Dear Weilhua Tang
ththank you for considering our question.I know these chang.Is it possible none of them will not be changed after dopping of nitrogen?
Usually doping means "very small amount" of an element. In so far it might be that you don't see any visual effect in your diffractogram. However, you should check this with some analytical software in order to register even small changes which are hard to see with your eyes. Another possibility is, that you have a strong diffusion gradient and only the outer surface of your particles is doped. Then it might be that the major information is coming from the volume of the particles (undoped) and the doped material is only as small fraction hidden in the signal. Nevertheless, you should find (all) which has been listed already by Tang Weihua.
Dear Hosein Kamani,
Could You specify the order of N doping You were aiming at, or suspect? Independently on the structure (anatase, brookite, rutile) the O site is a more or less distorted octahedron. N-3 ionic radius in tetrahedra (Shannon) is 1.46A, O-2 in octahedra (Shannon) is 1.4A. I don't have the data on N-3 anion in octahedral position, but You see, the difference is very small.
As Tang Weihua mentioned, You should see a change in peak position, intensity and FWHM.
If the substitution is in the order of 1% You should be able to see a slight shift of the diffractogram to smaller angles. From the Bragg formula:
lambda = d*sin(theta) = const. (lambda - wavelength of the X-ray beam used, d - interplannar distanse, theta - angle of incidence),
You may expect lattice expansion (rise of d) from larger N atoms. For the product to remain constant, the sin(theta) must get smaller, so the angle of incidence decreases.
The X-ray scattering factor of N and O are very similar, so the change in intensity will be very difficult to register. If the doping was very high, the intensities should go down. The intensity of a specific plane depends on the number of atoms lying in it and on their type, so the change can affect some planes more than others if N picks up one position more eagerly than others.
That is in the ideal case. If the TiO2 and TiO2:N have different: oxygen vacancy concentrations, grain sizes (especially if they're nanoscaled), have different levels of strains You won't be able to see a repeatable difference.
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