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We report the observation of local structural dipoles that emerge from an undistorted ground state on warming, in contrast to conventional structural phase transitions in which distortions emerge on cooling. Using experimental and theoretical probes of the local structure, we demonstrate this behavior in binary lead chalcogenides, which were believed to adopt the ideal, undistorted rock-salt structure at all temperatures. The behavior is consistent with a simple thermodynamic model in which the emerging dipoles are stabilized in the disordered state at high temperature due to the extra configurational entropy despite the fact that the undistorted structure has lower internal energy. Our findings shed light on the anomalous electronic and thermoelectric properties of the lead chalcogenides. Similar searches may show that the phenomenon is more widespread. 10.1126/science.1192759

The concept and design of a power-conditioning circuit for an autonomous low-power System-in-Package (SiP) is presented in this paper. The SiP's main power source is based on the use of micropiezoelectric generators. The electrical model of the power source, which has been obtained based on experimental measurements and implemented on Cadence Analog Artist's Spectre simulation environment, is explained. The model has been used to simulate the power source with the power-conditioning electronics over the entire design process. Finally, the simulated and experimental results of the developed integrated power circuits, which are formed by a rectifier and a low-power bandgap reference voltage source to define the threshold voltage for the closed-loop regulation process, are also shown. These circuits have been designed using a commercial 0.13-[micro]m technology from ST Microelectronics through the Multi-Projects Circuits (CMP) Techniques of Informatics and Microelectronics for Integrated Systems Architecture (TIMA) service. Index Terms--Electric power generation, energy scavenging, low-power electronics, power conditioning, vibrations.

Heterolayered Pb([Zr.sub.1-x][Ti.sub.x])[O.sub.3] thin films with different combinations of constituted layers are examined. The wake-up phenomenon is reduced at elevated temperatures, thus leading to fatigue degradation at a relatively lower number of switching cycles.

The reversible ferroelectric-ferroelectric transition of morphotropic relaxor-ferroelectric lead zinc niobate-lead titanate and lead magnesium niobate-lead titanate single crystals as accessed by the mechanical compression is presented. Implications of the observation for sound projectors are presented.

The influence of the progressive strain relaxation and the depolarizing-field effect on the thickness dependence of the out-of-plane dielectric response of epitaxial ferroelectric thin films sandwiched between extended metal electrodes is analyzed. The results have shown that the inverse of the measured capacitance has changed with the film thickness almost linearly in most part of the thickness range at the majority of temperatures.

The resonance method was used to study the elastic, dielectric, and piezoelectric properties of several soft and hard piezoelectric lead zirconate titanate (PZT) samples, with compositions near the morphotropic phase boundary (MPB), as a function of temperature ranging between165 to 195 degree Celsius. The results showed that the material coefficients of soft PZT varied significantly more than those of hard PZT under changing temperature conditions.

The short-circuit photocurrent (SC-PHC) in the 200-800 nm wavelength domain was used to investigate the photovoltaic properties of the metal-ferroelectric-metal structures having SrRu[O.sub.3] metal oxide electrodes and Pb(Zr, Ti)[O.sub.3] (PZT) as ferroelectric layer. The band-gap energies evaluated from the PHC spectral distribution for different PZT compositions range between 3.9 to 4.4 eV and it is constantly higher than the reported experimental values on polycrystalline films but agree well with theoretical values.

The effect of Ta substitution on the structural, microstructural, molecular and dielectric characteristics of Pb[Sc(sub)0.5Nb(sub)0.5]O(sub)3 (PSNT), synthesized by mechano-synthesis and conventional mixed oxide methods is studied. It is found that the ceramics show the formation of the materials in a single phase in the rhombohedral structure with the existence of nanodomain.

The microstructural effects on the mechanical and electrical properties of common density PZT95/5-2Nb materials under shock compression were investigated. The results indicate that differences in the porous microstructure of common density materials have little effect on mechanical and electrical shock properties.

Various x-ray diffraction experiments are employed to study the microscopic-scale structures of 0.72Pb([Mg.sub.1/3][Nb.sub.2/3])[O.sub.3]-0.28PbTi[O.sub.3] relaxor ferroelectrics in a high external dc field during phase transition. The results clearly prove that a change in the temperature also leads to a major change in the dominating cluster's orientation, as well as their interaction direction.

Several experiments are conducted to analyze and describe the concentration dependence of the fluorescence quantum efficiency in [Nd.sup.3+] doped lead lanthanum zirconate titanate (PLZT) transparent ferroelectric ceramics. It can be clearly inferred from the results that Nd:PLZT presents lower concentration quenching, as compared to any other laser materials.

Lead-free potassium sodium niobate piezoelectric single crystals substituted with lithium 0.95([K.sub.0.5][Na.sub.0.5])Nb[O.sub.3]-0.05LiNb[O.sub.3] are grown by Bridgman method and their dielectric and piezoelectric properties are analyzed. The observation suggest that 0.95([K.sub.0.5[][a.sub.0.5])Nb[O.sub.3]-0.05LiNb[O.sub.3] single crystal is a good lead-free piezoelectric material.

