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The intermetallic phase FeGa3 belongs to the rare examples of substances with transition metals where semiconducting behavior is found. The necessary electron count of 17 ve/fu can be formally derived from eight Fe-Ga and one Fe-Fe two-center-two-electron bond. The situation is reminiscent of the well-known Fe2(CO)9 scenario, where a direct Fe-Fe two-center-two-electron bond was shown to not be present. Fe-Fe interaction in FeGa3 and its substitution variants represents the crucial point for explanation of electronic, thermal transport, and optical properties of this material. Chemical bonding analysis in position space of FeGa3 and Fe2(CO)9 on the basis of the topology of the electron localizability indicator distribution, QTAIM atoms, two- and three-center delocalization indices, domain natural orbitals, IQA analysis, and an evaluation of the Fe-Fe dissociation energy yields a complete picture of the partially compensated Fe-Fe bond, which is nevertheless strong enough to be of decisive importance. Structural reinvestigation of differently synthesized single crystals leads to the composition Fe1+ xGa3 (0 ≤ x ≤ 0.018), where the additional Fe atoms are predicted from DFT/PBE calculations to yield a magnetic moment of about 2 μB/Fe2 atom and metallic in-gap states. Accompanying magnetization and ESR measurements are consistent with this picture.

Sb-based compounds such as CoSb 3 and FeSb 2 are interesting materials for thermoelectric applications. Their single crystal growth can be achieved from high-temperature solutions that are strongly enriched in Sb. In Bridgman growth using closed ampoules, effective mixing of the solution is an important prerequisite in order to minimize the high risk of liquid inclusion formation. We have successfully grown inclusion-free single crystal of CoSb 3 and FeSb 2 by rotating the ampoule in a Bridgman-type crystal growth set-up being inclined by 75° with respect to the vector of gravity. Numerical modelling as well as experimental growth studies have demonstrated the strong influence of forced convection that is achieved by this modified directional solidification technique called Inclined Rotary Bridgman method.

Intermetallic compounds have proved to be interesting alternatives to heterogeneous catalysts prepared from pure noble metals or their alloys. As to study their intrinsic properties, to determine the crystalline structures of specific surfaces and finally to understand elementary processes of heterogeneous catalysis, single crystals of these intermetallics are needed. Inspired by the recent discovery of Ga–Ni catalysts for carbon dioxide reduction to methanol, we have grown for the first time cm3-size single crystals of trigonal Ga3Ni2. We report in detail on the synthesis and Czochralski growth from high-temperature solution using Ga as native solvent. Inclusion formation of Ga-rich fluid proved to be the most severe problem that was minimized by using an extremely low pulling rate down to 25 µm/h.

Intermetallic compounds in the binary Ga-Pd system have proved to be superior as catalysts in the semi-hydrogenation of acetylene. Partial substitution of Ga by Sn even increases the activity. In order to study elementary processes of catalytic reactions, well-oriented surfaces of single-crystalline slaps are needed, i.e. single crystal growth is a prerequisite. For the first time, solid/liquid equilibria including the solid solutions Ga1−xSnxPd and Ga1−xSnxPd2 were studied. Based on these findings single crystal growth of the two solid solution series succeeded using the Czochralski method from (Ga,Sn)-rich solutions. Inclusion-free single crystals of a few cm3 in size could be obtained. Due to different crystal structures of the end members, Sn substitution in Ga1−xSnxPd is restricted to x ≈ 0.15 in the cubic phase. Although a complete solid solution range for Ga1−xSnxPd2 has been reported by Armbruster et al. (2018), mixed crystals of the 1:2 phase can be grown from a native ternary melt only up to approx. x = 0.54 due to missing solid/liquid equilibria at a higher ratio of Sn substitution for Ga.

Quite recently intermetallic compounds have been investigated as catalysts for heterogeneous catalysis as they can be highly active regarding a specific reaction and often show advantages in selectivity and long-term stability. The intermetallic phase InPd (CsCl structure type) is considered to be a possible catalyst for methanol steam reforming. Single crystals are needed to study the basic processes of catalysis. Using the Czochralski technique, InPd single crystals were grown from In-rich solutions as to reduce the vapor pressure of In. The crystals show some unusual rough surface morphology and gradients concerning the main components composition. By adjusting the growth parameters like growth temperature and growth rate we succeeded to get inclusion-free single crystals.

