Synthesis and characterization of ZnAI2O4 precursor in relation to different basic media

Central Glass and Ceramic Research Institute, Kolkata-700 032, India
Department of Chemistry, Jadavpur University, Kolkata-700 032, India
Ceramic Engineering Division, Department of Chemical Technology, University of Calcutta, 92, A. P. C. Road,
Kolkata-700 009, India
E-mail: tapanparya@yahoo.co.in Fax: 91-33-23519755
Manuscript received 18 July 2003, revised 6 January 2004, accepted 19 March 2004

The role of different basic media for the preparation of Zn-Al based hydroxy compounds, leading to the formation of ZnAI₂O₄
spinel at low temperature was investigated. Nitrate salts of respective cations with molar ratio for ZnO : Al₂O₃ as 1 : 1 were
used for coprecipitation. DTA, TGA, XRD, IR spectroscopy and SEM technique were utilised for characterization of the
precursor hydroxy compounds as well as the final products obtained by heat treatment of the hydroxy compounds at different
temperatures. It had been found that spinel formation was very much influenced by the nature of mixed hydroxide
precursors obtained by using different basic media. The thermal treatment of the coprecipitated gel powders led to the formation
of ZnAI₂O₄ at relatively low temperature (500°). Mixed hydroxide gel powder obtained by using NH₄OH-hexamethylene
tetramine (HMT) as basic medium was observed to exhibit best results so far as spinel formation at low temperature was concerned.