Grain Growth Kinetics of ZnO:Al Nanocrystalline Powders During Calcination from Sol–Gels

Abstract

The grain growth kinetics of Al-doped ZnO nanocrystalline powders have been studied using in situ, real-time synchrotron X-ray diffraction measurements during calcination at various temperatures (400–800 °C) from sol–gels with varying levels of Al dopant (0–4 mol %). Development of the crystallite size versus time was described using a relaxation model. A grain growth activation energy of 24 ± 3 kJ/mol was obtained for undoped ZnO, while for all of the Al-doped ZnO experiments the activation energy was 43 ± 4 kJ/mol. This difference is attributed to the segregation of Al to the crystallite interfaces, where it interferes with the ZnO grain growth, by inhibiting the motion of atoms across the grain boundaries.

Thermoelectric properties of pulsed current sintered nanocrystalline Al-doped ZnO by chemical vapour synthesis

“…2that the lattice microstrain increases with Al concentration indicating that Al is incorporated into the ZnO lattice. The findings are in agreement with previous studies 17,18. shows the STEM micrograph of undoped ZnO nanopowders, which consists of nearly spherical crystalline particles with a small degree of agglomeration and a mean diameter of 15 nm substantiating the XRD data.The XRD patterns of undoped and 8% Al-doped pellets sintered at 900°C are shown inFig.…”

Pinning effect on the band gap modulation of crystalline BexZn1−xO alloy films grown on Al2O3(0001)

“…In a similar case, B. Ingham et al reported that metallic Al atoms at grain boundaries restrict ZnO grain growth in the formation of spinel crystallites as ZnAl2O3. 44 Our AFM and XPS results showed a mean grain size that was inversely proportional to the amount of metallic Be on all film surfaces. Furthermore, one can expect that increasing Be content in the films contributed to increasing the volume fraction of Be particles at grain boundaries and thus a decrease in grain size.…”

On the agent role of Mn2+ in redirecting the synthesis of Zn(OH)2 towards nano-ZnO with variable morphology

“…There are several mechanisms proposed to explain the inhibition of the ZnO crystallites growth by the presence of impurities. [23][24][25] The reduced diffusivity in ZnO due to Zn concentration decrease in the doped samples suppresses the grain growth. Also, the presence of impurities produces a retarding force on the grain boundaries, impeding the grain growth.…”

“…Moreover, in Al doped ZnO the grain growth activation energy was determined to increase in the presence of impurities. 24 All these would contribute to a gradual decrease of the grain size with the increase of the impurities concentration.…”