it will be better to work under N2 ...or vaccum may give the required results

It will be better first go for  DSC (differential scanning calorimetry) measurement,  there u will get crystallization peak temperature. That temperature is u r calcination temperature. 

Better to work with Nitrogen atmoshere and/or vacuum.

during co-precipitation the products generally precipitates as complex hydroxides. to find out annealing temperature you can either carry out TGA or DSC of your sample. e.g. there should be weight loss at certain temperature and after some point the curve become flat. The point at which the TGA curve starts becoming flat is your proposed calcination temperature point. You can then anneal your products at that specified temperature for some period of time; say for example two to three hours. hope that you get your answer.

Dear surajith,

To find out calcination temperature for Fe3O4 nano particles, better go for TG/DTA analysis. From that you can find out temperature.

In any case one does not do such treatment in air. Even at RT it would oxydise. Use pure Nitogen or Argon;

In order to obtain magnetite (Fe3O4 try to calcine at elevated temperature (> 1000 C)

From the phase diagramme one can see that Fe3O4 is stable at T>1000C even in air. But the problem is to cool it to RT. In this case it is necessary to use intert atmosphere.

Thank you all,

Hope now my problem will be solved

Utrapure Nitogen or Argon

Nitrogen or Argon at 400 ºC would do. Vaccum also. Try to look at a Fe2O3-Fe3O4 phase diagram, to see equilibrioum lines.

try to calcine the hematite Fe2O3 at 1200°C or mor for the obtention of Fe3O4 without and it don't need vacuum or nitrogen, or between 400° to 500°C with vacuum or nitrogen atmosphere

Anyone share me articles(from known journals) that support the calcination of iron oxide nano particle synthesized by copreciptation method? Thank you!!