What parameters exactly the density will depend on? I tried densities are around 87% at 1350C at longer time periods. I tried higher temp also but densities are around that. Is there any possibility to improve densities above 95% by bulk method. There are some papers that mention doping with some elements increases density but I need only chromites with out doping.
Hi Venkat! Are you sintering a bulk sample? Could you explain more detail about the method you are using to make the your sample? If your method is hot-pressure, my suggestion is to increase the sintering pressure. 87% of density seems that there are still many pores inside your bulk sample, you can reduce them by press your sample harder.
Hi Venkat, I am afraid that your problem is the system itself. Chromites-based materials are quite difficult to sinter to high densities (even at temperatures>1600oC) in oxidizing atmospheres. This is due to the evaporation-condensation mechanism of gaseous Cr-O species controlling the sintering process rather than going through the typical solid-state diffussion process.
This is a common problem in Solid Oxide Fuel cells interconnect materials mainly based in chromites. You can find several papers related with that topic and addressing that problem.
If you do not want to use a dopant try to prepare your sample slightly deficient in Cr let say 3%. And better if the grain size of your starting power are in the sub-micrometer range or below.
Maybe u can try to re-mill ur sample, and apply pressure while re-sinter it. I agree with Juan, cause no way u can get high density while the evaporation still happen.
@Venkat: I think the problem is that the temperature and/or holding times of your hot-pressure system are not sufficient to sinter high density bulk. In that case, you can try other method like SPS (spark plasma sintering) or HIP (Hot isostatic pressing). Normally, HIP results in higher density than other methods because the sample is pressed from all directions.
That precursors do you use? Maybe you should decrease precursor particle size or use the "soft chemistry" precursors.
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