Single crystal growth of the intermetallic compounds GaPd 2 , GaPd, and Ga 7 Pd 3 is described for the first time. These phases have recently been explored as highly selective heterogeneous catalysts in the semi-hydrogenation of acetylene. Well-oriented single-crystalline surfaces are needed to perform fundamental studies on catalytic processes. The three Ga–Pd phases were grown using the Czochralski method from Ga-rich solutions. Thermodynamic properties of the Ga–Pd system determine very different growth temperatures reaching from less than 460 °C for Ga 7 Pd 3 to about 1200 °C for GaPd 2 . Avoiding mother liquid inclusion formation proved to be the key problem that could be solved by pulling rates sometimes as low as 25 µm/h and forced convection by high crystal rotation rates. In the last grown part of GaPd 2 crystals decomposition into GaPd 2 /Ga 3 Pd 5 lamellas occurred which can be explained either by spinodal decomposition or by nucleation caused by the GaPd 2 stability region that becomes narrower with decreasing temperatures.

A comprehensive study of the BaF2–Ba3(BO3)2 phase diagram has revealed a significant difference between the two intermediate phases Ba5(BO3)3F and Ba7(BO3)4−y F2+3y . The latter exhibited (BO3)3− ↔ 3F− anionic substitution which, unusually, strongly influences the solidus temperature. A comparison of the Ba5(BO3)3F and Ba7(BO3)4−y F2+3y crystal structures, along with consideration of other compounds demonstrating (BO3)3− ↔ 3F− isomorphism, allows for the disclosure of the mechanism of (BO3)3− ↔ 3F− heterovalent anionic substitution in fluoride borates via [(BO3)F]4− tetrahedral groups being replaced by four fluoride anions. No exception to this mechanism has been discovered among all known phases with (BO3)3− ↔ 3F− substitution.

Bulk AlN single crystals (3 mm thick and 1 in. diameter) were hetero-epitaxially grown on (0001) 6H–SiC substrates by the sublimation method. Double-crystal x-ray diffraction and micro-Raman results confirm the good crystallinity as well as structural homogeneity of the grown crystals. The presence of low-angle grain boundaries was observed by x-ray diffraction rocking curve analysis and also supported by defect-selective etching analysis. The estimated defect density of the 3 mm thick crystals is about (5–8)×10 5 cm −2 . 3D-microstructures with different morphology were observed on the as-grown crystal surfaces and were interpreted to be originated from screw dislocations. These screw dislocations are decorated by carbon impurities as evidenced by micro-Raman spectroscopic measurements. SiC incorporation in the grown crystals was found to be fairly low with 4 mol% at 2 mm distance from the interface and varies slightly between different sub-grains.

Complex metallic phases in the Al-Cr-Fe system are considered to beinteresting because of their enhanced resistance against corrosion.Single crystal growth of the Al(4)(Cr,Fe) and Al(13)(Fe,Cr)(4) phases,which is a prerequisite for detailed studies is presented herein for thefirst time. Along with their binary end members Al(4)Cr and Al(13)Fe(4)growth of cm(3)-size crystals was achieved by using the Czochralskimethod from Al-rich solutions at temperatures of approximately 1000degrees C. Special emphasis is put on the refinement of the Al-richcorner of the ternary phase diagram in determining the 1000 degrees Cequilibria between the incongruent melts and the corresponding ternarysolid solutions. Our findings confirm earlier data on the existenceregion of Al(13)(Fe,Cr)(4), but significantly differ from those withrespect to the so called Al(4)(Cr, Fe) phase. It is shown that theexistence region of Al(4)(Cr,Fe) decomposes into four regions ofstructurally different phases depending on the Cr/Fe ratio. Binarymu-Al(4)Cr crystallizes in the hexagonal space group P6(3)/mmc and candissolve only up to about 1 At-\% iron. More Fe-rich alloys crystallizein the orthorhombic space group Cmcm (about 2 At-\% iron) or Immm(containing between 3 and about 6 At-\% iron). For crystals containingabout 7 At-\% iron the structure belongs to the space group R (3) overbar. The grown single crystals were characterized by electron probemicroanalysis revealing only weak segregation effects. The structuralperfection of the orthorhombic phase was studied using X-ray topographywith the Lang technique. Significant anisotropic properties of thisphase allow to discuss structural similarities with decagonalquasicrystals.

