Ternary Single Crystals Research Articles

ChemInform Abstract: Growth Conditions, Electrical Resistivity, Microhardness, and Thermal Properties of Nb5Sn2Ga Single Crystals Synthesized from High-Temperature Tin Solutions.

Abstract Single crystals of a new ternary intermetallic compound Nb 5 Sn 2 Ga were prepared from high-temperature tin solutions by a self flux method using Nb and Ga metals as starting materials under a He gas. The crystal was examined by X-ray diffraction and chemical analyses. The ternary single crystals Nb 5 Sn 2 Ga were generally obtained in the form of prismatic shape extending in the [001] direction, and with (100) and (110) faces. The Vickers microhardness value on (001) plane and (100) or (110) planes of crystals is in the range of 8.5–10.1 GPa. The electrical resistivity determined on crystal is in the range of 253.1–276.7 μΩ cm. The oxidation of Nb 5 Sn 2 Ga crystal starts at about 562°C. The final oxidation products were NbO 2 , Nb 12 O 29 , Nb 2 O 5 , SnO 2 and Ga 2 O 3 .

The M A-type monoclinic phase and its dc electric/temperature responses studies in Pb(In 1/2Nb 1/2)O 3–Pb(Mg 1/3Nb 2/3)O 3–PbTiO 3 ternary single crystals by polarized light microscopy

The method to distinguish two types of monoclinic phases (M A and M B) in perovskite crystals by polarized light microscopy was developed. The M A-type monoclinic phase was observed in xPb(In 1/2Nb 1/2)O 3– yPb(Mg 1/3Nb 2/3)O 3– zPbTiO 3 ternary crystal by polarized light microscopy at room temperature. The phase transition of these monoclinic phases under dc electric field along [1 1 0] cub direction was investigated in real time. Two dielectric peaks were found in ferroelectric phases of the as-grown ternary single crystals near the morphotropic phase boundary (MPB) with increasing temperature, which indicate the phase transition of monoclinic M A → orthorhombic (O) → tetragonal (T).

High-pressure ac specific heat technique with cubic anvil apparatus

We report the development of ac specific heat technique under highly hydrostatic pressures using a cubic anvil apparatus. The constructed system is sensitive enough to detect a magnetic phase transition, pressure up to 8 GPa and temperature range between 2 and 30 K. We present the results of specific heat measurement of ternary iron arsenide EuFe2As2 single crystal up to 4.0 GPa with the technique presented here.

Electromechanical characterization of [Formula: see text] crystals as a function of crystallographic orientation and temperature.

Relaxor based [Formula: see text] ternary single crystals (PIN-PMN-PT) were reported to have broader temperature usage range [Formula: see text] and comparable piezoelectric properties to [Formula: see text] (PMNT) crystals. In this work, the orientation dependent dielectric, piezoelectric and electromechanical properties for PIN-PMN-PT crystals were investigated along [Formula: see text] and [Formula: see text] directions. The electromechanical couplings [Formula: see text] and [Formula: see text] for [Formula: see text] poled crystals were found to be 0.91 and 0.91, respectively, with piezoelectric coefficients [Formula: see text] and [Formula: see text] on the order of 925 and -1420 pC/N. Of particular significance was the mechanical quality factor [Formula: see text] for [Formula: see text] oriented crystals, which was found to be [Formula: see text], much higher than the [Formula: see text] values of [Formula: see text] oriented relaxor-PT crystals [Formula: see text]. The temperature dependence of the piezoelectric properties exhibited good temperature stability up to their ferroelectric phase transition [Formula: see text], indicating [Formula: see text] and [Formula: see text] oriented PIN-PMN-PT are promising materials for transducer applications, with the latter for high power resonant devices where low loss (high [Formula: see text]) was required.

