Single Crystals Of Pb Research Articles

Single-crystal Nb-doped Pb(Zr,Ti)O3 thin films on Nb-doped SrTiO3 wafers with different orientations

Single-crystal Nb-doped Pb(Zr,Ti)O3 (PNZT) films were grown on electric conducting single-crystal Nb-doped SrTiO3 (Nb:STO) wafers by a sol-gel method. Although the films were of the same composition and prepared under the same condition, different crystal phases with corresponding preferential film orientations were formed when the substrate orientation was changed. [001]-oriented tetragonal PNZT film was formed on the {100} surface of the Nb:STO substrate, whereas [111]-oriented rhombohedral PNZT film on the {111} surface. The PNZT films on SrTiO3 substrates showed considerably high remnant polarization and low coercive field, as compared with conventional PZT films on Si wafers. In particular, high d33 value was obtained in the [001]-oriented PNZT films.

Observations of interface premelting at grain-boundary precipitates of Pb in Al

This work reports direct observations showing the effect of size and interface structure on premelting behaviour of nanoscale inclusions. Using in-situ transmission electron microscopy it was possible to observe premelting of individual Pb inclusions in Al, each bounded by two distinctly different topotaxial interfaces. Such particles were generated by precipitating single-crystal Pb inclusions a few tens of nanometres in size at grain boundaries in Al. At equilibrium these particles adopt compound shapes, made from two segments whose shape and interface structure is characteristic of their misorientation with the matrix crystal. Only one of these interfaces premelts. In close agreement with a simple model, the width of the liquid layer depends reversibly on undercooling and interface curvature, and hence on particle size. The observed behaviour confirms previous reports on interface-dependent melting. By observing the selective melting of different interfaces for the first time on individual particles, it was possible to rule out experimental uncertainties and to show unambiguously that inclusion melting depends strongly on interface structure.

Growth of Pb((Zn1/3Nb2/3)0.91Ti0.09)O3Single Crystals Using an Allomeric Seed Crystal and Their Electrical Properties

Single crystals of Pb((Zn 1/3 Nb 2/3 ) 0.91 Ti 0.09 )O 3 (PZNT 91/9), 28 mm in diameter and 30 mm in length, have been successfully grown using a modified Bridgman technique with an allomeric seed crystal. X-ray fluorescence analysis (XRFA) measurement confirms that the effect of segregation is not serious. The segregation coefficient k for PbTiO 3 content during crystal growth is 0.99, which causes some fluctuation in the composition along the growth direction. The fluctuation of composition and the complicated domain structure cause a variation of electric properties. Dielectric measurement indicates that PZNT 91/9 crystals exhibit an almost normal ferroelectric phase transition at ∼183°C from the tetragonal phase to the cubic phase. In addition, a weak frequency-dependent ferroelectric-ferroelectric phase transition is observed at ∼85°C, which is attributed to partial conversion of the rhombohedral phase to a tetragonal phase. The dielectric thermal hysteresis behavior and the existence of polarization above the Curie temperature verify that the phase transitions at ∼85° and 183°C are first order with a slight diffuse character and first order, respectively. It is demonstrated that the effects of segregation can be decreased and the homogeneity of the obtained PZNT 91/9 single crystals can be improved by optimizing growth parameters.

Equilibrium characteristics and low-temperature photoluminescence of CdTe:Pb single crystals

Using the Bridgman-Stockbarger method, CdTe:Pb single crystals with various dopant concentrations in the solution (C Pb 0 =5×1018, 1019, and 5×1019 cm−3) were grown. Equilibrium characteristics of the material are controlled by deep acceptors with energy E v +(0.39±0.02) eV. The hole concentration decreases as the dopant concentration increases over the entire range of variation in C Pb 0 . The band caused by transitions in donor-acceptor pairs, as well as the edge emission band, is observed in the low-temperature photoluminescence spectra. As C Pb 0 increases, the intensity of the band associated with transitions from the conduction band to an acceptor in the edge region increases abruptly. The peak of the zero-phonon line of this radiation shifts to shorter wavelengths. The possible nature of transitions and the dynamics of variation in the photoluminescence spectra are analyzed in relation to the doping level.

