Report on the round-Robin test of revised XRD Gakushin-method

Abstract

The purpose of the round robin test is to establish the standard procedure for the X-ray diffraction (XRD) measurements of lattice parameters and crystallite sizes of carbon materials (revised Gakushin-method). 5 kinds of carbon samples, glassy carbon heat-treated at 2200°C, a raw coke, high modulus type of pitch based carbon fiber, isotropic graphite block and natural graphite powder, were prepared for the XRD round robin test as the first step in 2002. Two decades of participants (Japanese universities, institutes and companies) carried out the round robin test. The measurement of lattice parameters showed a high accuracy, being the measurement error within 0.0002 nm in the case of graphitized samples. However, the crystallite size measurements showed large scattered results. The coefficient of variation for the crystallite size measurements is more than 10 percent. To improve the accuracy of the crystallite size measurements, it is necessary to use a reliable silicon powder as the standard and to establish a judgment for suitable profile for the diffraction peaks of the standard silicon. In 2004, three samples using different kinds of silicon powder were prepared for the second step of the round robin test. As the consequence of the second step test, the sample with the commercial silicon powder for XRD measurement showed a relatively small scattered result. Moreover, permissible conditions for the profile of silicon diffraction peak were described on the procedure specification.