Diffusion-driven and size-dependent phase changes of gallium oxide nanocrystals in a glassy host

作者：Golubev N V; Ignat'eva E S; Sigaev V N; Lauria A; De Trizio L; Azarbod A; Paleari A^*; Lorenzi R

来源：Physical Chemistry Chemical Physics, 2015, 17(7): 5141-5150.

DOI：10.1039/c4cp05485g

Phase transformations at the nanoscale represent a challenging field of research, mainly in the case of nanocrystals (NCs) in a solid host, with size-effects and interactions with the matrix. Here we report the study of the structural evolution of gamma-Ga2O3 NCs in alkali-germanosilicate glass - a technologically relevant system for its light emission and UV-to-visible conversion - showing an evolution drastically different from the expected transformation of gamma-Ga2O3 into beta-Ga2O3. Differential scanning calorimetry registers an irreversible endothermic process at similar to 1300 K, well above the exothermic peak of gamma-Ga2O3 nano-crystallization (similar to 960 K) and below the melting temperature (similar to 1620 K). Transmission electron microscopy and X-ray diffraction data clarify that glass-embedded gamma-Ga2O3 NCs transform into LiGa5O8 via diffusion-driven kinetics of Li incorporation into NCs. At the endothermic peak, beta-Ga2O3 forms from LiGa5O8 dissociation, following a nucleation-limited kinetics promoted by size-dependent order-disorder change between LiGa5O8 polymorphs. As a result of the changes, modifications of UV-excited NC light emission are registered, with potential interest for applications.

• 出版日期2015
• 单位北京化工大学