The mixture of aq. Ba(NO3)2 and aq. urea in ethylene glycol was stirred at 110 oC for 12 h to afford the white precipitate. The obtained material is expected to be hydrated BaCO3, which was further subjected to calcination at 750 oC for 10 h to afford BaCO3.
Can anyone suggest the exact phases present before and after calcination in the attached data?
you should post your data as ASCII file. Only by comparison it is hard to say. And the radiation you used of course. Any additional information will be helpful, e.g. which instrument, which geometry, which slits etc.
At the first glance, you have witherite in both cases, but with lower crystalinity before calcination. But I agree with Gert, it is easy to miss something without real data.
Also, there is an additional difficulty with the heavy elements of the second group: their oxides/hydroxides easily absorb moisture from air and become almost invisible by the laboratory XRD. So even if your powder pattern has only BaCO3 peaks, I still recommend to make a classical chemical analysis to be sure that you really obtained what you expected.
Thanks Dr. Gert and Dr. Alexander. I have attached raw data of both materials.
X-ray diffraction (XRD) patterns were recorded on Rigaku Rotaflex spectrometer at 2θ range of 10–70° with Cu Kα radiation.
As Dr. Gert said u need to provide the full data information contains a spesific information of the instrument. With that one cud create the instrument profile if U wanna get another information sucha as crystalli size, strain, etc.
Also as Dr Alexander said; U need additional elemental analysis.
Anyway, if just from the diffractograms, it shows a single phase of BaCO, and a grain growth after calcination.
I attached a premliminary result from search-match with HSP and simple refienement. .
There are some details of your data that you should take into account.
1. The intensities do not correspond to the expected for BaCO3. I managed to make rough refinement of your data as a mixture of the 1/3 of randomly oriented particles and 2/3 of the particles with preferred orientation along (100) direction, but this still does not explain all features.
2. The shape of some peaks looks bad. I attach the plots of the {200} and {311} peaks. It looks like there are some narrow peaks on top of the broader ones. This may mean that you have large crystals with corresponding orientations.
These two observations might mean that your sample was not prepared properly. I would recommend to repeat the measurement after additional grinding. Also, check the literature about the ways of reducing the degree of preferred orientation.
3. There is a small peak at ~41.8 which is not described by BaCO3. However, it can also be just a distortion of the {122} peak of BaCO3 due to bad quality of the sample.
4. Even though the maximum at ~16.85 is close to the expected position of the {101} peak of BaCO3, it is too broad compared with all others. I would check the possibility of presence of Ba(OH)2 or its hydrates.
Thanks to Dr. Alexander and Dr. Maykel for your comments and explanation regarding my query.
Given the details you provided witherite is what you would expect. From a visual inspection this looks sensible, ref below. Additional phase may not be crystalline so will not be observed in the XRD data, the higher temperature polymorph of BaCO3 (R-3m) has significant reflection overlap with witherite nd at low concentrations might not be obvious. Knowing why you want to know which phases are present would explain what level of answer is required. As the structure of witherite looks to be layered it is conceivable you have stacking faults which would be difficult to model using a standard Rietvled program. If so modelling these could make up the chapter in a PhD or masters thesis.
"BaCO3: high-temperature crystal structures and the Pmcn - R3m phase transition at 811 °C". Antao S.M., Hassan I. Phys. Chem. Miner. 34, 573,580 (2007).
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