Solid Solution Single Crystals Research Articles

Efficient lasing in diode-pumped Yb3+:CaF2–SrF2 solid-solution single crystals

Single crystals of solid solutions of a high optical quality are grown in the concentration vicinity of the saddle point of the ternary CaF2–SrF2–YbF3 system. Efficient lasing with a small Stokes shift (at 1025 nm) was obtained in 980-nm diode-pumped single crystals. The total lasing efficiency (with respect to the absorbed average pump power) was 59% and the slope efficiency was 83%.

Temperature and electric field dependence of ultrasonic wave propagation and attenuation in PZN-PT single crystal in vicinity of a phase transition

The longitudinal and transverse modes of ultrasound propagation in Lead Zinc Niobate–Lead Titanate (PZN–PT) single crystal solid solutions are investigated as a function of temperature. The influence of an electric DC bias field on the elastic stiffness at various temperatures is studied. The presence of more stable phases induced by this electric field is observed. The polarization directions are modeled in terms of free energy function. The experiments are conducted in a dedicated temperature chamber working in a wide temperature range from 200 up to 470 K for ultrasonic measurements thin plate samples with the option for DC bias fields. The bias field was applied by a high voltage amplifier Trek model 610D. Crystal cuts of [001], [110] and [111] were used for the study of electric field poling conditions and temperature influence on structure induced by polarization orientation. A study of anomalies in sound velocity and relative attenuation near ferroelectric transitions is performed. It is well established that near the temperature of a second-order structural phase transitions, and in particular near the Curie point of ferroelectrics, anomalously strong ultrasonic absorption occurs.

Growth and optical properties of transition metal oxides single crystal solid solutions

NiO, CoO, MnO single crystals and single crystal solid solutions of Ni c Mg 1− c O, Co c Mg 1− c O and Mn c Mg 1− c O were grown by the method of chemical transport reaction (the “sandwich” technique). The nature of the observed absorption and luminescence bands is explained in terms of the electronic transition of bivalent nickel, cobalt and manganese. The fine structure of the observed bands in NiO and MnO are connected to the pure exciton transition and to the exciton-magnon excitation.

Observation of nanostructure by scanning near-field optical microscope with small sphere probe

Step and terrace structure has been observed in an area of 1 μm × 1 μm on the cleaved surface of KCl–KBr solid-solution single crystal by scanning near-field optical microscope (SNOM) with a small sphere probe of 500 nm diameter. Lateral spatial resolution of the SNOM system was estimated to be 20 nm from the observation of step width and the scanning-step interval. Vertical spatial resolution was estimated to be 5–2 nm from the observation of step height and noise level of photomultiplier tube (PMT). With applying a dielectric dipole radiation model to the probe surface, the reason why such a high spatial resolution was obtained in spite of the 500 nm sphere probe, was understood as the effect of the near-field term appeared in the radiation field equations.

Growth of AlN and AlN-SiC Solid Solution by Sublimation Method

AlN is considered as the most suitable substrate material for further development of high quality and high performance nitride-based micro- and opto-electronics. AlN ingots are often grown on SiC seeds. To solve the formation of cracks due to the difference in lattice parameters between seed and crystal we chose to “adapt” the lattice mismatch by a buffer layer of the (AlN)x(SiC)1-x solid solution. This paper gives some inputs on the growth of AlN and the solid solution by the sublimation technique, in terms of materials compatibility, hetero- and homo-epitaxial growth of AlN and on the preparation of crack-free solid solution single crystals.

Atomic structure of Cd1 − x Zn x Te solid solution single crystals and structural prerequisites of their ferroelectricity

Precision X-ray structural investigation of Cd{sub 1-x}Zn{sub x}Te single crystals (x = 0.04, 0.10, 0.21, 0.30, 0.40) is performed at temperatures below and above the ferroelectric phase transition. The regularities associated with the increase in the concentration of Zn atoms in solid solutions are revealed. It is established that the unit cell parameter of the crystals varies according to the Vegard law. The thermal parameters of Te and Zn atoms are strongly overestimated within the model of a sphalerite-type average structure. It is found that the positions of the Zn cations are split and the anion sublattice is disordered in such a way that the Te anions are predominantly displaced along the threefold axes. The Zn atoms can serve as off-center impurities. This phenomenon offers strong possibilities for manifesting the ferroelectric properties in the solid solutions under investigation.