Directional solidification of ternary melts in a series of Al-based systems (Al–Co–Cu, Al–Co–Ni, and Al–Cu–Fe) has been studied using the Bridgman technique at a very low growth rate. These systems have been chosen to investigate the phase equilibria of quasicrystals and structurally complex crystalline compounds in the vicinity of quasicrystal-forming composition regions. The Bridgman-grown ingots were characterized by optical microscopy, electron microprobe analysis, powder X-ray diffraction, and differential thermal analysis. Using this combination, it was possible to study phase equilibria and crystallization processes with respect to the liquidus surface projection. The solidification paths for the ternary quasicrystal-forming alloys and structurally complex crystalline phases traced in the Bridgman-grown specimens have been discussed within the framework of the Scheil–Gulliver solidification model. It has been proved that the Bridgman method is a feasible tool to study the complex solidification processes of ternary alloys.

In the ternary Al–Co–Ni system, decagonal quasicrystals occur that have proved thermodynamically stable. Large single crystals can be grown using rather conventional crystal growth techniques from incongruent melts. Decagonal quasicrystals combine two different types of order, periodicity along the 10-fold rotational axis and non-periodic order perpendicular to it, which makes them particularly interesting for solid state physics. Based upon X-ray structure analysis data obtained from AlCoNi single crystals, the question has been discussed whether or not inclined net planes exist that intersect periodic as well as non-periodic directions in these quasicrystals. Several inclined net planes were proposed and ranked with respect to their structure amplitudes. We have studied single crystal growth of large decagonal Al72Co9Ni19 quasicrystals using the Czochralski method from Al-rich melts. The crystal surfaces show a remarkable faceting. Exact angle measurements by optical goniometry revealed that the observed morphological faceting perfectly corresponds to some of the theoretically predicted inclined net planes. Besides the two different decagonal prisms { 1 0 0 0 0 } and {1 0 1¯ 0 0} and the pinacoid { 0 0 0 0 1 } we have found the inclined planes of two decagonal dipyramids {0 0 1¯ 1¯ 1} and {1 0 1¯ 0 2}.

The solubility of gallium orthophosphate (GaPO 4 ) in 15 M phosphoric acid has been studied in the temperature range between 150°C and 250°C. The data were determined using an experimental set-up, which was especially designed for the purpose of dissolution as well as crystallization experiments. The measured values are discussed with respect to the question whether or not a considerable region of metastability exists. The temperature coefficient of the solubility has been found negative for temperatures up to about 250°C.

Single crystals of gallium orthophosphate (GaPO 4 ) being isostructural to low-quartz are usually grown from strong acidic solutions. To maintain a good structural perfection of the crystals, the growth rate of the respective growing interface has to be controlled. It is shown that striations are formed due to growth temperature changes, which are marked by a higher density of mother liquid inclusions. These induced striations have been used to determine the individual growth rates of the pinacoid {001} and the rhombohedral faces {011} at GaPO 4 single crystals.

Etch figures on gallium orthophosphate (GaPO4) crystals are presented for the {001}, {010},f2 10 g,f210 g and {101} faces. Primarily they are used in detecting possibly occurring domains of twinning. Generally, the etch figures of GaPO4 show similarities as well as dierences compared to those of low-quartz modifications of SiO2 and AlPO4. # 2000 Elsevier Science B.V. All rights reserved. PACS: 77.84; 61.72; 61.72.F; 61.72.M

A single crystal of Al4(Cr,Fe) with composition Al78Cr19Fe3 grown by the Czochralski method was studied by neutron diffraction for the first time. As a preliminary result the neutron diffraction experiment suggests a body-centered orthorhombic space group Immm with a = 1.24985(3) nm, b = 1.25500(3) nm and c = 3.0512(2) nm as found by Deng et al. (Pearson symbol: oI366-59.56) [1] using single crystal X-ray diffraction. Additionally, more or less diffuse maxima at positions with k = n/2 (n = odd) are clearly observable.

Phase transitions of gallium orthophosphate (GaPO4) have been studied by thermal analysis between ambient temperature and 1100°C. In situ X-ray powder diffraction at selected temperatures confirmed the three known polymorphic structure types of low-quartz, low-cristobalite and high-cristobalite GaPO4, respectively. Whereas the as-synthesized powder retained its low-quartz structure up to 970°C, powders cycled up to 1100°C exhibited three phase transitions (low-cristobalite → (≈620°C) high-cristobalite → (≈800°C) low-quartz →(≈970°C) high-cristobalite) while heating up and one phase transition (high-cristobalite → (≈590°C) low-cristobalite) while cooling down. However, the high-cristobalite/low-quartz heating transformation was found to be kinetically hindered. Isothermal in situ X-ray powder diffraction revealed a remarkable temperature dependence of this reaction kinetics.

