Synthesis and characterisation of MgCr2O4 spinel precursor

Central Glass & Ceramic Research Institute, Kolkata-700 032, India
Department of Chemistry. Jadavpur University, Kolkata-700 032, India
Ceramic Engineering Division, Department of Chemical Technology, Calcutta University,
92, Acharya Prafulla Chandra Road, Kolkata-700 009, India
E-mail : tapanparya@yahoo.co.in
Manuscript received 25 November 2004. revised 28 July 2005, accepted 5 August 2005

MgCr₂O₄ spinel was synthesized from Mg-Cr based hydrogels precursors prepared by coprecipitation technique. Ammonium hydroxide, ammonium carbonate and hexamethylene tetramine (HMT) used as different basic media for coprecipitation. Magnesium nitrate and ammonium dichromate were used as starting materials for the preparation of mixed solution containing Mg²⁺ and Cr³⁺ in molar ratio for MgO : Cr₂O₃ as 1 : 1. It had been noticed that spinel formation was influenced by the mixed hydroxides precursors derived by using different basic precipitating agents. DTA, TGA, XRD, IR spectroscopy and SEM technique were utilized to characterize the coprecipitates as well as the final products generated by heat treatment of the coprecipitates at different temperatures. Thermal treatment of the coprecipitates led to the formation of MgCr₂O₄ spinel at low temperature (500°C). Mixed hydroxides derived by using ammonium hydroxide medium was the most effective one towards the formation of MgCr₂O₄ spinel at relatively low temperature.