title: Diffusion-driven and size-dependent phase changes of gallium oxide nanocrystals in a glassy host.
abstract: 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 γ-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 γ-Ga2O3 into β-Ga2O3. Differential scanning calorimetry registers an irreversible endothermic process at ∼1300 K, well above the exothermic peak of γ-Ga2O3 nano-crystallization (∼960 K) and below the melting temperature (∼1620 K). Transmission electron microscopy and X-ray diffraction data clarify that glass-embedded γ-Ga2O3 NCs transform into LiGa5O8via diffusion-driven kinetics of Li incorporation into NCs. At the endothermic peak, β-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.
authors.affiliation: P.D. Sarkisov International Laboratory of Glass-based Functional Materials, Mendeleev University of Chemical Technology of Russia, Miusskaya Square 9, 125047 Moscow, Russia.
authors.forename: N V
authors.initials: NV
authors.lastname: Golubev
authors.forename: E S
authors.initials: ES
authors.lastname: Ignat'eva
authors.forename: V N
authors.initials: VN
authors.lastname: Sigaev
authors.forename: A
authors.initials: A
authors.lastname: Lauria
authors.forename: L
authors.initials: L
authors.lastname: De Trizio
authors.forename: A
authors.initials: A
authors.lastname: Azarbod
authors.forename: A
authors.initials: A
authors.lastname: Paleari
authors.forename: R
authors.initials: R
authors.lastname: Lorenzi