The behaviour of the lattice parameters in the Bi-Sn-Zn system

Abstract

Lattice parameters, coefficients of thermal expansion and mass density were determined by means of X-ray powder diffraction between 30 and 180 ºC (or 240 ºC - depending on samples' composition).Rietveld refinement was performed in order to obtain phases' lattice parameters at each temperature.The Panalytical XŽPert Pro MPD was used for room temperature X-ray diffraction experiments (RTXRD)with bulk samples. The aim was to identify the phases that were present in the sample, as wellas, their lattice parameters. For some samples, powder high temperature X-ray diffractionmeasurements (HT-XRD) were also performed, under a vacuum of 10-5 mbar or an argonatmosphere.It was found that the lattice parameters of (Bi), (Sn) and (Zn) don't change with the composition, atroom temperature, as expected since all samples belong to the three phase region. It was alsoconcluded that (Bi) behaves like an isometric crystalline solid on the contrary of (Zn) that hasdifferent expansion coefficients for different crystallographic directions a (= b) and c.