Evidence for magnetic state of uranium in U 2(Fe 1− xCo x) 13.6Si 3.4

Single crystals of solid solutions U 2(Fe 1− x Co x ) 13.6Si 3.4 (0 ≤ x ≤ 1) having the hexagonal Th 2Ni 17 crystal structure were grown by a Czochralski method. Magnetization measurements along the principal axes reveal the easy-plane magnetic anisotropy in compounds with x up to 0.95, whereas terminal compound U 2Co 13.6Si 3.4 has the uniaxial anisotropy. Magnitudes of the anisotropy constants K 1 and K 2 for x up to ∼0.8 are high enough to suggest a U contribution to the anisotropy, i.e., a magnetic state of U. The observed rapid weakening of the anisotropy and the change of its type at highest Co content are attributed to the 3d-metal sublattice, namely to the considerable change of c/ a ratio at the Fe Co substitution in the “dumbbells”.

A low-temperature plasticity anomaly of concentrated fcc solid solutions: the Pb–In system

This paper discusses the regularities of the plastic strain of single crystals of solid solutions of the Pb–In system at low and very low temperatures, 0.5 K<T<30 K. For Pb alloys with 5, 10, and 20 at. % In, the temperature dependences of the yield strength, τ0(T), and of the increment of the deforming stress, Δτ(T), are measured after a tenfold increase of the strain rate. Specific features (anomalies) of these dependences are detected that do not correspond to concepts of thermally activated motion of dislocations through impurity barriers. It is established that the character of the anomalies substantially changes as the indium concentration varies from moderate values (5 and 10 at. %) to high values (20 at. %). The low-temperature plasticity anomaly of moderately concentrated alloys is interpreted on the basis of the concepts of thermal-inertial and quantum-inertial motion of dislocations through a system of single impurity atoms. In the case of the highly concentrated alloy, the anomaly is interpreted in terms of a model of an inhomogeneous impurity distribution—the presence in the alloy of small clusters that create stronger barriers for the motion of dislocations than do single impurity atoms. The high level of efficient deforming stresses under conditions of deep cooling results in a dynamic regime of dislocation motion through the system of clusters and single impurities, with the yield strength τ0 of the alloy being determined by impurity inhibition of dry-friction type, while the rate sensitivity Δτ of the deforming stress is determined by viscous inhibition by electrons and phonons. The athermal character of impurity dry friction and the sharp decrease of viscous friction upon cooling determine the character of the anomaly in this case.

Pressure-Induced Anomalous Phase Transitions and Colossal Enhancement of Piezoelectricity inPbTiO3

We find an unexpected tetragonal-to-monoclinic-to-rhombohedral-to-cubic phase transition sequence induced by pressure, and a morphotropic phase boundary in a pure compound using first-principles calculations. Huge dielectric and piezoelectric coupling constants occur in the transition regions, comparable to those observed in the new complex single-crystal solid-solution piezoelectrics such as Pb(Mg(1/3)Nb(2/3))O3-PbTiO3, which are expected to revolutionize electromechanical applications. Our results show that morphotropic phase boundaries and giant piezoelectric effects do not require intrinsic disorder, and open the possibility of studying this effect in simple systems.

Effects of growth conditions on the domain structure and dielectric properties of (1 − x)Pb(Sc 1/2Nb 1/2)O 3– xPbTiO 3 single crystals

The studies of the (1 − x)Pb(Sc 1/2Nb 1/2)O 3– xPbTiO 3 (PSN–PT) single crystals reveal that the chemical and physical properties of the materials are affected by the growth conditions. By the measurements of the dielectric constant as a function of temperature upon cooling, it is found that crystals grown from the same charged stoichiometric composition ( x = 0.425), but under different flux environments (i.e. the composition of flux and the flux to PSN–PT ratios are varied), show anomalies (i.e. phase transitions) at different temperatures. This phenomenon is attributed to the complex local chemical structure of the PSN–PT solid solution single crystals with B-site random occupancy of three different cations (Sc 3+, Nb 5+ and Ti 4+). The dielectric and domain structure of the PSN–PT crystals with composition near the morphotropic phase boundary (MPB) are investigated, showing much more complex situations compared with Pb(Sc 1/2Nb 1/2)O 3.

Additivity of the Crystal Structure and Properties of Solid Solutions of Rare Earth Metal Hexaborides

Single crystals of solid solutions of the rare earth metal (REM) hexaborides LaB6-CeB6 and EuB6-SrB6 have been grown from solutions in aluminum melt. The chemical compositions of the samples were determined by energy-dispersive X-ray spectroscopy; the crystal lattice periods were determined by X-ray diffraction; and the microhardness on a {001} cubic face in the 0° (90°) azimuthal direction was measured using the Knoop indenter. The properties of the mixed solid solutions of REM hexaborides are described using the concept of additivity, whereby the lattice period and the microhardness are determined as linear functions of the concentrations (atomic fractions) of both metals. It is established that both characteristics obey the corresponding linear relationships and vary between the values for the initial pure hexaborides. The accuracy of the calculated additive characteristics depends on the precision of determination of the chemical composition of samples. The accuracy of experimental data is determined by the precision of particular techniques, the structural perfection of single crystals, and (for microhardness) the state of the sample surface.

