Introduction

      X-ray diffraction (XRD) analysis is the primary method of qualitative characterization of the materials. Generally, XRD is used for identification of the phases present in powder and solid material. It is also used to identify the crystal structure of an unknown material, measure the crystalline content of materials and determine the crystallographic lattice parameters. The identification is achieved by comparing the XRD pattern-'diffractogram' obtained from an unknown sample with an  internationally recognized database, Internationally Committee for Diffraction Data (ICDD). The ICDD which owned by Cluster Sustainable Engineering, School of Materials Engineering contained the latest database until 2013 and the contained references patterns are more than 200,000 phases.

Figure 1: Powder pattern information content.

               

     Generally, XRD has three main components, which is X-ray tube, sample holder and X-ray detector. Cathode ray tube generates the X-ray by heating a filament to produce the electron, the electron is accelerated toward the target by applying voltage and bombards the target material with electron. X-ray spectra ( Kα₁ and Kα₂₎ is produced when the electron has sufficient energy to remove from the inner shell electron of the target material. It obeys the Bragg's law:

nλ = 2d sin θ  

where the  
λ is the wavelength of the incident X-ray beam  (λ_Cu= 1.5406Å)      

d is the distance between atomic layers in a crystal

θ is Bragg's angle ( half value of the peak position)                  
    

Figure 2: Bragg's law reflection

          The XRD at Cluster of Sustainable Engineering is a type of powder X-ray Diffactometer.  X-ray tube is copper (Cu) type (wavelength of Kα₁=1.5406Å) and generated at 30kV and 10mA. This modern XRD has the geometry of theta/theta which means that the sample position is not moved but only both X-ray sources and X-ray detector are moved during operation.

Figure 3: XRD of Cluster of Sustainable Engineering, School of Materials.

             Our XRD lab is equipped with EVA program which is a versatile tool to analyze diffractograms.   
X-ray diffactogram will be saved as a raw file with extension of .BRML or .RAW. The EVA program uses five different kinds of data objects such as SCAN, PATTERNS, PEAKS, AREAS and LEVELS.

          •SCAN – a diffractogram resulting from the collection of scattered X-ray radiation when analyzing   

                 sample. Original file will never change.

 •PATTERN – a pattern is the set of peaks of a given phase. It is a signature of crystalline phase. Use

                      PDF (ICDD) or COD to match pattern.

•PEAKS – automatic peak search treatment from the scan. Peak list is created. Information like 

                  intensity and 2 theta angle.

•AREAS – Calculate net intensity, full width at half maximum (FWHM).

•LEVELS -  working with multi-range data on plotting into one page.