The single crystal growth of decagonal quasicrystals in the Al–Co–Ni system has been investigated using the Czochralski method. Using a ceramic tip instead of a native seed, single-grain quasicrystals of average composition Al71Co18Ni11 and approximately 1 cm3 in size have been grown. Very low pulling rates (0.25–0.5 mm/h) were used. Axial segregation and structural perfection were investigated by electron-probe microanalysis and neutron diffraction. The liquidus temperature of the starting melt and composition of the decagonal phase agree well with the published phase diagram data.

Defects resulting from the crystallization of mother liquid inclusions are a common occurrence in crystals grown by the travelling heater method. The need to distinguish these defects from defects formed by solid-state precipitation is stressed. This paper reports on an investigation of Te inclusions in Cd 1− x Zn x Te crystals which were grown from Te-rich solution zones and it gives an explanation of the mechanism of their formation by interpreting the composition changes of the matrix surrounding them.

Using the submerged heater method for crystal growth from the melt, steady-state longitudinal segregation may be reached. The submerged heater suppresses convective motion ahead of the phase boundary. However, it also restricts the extension of the diffusion profile in the melt, thus superimposing diffusion-controlled steady-state conditions and a zone configuration. It is similar to the same situation described a long time ago as “zone melting in a diffusion-controlled regime”. Consequences for the growth of variously doped crystals by the submerged heater method are discussed and proved by experiments varying the crystallization rate for Te-doped InSb. The mentioned distribution function is shown to describe the general case of axial segregation with the submerged heater method. Previous interpretations, in terms of diffusion-controlled conditions only, are shown to be limiting cases for high crystallization rates.

“Delta” crystals are solid solutions of miscible materials with large lattice parameter differences which contain high concentration gradients in one direction (parallel to a lattice plane strongly diffracting X-rays). The system GaSb-InSb has been chosen as suitable for study. By means of a “gradient projection method”, the growth of nearly linear composition profiles with relatively steep slopes of the lattice parameter (up to (Δa/ā) / Δz = 8.3% cm-1), adjustable by the temperature gradient, have been performed. However, the grown ingots were not monocrystalline due to the use of too high a growth rate.

Proucavan je Hallov efekt u monokristalima monoklinskog Y-Al-Ni-Co [1], ortorompskog o-Al13Co4 [2] i monoklinskih m-Al13Fe4 i m-Al13(Fe, Ni)4 [3] aproksimanata dekagonalnih kvazikristala za sve kombinacije smjerova elektricne struje i magnetskog polja duž glavnih kristalnih osi u temperaturnom intervalu od 90 do 370 K. U sva cetiri spomenuta intermetalna spoja, koji pripadaju Al13TM4 (TM = prijelazni metal) klasi aproksimanata dekagonalnih (d) kvazikristala, Hallov koeficijent RH pokazuje dobro definiranu anizotropiju. RH je pozitivan (supljinskog karaktera) ili nula za magnetsko polje paralelno s ravninom koja odgovara kvaziperiodicnoj ravnini kod dekagonalnih kvazikristala, a negativan (elektronskog karaktera) ili nula za magnetsko polje okomito na tu ravninu. Jedini izuzetak je RH kod Al13Fe4, za polje usmjereno okomito na ravninu, gdje RH mijenja predznak od pozitivnog u negativni s porastom temperature. Rezultati anizotropije za RH korelirani su s anizotropijom RH u d-Al-Ni-Co [4] kvazikristalu i dan je kratak pregled teorijskih rezultata. Navedena istraživanja provode se u okviru European Integrated Centre for the Development of New Metallic Alloys and Compounds (C-MAC) i MZOS projekata broj 035-0352826-2848 i 286-0000000-3212. [1] A. Smontara, et al., Phys. Rev. B 78 (2008) 104204. [2] J. Dolinsek, et al., Phys. Rev. B 79 (2009) 184201. [3] P. Popcevic, et al., Phys. Rev. B 81 (2010) 184203. [4] P. Popcevic, et al., rad u pripremi ; D. Cmrk et al., poster na ovom ZS.

The accelerated crucible rotation technique (ACRT) has been applied to the THM growth of Hg1−xCdxTe crystals to grow the crystals at a higher rate. These higher growth rates, which should be achieved by extending the regions of conventional stirring towards the interfaces, have been used in an attempt to explain the results in terms of simple constitutional supercooling arguments. Some different ACRT cycles which fulfil simple hydrodynamic and geometric criteria have been studied. The grown crystals were investigated with respect to their metallurgical homogeneity and their structural perfection. These properties have not been degraded by increasing the growth rate from 1.5 to 8.5 mm per day.