Growth and characterization of Si xGe 1−xO solid solution single crystals with quartz structure

Experimental investigations of the development of a reliable and reproducible growth method of Si x Ge 1− x O 2 solid solutions single crystals with quartz structure (α-Si x Ge 1− x O 2) have been performed under hydrothermal conditions. Effects resulting from solution compositions, T– P parameters and growth rates of different faces in morphology and internal structure of crystals as well as capturing and distribution of Si and Ge were also studied. The main crystallochemical characteristics and properties of the crystals have been fixed. α-Si x Ge 1− x O 2 crystals were studied by X-ray, refracting indexes determination methods, DTG-DTA, IR and Raman spectroscopy and they showed the high probability of the isomorphic substitutions of Si–Ge.

The Solid Solution TmNi1–x–yIn1+x

Abstract The thulium nickel indide TmNiIn forms solid solutions TmNi1−x−yIn1+x. Several samples have been prepared by arc-melting of the elements under argon. The structure of TmNiIn contains two crystallographically different nickel sites. The Ni1 atoms have a trigonal prismatic coordination by indium, while the Ni2 sites have six thulium neighbors in a trigonal prismatic arrangement. The Ni1 sites show defects in the solid solution, while the Ni2 sites have Ni2/In mixing with a maximal occupancy of 32 at.-% indium. The structures of three single crystals of solid solutions have been refined, leading to the compositions TmNi0.88In1.10 (a =747.06(7), c = 367.8(1) pm, wR2 =0.0342, 323 F2 values, 16 variables), TmNi0.80In1.16 (a= 752.94(7), c =366.5(1) pm, wR2=0.0475, 503 F2 values, 16 variables), and TmNi0.76In1.21 (a = 758.4(1), c = 366.68(7) pm, wR2 = 0.0949, 226 F2 values, 16 variables). The crystal chemical peculiarities and the differences in chemical bonding are briefly discussed.

Characterization of perovskite piezoelectric single crystals of 0.43BiScO3–0.57PbTiO3 with high Curie temperature

The perovskite single crystal solid solution of 0.43BiScO3–0.57PbTiO3 (BSPT57) was reported to possess a high Curie temperature (TC∼402 °C) and rhombohedral to tetragonal phase transition temperature (TR–T∼349 °C) with excellent electromechanical properties (k33∼90%). In this work, the resonance method was used to determine all of the eleven electromechanical coefficients of the BSPT57 piezocrystals using five Z-cut samples. The complete set of materials constants, including the elastic sij, cij, piezoelectric dij, eij, gij, hij, dielectric εij, βij, and electromechanical kij values were derived from the experimental data. The BSPT57 crystal was found to be a promising material for piezoelectric applications, which is comparable to the properties of the Pb(Zn1/3Nb2/3)O3–PbTiO3 and Pb(Mg1/3Nb2/3)O3–PbTiO3 relaxor-PT single crystals, but has a much high-temperature stability.

Effect of Electric Field on Hydrostatic Piezoelectric Coefficients of Single Domain PZN-PT Crystals

The effect of dc bias electric field on the hydrostatic piezoelectric coefficient dh in Lead Zinc Niobate-Lead Titanate (PZN:PT) single crystal solid solutions in the vicinity of the morphotropic phase boundary (MPB) is studied. The hydrostatic measurements can be very important to gain insight into these materials. In particular, the discrepancy between sum of piezoelectric coefficients d33+ 2 d31 vs. hydrostatic dh coefficient measured directly suggests the importance of extrinsic contributions. Limiting values of measured hydrostatic piezoelectric coefficients dh for high electric fields are compared with calculated theoretic values from the Landau-Devonshire-Ginzburg (LGD) phenomenological theory. The influence of complicated microstructure within the single domain region is studied. Such microstructure could possibly account for the inability of the LGD phenomenology to give correct electric field bias dependence of dielectric constant.

