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Hydrothermal Synthesis of ZnAlGaO₄ and the Effect of the Post-Heat Treatment on the Enhancement in Crystallinity

K. Sakoda, M. Hirano

Journal of Ceramic Science and Technology, Vol. 6, No. 1 (2015), pp. 9-16

DOI: 10.4416/JCST2014-00031

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Abstract

Spinel-type nanoparticles with a ZnAlGaO4 composition were directly synthesized from the aqueous precursor solutions of ZnSO4, Al(NO3)3 and Ga(NO3)3 under hydrothermal conditions at 150 ∼ 240 °C for 5 h in the presence of tetramethylammonium hydroxide. The resulting changes in the structure and properties of as-prepared ZnAlGaO4 spinel in the course of heating in air up to 1000 °C were investigated. The cell size of the as-prepared spinel phase slightly decreased as the hydrothermal treatment temperature increased from 150 to 240 °C. The nano-sized crystallite at around 8 nm of as-prepared spinel phase formed at 180 °C was maintained up to 600 °C and grew to 44 nm as the heat-treatment temperature rose from 600 to 1000 °C. The cell size of the spinel nanoparticles slightly and gradually changed during heat treatment up to 800 °C, and it almost accorded with the ideal value reported in the reference after heat treatment higher than 800 °C. The UV-blue light emission centered at 360 nm with relatively high intensity that was observed in the as-prepared spinel under excitation at 270 nm changed depending on the heat-treatment temperature. After heating at 800 °C, the spinel showed broad-band emission centered at around 430 nm.

Keywords

Oxides, chemical synthesis, spinel, crystal structure, optical properties

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