DETERMINING THE DEGREE OF CRYSTALLINITY IN SEMICRYSTALLINE MATERIALS BY MEANS OF THE RIETVELD ANALYSIS

Rietveld analysis has enabled a determination, by an internal approach, of the degree of crystallinity of a sample of polyethylene terephthalate (PET) and three samples of zirconium oxide obtained by precipitation from ZrOCl2 followed by crystallization at a different temperature. After subtraction of the air scattering, a global diffuse scattering produced by the amorphous phase, by the thermal and lattice disorder and, lastly, by the incoherent or Compton scattering, was built up in the frame of the DBWS-9006PC computer program written by Sakthivel and Young [(1990), Georgia Institute of Technology, Atlanta, GA, USA], modified as described by Riello, Fagherazzi, Clemente and Canton [J. Appl. Cryst. (1995), 28, 115-120]. All these contributions (and the corresponding spending scale factors) were simultaneously optimized, together with the crystalline peak profiles. On the basis of the modified Rietveld analysis, an equation has been suggested that calculates the degree of crystallinity. The value found in the examined PET sample is very close to that already calculated [Polizzi, Fagherazzi, Benedetti, Battagliarin and Asano (1990). J. Appl. Cryst. 23, 359-365] with nonstructural fitting procedure.