TITLE:
Quantitative Phase Analysis Based on Rietveld Structure Refinement for Carbonate Rocks
AUTHORS:
Mehmet Tamer
KEYWORDS:
Quantitative Phase Analysis; Rietveld Structure Refinement; Reference Intensity Ratio; Calcite; Dolomite; TOPAS
JOURNAL NAME:
Journal of Modern Physics,
Vol.4 No.8,
August
28,
2013
ABSTRACT: QPA (Quantitative Phase Analysis) of carbonate rocks bearing calcite
and dolomite using X-ray diffractometry (XRD) can be performed using the
combined Rietveld Structure Refinement (RSR) and semiquantitative Reference
Intensity Ratio (RIR) methods, providing an estimation of crystalline phase in
a mixture. Different ratios of five samples were prepared by mixing these
crystal minerals with high sensitively. The scan speeds, adequate to determine
mineral phases in rock samples, were used as 6 degrees per minute with 0.08
steps. The XRD analysis with commercial TOPAS 3.0 program, defined by a new
generation of profile and structure analysis software, based on RSR provides Bragg
reflection profiles and the dimension of the unit cell of a phase. The weight
fractions of each phase were found by Le Bail and Pawley methods in RSR using a
pseudo-Voigt peak shape model. The samples were also characterized by using
X-ray fluorescence (XRF) and
atomic absorption spectrometer (AAS). These analyses were conducted to compare
these results with those obtained from the RSR. In addition to these, RSR of
phases is very important to improve the goodness of fit (GOF). Therefore, the
discussions of refinement of the carbonate mixing were made and a refinement
procedure was given for these mixing in detail. Taking advantage of the RSR
with the addition of an internal standard, the phase fraction of all the
crystalline phases as well as the amorphous component, has been accurately
determined. RSR technique offers a valid support for the characterization of
marble in the light of industrial products.