Hello Serdar

I guess the following:

- If you overheat metal oxides (under air or under inert atmosphere) the oxygen is lost

Therefore, to enrich with oxygen, heat the material at mild temperatures under oxygen. Try this please.

In principle, if an oxide is a perfect crystal you can't add oxygen more than its structure permits. However, various oxides have hydrated forms, so that you can add oxygen by adding water. Moreover, with not equilibrium techniques (for example ion implantation) you can add more oxygen by preparing unstable crystals.

I guess, B is Fe, isn't it? It is not simple task to oxidise all Fe to +4. Using ceramic synthesis it will require very high oxygen pressure (see for example Journal of Solid State Chemistry, V. 63 (1986) pp. 237–249). Using sol-gel synthesis and 1 atm oxygen stream you will probably manage to obtain the composition close to AFeO2.9.

thank you all, B is Co and when you increase to oxygen content the crystal structure will change. Some paper are said using high pressure synthesis can cause the formation of ABO3 structure, I need simple another technique

Dear Altin,

It seems to be possible when Oxygen ion beam at inert atmosphere irradiated in to the sample. Is it? Please comment on this.

the idea of oxygen ion irradiation is not useful idea whether possible or not

thank you, dear Vadim Sergeevich Gorshkov, your reply is more useful one,

As it has been already mentioned by others that it depends on which oxide material you want to use. In case of simple oxide (TiO2/SnO2), you can heat the sample in oxygen rich environment to increase the number oxygen. But keep in mind that this additional oxygen may not go into the lattice rather can be pre-adrosbed on the surface. In case of binary oxides ABOx, the oxidation state of A or B can be altered by heating in oxygen rich environment. For example if you have Ti and Al and you want to create TiAlOx, then there is a high possibility that you will have some phases of TiOx and AlxOy oxides, depending on the content of secondary material (in this case Al). If the chemical content of Al is very low then the possibility of creating Al2O3 is very little. 

I agree with Azhar.  Another possibility is your material might spontaneously form oxygen vacancy defects. Depending on the material,  morphology or size (e.g. Nanoparticles) the contributions from such a highly defective structure may add up. I would imagine heating the sample in air or a humid environment would help the stoichiometry,  but be aware for impurity phase formation. 

 There is possibility to increase oxygen content by grain boundary engineering introducing more defects. Another possibility is to heat the material in oxygen rich atmosphere and quench down. Bu you need to be careful in heating the materials because some materials dissociates at high temperature. You can put the material under electrical bias. It completely depends on character of your materials and application.

You can sinter-anneal the powder/film in oxygen rich atmosphere. You must know the optimized temperature, oxygen flow and time-temperature profile to induce the oxygen rather than deoxygenating it.

thank you all, according to The comments, we decided to use the high pressure over 30 tons and then annealing at high temperature under rich oxygen atmosphere. After xrd I will share the results with all of you