A horizontal travelling heater method (THM) for growing cylindrical cyrstals from a partially filled solution zone has been investigated for the first time. By applying ampoule rotation, the whole cross section of the crystal is successively brought into contact with the liquid solution, which is effectively stirred by forced convection. This approach was used to grow single-crystalline Hg1−xCdxTe ingots from a Te-rich solution zone. The structural perfection and metallurgical homogeneity are equivalent to vertically-grown THM material.

The electrical (σ) and thermal conductivity (λ) of Al76Co22Ni2 decagonal approximant has been measured along three orthogonal directions a *, b and cof the Al76Co22Ni2 unit cell, where (a, c) monoclinic atomic planes are stacked along the perpendicular b direction. Electrical conductivity is relatively high in all crystalline directions, appearing in the order σb >> σc > σa* . Thermal conductivity appears in the same order λb > λc > λa*, so that b is the most conducting direction for both electricity and heat. The results are compared to the reported anisotropic electrical and thermal conductivity of the d-Al–Ni–Co decagonal quasicrystal.

We have investigated anisotropic electrical resistivity and thermoelectric power of the ypsilon-phase Al–Ni–Co (Y–Al–Ni–Co) decagonal approximant with composition Al76Co22Ni2. The crystalline-direction-dependent measurements were performed along three orthogonal directions a*, b and c of the Y–Al–Ni–Co unit cell, where (a, c) monoclinic atomic planes are stacked along the perpendicular b direction. Anisotropic electrical resistivity is low in all crystalline directions, appearing in the order ρ a* > ρ c > ρ b and showing positive temperature coefficient typical of electron-phonon scattering mechanism. Thermopower shows electron-phonon enhancement effect. Anisotropic bare thermopower (in the absence of electron-phonon interactions) was extracted, appearing in the same order as the resistivity, ΙS a* bare/TΙ > Ι S c bare/T Ι > Ι S b bare/T Ι.

Crystal growth studies starting from spherical surfaces of singlecrystals can reveal morphological features that cannot be obtained inusual growth experiments. Especially, facets of a greater variety ofcrystallographic forms may occur that are otherwise hidden by theslowest growing faces which dominate the crystal’s morphology. We did asphere growth experiment with a decagonal Al(72)Co(9)Ni(19) quasicrystalprepared from a large single-grain sample formerly grown using theCzochralski method from an off-stoichiometric melt. By heating thepolished crystalline half-sphere to a temperature slightly higher thanits own growth temperature a thin liquid layer of self-flux formed. Apartial evaporation of Al being the solvent of this system causedre-crystallisation at the surface of the quasicrystalline sphere. Afterseveral times repeating this process at further increasing temperatures,tiny faces of four different crystallographic forms developed. By usingan optical goniometer and electron scanning microscopy indexing of thesefacets was possible. With the only exception of the decagonal prism5100006 they had not been observed so far in contact to the melt. Theresults are discussed with respect to the inclined net plane conceptestablished by Steurer and Cervellino [Acta Cryst. A57 (2001)333-340]. The experimental approach is not specific to sphere growthstudies of quasicrystals but can be applied to other high-temperaturesolution growth systems as well.

Crystal growth by the travelling heater method (THM) is reported using a source material preparation process that is different from all methods used before. Non-stoichiometric (Hg, Cd)Te melts were homogenized and quenched to prevent macroscopic segregation effects. Inclusions of excess Te were removed during a first THM pass, resulting in stoichiometric solid alloys with a shift of the mole fraction towards higher CdTe contents. The amount of the shift, dependent on the Te excess and on the equilibrium temperature of the first THM run, was calculated and taken into account in the preparation of x=0.22 and x=0.30 Hg1-xCdxTe single crystals. Source material ingots, as well as THM single crystals, were characterized with special emphasis of the compositional homogeneity. Radial as well as axial homogeneity are comparable with the best results on THM crystals reported so far. The described method can be used in growing all materials for which THM is possible. However, quantitative calculation requires the exact knowledge of the particular ternary phase diagram.

Zeitschrift für Kristallographie, 223 (11-12), ISSN:1433-7266, ISSN:2194-4946, ISSN:0044-2968, ISSN:2196-7105

The defect structure of single crystals of Hg1-xCdxTe grown by the travelling heater method (THM) has been investigated using X-ray double crystal topography and a chemical etching technique. The structural perfection is found to depend on the ratio of growth and solidus temperature Tg/Ts.