Characterization of Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 ferroelectric crystal with enhanced phase transition temperatures

The full set of material constants for relaxor-based ternary single crystals Pb(In(12)Nb(12))O(3)-Pb(Mg(13)Nb(23))O(3)-PbTiO(3) (PIN-PMN-PT) were determined and compared to binary Pb(Mg(13)Nb(23))O(3)-PbTiO(3) (PMNT) crystals. The Curie temperature for rhombohedral compositions of PIN-PMN-PT was found to be in the range of 160-200 degrees C with ferroelectric rhombohedral to tetragonal phase transition on the order of 120-130 degrees C, more than 30 degrees C higher than that found for PMNT. The piezoelectric coefficients (d(33)) were in the range of 1100-1500 pCN, with electromechanical coupling factors (k(33)) about 89%-92% comparable to PMNT crystals. The coercive field of the ternary crystal was found to be 5.5 kVcm, double the value of the binary counterparts. The dielectric behavior under varying dc bias exhibited a similar trend as observed in PMNT with a much broader usage temperature range. Together with its enhanced field induced phase transition level, the ternary PIN-PMN-PT crystals are promising candidates for high temperature and high drive transducer applications.

Growth and pyroelectric properties of high Curie temperature relaxor-based ferroelectric Pb(In1∕2Nb1∕2)O3–Pb(Mg1∕3Nb2∕3)O3–PbTiO3 ternary single crystal

To enhance the service temperature of relaxor-PbTiO3 pyroelectric single crystals, high quality ternary perovskite single crystal was grown by a modified Bridgman technique. Analyzed by x-ray fluorescence, the as-grown crystal is 0.41Pb(In1∕2Nb1∕2)O3–0.17Pb(Mg1∕3Nb2∕3)O3–0.42PbTiO3 [PIMNT(41/17/42)], which appears to be a tetragonal ferroelectric phase with relatively high Curie temperature of 253°C. It exhibits the relative permittivity of 487 and low dielectric loss of 0.3% at 50Hz and room temperature. The pyroelectric properties with a pyroelectric coefficient of 5.7×10−4C∕m2K and a detectivity of 6.34×10−5Pa−1∕2 would satisfy the needs of operation as a high Curie temperature material. The results show that PIMNT crystal with better temperature stability, compared with the pure PMNT single crystals, is a good candidate as an infrared detector material.

Growth of InGaAs and SiGe homogeneous bulk crystals which have complete miscibility in the phase diagrams

Growth of binary and ternary single crystals which have complete miscibility in the phase diagrams, have been studied by several newly developed methods such as the liquid encapsulated Czochralski, Bridgman, and multi-component zone melting methods for InGaAs bulk crystals, and the multi-component zone melting methods and Bridgman methods for Ge-rich and Si-rich SiGe bulk crystals. Crystals grown by these methods are compared with each other, to find the proper growth conditions to obtain single crystals with uniform composition. Techniques for the precise control of the temperature at the growing interface and for the continuous supply of the depleted solute elements to the growth melt were developed. InGaAs bulk crystals with uniform composition were obtained by the multicomponent zone melting method. Si-rich and Ge-rich SiGe bulk crystals with uniform composition were obtained in the Ge compositional range from 10 to 78%. The advanced technologies to obtain the InGaAs and SiGe bulk crystals with much higher-quality are discussed in this paper.

The effect of substitutional elements on the strain-induced ferromagnetism in B2-structured Fe–Al single crystals

Strain-induced ferromagnetism in B2-structured Fe–Al arises mostly from anti-phase boundary (APB) tubes where groups of moment-bearing Fe atoms with at least three like nearest-neighbors are large enough to be magnetically coupled and behave ferromagnetically. Following our previous work on binary Fe–Al, strain-induced ferromagnetism in ternary single crystals of Fe–40 at.%Al–3 at.%Cu and Fe–40 at.%Al–3 at.%Cr was studied. When deformed to similar rolling strains along the same orientation, the saturation magnetization, M S, was found to be greatest for Fe–40 at.%Al, followed by Fe–40 at.%Al–3 at.%Cu, Fe–40 at.%Al–3 at.%Cr and Fe–43 at.%Al. This behavior can be explained by the site preferences of the Cu and Cr atoms on the Fe and Al sublattices, which both change the probability of a Fe atom having like nearest-neighbors in the APB tubes and affect the energy of the anti-phase boundaries. Calculations of M S at 0 K of rolled Fe–40 at.%Al–3 at.%Cu and Fe–40 at.%Al–3 at.%Cr specimens, based on APB tube densities and considerations of the APB tube size and geometry, were found to be in reasonable agreement with experimentally determined values. APB tubes were observed by transmission electron microscopy in Fe–40 at.%Al, Fe–40 at.%Al–3 at.%Cu and Fe–40 at.%Al–3 at.%Cr.

