TY  - JOUR
AU  - Gonzalez-Julian, J.
AU  - Neuhaus, K.
AU  - Bernemann, M.
AU  - Pereira da Silva, J.
AU  - Laptev, A.
AU  - Bram, M.
AU  - Guillon, O.
TI  - Unveiling the mechanisms of cold sintering of ZnO at 250 °C by varying applied stress and characterizing grain boundaries by Kelvin Probe Force Microscopy
JO  - Acta materialia
VL  - 144
SN  - 1359-6454
CY  - Amsterdam [u.a.]
PB  - Elsevier Science
M1  - FZJ-2018-00195
SP  - 116 - 128
PY  - 2018
AB  - The sintering behavior of nanocrystalline ZnO was investigated at only 250 °C. Densification was achieved by the combined effect of uniaxial pressure and the addition of water both in a Field Assisted Sintering Technology/Spark Plasma Sintering apparatus and a hand press with a heater holder. The final pure ZnO materials present high densities (>90% theoretical density) with nano-grain sizes. By measuring the shrinkage rate as a function of applied stress it was possible to identify the stress exponent related to the densification process. A value larger than one points to non-linear relationship going beyond single solid-state diffusion or liquid phase sintering. Only a low amount of water (1.7 wt%) was needed since the process is dictated by the adsorption on the surface of the ZnO particles. Part of the adsorbed water dissociates into H+ and OH− ions, which diffuse into the ZnO crystal structure, generating grain boundaries/interfaces with high defect chemistry. As characterized by Kelvin Probe Force Microscopy, and supported by impedance spectroscopy, this highly defective grain boundary area presents much higher surface energy than the bulk. This highly defective grain boundary area with high potential reduces the activation energy of the atomic diffusion, leading to sinter the compound at low temperature.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000424067100012
DO  - DOI:10.1016/j.actamat.2017.10.055
UR  - https://juser.fz-juelich.de/record/841898
ER  -