Functional homo- and heterometallic alkoxides as precursors for sol–gel routes to transparent ZnGa2O4coatings

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Abstract
New homo- and heterometallic [M(OR)3]m and [ZnM2(OR)8]m species (M = Al, Ga; R = C2H4OMe, C2H4NMe2) have been prepared and characterised by elemental analysis, electrospray mass spectrometry, FT-IR and multinuclear NMR. Hydrolyses of the heterometallic compounds were investigated and the particle sizes were determined. The thermal behaviour of the hydrolysed products was studied by TGA/DTA and the nature of the phases was analysed by powder X-ray diffraction. Various sol–gel processing parameters were studied in order to stabilise nanosized colloidal suspensions for access to thin films by spin coating. [ZnGa2(OC2H4OMe)8]2 was the best candidate for sol–gel processing, allowing crystalline ZnGa2O4 solids to be obtained at 300 °C. Films, obtained on glass and MgO substrates, were transparent (>95%) and characterised by UV-visible and X-ray photoelectron spectroscopies, tapping mode AFM, SEM, EDX and X-ray diffraction.