How can we determine the cation distributions in ZnFe2O4/CuFe2O4/CoFe2O4?

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How can we determine the cation distributions in ZnFe2O4/CuFe2O4/CoFe2O4?

Post by support » 23 May 2017, 13:49

Dear all,

In the literature, I found that the simplest way is to calculate the intensity ratios of diffraction lines I(220)/I(440), I(220)/I(400) and I(4 00)/I(4 40). These ratios are considered to be sensitive to the cation distribution. However, I don't know what I have to do exactly after I calculated these ratios. How can I find the distribution parameters (inverse parameter) ?

I hope someone can help me. Thank you for your time and consideration

How can we determine the cation distributions in CuFe2O4 or CoFe2O4 ?. Available from: https://www.researchgate.net/post/How_c ... or_CoFe2O4 [accessed May 23, 2017].
How did you calculate the intensity ratios without using the cation distributions?

Do you mean you calculated the experimental values?

Theoretically, There are many factors affecting the intensity of the diffracted X-rays spectrum, I, from powder samples such as the structure factor (F), multiplicity factor (MF), Lorentz factor (LF), polarization factor (PF), absorption factor (AF) and temperature factor (TF). These factors can be written as:

 I = (F)2 (MF) *(LF)*(PF)*(AF)*(TS)

 The multiplicity factor (MF) represents the number of the crystal planes, which have different orientations but with same spacing and structure factors. The values of the multiplicity factor for different crystalline structure planes can be found in many X-ray books.The polarization factor (PF) takes into account the X-rays diffracted part, which has connection with polarization property. The Lorentz factor (LF) for powder samples (which takes into account the sample size on the integrated intensity) depends on the diffraction angle. The polarization factor (PF) is usually combined with the Lorentz factor (LF) to give the combined Lorentz-Polarization factor, (LP)={[1+cos2(2θ)]/[sin2(θ).cos(θ)]}.

Ignoring the temperature effects and after some approximation this equation will be reduced to:

 Ith = (Absolute F)2 * (MF) * (LP).

Now you have to calculate F using the proposed cation distribution. At the end you are going to have the experimental and theoretical ratios of the intensity. If you find a differences between them  you have to go back to the proposed cation distributions and changed it then redo the calculation. Repeat till you find the acceptable cation distributions.

Good Luck

How can we determine the cation distributions in CuFe2O4 or CoFe2O4 ?. Available from: https://www.researchgate.net/post/How_c ... or_CoFe2O4 [accessed May 23, 2017].

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First off all, to the ans, there are no of experiments which can give you cation distribution, like....XRD, Mossbauer, XANES or even SQUID. But every expt has its own limitation. Thus exact quantification of the distribution is tough. Every case the analysis is mathematical.

You can also use Rietveld refinement of the PXRD data to find out the distribution. 

How can we determine the cation distributions in CuFe2O4 or CoFe2O4 ?. Available from: https://www.researchgate.net/post/How_c ... or_CoFe2O4 [accessed May 23, 2017].


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