Synthesis and characterization of nanocrystalline zinc aluminate spinel by sol–gel technique using modified alkoxide precursor

• Published in: Journal of sol-gel science and technology 2008-05, Vol.46 (2), p.152-160
• Main Authors: Kurajica, S., Tkalcec, E., Sipusic, J., Matijasic, G., Brnardic, I., Simcic, I.
• Format: Article
• Language: English
• Subjects: Aluminum; Ceramics; Chelating agents; Chelation; Chemistry; Chemistry and Materials Science; Colloidal gels. Colloidal sols; Colloidal state and disperse state; Composites; Crystallites; Crystallization; Differential thermal analysis; Exact sciences and technology; Fourier transforms; Gels; General and physical chemistry; Glass; Gravimetric analysis; Heat treatment; Infrared analysis; Inorganic Chemistry; Materials Science; Nanocrystals; Nanotechnology; Natural Materials; Nitrates; Optical and Electronic Materials; Original Paper; Photomicrographs; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Sintering (powder metallurgy); Sol-gel processes; Spinel; Thermal evolution; Transmission electron microscopy; X-ray diffraction; Zinc
• ISSN: 0928-0707; 1573-4846
• DOI: 10.1007/s10971-008-1707-2

Nanosized zinc aluminate spinel (gahnite, ZnAl 2 O 4 ) powders were prepared by sol−gel technique at low sintering temperatures. Aluminium- sec- butoxide [Al(O s Bu) 3 ] and zinc nitrate hexahydrate Zn(NO 3 ) 2  . 6H 2 O were used as starting materials. Gels with and without chelating agent were prepared. Ethyl-acetoacetate (C 6 H 10 O 3 ) was used as a chelating agent in order to control the rate of hydrolysis of Al(O s Bu) 3 . The dried gels and thermally treated samples were characterized by means of Differential Thermal Analysis and Thermo-Gravimetric Analysis (DTA, TGA), X-ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR) and Transmission Electron Microscopy (TEM). The surface area was measured by Brunauer-Emmet-Teller (BET) adsorption–desorption isotherms. It has been established that chelation enables to obtain a transparent gel. The thermal evolution of gels was characterized by two crystallization processes in the range 200–400 °C and 600–700 °C. Both processes yielded pure ZnAl 2 O 4 as evidenced by XRD, i.e. zinc aluminate spinel powders were produced by gel heat-treatment at temperatures as low as 300 °C. The average gahnite crystallite size for the samples sintered in the temperature range of 400–1000 °C has been calculated from the broadening of XRD lines revealing that nanocrystalline powders were prepared. The surface areas measured for the samples fired at 700 °C for 2 h were 43.1 and 62.6 m 2  g −1 , for sample without and with the chelating agent, respectively. TEM micrographs confirmed the nano-scale size of particles.