Which information can you acquire from an XRD measurement?
crystalline phases (qualitative and quantitative)
structural paramenters (crystalline size, crystallinity, strain, crystal defects)
preferred crystal orientation
Name the crystal systemsand their shape.
What are the 14 bravais lattices?
Triclinic P
Monoclinic P, C
Orthorombic P, C, I, F
Tetragonal P, I
Hexagonal, Rhomboedrical
Cubic P, I, F
Simple or primitive (P) Body-centered (I) Face-centered (F) Base-centered (C)
Bragg equation?
d spacing for a cubic crystal
How is a x-ray diffraction for a single crystall conducted?
Shooting an x-ray through the crystal and analysing the diffraction.
What is the difference in the diffraction pattern between single crystals and powder samples (qualitatively)?
Single crystal: multiple single spots
powder: multiple rings
Describe the structure of a Bragg brentano diffractometer with a theta-2theta goniometer
What is the optimal grain size of powders for XRD?
d spacing for a tetragonal crystal?
What is the difference between Kalpha1, Kalpha2 and Kbeta radiation?
Kalpha1: Radiation of the highest energetic electron from the L orbit relaxating to the K orbit
Kalpha2: Radiation of the second highest energetic electron from the L orbit relaxating to the K orbit
Kbeta1: Radiation of the highest energetic electron from the M orbit relaxating to the K orbit
What is a qualitive and a quantitive analysis in the context of x-ray diffraction
qualitative: determine which phases are present
quantitative: determine how much of each phase is present
Which are the main fitting methoods for peak profiles?
Gaussian
Lorentzian
Pseudo-Voigt
What is the meaning of FWHM?
Full width at half maximum: the width of the peak at the half of the maximum intensity.
What is the definition of the integral breadth (IB)?
Integral of the peak divided by peak height (I_max)
What is the effect of preffered orientation (texture) on a xrd sample?
Distorting and moving the diffraction pattern
What are the effects of lattice strain?
uniform strain: movement of the peaks (residual stresses)
nun uniform strain: peak broadening
What is the difference between cristalline and amourphous polymers in XRD?
amorphous: no distinct peaks, very broad overall peak (halo)
crystalline: sharp narrow distinct peaks
What is the difference in analytical methods for xrd between without standard, with internal standard and with external standard?
without standard: intensity comparison between the different phases
with internal standard: mixture of sample wiht foreign material and comparison in intensity
with external standard: line intensity compared to pure phase of previous measurement
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