High-resolution time-of-flight measurements of the lattice parameter and thermal expansion of the icosahedral phase Al62Cu25.5Fe12.5

Abstract

The lattice parameter of the stable icosahedral phase Al62Cu25.5Fe12.5 has been accurately measured over a wide temperature range from liquid nitrogen up to 873 K by powder diffraction. The experiment has been carried out on the High‐Resolution Powder Diffractometer time‐of‐flight instrument at the ISIS spallation source and a particular analysis of the peak profiles is given. The thermal‐expansion coefficient at room temperature of the i‐AlCuFe is half the value of pure aluminium but its temperature dependence is the same.

Icosahedral AlCuFe quasicrystal at high pressure and temperature and its implications for the stability of icosahedrite

“…The observed linear increase of d -spacings with temperature, as well as the absence of significant anisotropy during thermal expansion are evidence of the stability of i-AlCuFe at high pressure within the duration of our experiments. Further, the thermal expansion coefficients obtained from the fits are consistent with those discussed above reported by Quivy et al29 from ambient pressure measurements and show the large kinetic stability. However, it should be noted that approximant phases might form as the icosahedrally symmetric phase is unstable.…”

“…This data can be fit using a second-order polynomial equation, where a 6D0 = 12.49 Å, T is the temperature in Kelvin, and α and β are the thermal expansion coefficients. Interestingly, we fit our data using equation (2) with the values of α and β obtained by Quivy et al29 for Al 62 Cu 25.5 Fe 12.5 (4.67 × 10 −5 Å −1 K −1 and 5.22 × 10 −8 Å −1 K −2 , respectively). The good fit indicates either that effects of chemical variations in the thermal expansion coefficients are small or that there is a negligible pressure effect on the volumetric expansion of icosahedrite.…”

A high temperature furnace for in situ and time-resolved x-ray diffraction studies

“…This is in agreement with the small thermal gradient measured by means of both a pyrometer and a second inner thermocouple with variable position at the sample holder. Figure 4 shows the lattice parameters obtained by measuring ten Bragg peaks of the quasicrystal at each temperature ͑squares͒ compared with the dependence reported by Quivy et al 16 ͑solid line͒. The difference between the thermocouple reading and the sample temperature observed in Fig.…”

“…The calibration of the thermocouple reading was made using the phase transformation and melting point of some well known compounds 9 and, in a continuous way, by following the variation of a lattice parameter of the Al 62 Cu 25.5 Fe 12.5 quasicrystal up to 1100 K. This lattice temperature dependence was accurately measured by Quivy et al 16 This system was chosen due to its high sensitivity to oxidation and contamination which allowed us to test the vacuum level and heater pollution. This quasicrystal structure has the advantage of having very narrow diffracted peaks ͓full width half maximum ͑FWHM͒ of 0.0012°͔ that permits the determination with a high accuracy of the peak positions and the presence of any temperature gradient in the sample.…”