Shear resonance behavior of single-domain PZN-PT single crystals

The shear resonance behavior of rectangular-shaped samples of single-domain PZN-PT single crystal samples of 3m symmetry and having three faces parallel to the (111), (112), and (110) crystal planes has been examined. Sample geometries with separable resonance peaks are identified, which give shear properties consistent with 3m symmetry, namely, k15 approximately k24 and d15 approximately d24. Sample geometries with inseparable resonance peaks are also distinguished. The latter sample geometries are not suitable for shear property characterization of piezoelectric single crystals of 3m symmetry as the broad coupled resonance peak often results in inflated k15 and d15 values.     

Estimation of piezoelastic and viscoelastic properties in laminated structures

An inverse method for material parameter estimation of elastic, piezoelectric and viscoelastic laminated plate structures is presented. The method uses a gradient based optimization technique in order to solve the inverse problem, through minimization of an error functional which expresses the difference between experimental free vibration data and corresponding numerical data produced by a finite element model. The complex modulus approach is used to model the viscoelastic material behavior, assuming hysteretic type damping. Applications that illustrate the influence of adhesive material interfaces and viscoelastic parameter identification are presented and a few simulated test cases aid the interpretation of results.     

Relation between kinetic properties of single crystals and of oriented polycrystalline materials

It is demonstrated that the characteristics of a single crystal can be calculated from available data on the properties and the orientation of polycrystalline materials.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 47, No. 3, pp. 418–421, September, 1984.     

Dielectric properties of LiF single crystals

The dielectric constant,, loss, tan, and a.C. Conductivity, , of high quality single crystals of LiF have been measured in the frequency range 10² to 10⁵ Hz and in the temperature range 30 to 400° C. of LiF at 30° C is 8.3 and is frequency independent; tan was below detection level (tan<0.0001). increases slowly with temperature up to about 150° C (frequency independent region) beyond which it rises rapidly, being frequency dependent with larger values at lower frequencies. A similar behaviour is exhibited by tan . The activation energy for conduction in the high temperature region is calculated to be 0.93 eV from log against 1/T graphs. Log () against 1/T plots (where is the difference between the dielectric constant at any temperature and the value at room temperature, 30° C) yields an activation energy value of 1.0 eV in the high temperature region. This activation energy is found to be independent of frequency. This agreement between the two activation energy values, one for the a.c. conductivity and the other for the increase with temperature. This suggests that the same charge carriers are responsible for the two processes in the high temperature region.     

Growth and properties of CuInS2 single crystals

CuInS₂ single crystals 14–16 mm in diameter and up to 40 mm in length were grown by the traveling solvent method. The crystals were found to ben-type, with a conductivity of 0.1–10 S/cm, carrier concentration of 10¹⁶–10¹⁷ cm⁻³, and carrier mobility of 150–220 cm²/(V s). The anisotropic thermal expansion of the crystals was measured.     

Growth and properties of strontium cobaltate single crystals

Single crystals of strontium cobaltate with oxygen-deficient composition have been prepared by the floating-zone method using a lamp image furnace. Chemical and X-ray analyses showed that the composition was SrCoO_2.70 with a doubled perovskite structure of cubic cells, a ₀=7.710±0.001 Å. The crystal was ferromagnetic and its Curie temperature was 150 K. The effective Bohr magneton per ion of Co⁴⁺ was 1.21, suggesting that Co⁴⁺ is almost in the low spin state.     

Electrical properties of undoped single CoO crystals

Electrical conductivity and Seebeck coefficient measurements have been carried out on undoped single CoO crystals in the temperature range of 289 to 548 K. All samples were found to be p type semiconductors. The mobility of charge carriers has been determined and the results are explained on the basis of hopping mechanism.     

The cryogenic properties of Al-Li single crystals

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Mechanical properties and dislocation mobility in barium fluoride single crystals

Conclusions The elastic limit temperature dependence between 50 and 1000°C consists of three regions differing in the mechanisms governing dislocation motion. The general form of the dependence, however, is similar to that for metals. Schmid's law is not obeyed between 50 and 250°C for compressional deformations along the [110] and [112] directions. The increased elastic limit for the [110] orientation is explained by an additional interaction between dislocations lying in the same slip plane but pertaining to different systems.The dislocation velocity dependence on applied shear stress is rapid at 150°C (m-12–18) but decreases quite strongly as the impurity content changes. According to calculations the activation area is (100–200)b² for all the studied BaF₂ crystals. This indicates that dislocation motion is not limited by Peierls' barriers in the stress region in question, but by barriers connected with point defects.Chernogolovka, Leningrad. Institute of Solid-State Physics, Academy of Sciences of the USSR, Moscow. S. I. Vavilov State Optical Institute. Translated from Problemy Prochnosti, No. 6, pp. 10–16, June, 1970.     

