Preeti Yadav
Not sure what you mean. Are you saying that you have the correct XRD data? After sol-gel did you calcine the sample? If so at what temperature?
Sorry, but we won't find anything closer from the picture. BiFeO3 has a perovskite structure and a space group R3c. The diffraction pattern in the attached figure is too complex for this trigonal group. It can be a mixture or something else. And what exactly is the question?
yeah, exactly my question i used sol gel method and for synthesis took nitrate subrates....i also got a homeogenous brown colour solution and then dried and calclined it at 800°C then what should be the problem with my sample?
Dear Preeti Yadav,
What is the problem with the sample? Most likely it is not BiFeO3, but something else, maybe a mixture of several phases. And how can you further fix this? It is necessary to perform a qualitative evaluation by comparing the measured diffraction data with the database. Alternatively, you can attach a raw or dat measurement file here. Maybe someone will evaluate it. I can try, but not until September.
Preeti Yadav
Mixtures may be tough to analyze - Rietveld may hold out some hope. I'd be looking for FeO, Fe2O3, Fe3O4, Bi2O3 and so on, as well as the different possible (ferrite) phase compositions. Your first port of call is the phase diagram for the system. You can find this in a fully available article on RG:
Article Synthesis, microstructure and properties of BiFeO3-based mul...
I attach this too. The phase diagram is Figure 4. Looking at this diagram will indicate the complexities of the system around 800 C.
Also look at the Ellingham diagram for the oxides - this will show the Gibbs free energy as a function of temperature. Figure 2 shows part from a (freely available) publication: Recovery of Antimony: A Laboratory Study on the Thermal Decomposition and Carbothermal Reduction of Sb(III), Bi(III), Zn(II) Oxides, and Antimony Compounds from Metal Oxide Varistors
Also on Wkipedia there's a really good section on (the complexity of) bismuth oxides: https://en.wikipedia.org/wiki/Bismuth(III)_oxide
The solid phases of Bi2O3 are important as these different structures will give you different XRD patterns.
Don't be fazed by all of this - a true scientist will act as a detective here combining all the evidence.
Preeti Yadav
I'm also interested in details of your synthesis route. You state that you used 'nitrate subrates'. Now the decomposition of bismuth nitrate is very complicated. From Wiki (https://en.wikipedia.org/wiki/Bismuth_oxynitrate) we have:
The thermal decomposition of bismuth nitrate pentahydrate proceeds through the following stages[16]
At < pH 1, Bi6O4(OH)4(NO3)6.4H2O (BiNO3.H2O) is the first solid product, which when heated produced Bi6H2O(NO3)O4(OH)4 (BiNO3. 0.5H2O.
Between pH 1.2 and pH 1.8, further hydrolysis occurs and Bi6O5(OH)3(NO3)5.3H2O is formed. The final oxynitrate product of thermal dehydration is believed to be Bi5O7NO3,[14] which is isostructural with β–Bi5O7 and has a layer structure.[17] The ultimate stage of thermal decomposition of oxynitrates is bismuth(III) oxide, Bi2O3.
I have retained the reference numbers present in the original. Now 'iron nitrate' could be in the ferrous (II; 2+) or ferric (III; 3+) states. We have in the latter case Fe(NO3)3·9H2O and again I suspect a possibly complicated decomposition. Iron (II) nitrate probably wasn't used as it is unstable to heat at room temperature and oxidizes to the III form.
The phase diagram above indicates that you have to be really careful with the molar proportions of the precursor oxides and temperature to form BiFeO3. Lots can go wrong and possibly did... Happy Bismuth to you...
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