Doped Pb Research Articles

Effect of Microstructure on Ferroelectric and Piezoelectric Properties of A-Site and B-Site Modified PLZT

Ba modified (Pb,La,Ag)(Zr,Ti)O3 ceramics synthesized by conventional mixed-oxide method with chemical formula [Pb0.983 − zLa0.012Ag0.005Baz] [(Zr0.52Ti0.48)0.99825]O3 were investigated for ferroelectric and piezoelectric properties. XRD studies indicate that increment of Ba concentration resulted in strong tetragonality in the ceramics. Grain growth (3.08 μ m) inhibited and apparent density (7.54 gm/cm3) enhanced up to 1.5 mole% Ba respectively. As Ba content increased dielectric properties showed maximum values (εRT = 2347, εTc = 23449) while Tc constantly decreased. The remanent (Pr = 34.72 μ C/cm2) and spontaneous polarization (Ps = 41.84 μ C/cm2) were optimum in 1 mole% Ba respectively while Ec showed increasing trend throughout the series. Piezoelectric properties attained maximum values of d33 = 438 pC/N in 1.5 mole% Ba while kp = 0.533 and kt = 0.412 in 1 mole% Ba doped (Pb,La,Ag)(Zr,Ti)O3 ceramics respectively.

Grain size effect on the poling of soft Pb(Zr,Ti)O 3 ferroelectric ceramics

The properties of piezoelectric ceramic materials are strongly dependent on the degree of polarization as set by the poling process. As the polarization depends on the domain wall mobility, which in turn depends on the domain size and grain size, the current study focuses on the effect of the grain size on the poling process and dielectric and piezoelectric properties. Polarization and pyroelectric, dielectric and piezoelectric properties of modified donor doped ferroelectric Pb(Zr,Ti)O 3 ceramics having different grain sizes have been studied. The dielectric and piezoelectric parameters greatly improved at room temperature with increasing grain size. The Curie temperature (160 °C) is found to shift slightly (by about 7 °C) towards higher temperatures as the grain size increases (2–10 μm). It is concluded that, an optimum choice of a combination of poling field and grain size leads to optimum physical properties. A limited dependence of the dielectric properties on the grain size in non-poled state exists. The dominant contribution to the dielectric properties in the different conditions of the material is discussed.

Correlation between modulation structure and electronic inhomogeneity on Pb-doped Bi-2212 single crystals

The correlation between nanometer-size electronic states and surface structure is investigated by scanning tunneling microscopy/spectroscopy (STM/S) on Pb-doped Bi 2− x Pb x Sr 2CaCu2O 8+ y (Pb–Bi-2212) single crystals. The advantage of the Pb–Bi-2212 samples is that the modulation structure can be totally or locally suppressed depending on the Pb contents and annealing conditions. The superconducting gap ( Δ) distribution on modulated Pb–Bi-2212 samples showed the lack of correlation with modulation structure except a slight reduction of superconducting island size for the b-axis direction. On the other hand, the optimal doped Pb–Bi-2212 ( x = 0.6) samples obtained by reduced-annealing showed totally non-modulated structure in topography, however, the spatial distribution of Δ still showed inhomogeneity of which features were quite similar to those of modulated samples. These results suggest that the modulation structure is not the dominant origin of inhomogeneity although it modifies the streaky Δ structure sub-dominantly. From the gap structure variation around the border of narrow gap and broad gap regions, a trend of the coexistence of two separated phases i.e., superconducting phase and pseudogap like phase, is detected.

Optical and electrical properties of doped Pb 1− x(Mg 1− ySr y) xS thin films prepared by hot-wall epitaxy

We have investigated the optical and electrical properties of Bi- or Tl-doped Pb 1− x (Mg 1− y Sr y ) x S thin films. The films with carrier concentration sufficient for use as cladding layers in a laser diode, were obtained by doping with Bi as n-type impurity or Tl as p-type impurity. Optical absorption was observed at far-infrared region on the Bi-doped films, and the relation between absorption coefficient α and carrier concentration n was found to be expressed as α=0.27 n 0.21 at 6 μm.

