acetic acid to the aqueous solution in CSP produced bulk densities above 90 % theoretical below 100 °C, grain microstructures and conductivities comparable to conventionally sintered samples, and confirmed genuine grain growth at low temperatures.

Abstract

Abstract With the cold sintering process ( CSP ), it was found that adding acetic acid to an aqueous solution dramatically changed both the densities and the grain microstructures of the ZnO ceramics. Bulk densities >90% theoretical were realized below 100°C, and the average conductivity of CSP samples at around 300°C was similar to samples conventionally sintered at 1400°C. Frequently, ZnO is also used as a model ceramic system for fundamental studies for sintering. By the same procedure as the grain growth of the conventional sintering, the kinetic grain growth exponent of the CSP samples was determined as N =3, and the calculated activated energy of grain growth was 43 kJ/mol, which is much lower than that reported using conventional sintering. The evidence for grain growth under the CSP is important as it indicates that there is a genuine sintering process being activated at these low temperatures and it is beyond a pressurized densification process.