The Effect of Mn Concentration on Curie Temperature and Magnetic Behavior of MOCVD Grown GaMnN Films

ABSTRACTWe report on the growth and characterization of dilute magnetic semiconductor GaMnN showing ferromagnetism behavior above room temperature. GaMnN films were grown by MOCVD using (EtCp2)Mn as the precursor for in-situ Mn doping. Structural characterization of the GaMnN films was achieved by XRD, SIMS and TEM measurements. XRD and TEM confirmed that the films were single crystal solid solutions without the presence of secondary phases. SIMS analysis verified that Mn was incorporated homogeneously throughout the GaMnN layer which was ∼0.7μm thick. Ferromagnetic behavior for these films was observed along the c-direction (out of plane orientation) in a Mn concentration range of 0.025–2%. The saturation magnetization ranged from 0.18–1.05 emu/cc for different growth conditions. Curie temperatures of the GaMnN films were determined to be from 270 to above 400K depending on the Mn concentration. This dependence of Curie temperature on concentration of Mn in GaMnN indicates that the grown films are random solid solutions. SQUID measurements ruled out the possibility of spin-glass and superparamagnetism in these MOCVD grown GaMnN films. The grown films were electrically semi-insulating; however PL measurements showed that the films were still optically active after Mn doping. This study showed that the growth of III-Nitride films doped with Mn requires a small window of growth conditions that depend on growth temperature and (EtCp)2Mn flux to achieve ferromagnetism above room temperature, and the magnetic response of the film depends on the Fermi level position. We suggest that ferromagnetism occurs when the Fermi level lies within the Mn energy level which is 1.4 eV above the GaN valence band.

Vapour growth of II–VI solid solution single crystals by contact-free technique

A modified vapour phase contact-free method to grow homogeneous single crystals of solid solutions (SS) of II–VI compounds is presented. Single crystals of Cd(S, Se), Zn(S, Se), (Zn, Cd)Se, (Zn, Cd)S, Zn(S, Te), Zn(Se, Te), and Cd(S, Te) up to 55mm in diameter were grown. Different applications of the crystals are discussed.

Effect of Electric Fields on Domain Structure and Dielectric Properties of Pb(In1/2Nb1/2)O3-PbTiO3 near Morphotropic Phase Boundary

Domain observation in Pb(In1/2Nb1/2)O3–PbTiO3[PIN-PT] solid-solution single crystals near the morphotropic phase boundary (MPB) was carried out by polarized light microscopy. The rhombohedral (R)-to-tetragonal (T) phase transition began to take place abruptly in the (110) plane at about 6 kV/cm in the rhombohedral (001) 0.72PIN-0.28PT plate with the dc electric field applied along the <010> direction. The phase boundary between the R and T phases along the (110) plane approached the R region at the expense of the R region, and the R and T phases coexisted in a wide dc field range from 6 kV/cm to 12 kV/cm. The electric-field-induced R-to-T phase transition was very diffuse. The (110) plane plays an important role in this phase transition. The effects of the dc electric field on the domain configuration and permittivity of the rhombohedral (110) 0.69PIN-0.31PT plate were simultaneously investigated, and the contributions of the 109° and 71° polarization configurations to permittivity were discussed on the basis of the Ishibashi theory.

Elastic constants of face-centered cubic and L12 Ni-Si alloys: Composition and temperature dependence

The adiabatic elastic stiffness constants C ij of Ni-Si single-crystal solid-solution alloys of two slightly different compositions, 10.78 and 11.17 at. pct Si, were measured over the temperature range from 20 °C to 900 °C using the rectangular parallelepiped resonance method. The isotropic elastic constants of the polycrystalline ordered intermetallic compound Ni3Si containing 23 at. pct Si were also measured over this temperature range. Values of the C ij for Ni3Si were estimated from the data on the polycrystalline alloy, as well as from published data in the literature on isomorphous ternary ordered intermetallic compounds containing different amounts of Si. Using measured values and previously published data, the stiffness constants of Ni3Ti were estimated; these are the only available data on this alloy. The estimated single-crystal elastic constants of Ni3Si, as well as the experimentally measured bulk modulus, are considerably smaller than published values calculated from first-principles methods. The same is true for the C ij of Ni3Ti, but the discrepancies are smaller.

Dielectric relaxation in the Pb(Yb1/2Nb1/2)O3–PbTiO3 solid solution single crystal near the morphotropic phase boundary

The dielectric properties in 0.47Pb(Yb1/2Nb1/2)O3–0.53PbTiO3 (0.47PYN–0.53PT) single crystals near the morphotropic phase boundary (MPB) were investigated in the frequency range from 10 kHz to 1 MHz. Remarkable dielectric relaxation was observed along the polar 〈001〉 direction in the tetragonal 0.47PYN–0.53PT single crystal near the MPB. An increase of the dielectric relaxation time was observed as the Curie temperature was approached. The real part and the imaginary part of the complex relative permittivity obeys the Cole–Cole arc law, and the Debye type dielectric dispersion with the polydispersive type among the order-disorder type ferroelectrics was observed.