Investigation on the Dielectric and Polarization Behavior of Sol-Gel Derived Erbium Doped Pb(Zr 0.53 Ti 0.47 )O 3 Thin Films

We have studied the effect of Er 3+ doping on the dielectric and polarization hysteresis behavior of sol-gel derived Pb 1.05 (Zr 0.53 Ti 0.47 )O 3 thin films. Up to 1 at% Er doping, the dielectric constant of undoped PZT increases from 1245 to 1477 (measured at 50 kHz, 500 mV oscillation voltage), whereas the remnant polarization increases from 30 to 41 w C/cm 2 . Under the subswitching external field, the dielectric permittivities follow the Rayleigh law. The Rayleigh coefficient ( f ) was considered as a measure of the ease of domain wall motion. Up to 1 at% Er doping, the increase of f indicates minimal defect-domain wall interaction due to lower defect concentration. Under the switching field, the irreversible part of the switchable polarization was estimated from the C-V and hysteresis measurements. At the saturation field it was observed that up to 1 at% Er doping the irreversible component at switchable polarization increases and reversible component remains low. The improvements of dielectric and ferroelectric properties for up to 1 at% Er doping have been correlated to the relative site occupancy of Er 3+ as a function of Er content in PZT host lattice.

Comparison of sputtered SBTN and PLZT thin film capacitors for FRAM applications

Thin films of the solid solution SrBi2Ta2O9-SrBi2Nb2O9 (SBTN) and Ca and Sr doped (Pb, La)(Zr, Ti)O3 (PLZT) were prepared by conventional, single target, rf-magnetron sputtering. The films were deposited onto Pt coated substrates with a diameter of 6 inches. The electrical properties were characterized by hysteresis and pulsed field switching measurements. A ferroelectric performance comparison between two types of capacitors will be presented. The recent improvement in PLZT capacitor processing have greatly extended fatigue resistance beyond what is usually observed and reported for SBTN capacitors.

Superconducting properties of sodium doped (Pb,Cd)-1212 type compounds

The effect of sodium doping (3–8 mol%) on the structural, thermal and superconducting properties of (Pb 0.5,Cd 0.5)Sr 2(Y 0.6,Ca 0.4)Cu 2O 7− δ has been studied. For 5 mol% NaNO 3 doping, relatively pure superconducting phase was formed without SrCuO 2 and Sr 5Pb 3CuO 12 impurities as observed in both 3% and 8% doped as well as undoped superconductors. The cell parameters and cell volumes are also found to be minimum for the 5% doped superconductor, but were slightly larger than for the undoped superconductor. Highest T c of 55 K was also observed for 5% doped sodium containing sample and the T c enhancement was 15 K above the sodium free superconductor. The effect of calcium content on the T c enhancement by 5% sodium addition was investigated for (Pb 0.5Cd 0.5)Sr 2(Y 1− x Ca x )Cu 2O 7− δ ( x=0.3, 0.5) superconductors. The sodium free superconductors show only onset of superconductivity ( T c,onset), which increases from 23 to 49 K with increasing calcium content. The resistivity behaviour before T c changes from semiconducting to metallic nature. Addition of sodium leads to the observation of zero resistance ( T c,zero) at 25 K only for x=0.5 sample, which is however lower than the T c,zero of 30 K exhibited by the superconductor with x=0.4 calcium content. The lowering of melting point and denser microstructure with larger grains were observed upon 5% sodium doping on (Pb 0.5,Cd 0.5)Sr 2(Y 0.6,Ca 0.4)Cu 2O 7− δ superconductor.

Production and characterisation of composite relaxor ferroelectric multi-layer structures

The drive for miniaturisation of passive capacitor and filter devices requires dielectric materials with higher relative permittivities than can be attained using normal ferroelectrics. Relaxor ferroelectrics possess the required high relative permittivities but are incapable of being chemically doped to give a temperature stable capacitance. Work is presented detailing the design and development of a new class of temperature stable high volumetric efficiency multi-layer capacitors. Various compositions of high relative permittivity relaxor ferroelectrics are co-sintered in to a multi-layer capacitor with controllable temperature characteristics. The materials used are all doped perovskite Pb(Mg 1/3Nb 2/3)O 3 (PMN) compositions. The ceramic powder-processing route required to make such structures is summarised with reference to the unique device fabrication problems encountered. Dielectric measurements of the prototype devices are presented. ©

Determination of the ordered structures of Pb(Mg1/3Nb2/3)O3 and Ba(Mg1/3Nb2/3)O3 by atomic-resolution Z-contrast imaging

The atomic structure of ordered domains in Ba(Mg1/3Nb2/3)O3 and La-doped and undoped Pb(Mg1/3Nb2/3)O3 is studied by high-resolution Z-contrast imaging. The ordered domain structure in both doped and undoped Pb(Mg1/3Nb2/3)O3 is determined to be in agreement with the charge balanced random-layer model and inconsistent with the space-charge model. It is shown that La doping in Pb(Mg1/3Nb2/3)O3 enhances not only the domain size but also the degree of ordering.

