TY - JOUR
T1 - In situ X-ray diffraction study of the solvothermal formation mechanism of gallium oxide nanoparticles
AU - Nielsen, Ida Gjerlevsen
AU - Kløve, Magnus
AU - Roelsgaard, Martin
AU - Dippel, Ann Christin
AU - Iversen, Bo Brummerstedt
PY - 2023/3
Y1 - 2023/3
N2 - Gallium oxides are of broad interest due to their wide band gaps and attractive photoelectric properties. Typically, the synthesis of gallium oxide nanoparticles is based on a combination of solvent-based methods and subsequent calcination, but detailed information about solvent based formation processes is lacking, and this limits the tailoring of materials. Here we have examined the formation mechanisms and crystal structure transformations of gallium oxides during solvothermal synthesis using in situ X-ray diffraction. γ-Ga2O3 readily forms over a wide range of conditions. In contrast, β-Ga2O3 only forms at high temperatures (T > 300 °C), and it is always preceded by γ-Ga2O3, indicating that γ-Ga2O3 is a crucial part of the formation mechanism of β-Ga2O3. The activation energy for formation of β-Ga2O3 from γ-Ga2O3 is determined to be 90-100 kJ mol−1 in ethanol, water and aqueous NaOH based on kinetic modelling of phase fractions obtained from multi-temperature in situ X-ray diffraction data. At low temperatures GaOOH and Ga5O7OH form in aqueous solvent, but these phases are also obtained from γ-Ga2O3. Systematic exploration of synthesis parameters such as temperature, heating rate, solvent and reaction time reveal that they all affect the resulting product. In general, the solvent based reaction paths are different from reports on solid state calcination studies. This underlines that the solvent is an active part of the solvothermal reactions and to a high degree determines different formation mechanisms.
AB - Gallium oxides are of broad interest due to their wide band gaps and attractive photoelectric properties. Typically, the synthesis of gallium oxide nanoparticles is based on a combination of solvent-based methods and subsequent calcination, but detailed information about solvent based formation processes is lacking, and this limits the tailoring of materials. Here we have examined the formation mechanisms and crystal structure transformations of gallium oxides during solvothermal synthesis using in situ X-ray diffraction. γ-Ga2O3 readily forms over a wide range of conditions. In contrast, β-Ga2O3 only forms at high temperatures (T > 300 °C), and it is always preceded by γ-Ga2O3, indicating that γ-Ga2O3 is a crucial part of the formation mechanism of β-Ga2O3. The activation energy for formation of β-Ga2O3 from γ-Ga2O3 is determined to be 90-100 kJ mol−1 in ethanol, water and aqueous NaOH based on kinetic modelling of phase fractions obtained from multi-temperature in situ X-ray diffraction data. At low temperatures GaOOH and Ga5O7OH form in aqueous solvent, but these phases are also obtained from γ-Ga2O3. Systematic exploration of synthesis parameters such as temperature, heating rate, solvent and reaction time reveal that they all affect the resulting product. In general, the solvent based reaction paths are different from reports on solid state calcination studies. This underlines that the solvent is an active part of the solvothermal reactions and to a high degree determines different formation mechanisms.
UR - http://www.scopus.com/inward/record.url?scp=85149071455&partnerID=8YFLogxK
U2 - 10.1039/d2nr07128b
DO - 10.1039/d2nr07128b
M3 - Journal article
C2 - 36810774
AN - SCOPUS:85149071455
SN - 2040-3364
VL - 15
SP - 5284
EP - 5292
JO - Nanoscale
JF - Nanoscale
IS - 11
ER -