Crossover in magnetization behavior of Bi2212:Pb single crystal

Abstract Magnetic flux penetration in Bi 1.9 Pb 0.3 Sr 2 CaCu 2 O 8 single crystals in crossed fields is studied by magnetooptic technique. The anisotropy of the flux penetration induced by in-plane field is observed at temperatures below T m =54±2 K . The anisotropy increases with temperature if T T m . No correlation between the in-plane field and the out-of-plane flux penetration is observed for T > T m . This anisotropy is an evidence of a strong correlation between pancake vortices in different CuO planes. The vortex lattice behaves like 3D system at T T m and like 2D one at T > T m .

Origin of Giant Piezoelectricity in Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 Single Crystals

We found the giant electromechanical coupling factor of k31 mode to be over 80% and the piezoelectric d31 constant to be nearly −1700 pC/N in ferroelectric single crystals of Pb[(Zn1/3Nb2/3)0.91 Ti0.09]O3 (PZNT91/09). The origin of the giant k31 was as follows: the crystal with multi-domains changed into one having a mono-domain in the direction perpendicular to the poling field (k31 mode) as well as in the direction parallel to the poling field. The discovery of the giant k31 found a key to clarify the origin of the high piezoelectricity in PZNT91/09. Investigating the crystal orientation dependence of k31 and their aging characteristics, the giant k31 and d31 accompanied with the superior aging characteristics could be obtained in the case of the rhombohedral (100) crystal poled along [001] of the original cubic direction. Furthermore, it is found that the Young's modulus Y (0.89×1010 N/m2) in rhombohedral PZNT91/09 with giant k31 is remarkably small. Therefore, we believe that the high piezoelectricity including the giant k31 in PZNT91/09 is due to the remarkable softness of the rhombohedral phase, not the existence of a M.P.B. for easy to deform symmetrically by poling field.

Investigation on optical transmission spectra of (1− x)Pb(Mg 1/3Nb 2/3)O 3– xPbTiO 3 single crystals

The optical transmission spectra from 0.3 to 11 μm of relaxor ferroelectric single crystals (1− x)Pb(Mg 1/3Nb 2/3)O 3– xPbTiO 3 (PMN– xPT) were systematically studied at room temperature in this paper. The crystal is transparent between 0.45 and 5.5 μm and becomes completely absorbing around 0.4 μm in near UV region and 10 μm in infrared region. But the wavelength cutoff in near UV is much sharper than the long wavelength cutoff. As compared with other configurations, tetragonal single crystals possess the optimal transmission properties. The optical transmittance in the wavelength region from 0.45 to 5.5 μm is about 70%. The results show that tetragonal PMN– xPT single crystals are promising for a wide range of optical applications. Some discussions about the oxygen-octahedra structure that determines the basic energy level of the crystals are also presented on the optical properties of PMN– xPT single crystals.

Anisotropic flux creep in Bi2212:Pb single crystal in crossed magnetic fields

An experimental study of magnetic flux penetration under crossed magnetic fields in Bi2212:Pb single crystals is performed by the magneto-optic technique. The anisotropy of the flux creep rate induced by the in-plane magnetic field is observed at T<54±2 K. This observation confirms the existence of the three-dimensional flux line structure in Bi2212:Pb at low temperatures. An asymmetry of the flux relaxation with respect to the direction of the in-plane field is found. This effect can be attributed to the influence of the laminar structure on the pinning in Bi2212:Pb single crystals.