Mixed electron emission from doped Pb(Zr,Ti)O3 ceramics: Microstructural aspects

A mixed type electron emission, i.e., simultaneous ferroelectric and plasma emission, was observed with a negative driving pulse applied to doped Pb(Zr,Ti)O3 ceramics in the absence of any external potential on the electron collector. During these emission studies, significant microstructural changes on the emission surface were observed, and corresponded to the different emission modes. Erosion craters at the edge of the electrode and small particles near these craters reflected the formation of a dense plasma there. Comparatively, cavities, i.e., grain pullouts, accumulated on the bare ferroelectric surface, the frequency of which depended upon its distance from the grid. This phenomenon is proposed to be a result of fringing fields and the associated strain energy due to 90° domain switching, which could be seen as an evidence that ferroelectric emission occurred in these areas.

Behavior of Sequential Extraction of Lead from Thermally Treated Lead(II)‐Doped Alumina

AbstractThere are environmental concerns about emission of heavy metals in flue gases during incineration of hazardous wastes. Low temperature injection of sorbents has been suggested as a way to reduce the heavy metal content of the emitted gases. We investigated the extractive behavior of Pb in thermally treated Pb2+‐doped alumina using the USEPA toxicity characteristics leachability procedure (TCLP) and a sequential extraction method to obtain information on the Pb‐alumina reaction. Thermal treatment of Pb2+‐doped alumina was in the 100 to 900°C range for 10 to 60 min. Results indicated that the Pb2+‐doped alumina treated at higher temperature for longer duration was resistant to the TCLP and to the sequential extraction for the first four fractions, but not for the residual fraction (Fraction 5). The relationship between total extracted Pb of the first four fractions and the TCLP concentration was strong (r = 0.993 for the 100°C and r = 0.996 for the 500°C treatments). Almost all of the doped Pb was distributed between conceptual fractions that were either bound to carbonates or were residual that was extracted with 10% HF and H2O2. The shift in distribution of Pb that was carbonate‐bound to that bound in the residual fraction as treatment temperature increased from 100 to 500°C was more than that which shifted from 500 to 900°C. After treatment at 900°C most of the Pb was associated with the residual fraction (indicating a strong sorption between Pb and alumina) and the TCLP concentration dropped to nondetectable levels.

Temperature Dependence of the Initial Ageing of Dielectric Constant in a Lead Magnesium Niobate Based Ceramic

The initial dielectric ageing behaviors of a doped Pb[Mg1/3Nb2/3]O3-based ceramic were investigated over a wide temperature range. The dielectric constant and logarithmic ageing time were regressed in terms of a linear relationship and the temperature dependence of ageing rate at different frequencies was obtained. The strongest ageing at a particular measurement frequency is confirmed to take place at the temperature of maximum dielectric constant of the deaged ceramic at that frequency. When the ageing temperature differs from this temperature, the ageing rate decreases. The curve of ageing rate against temperature, which is found to be symmetrical in shape, is fitted by a Gaussian equation. Microstructural factors responsible for the phenomenon are analysed.

Banding and electronic structures of metal azides——Sensitivity and conductivity

By using both DV-Xα and EH-CO methods, the calculation studies of the structure-property relationships of a series of metal azides, of their clusters' electronic structures in ground and excited states, of their systems with cation vacancy and the doped Pb(N3)2, as well as their crystal band structures have been conducted. The results show that the sensitivity of ionic-type metal azides varies with the degree of difficulty of electronic transition of the losing charge on N3. A metal azide with cation vacancies has a greater sensitivity than the perfect one. When doped with monovalent metal ions, lead azide's sensitivity increased; when with trivalent ones, its sensitivity decreased; when with divalent ones, little of it changed. Compared with heavy metal azides. an alkali metal azide has a larger band gap, a smaller band width and a greater transition energy of frontier electron with a smaller amount of losing charge on N3, and thus has lower sensitivity and conductivity than heavy metal azides.

Photovoltaic effect for the linearly polarized light in (Pb,La)(Zr,Ti)O3 ceramics

The bulk photovoltaic effect in non-centrosymmetric crystals is caused by asymmetric generation, recombination or scattering of excited non-equilibrium electronic carriers. Photovoltaic effects in (Pb,La)(Zr,Ti)O3-based ceramics have been investigated using linearly polarized light. Angular dependence of the photovoltaic voltage and current on the polarization direction of the light was observed in doped (Pb, La)(Zr,Ti)O3 ceramics. A phenomenological model was proposed to fit the experimental results from which the photovoltaic coefficients were calculated.