Positron lifetime measurements have been performed to study vacancy defects in Hg0.78Cd0.22Te. Post-growth annealing under various Hg vapour pressure conditions have been used to create a well-defined number of Hg vacancies. The sensitivity range of the positron annihilation method was found to be 1015 < cHgvac

Complex metallic alloys are long-range ordered materials, characterized by large unit cells, comprising several tens to thousands of atoms [1]. These complex alloys often consist of characteristic, cluster building blocks, which in many cases show icosahedral symmetry. Numerous complex phases are known, that can be described in a rather simple way as the periodic or quasi-periodic packing of such atomic clusters. The lattice dynamics of CMAs has been the subject of both theoretical and experimental investigations in view of their interesting macroscopic properties such as low thermal conductivity. In aperiodic crystals in the higher wave-vector regime, theory predicts that the lattice modes are critical: they are neither extended as in simple crystals nor localized as in disordered systems [2]. Experimentally phonons have been studied in different CMAs systems like clathrates, approximant-crystals and quasicrystals. For all of them, acoustic modes are well-defined for wave-vectors close to Brillouin zone centres, but then broaden rapidly as the result of coupling with other excitations [3]. We will present a combined experimental and atomistic simulation study of the lattice dynamics of the complex metallic alloy Al13Co4 phase [4], which is a periodic approximant of the decagonal phase. Particular attention will be paid to the differences between the periodic and `quasiperiodic' directions. Inelastic neutron scattering measurements carried out on a large, single grain on a triple-axis spectrometer will be compared to simulations, focussing on the dispersion relations and the intensity distribution of the S(Q,ω) scattering function, which is a very sensitive test of the model [3]. Simulations are performed with DFT methods and empirical, oscillating, pair potentials [5]. In addition, thermal conductivity calculations, based on the Green-Kubo method, will be compared with measurements, which show a weak anisotropy [6-7]. In this way, the structure-dynamics-properties relation for CMAs is thoroughly explored.

In quasicrystal-forming systems very often complex metallic phases exist which show similar structure motifs as the neighbouring quasicrystals but are periodic in all three directions. Therefore these phases are called approximants. They have similar chemical compositions as their parent quasicrystalline phases and can show the same periodicity of stacking of planes as for example found in decagonal quasicrystals. Using the Czochralski method cm3-size single-grain approximants of the Al4TM type, as orthorhombic Al4(Cr,Fe) and hexagonal Al4Cr and of the Al13TM4type, as monoclinic Al13(Co,Ni)4, orthorhombic Al13Co4, monoclinic Al13Fe4and its ternary extensions Al13(Fe,Cr)4and Al13(Fe,Ni)4have been grown from Al-rich solutions [1,2]. The Czochralski method has proven to be a suitable technique for growing single crystals from off-stoichiometric melts due to easy seeding, good mixing of the melt and by allowing good observation of the growth process. To meet the special needs of Al-rich melts a fully metal-sealed growth chamber is used to prevent almost any contact to traces of oxygen. Simultaneously to pulling the change of the liquidus temperature during the growth process has to be compensated by slightly decreasing the temperature using ramps of -(0.1 - 0.8) K/h. For seeding native seeds in different orientations were used. Pulling rates as low as (0.05 - 0.15) mm/h were necessary for growing because of matter transport limits in solution growth and kinetic reasons. Growing the approximant phases the same slow growth kinetics as known from the decagonal quasicrystals was found. Therefore, it might be concluded that the growth of quasicrystalline phases is primarily not limited by the absence of periodicity but by the large clusters that are a common feature in the crystal structures of both, quasicrystals and their approximants.

Combined photoluminescence (at 10 ⩽ T ⩽ 300 K) and electron microprobe investigations have been carried out with HgCdTe samples grown from the melt or from solution. By exciting the samples through metallic masks with 200 μm diameter holes fixed with respect to the sample care was taken to pick-up both characteristic X-ray radiation as well as the photoluminescence from the same sample area. The E g versus x relation determined in this way at T = 30 K has been compared with data from the interband absorption edge by other authors.

Low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) results are used to study the pseudo-6-fold nature of the (100) surface of the orthorhombic quasicrystal approximant Al4(Cr, Fe). LEED patterns are also presented from the pseudo-10-fold (010) surface of this material. In each case the results are compared with the known bulk structure of this complex metallic alloy.

Single crystals of Tl doped PbTe were grown using the travelling heater method (THM) and the electrical properties were evaluated at 77 K and found to be p-type.