EXPERIMENTAL SET-UP FOR DETERMINING THE TEMPERATURE-OXYGEN PARTIAL-PRESSURE CONDITIONS DURING SYNTHESIS OF SPINEL OXIDE NANOPARTICLES

Nanometric spinel oxide powders, Fe3-xMxO4, where M is a transition el ement, have been synthetized by soft chemistry. This method generally leads to a non-stoichiometric phase, Fe3-xMxO4+delta where delta is th e deviation from stoichiometry so that further annealing at low temper atures around 450 degrees C and low oxygen partial pressure around 10( -25) Pa given by N-2/H-2/H2O gas mixtures is required: this enables a stoichiometric compound to be obtained and a nanometric size to be mai ntained. The complete set up consisting of a gas mixer, a thermogravim etric apparatus and a preparative furnace is described. Some results c oncerning the conditions of temperature and oxygen partial pressure le ading to stoichiometry are given in the case of vanadium ferrites cont aining or without Co.