Top-Seeded Solution Growth of Pb[(In1/2Nb1/2),(Mg1/3Nb2/3),Ti]O3 Single Crystals

The crystal growth of relaxor-based ferroelectric single crystals Pb[(In1/2Nb1/2),(Mg1/3Nb2/3),Ti]O3 (PIMNT) was investigated using the top-seeded solution growth (TSSG) method. The concentration of Pb(In1/2Nb1/2)O3 in a melt was chosen to be 0.24 mole, and that of Pb(Mg1/3Nb2/3)O3 was changed from 0.36 to 0.42 mole. A mixture of PbO+B2O3 was used as a flax and the melt composition was PIMNT/PbO/B2O3=70/29/1 wt%. The obtained crystals showed that the concentration of Pb(In1/2Nb1/2)O3 slightly changed but that of Pb(Mg1/3Nb2/3)O3 increased by about 12%, 0.05 mole, compared to those of the melt. All crystals had a complete perovskite structure. A crystal with a composition of Pb[(In1/2Nb1/2)0.24(Mg1/3Nb2/3)0.43Ti0.33]O3 was obtained, and its Curie temperature was Tc = 208°C and rhombohedral-to-tetragonal phase transition temperature was Trt = 120°C. A phase diagram for crystal growth near the morphotropic phase boundary mentioned above was obtained.

E-field-induced polarization rotation in Pb(Mg1/3Nb2/3)1−xTixO3 crystal

A sequence of field-induced phase transformations was observed by means of a polarizing microscope on a (111)-cut single crystal Pb(Mg1/3Nb2/3)0.67Ti0.33O3 at room temperature with an electric field applied along the [111] direction. As electric field increases, polarizations of the rhombohedral R domains whose polar directions are not along [111] rotate first toward a tetragonal T phase associated with 90° domain walls. Then the crystal gradually reaches total optical extinction for all polarizer angles at 12 kV/cm, indicating a single [111] rhombohedral R111 domain with polarization aligned with the electric field. These field-induced phase transformations are irreversible and proceed most likely through MA-type monoclinic distortions, i.e., R→MA→T→MA→R111.

Flux Bridgman growth of Pb[(Zn 1/3Nb 2/3) 0.93Ti 0.07]O 3 piezocrystals

Relaxor ferroelectric single crystals Pb[(Zn 1/3Nb 2/3) 0.93Ti 0.07]O 3 (PZNT93/7) have been grown by the modified Bridgman method using 50 mol% PbO as a flux. A gas cooling system was assembled at the bottom of the platinum crucible to induce single nucleation as well as form a large temperature gradient in the furnace. The oxygen gas flow was controlled at a rate of 1.6 l/min and the lowering rate of the crucible was less than 0.5 mm/h. PZNT93/7 crystal up to 33 mm in diameter and 28 mm in length was obtained. The double-crystal X-ray rocking curve was measured and the FWHM value is about 505 arcsec. The dielectric constants and dielectric loss were measured at frequencies of 100 Hz, 1 kHz, 10 kHz and 100 kHz. The Curie temperature of as-grown PZNT crystal was 179°C. The transition temperature of rhombohedral–tegragonal phase was about 120°C, which was 40°C higher than that of PZNT91/9 crystals.

In situ EC-AFM observation with atomic resolution of Pb(1 0 0) and Pb(1 1 1) single crystals in sulfuric acid solution

Pb(1 0 0) and Pb(1 1 1) single crystals in 50 mM H 2SO 4 aqueous solution have been investigated by in situ electrochemical atomic force microscopy (EC-AFM) under potential control. We have succeeded in observating high resolution images of Pb(1 0 0) and Pb(1 1 1) single crystals, as well as high resolution and morphological images of PbSO 4 crystals formed on the Pb single crystals. We found that the top face of PbSO 4 crystals formed on Pb(1 0 0) is PbSO 4(0 0 1), while that on Pb(1 1 1) is PbSO 4(1 0 0). We also found that the atomic rows along the [1 0 0] and [0 1 0] direction of PbSO 4(0 0 1) surface were parallel with those along the [0 1 1] and [0 1 1̄] direction of the Pb(1 0 0) substrate, while those along the [0 1 0] and [0 0 1] direction of the PbSO 4 (1 0 0) surface were parallel with those along the [0 1 1̄] and [1̄ 1 1] direction of the Pb(1 1 1) substrate.