Interaction between liquid aluminum and NiO single crystals

The wetting behavior of NiO single crystal by liquid aluminum has been studied by the sessile drop method under vacuum at 973–1273 K for 2 h. Optical microscopy, SEM, EDS and X-ray analysis were applied to characterize the structure and chemistry of solidified cross-sectioned sessile drop couples. Under tested conditions, molten Al wets and reacts with NiO to form Al₂O₃ and Ni. This leads to alloying of the initially pure Al drop with Ni to the hypereutectic composition and to the formation of a thick reaction product region inside the NiO substrate, whose structure presents interpenetrated networks of fine alumina precipitates and an Al–Ni matrix. After solidification the Al–Ni matrix and the drop have the same phase composition, which is in agreement with Al–Ni phase diagram, showing the formation of Al₃Ni at T < 1128 K and Al₃Ni₂ at 1128 K < T < 1406 K. The strong reactivity of Al/NiO couples, accompanied with the drop deformation, fragmentation of the reaction product region and development of a crater under the drop, contributes to the perturbation of the triple line and to the formation of apparent contact angles at 1073–1273 K. This leads to unusual changes of measured contact angles with temperature, decreasing from 84^° at 973 K to 36^° at 1073 K, and then increasing to 75^° at 1273 K, while structural analysis suggests complete wetting at 1073 K.     

Crystallization and physical properties of SbTiTaO6 single crystals

Optimum physicochemical conditions for a hydrothermal crystallization of antimony titanium tantalate SbTiTaO₆ (STT) at 190–225°C in the SbTiTaO₆-H₂SO₄-HCl-H₂O₂-H₂O system with various concentrations of acids and hydrogen peroxide. The dielectric and pyroelectric properties of synthesized STT single crystals were studied.     

Determination of directional strength properties in face-centered single crystals

A procedure is given for evaluating the stress-rupture strength of structures made of single-crystal materials from values for stress-rupture strength in characteristic crystal directions [100], [110], [111].Translated from Problemy Prochnosti, No. 11, pp. 47–49, November, 1990.     

Optical properties of undoped and chromium-doped VA-VIA-VIIA single crystals

SbSl∶Cr, SbSel∶Cr, BiSl∶Cr, and BiSel∶Cr single crystals were grown by the vertical Bridgman technique using the ingots synthesized from the high-purity (99.9999%) elements antimony, bismuth, sulphur, selenium, iodine and chromium. The grown single crystals crystallized in the orthorhombic structure and had an indirect energy-band structure. The temperature dependence of the optical energy gap was well fitted by the Varshni equation. When chromium was doped into the single crystals, impurities in the optical absorption peaks appeared, and were attributed to the electron transitions between the energy levels of Cr²⁺ ions sited at the T_d symmetry point in the host lattice.     

Growth and properties of sodium tetraborate decahydrate single crystals

Sodium tetraborate decahydrate (Na₂B₄O₇·10H₂O) single crystals were grown from aqueous solution by slow solvent evaporation method and its functional groups have been confirmed by FTIR. Grown crystals were found to be hard in nature (n = 1.8). From optical studies band gap of the material was found to be 4.1 eV and PL emission peak was found at 340 nm which can be due to annihilation self trapped excitons present in borate crystals. Dielectric constant was found to increase with temperature up to 70 °C. Conductivity obeys Jonscher's power law as seen at different temperatures. Activation energy of the crystal was found to be 2.05 eV.     

Growth and some properties of sodium-cadmium formate single crystals

The growth of sodium-cadmium formate NaCd(HCO₂)₃ single crystals by slow cooling method and their characterization by selective stching, X-ray diffraction and IR absorption spectral techniques are reported. The dislocation density in the crystals is found to be 5·10² ? 2·10³ cm^?2. The compound crystallizes in orthorhombic unit cell with space group Pcca and Z = 4. The influence of metal ion on carboxylate stretching frequencies of polycrystalline samples is investigated and the possible correlations between spectra and structure considered.     

Interaction between a dislocation and impurities in KCI single crystals

The strain-rate cycling test during the Blaha effect at 77–220 K has been carried out for three kinds of single crystals, KCI, KCI doped with Sr²⁺, and KCI doped with various impurities. The temperature and impurity dependence of the relation between strain-rate sensitivity and stress decrement, as well as the effective stress, _p1, due to only one type of impurity lying on the dislocation with the largest separation, has been investigated. From the temperature dependence of _p1, the force-distance profile between a dislocation and impurities was obtained. The critical temperature,T _c, for KCI: Sr²⁺ was found to be about 227 K.