Growth of bulk single crystals under applied magnetic field by liquid phase electroepitaxy

Binary (GaAs) and ternary (InGaAs) bulk single crystals have been grown by the growth process of liquid phase electroepitaxy (LPEE with and without the application of an external static magnetic field. Two significant achievements were made: first is the development of a new, improved LPEE system to grow, flat, thick and uniform single crystals of In 0.04Ga 0.96As, and the second is the significant improvement of the LPEE growth rate by the application of an external static magnetic field. Experiments performed under no magnetic field have shown that LPEE can grow large (thick) and flat single crystals of In 0.04Ga 0.96As with uniform composition. Experiments have also proved the reproducibility of LPEE growth of such single crystals in terms of crystal thickness, flatness, and compositional uniformity. It was possible to use higher electric current density levels (up to 7 A/cm 2) in spite of the achievement of large crystal thicknesses. Experiments conducted under various magnetic field levels have shown that the LPEE growth process at the 4.5 kG and lower magnetic field levels yields satisfactory growth. However, the growth experiments at higher magnetic field and electric current density levels were unsatisfactory and unstable. Although the crystals were still grown, large holes and unstable interfaces were observed in the grown crystals. However, lower magnetic field and electric current levels had very beneficial effects, namely flat growth interfaces and prolonged growth due to weak convection in the liquid zone, and a substantial increase in the growth rate (about up to 20 times higher at 4.5 kG and 7 A/cm 2 levels). Such a significant increase in the growth rate under a static magnetic field can be attributed to the positive effect of applied magnetic field on the mechanism of “electromigration”. The performed electron probe micro analysis (EPMA) and the energy dispersive X-ray spectroscopy (EDS) measurements have shown that the indium composition distribution in grown crystals was uniform in both the radial and growth directions. Advances made through this work may be considered as a significant initial step towards the commercialization of the LPEE technique for growth of high-quality, bulk single crystals.

A one-dimensional model to predict the growth conditions of In xGa 1− xAs alloy crystals grown by the traveling liquidus-zone method

The traveling liquidus-zone (TLZ) method has been used effectively to grow ternary alloy single crystals of uniform composition. In this study, a one-dimensional model is presented to predict the growth conditions of this technique. It was shown that under the assumed growth conditions, the model gives accurate predictions for the growth conditions of the TLZ method including the composition of the grown crystals. Numerical results agree with those of experiments.

Growth and transport properties of tin monosulphoselenide single crystals

The binary and ternary mixed single crystals of the orthorhombic IV–VI family in the form of SnS x Se 1− x (where x=0, 0.25, 0.50, 0.75 and 1) were grown by direct vapor transport technique. The lattice parameters of each grown crystal were determined from the X-ray diffraction analysis. The grown crystals were examined under the optical zoom microscope for their surface microstructure study. The low-temperature resistivity measurements were carried out in the temperature range 123–303 K using four-probe method. The Hall coefficient, carrier concentration and Hall mobility of each sample was determined from Hall effect measurements at room temperature. From the optical absorption spectra obtained in the range 1000–1500 nm, optical band gap of each sample was determined at room temperature. The results obtained are reported systematically.

The effect of applied magnetic field on the growth mechanisms of liquid phase electroepitaxy

Binary (GaAs) and ternary (InGaAs) single crystals were grown by the growth process of liquid phase electroepitaxial (LPEE) under an applied static magnetic field. The effect of the applied magnetic field on two main growth mechanisms of the LPEE growth process, namely the “electromigration” and “natural convection” in the liquid zone, were examined numerically and experimentally. Numerical results show that the flow and concentration patterns exhibit three distinct stability characteristics: stable structures up to the magnetic field level of 2.0 kG, transitional structures between 2.0 and 3.0 kG, and unstable structures above 3.0 kG. In the stable region, the applied magnetic field suppresses the flow structures, and the intensities decrease with the increasing magnetic field level. In the transitional region, the flow intensity increases dramatically with the magnetic field strength, and concentrations show very different patterns leading to a wavy growth interface. Under strong magnetic field levels, the flows cells are confined to the vicinity of the vertical wall and exhibit significant non-uniformity near the growth interface. Experiments performed under various magnetic field levels show that the growth process at the 4.5 kG field level yields satisfactory growths. However, the growth experiments at higher field levels were unsatisfactory and unstable. Although the crystals were still grown, large wholes were observed in the grown crystals. This observation was attributed to the strong interaction of the applied electric and magnetic fields, making the convective flow in the solution very strong and unstable. However, lower magnetic field and electric current levels had very beneficial effects, namely flat growth interfaces and prolonged growth due to weak convection in the liquid zone, and a substantial increase in the growth rate (about 5–10 times higher) due to the effect of magnetic field on the mechanisms of “electromigration”. Such positive developments give the LPEE growth process the potential of becoming a commercial technique.