Top-Seeded Solution Growth of Pb[(Zn1/3Nb2/3)0.93Ti0.07]O3 Single Crystals

Top-seeded solution growth (TSSG) of relaxor-based ferroelectric single crystal Pb[(Zn1/3Nb2/3)0.93Ti0.07]O3 (PZNT93/7) was investigated. PbO and PbO+B2O3 were used as fluxes. The solution compositions were (PZNT93/7)/PbO]=70/30 wt% and (PZNT93/7)/PbO/B2O3=70/29/1 wt%. A platinum stick, PZNT93/7 single crystal and Pb[(Mg1/3Nb2/3)0.65Ti0.35]O3 (PMNT65/35) single crystal were used as seeds. The addition of B2O3 was used to lower the growth temperature and reduce the rate of PbO evaporation. Crystals grown inside the melting solution had a pure perovskite structure and their Curie temperature was 168°C, corresponding to PZNT93/7 composition. However, it was found that the perovskite crystals decomposed little by little from the crystal surface to undesirable pyrochlore after being pulled out of the melt and exposed to air during the growth. Crystals grown at the melt surface were originally of pyrochlore structure. The investigated results revealed the possibility of growing these single crystals by a continually charged TSSG technique.

Seeded Growth of Relaxor Ferroelectric Single Crystals Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 by the Vertical Bridgman Method

Relaxor ferroelectric single crystals Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 (PZNT91/9) with a dimension of 30 mm in diameter and 25 mm in length have been grown by the modified vertical Bridgman method using PbO as the flux. Initially, seed crystals were obtained by cooling high-temperature solutions at the rate of 0.8–2°C/h. PZNT91/9 crystals were grown in a platinum crucible with a seed well of φ10 mm×60 mm from different solutions. It is difficult to grow perovskite PZNT crystals from 91 mol% Pb(Zn1/3Nb2/3)O3–9 mol% PbTiO3 melts with a surplus of PbO due to the competition of the pyrochlore phase. Additionally, a Pt crucible is prone to severe erosion by PbO at high growth temperatures. The optimum flux concentrations were found to be 45–55 mol% and the growth rate was 0.3–0.6 mm/h. Twelve pieces of PZNT wafers without any PbO striation were obtained. The dielectric properties of the grown crystals were determined.

Holographic imaging of atoms using thermal neutrons.

In a recent paper [L. Cser, G. Krexner, and Gy. Török, Europhys. Lett. 54, 747 (2001)]] the use of thermal neutrons with wavelengths close to interatomic distances in condensed matter was proposed to obtain holographic images on an atomic scale. Two experimental methods were considered which either put the radiation source inside and the detector outside the object or vice versa. The second approach, called the inside-detector concept, requires strongly neutron-absorbing isotopes acting as pointlike detectors in the sample. In the present work, we demonstrate the feasibility of this technique by recording a holographic image of a lead nuclei in a Pb(Cd) single crystal.

Phase transition in a vortice lattice in a Bi2212:Pb single crystal

The magnetooptical method was used to investigate the penetration of a magnetic flux into a single crystal of a high-temperature superconductor (Bi0.84Pb0.16)2.2Sr2CaCu2O8 in crossed magnetic fields. It is shown that at low temperatures the penetration of the magnetic flux is anisotropic: the flux moves preferentially along the magnetic field applied in the plane of the sample, and the anisotropy grows as the temperature increases. At a temperature T m = 54±2 K, there occurs a sharp change in the character of penetration of the magnetic field into the superconductor; the direction of the flux ceases be dependent on the direction and magnitude of the magnetic field applied in the plane of the sample. In this case, the transition temperature T m is independent of the applied magnetic field. The effect is interpreted in terms of the concepts of a phase transition in the system of vortices, which is related to a sharp decrease in the correlations in the position of vortices in various CuO planes, i.e., with the transition from three-dimensional to two-dimensional behavior of the vortex structure.

