Synthesis of chemically pure b-phase powders of gallium(III) oxide

Abstract

The purpose of our study was to develop an optimal procedure for the synthesis of the b-phase of gallium(III) oxide with a high degree of chemical purity. Based on the analysis of the possible synthesis methods of the b-phase of gallium(III) oxide, we suggested a procedure which uses gallium(III) nitrate crystallohydrate as a precursor for obtaining the final product. The article demonstrates that during the synthesis of gallium(III) nitrate by means of direct interaction between metallic gallium and concentrated nitric acid, a hygroscopic crystallohydrate is formed with the formula Ga(NO3)3· 9H2O. Powders of the b-phase of Ga2O3 were synthesised by means of the thermal decomposition of gallium(III) nitrate in an oxygen atmosphere. Electron probe microanalysis (EPMA) and X-ray phase analysis (XRD) were used to determine the quantitative chemical composition, stoichiometry, and crystal structure of the gallium(III) oxide samples synthesised at different temperatures. The EPMA of the powders calcinated at temperatures Tcalc = 500–950 °C demonstrated that the ratio of the elements was constant and corresponded to the stoichiometric composition of Ga2O3. A comparative analysis of the X-ray diffraction peaks demonstrated that with an increase in the decomposition temperature within the range Tcalc = 500–950 °C, the symmetry of the structure of the Ga2O3 powders decreased from the cubic to the monoclinic. The study also determined that the samples of gallium(III) oxide synthesised at Tcalc = 950 °C are single-phase and consist entirely of the monoclinic b-phase. The XRD data was used to calculate the crystal lattice parameters of the samples of the b-phase of Ga2O3 synthesised at Tcalc = 950 °C

Keywords

• gallium (iii) oxide
• gallium (iii) nitrate
• polymorphous modifications
• stoichiometry
• crystal structure
• monoclinic crystal system
• lattice parameters