Growth and electrical properties of Pb(Sc 1/2Nb 1/2)O 3–Pb(Mg 1/3Nb 2/3)O 3–PbTiO 3 ternary single crystals by a modified Bridgman technique

Single crystals of 0.05Pb(Sc 1/2Nb 1/2)O 3–0.63Pb(Mg 1/3Nb 2/3)O 3–0.32PbTiO 3 have been grown directly from melt by a modified Bridgman technique. The crystals with perovskite structure were 15 mm in diameter and 20 mm in length. The segregation during the growth of the single crystals was studied by means of X-ray diffraction analysis. The results show that PbTiO 3 content increases throughout the crystal growth. The electrical properties of the single crystals oriented along the [0 0 1] axis have been characterized. The plates cut from the seed end of a boule exhibited a permittivity ( ε 33 ε 0 ) of about 3500, dielectric loss tangent (tg δ)<1%, dielectric constant peaks at 162°C, piezoelectric constant ( d 33)≈1200 pC/N, and electromechanical coupling factor ( k t)≈60% for the thickness mode. Our results show that xPb(Sc 1/2Nb 1/2)O 3– yPb(Mg 1/3Nb 2/3)O 3–(1- x- y)PbTiO 3 single crystals are promising for a wide range of electromechanical transducer applications.

Creep deformation of single crystals of binary and some ternary MoSi2 with the C11b structure

The creep deformation behavior of binary and some ternary MoSi2 single crystals with the soft [0 15 1] and hard [001] orientations has been investigated in the temperature range from 1200 to 1400°C in compression. The alloying elements studied include Nb and Al that form a C40 disilicide with Si and W and Re that form a C11b disilicide with Si. The creep strain rate for the [001] orientation is significantly (2 orders of magnitude) lower than that for the soft [0 15 1] orientation. The creep strain rate for the [0 15 1] orientation is improved by an order magnitude upon alloying with Re and Nb while alloying with W and Al causes a decline in the creep properties of this orientation. The creep strain rate for the [001] orientation is further improved upon alloying with Re, Nb, W and Al with the extent of improvement significantly larger for the Re addition.

Effect of substitutational elements on plastic deformation behaviour of NbSi 2-based silicide single crystals with C40 structure

Plastic deformation behaviour of binary NbSi 2 and ternary NbSi 2-based silicide single crystals with the C40 structure was examined at high temperatures and compared with the results in MoSi 2 with the C11 b and TiSi 2 with the C54 structure, focusing on anomalous strengthening. Addition of substitutional alloying elements affected the anomalous strengthening in NbSi 2-based silicides; addition of Mo and W strongly affected the anomalous strengthening, while Ti and Al additions showed little effect. The substitutional impurity atoms may gather and form a dragging atmosphere around 1/3〈21̄1̄0] moving dislocations containing a superlattice intrinsic stacking fault in NbSi 2-based silicides, resulting in anomalous stress increase. The effect of the dragging atmosphere and diffusion path of additional elements on an anomalous strengthening is discussed, focusing on the atomic arrangement on slip planes and the phase stability of the C40 structure with respect to the C11 b and C54 structures.

