Cluster packing from a higher dimensional perspective

The way to find the optimum packing of quasicrystal-constituting clusters is discussed based on the projected-cell approach. We illustrate why the quasiperiodic arrangement of partially overlapping clusters with decagonal or icosahedral symmetry is the most efficient one, by relating it to the packing of unit cells in hypercubic lattice

Diffuse and weak Bragg scattering from quasicrystals: pitfalls and opportunities

The influence of limited experimental reciprocal space resolution on the appearance of diffraction patterns from quasicrystals is discussed. Using simulated data from a perfectly ordered one-dimensional Fibonacci chain it is shown that realistic experimental resolution effects may lead to artificial ‘diffuse scattering' of significant intensity. Two different diffuse features are identified in simulations of macroscopically sized crystals. A broad and almost smooth diffuse background is found, which strongly inceases with decreasing reciprocal space resolution. In addition, a set of of narrow diffuse peaks having profiles similar to thermal and phasonic diffuse scattering is present, which is only seen in high resolution patterns. The former diffuse scattering represents unresolved Bragg reflections, while the latter is due to truncation effects coming from the finite crystal size. The relevance of the findings for the understanding of real experimental diffraction patterns is discussed on the examples of diffuse scattering from d-Al70Co12Ni18 and i-Al64Cu23Fe13. Finally, some criteria for distinguishing disorder diffuse scattering from artificial diffuse scattering are give

Laue centennial-100 years of X-rays diffraction Preface

ISSN:1433-7266ISSN:2194-4946ISSN:0044-2968ISSN:2196-710

Calcia-doped yttria-stabilized zirconia for thermal barrier coatings: synthesis and characterization

Doping with other oxides has been a stabilization method of ZrO2 for thermal barrier coating applications. Such a stabilized system is 7-8mol% YO1.5-doped zirconia (7YSZ), which has been in use for around 20years. In this study, calcia (CaO) and yttria (Y2O3) have been used for doping ZrO2 to produce a stable single-phase cubic calcia-doped yttria-stabilized zirconia (CaYSZ). This has been synthesized using wet chemical synthesis as well as by solid-state synthesis. Unlike partially stabilized zirconia where 5mol% CaO is doped into ZrO2, CaYSZ has been found to be stable up to 1600°C. Detailed CaYSZ synthesis steps and phase characterization are presented. Wet chemical synthesis resulted in a stable single-phase CaYSZ just after 4h treatment at 1400°C, whereas a 36h annealing at 1600°C is required for CaYSZ synthesis during solid-state processing. The CaYSZ has been found stable even for 600h at 1250°C. Coefficient of thermal expansion and sintering temperature of CaYSZ was found to be 11×10−6K−1 and 1220°C, respectively, which are comparable to 7YSZ. An increase in sintering rate with increasing dopant concentration has also been observe

Compressibility of Al64Pd30.4Fe5.6

The stability of C2-Al64Pd30.4Fe5.6, an approximant phase to the icosahdral Al-Fe-Pd quasicrystal, has been investigated by high-pressure X-ray diffraction using a diamond-anvil cell and synchrotron radiation up to 24.30(1) GPa. The material is structurally stable within the framework of the experiment. The unit cell volume as a function of pressure follows a second-order Birch-Murnaghan equation of state with K0 = 169.5(2.5) GPa. This value is comparable to that of other quasicrystals and approximant phases containing Al and heavy transition metal

Compressibility of Al64Pd30.4Fe5.6

The stability of C2-Al64Pd30.4Fe5.6, an approximant phase to the icosahdral Al-Fe-Pd quasicrystal, has been investigated by high-pressure X-ray diffraction using a diamond-anvil cell and synchrotron radiation up to 24.30(1) GPa. The material is structurally stable within the framework of the experiment. The unit cell volume as a function of pressure follows a second-order Birch-Murnaghan equation of state with K0 = 169.5(2.5) GPa. This value is comparable to that of other quasicrystals and approximant phases containing Al and heavy transition metal