Your question is confusing. Are you looking to make, for example, a 5% Pd on CeO2 material? If so, then you need a reduction not a calcination step.

Dear Vijaya Kumari

Calcination at 500C is necessarily as a must for structural densification and thermal stability beside obtaining highest practical performance for these composites as by :

elimination of the polymer templates in case you going for the fabrication of hollow Pd–CeO2 nanocomposite spheres by hard-polymeric template method in an aqueous phase.

At higher calcination temperature 700C some Pd atoms may dissociate from Pd particles and commonly be incorporated into the CeO2 crystallites during the calcination at 700C and even more at 800C, which causes an increase in the concentration of surface Pd species.

At 700 -800C, the growth of CeO2 crystallites leads to the surface shrinkage of the ceria and a decrease in its surface area. Thus the Pd NP number per square meter would increase, resulting in the higher surface concentration of Pd species for the sample calcined at 700 C than that of the sample calcined at 500 C.

So the calcinations process is necessarily for obtaining stable and high product performance

Best regards

Just ensure that while doing calcination you should use reducing environment of H2 gas. Otherwise Pd will get oxidised.

Yes dear Ranjit Kumar thank you for your valable and interesting comment.

I would like to introduce the oxidation concept of Pd as that palladium oxide found to dissociate to Pd metal and oxygen at 800°C in air at atmospheric pressure so most calcinations process for Pd- CeO2 composite done in simple muffle furnaces.

Best regards

Mohammed Hussein j. H. Al'Atia

PdO will reduce to the metal at room temperature with H2....

Dear Alan F Rawle thank you for your vital comment.

As I said in my first answer; the function of the high temperature calcination is to obtain the required structural densification and thermal stability, and so revealing the highest composite operating performance. So the palladium oxide reduction is not the only the target which is easy to done at room temperature with H2.

Best regards…