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Need information

  1. Sep 30, 2009 #1
    need urgent information

    Dear All,

    Can anyone inform me the following things on urgent basis ?

    - The crystal structure of Bi2Te3 is Rhombohedral or Hexagonal ?
    - How can I calculate the grain size from the XRD data/curve for Bi2Te3 ?
    - how to calculate the lattice parameter of Bi2Te3 (Rhombohedral/Hexagonal crystal structure) from the XRD data/curve ?

    Providing such information would be very much helpful to me.

    Sincerely
    Mahedi
     
  2. jcsd
  3. Oct 1, 2009 #2

    drizzle

    User Avatar
    Gold Member

    Re: need urgent information

    not so sure about your first question, Bi2Te3 can posses both structures..
    to calculate the grain size [g]:
    g=0.9λ/Bcosθ
    where,
    0.9 is the shape factor
    λ is the wavelength of the Cu Kα1 radiation [λ =1.5406×10-10 m]
    B is the band width at half maximum [BWHM], and here’s how to get it:
    in the diffraction pattern and at an exact Bragg angle, find the maximum intensity value, divide it by 2, you would have 2 points with the same value on both sids of the peak [illustrated below]:
    http://img12.imageshack.us/img12/5416/31327198.png [Broken]

    B= 2θ2-2θ1 [B should be measured in Radians]

    To find the lattice parameters, you use two equations
    1] Bragg’s law:

    n λ= 2d(hkl)sinθ
    set n=1

    2] the function that describe the inter-planar distance [d] as a function of the unit cell parameters and Miller indices, h, k and l. i.e. in the case of the hexagonal system:

    1/d2(hkl)=4/3[h2+hk+k2]/a2 + l2/c2

    hope I’m helping, good luck.
     
    Last edited by a moderator: May 4, 2017
  4. Oct 4, 2009 #3
    Re: need urgent information

    Dear Sir,
    Thanks for your kind information regarding my inquiry. Sorry for late reply as I was in vacation.
     
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