X-ray absorption near-edge studies of BaBiO3, BaBi1-xPbxO3 and Ba1-xKxBiO3 systems

The valence state of Bi in pure and doped (Pb, K) BaBiO3 has been determined by X-ray absorption near-edge structure (XANES) spectroscopy. In all materials the Bi valence is found to be close to IV. A disproportionation of Bi(IV) into Bi(III) and Bi(V) is not indicated by analysis of the XANES data. The valence state of Pb is also found to be IV in BaBi1-xPbxO3.

Far-infrared study of in doped Pb 0.75 Sn 0.25 Te single crystals

We present far-infrared reflectivity spectra of Pb 0.75Sn 0.25 Te single crystals doped with 0.5 at% of indium. The experimental spectra are analysed using a numerical fitting procedure based on the plasmon-phonon interaction model. The plasma frequency is found to decrease on cooling from 300 to 30 K and a sharp drop in ω itp was observed between 30 K and 5 K. If the free carrier distribution over sample thickness is taken into account, experimental and calculated spectra agree well over the above temperature range. The results of galvanomagnetic measurements are also presented.

Enhancement of superconducting transition temperature by photo-carriers in indium doped Pb 1−XSn XTe film with lead inclusion

The electrical resistivity and the Hall coefficient of 1% In doped Pb 1−XSn XTe (X=0.25) films with Pb precipitates are measured in the range of 1.5 K< T<300 K. In these films, the superconducting transition occurs below 6K because of the proximity effect by Pb grains. By exposure to light, a large photoconductivity excited from In impurity enhances the superconducting transition temperature. The enhancement will be understood by considering that the coherence length of superconductivity in semiconducting region is extended by the photo-carriers.

Composition dependence of high T c phase formation in Pb-doped Bi-Sr-Ca-Cu-O thin films

We studied the composition dependence of high Tc phase Bi2Sr2Ca2Cu3Ox formation in Pb-doped Bi system thin films. Films were prepared by rf magnetron sputtering using three targets and post-annealed to synthesize superconducting films. In addition to a Bi-Sr-Ca-Cu-O target, PbO and CuO targets were used to dope sufficient Pb into the films and to optimize the Cu content. Although heavily Pb-doped thin films form the high Tc phase rapidly, they are multiphased and have poor morphology. The Cu content decreases slightly during sintering. Minimizing the amount of doped Pb needed for the high Tc phase formation improves morphology, and slightly Cu-rich composition is effective in forming the high Tc phase. Nearly single-phase high Tc films were obtained from the as-deposited compositions of Bi:Pb:Sr:Ca:Cu=1.02:0.80:1.00:0.99:1.64 after only one hour of sintering in air at 851 °C. The single-phase high Tc film forms in a very narrow sintering temperature range.

Ordering Structure and Dielectric Properties of Undoped and La/Na‐Doped Pb(Mg1/3Nb2/3)O3

Transmission electron microscopy was used to study the ordered domain structures in undoped and La/Na‐doped Pb(Mg1/3Nb2/3)O3 (PMN), where the compositions of the doped samples were specifically chosen so as to elucidate the ordering mechanism. The results showed that the Mg2+ ions and Nb5+ ions are short‐range ordered on the B‐site sublattice in undoped PMN, with a domain size of 2 to 5 nm. This short‐range ordering gives rise to B‐site composition fluctuations occurring on a nanometer scale, and it is this compositional inhomogeneity which is believed to be responsible for the diffuse phase transition behavior. Donor doping with La2O3 can compensate for the local charge imbalance resulting from the short‐range order and thus enhances the degree of ordering. Acceptor doping with Na2O, however, increases the charge effect, and hence ordering is suppressed. The effect of Na doping and La doping on the dielectric properties of PMN is also discussed.

Lead-europium-chalcogenide films and superlattices for 3 μm laser

Pb 1−xEu xTe multiple quantum well and double heterostructure lasers were prepared by hot wall epitaxy. Pulsed laser operations were observed for the multiple quantum well laser up to 230K (3.8 μm), and 205K (3.4 μm) for the double heterostrucsture laser. Pb 1−xEu xS films and superlattices were also prepared. Step-like absorptions corresponding to interband electron transitions between valence and conduction subbands were observed in the optical transmission spectra of the superlattices. Electrical properties of doped Pb 1−xEu xS films were also measured. High carrier concentration n-type films were obtained by doping bismuth, but films doped by acceptor impurities had always small carrier concentration, owing to the deep donor levels due to europium.