Growth conditions, electrical resistivity, microhardness and thermal properties of Nb 5Sn 2Ga single crystals synthesized from high-temperature tin solutions

Single crystals of a new ternary intermetallic compound Nb 5Sn 2Ga were prepared from high-temperature tin solutions by a self flux method using Nb and Ga metals as starting materials under a He gas. The crystal was examined by X-ray diffraction and chemical analyses. The ternary single crystals Nb 5Sn 2Ga were generally obtained in the form of prismatic shape extending in the [001] direction, and with (100) and (110) faces. The Vickers microhardness value on (001) plane and (100) or (110) planes of crystals is in the range of 8.5–10.1 GPa. The electrical resistivity determined on crystal is in the range of 253.1–276.7 μΩ cm. The oxidation of Nb 5Sn 2Ga crystal starts at about 562°C. The final oxidation products were NbO 2, Nb 12O 29, Nb 2O 5, SnO 2 and Ga 2O 3.

Transition behaviour of deformation mode from shearing to looping in an Al-Li-Ag ternary single crystal

The transition behaviour of the deformation mode from shearing to Orowan looping has been investigated in ternary Al- 2.0 wt% Li-0.4 wt% Ag single crystals using transmission electron microscopy. The critical loop size corresponding to the critical planar particle size for the transition and the dislocation pair spacing are distinctively small compared with those in an Al-Li binary single crystal. The antiphase-boundary energy of the delta phase is thus estimated to be distinctively large (about 0.123 J m ) compared with the binary crystal (about 0.100 J m ). The significant enhancement of the antiphaseboundary energy of the delta phase in an Ag-containing crystal is believed to be due to a strong enrichment of the delta phase with Ag.

Application of single crystals to achieve quantitative understanding of weld microstructures

AbstractThe inter-relationship between the weld pool shape and the weld microstructure is a critical factor that determines the physical integrity and other important properties offusion welds. In the present work, large single crystals of an Fe–15Ni–15Cr alloy have been used to increase basic understanding of the factors that influence the development of weld microstructures. Oriented ternary alloy single crystals were used to make electron beam welds along various principal directions lying in different principal crystallographic planes. Using oriented single crystals it was possible to obtain crucial microstructural information that is ordinarily lost when welds are made on normal polycrystalline specimens. This quantitative information regarding the microstructural properties of electron beam welds has provided valuable new insight into the fundamentals of the relationships between weld pool shapes and weld microstructures. A new three-dimensional geometrical analytical method has been developed to in...

Growth Conditions and Some Properties of TmB4 and TmAlB4 Single Crystals Obtained from High-Temperature Aluminium Metal Solution

TmB4 and TmAlB4 single crystals were obtained by the high-temperature aluminium solution method using thulium oxide powder and crystalline boron powder as starting materials. The optimum conditions to obtained relatively large crystals mentioned above were found to include soaking temperature 1500°C, soaking time 10 h, cooling rate 50°C·h-1 and the atomic ratios of starting materials: B/Tm=5.5, Al/Tm=119.25 for TmB4; B/Tm=2.0, Al/Tm=119.25 for TmAlB4. In the case of TmB4, polyhedra single crystals were obtained. The ternary single crystals TmAlB4 were generally obtained in the form of prismatic shape extending in the <001> direction or with well developed (100) faces. The as-grown TmB4 and TmAlB4 single crystals were used for chemical analysis and measurements of unit cell dimensions. Densities, microhardness and electrical resistivity of the as-grown crystals was studied.

The Compression Creep Behavior of Ni3Al-X Single Crystals

ABSTRACTCompressive creep behavior is investigated in ternary Ni3Al single crystals containing Ti, Si, Hf and Cr with stress axes parallel to the crystallographic orientation near [001]. Then a comparison is made with the results of high temperature compression tests under a constant strain rate for the same orientation where plastic behavior is characterized by a distinct yield drop followed by steadystate deformation. It is found that the deformation mechanism for the two cases is identical, namely octahedral viscous flow being expressed by the state equation of the power-law type with a stress exponent of about 3 to 4. The effect of offstoichiometry on the creep resistance is then examined in Ni3(Al,5 at%Ti) alloys with different Ni concentrations. The results support the observation in the polycrystalline compound where the creep resistance increases with Ni concentration on both sides of stoichiometry exhibiting a discontinuity at stoichiometry. Finally, the apparent activation energy in the power-law type state equation for the steady state creep deformation is estimated for all the ternary alloys examined. They are in general in good agreement with that for diffusion of ternary elements in Ni3Al. However, the relative magnitude of the value can not simply be compared since the activation energy depends on deviations from stoichiometry.