Study On Morphology And Property Of Nano-Sized Gallium Oxide And Zinc Gallate By Hydrothermal Method

This paper is the study on synthesis of nano-galium Oxide and its salt by hydrothermal method. In our study, GaOOH,α-Ga2O3 andβ-Ga2O3 nanowires and nanoparticles were fabricated through a facile hydrothermal method under mild conditions with adding sodium dodecyl benzene sulfonate at 140℃. The diameter of GaOOH nanowires are 20 nm and length are 2μm (ratio=100).α-Ga2O3 andβ-Ga2O3 nanowires could also be obtained via a thermal decomposition method by using GaOOH nanowires as the precursor. GaOOH nano-particles of 5 nm were obtained by adding sodium acetate to the solution at 170℃. From the PL spectrum of GaOOH nanowires, the emission peak at about 390 nm was first measured and which may be ascribed to the anionic vacancies of OH-while no emission peak could be observed at the GaOOH nano particles. This observation indicates that the unique structures of the GaOOH have important influence on their PL properties. The emission peak ofα-Ga2O3 nanowires was at about 450 nm and the emission peak ofβ-Ga2O3 nanowires was at about 437 nm. The reason is the combination of an electron on a donor formed by oxygen vacancies and a hole on an acceptor formed by gallium vacancies and gallium-oxygen vacancy pairs. The PL intensity ofβ-Ga2O3 is higer than that ofα-Ga2O3, which can be ascribed to the surface defects and crystallinity of samples.Eu-doped GaOOH nanoparticles were prepared by hydrothermal thermal method using SDBS and the particle size of nanosized GaOOH:Eu3+was 5-8 nm. Eu-dopedα-Ga2O3 andβ-Ga2O3 were further fabricated by annealing GaOOH:Eu3+and the morphology remained unchanged but the particle size grew to 50 nm. The particle size of GaOOH:Eu3+nanoparticles by adding SA at 170℃was 5 nm. The five emission bands of nanoparticles by adding SDBS corresponded to 5D0→7Fj (j=0-4) transitions of Eu3+and the samples by SA only have two emission bands which corresponded to 5D0→7F1 and 5D0→7F2. The emission intensity ofα-Ga2O3:Eu3+is superior to that ofβ-Ga2O3:Eu3+ and GaOOH:Eu3+also has high emission intensity. This phenomenon could be explained according to the crystal structure of GaOOH,α-Ga2O3 andβ-Ga2O3 and the size of the particles. The crystal structure of GaOOH was reported to be analogous to the diaspore (α-AlOOH) type, consisting of double chains of an edge-shared octahedron Ga3+O6 connected with O-H. The structure of GaOOH:Eu itself is asymmetry, and it is reported that the 5D0→7 F2 red emission of Eu3+belongs to hypersensitive transitions, which is strongly influenced by the outside surroundings.α-Ga2O3 has the corundum structure with R 3C symmetry. The oxygen ions are approximately hexagonal close packed. The crystalline structure can be described in terms of GaO6 octahedra. The monoclinic phase ofβ-Ga2O3 has C2/m symmetry. The Ga atoms have GaO4 tetrahedral and octahedral coordinations in the lattice and the two kinds of Ga3+ions are in equal quantity. It is easier for Eu3+to replace the octahedral Ga3+than the tetrahedral Ga3+in the host lattices. A lower symmetry local site can result in a higher emission intensity, so the emission intensity ofα-Ga2O3:Eu3+is higher than that ofβ-Ga2O3:Eu3+. The maximium doping concentration of GaOOH:Eu3+,α-Ga2O3:Eu3+,β-Ga2O3:Eu3+with SDBS is 7 mol% and the doping concentration of samples with S A is 10 mol%.The particle size of ZnGa2O4:Eu3+nanoparticles by hydrothermal method with SDBS is about 5-8 nm at 170℃. The emission peaks at 591 nm and 618 nm were obtained. The emission at 591 nm originates from the magnetic dipole allowed 5D0→7F1 transition, indicating that Eu3+ions occupy a site with inversion symmetry and 618 nm from electric dipole allowed 5D0→7F2 transition, which results in a large transition probability in the crystal field with inversion antisymmetry. The maximium doping concentration of ZnGa2O4:Eu3+phosphor was 11 mol% and the Eu3+ concentration is 3.3 times of the samles that had been reported. ZnGa2O4:Dy3+ and Ga2O4:Mn2+synthesised by hydrothermal method had only blue emission of broud band and this indicates that they can not be synthesised by hydrothermal method.