Hi Linshina Thuluvath

In magnetite iron oxide Fe2+, and Fe3+ both present

In maghemite Fe3+ oxide

For the preparation of magnetite controlled reaction condition is required. You may use Fe(II) salt and Fe(III) salt for the preparation and may change the ration to get optimize result. For Fe(II) you may use Mohr's salt.

Hope for better result.

Regards

Hi Linshina Thuluvath

Adding to Arnab Mukherjee 's answer -

Also make sure you don't have significant oxidation of your Fe(2+) in the solution during the precipitation. This would mean working under nitrogen (if you are not doing this already).

In addition, you may try to vary the pH as well by changing the ammonia concentration, because Fe(3+) oxide tends to precipitate first and at lower pH and it may do so without coprecipitation of much Fe(2+), leading to maghemite instead of magnetite. Higher ammonia concentration should improve your odds.

Please see our recent publication

https://doi.org/10.1002/slct.202202976

I don't know your procedure, but in my tests I have found out that strong mixing and slow addition of basic solution (in reaction I have used, with iron chlorides, mixing and dripping the base in) also has bad effect.

The only difference between magnetite and maghemite is the Fe+2 on the inversed spinel structure. Thus, the oxidation atmosphere during the synthesis, drying and storage process should be considered. Otherwise, you won't be able to control its ratio.

You should adding ratio between Fe+2and Fe+3 1:2M than Ph equal 9