Critical behaviour of the curved region near 111-facet edge of equilibrium shape cuprous selenide large single crystals

Several millimetres large spherical cuprous selenide single crystals with well developed (1 1 1) facets grown at about 30 K below the roughening temperature ( T R≈830 K) and rapidly cooled to room temperature were used to test the universality and value of critical exponent describing the surface profile behaviour near the facet edge. Enlarged photographs (52.5 times) of part of the crystal profile were digitised with resulting spatial resolution of 0.1904±0.0001 μm. After FFT low pass filtering, the position of crystal silhouette edge was determined as the loci of the extremes in the first derivative of each image row intensity profile. For assumed critical dependence z= A( x− x 0) θ , the inverse logarithmic derivative applied to crystal profile data points disclosed the extent of intervals of different behaviour, giving independently the respective indicative values of fitting parameters θ and x 0. In three distinct regions non-linear Levenberg–Marquardt fitting was applied to original data sets. In the region farthest away from the facet, the behaviour is well described by θ≈2.5 or by Andreev formula z= A( x 0− x) 2+ B( x 0− x) 4 . In the stepped region, for ϕ=13.98–17.12° (tilt angle relative to facet plane), the critical exponent θ=1.499±0.003 is found, in agreement with Pokrovsky–Talapov universality class predicted value of θ= 3 2 . The step interaction energy, step free energy and facet free energy ratios obtained from data fitting parameters only, are compared to published values for 4He, Si and Pb single crystals. The behaviour in the immediate vicinity of the facet edge is discussed in the light of dynamics features recently observed on different single crystals during growth (cuprous selenide, 4He) and equilibration (Pb).

Present and future of piezoelectric single crystals and the importance of B-site cations for high piezoelectric response.

High quality piezoelectric single crystals, such as Pb(Zn(1/3)Nb(2/3))O3-PbTiO3 (PZNT) and Pb(Mg(1/3)Nb(2/3))O3-PbTiO3 (PMNT), have been investigated, and, because their piezoelectric properties are greatly superior to those of Pb(Zr(1-x)Ti(x))O3 (PZT) ceramics, they have been used for certain transducer applications since the late 1990s. The present situation for these relaxor-PT (lead titanate) single crystals is summarized. In this review, some possible high Tc > 200 degrees C single crystals are also introduced. Single crystals of Pb(In(1/2)Nb(1/2))O3-PbTiO3 (PINT) binary system and Pb(Mg(1/3)Nb(2/3))O3-Pb(Sc(1/2)Nb(1/2))O3-PbTiO3 (PSMNT) tertiary system have been synthesized, and their electrical properties are reported. In addition, a novel guiding principle for discovering excellent piezoelectric materials, namely the presence of low molecular mass B-site ions that can enter the lead-perovskite Pb(B'B'')O3 structure, is introduced.

Single crystallization of Pb in carbon nanotubes

The formation mechanism of Pb single crystals in carbon nanotubes is considered in terms of the classical nucleation and growth theory modified by our models for size-dependent solid–liquid interface energy and size-dependent melting temperature. It is found that since the growing time of a cylindrical nucleus of Pb along carbon nanotubes is much shorter than the time to form the nucleus, a single crystallization is present. Moreover, the possible smallest diameter of crystalline nanowire is discussed.

Absorption of ballistic phonons by quasiparticles in superconducting Pb

Phonon imaging of single-crystal Pb at T=2 K shows strong absorption of ballistic longitudinal phonons with wave vectors in {1 1 1} planes. A calculation of the phonon-scattering from quasiparticles on the anisotropic Fermi surface of Pb indeed shows concentrated scattering in these planes; however, the temperature dependence of absorption suggests an anisotropic gap with a minimum that is much lower than the accepted gap of Pb.