A study was conducted to investigate magnetoelectric resonance behavior of a simple, bilayered structure of Pb(Zr, Ti)[O.sub.3] ceramic chip and (Tb, Dy)[Fe.sub.2]/epoxy mixture layer. The results have shown three kinds of resonance, which are attributed to the first-order flexural, second-order flexural, and radial resonance modes, respectively.

The influence of stress on phase diagrams and dielectric properties in epitaxial BaTi[O.sub.3] and PbTi[O.sub.3] thin films grown on the dissimilar orthorhombic substrates is analyzed by using a phenomenological Landau-Devonshine theory. The dielectric properties and the tunability of both the films are studied and it is found that the external stress dependence of phase diagrams and dielectric properties depends on the strain anisotropy.

The impact of sintering temperature on the phase transition and dielectrical response in the relaxor ferroelectrics of 0.5PB([Zn.sub.1/3][Nb.sub.2/3])[O.sub.3]-0.5Pb([Zr.sub.0.47][Ti.sub.0.53])[O.sub.3] (0.5PZN-0.5PZT) ceramics near the morphotropic phase boundary (MPB), fabricated by conventional ceramic method are studied. It is observed that the phase of material varied from rhombohedral structure initially to a MPB and then a tetragonal structure as the sintering temperature rose from 900 to 1250 degree Celsius.

Wedge-cut samples of fatigued ferroelectric lead zirconate titanate (PZT) ceramics are investigated using piezoresponse force microscopy along with conventional electrical hysteresis measurements. A broad distribution of coercive fields is observed for PZT/Pt.

The current-voltage (I-V) characteristics are studied in fully integrated commercial Pb[Zr.sub.0.4][Ti.sub.0.6][O.sub.3] thin film (PZT) capacitors with Pt bottom and Ir/IrO2 top electrodes. It is found that standard automated I-V tests are not always appropriate for ferroelectrics due to the large difference in relaxation times for current transients at different fields.

A study on the influence of domain switching on the evolution of macroscopic polarization in the ferroelectric [Pb(Mg1/3Nb2/3).sub.1-x][Ti.sub.x]O3 material is conducted. Results reveal that stress depolarization is controlled by 90 degree domain reorientation.

Abstract -- The use of a wall-jet detector for determining heavy metals by their intrinsic electrochemiluminescence at an aluminum electrode is described. The possibility of rapidly determining tin, lead, mercury, [...]

Relaxor-type ferroelectric (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) films, 2-3 mum in thickness, with a PbTiO3 content (x) ranging from 0 to 1 were grown on [(100).sub.c]SrRuO3 ll (100)SrTiO3 substrates at 650 degree Celsius by metal-organic chemical vapor deposition. The constituent phase changed from a rhombohedral (pseudocubic) single phase, a mixture phase of rhombohedral (pseudocubic) and tetragonal phases, and a tetragonal single phase, with increasing x.

Relaxor-type ferroelectric (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) films, 2-3 mum in thickness, with a PbTiO3 content (x) ranging from 0 to 1 were grown on [(100).sub.c]SrRuO3 ll (100)SrTiO3 substrates at 650 degree Celsius by metal-organic chemical vapor deposition. The constituent phase changed from a rhombohedral (pseudocubic) single phase, a mixture phase of rhombohedral (pseudocubic) and tetragonal phases, and a tetragonal single phase, with increasing x.

Abstract--A new sequence of leaching reagents was proposed for fractionating element species from natural solid samples. The dynamic extraction of Cu, Zn, and Pb species from soil, silt, and bottom [...]

A reverse cation-exchange approach is described for the synthesis of hollow PbSe nanospheres, which involves a step wise, in-situ template-based evolution from spherical amorphous Se colloids to Se/[Ag.sub.2]Se core/shell colloids, then to hollow PbSe nanospheres. The characterization results show that hollow PbSe nanospheres with polycrystalline and cubic structure are prepared and the conformation is beneficial to the improvement concerning the applications of PbSe nanostructures.

Size-controllable monodisperse PbSe and PbSe/PbS nanocrystals (NCs) are successfully synthesized with a solvothermal method. These narrow-band-gap semiconductor NCs with tunable size are expected to have potential applications in near- and mid-IR telecommunication laser sources, electroluminescence, and solar cell materials.

Abstract -- The determination of Pb and Cd by electrothermal atomic absorption spectroscopy with the slurry sampling of carbonized samples into a graphite furnace was considered. Textural and chemical properties [...]

A heteroepitaxial PbZr(sub 1-x)Ti(sub x)O3 (PZT) thin film was fabricated by means of hydrothermal epitaxy at 210 degree Celsius below Curie temperature without undergoing the paraelectric to ferroelectric phase transition. From transmission electron microscope and piezoresponse force microscope observations, it was confirmed that the fabricated PZT thin films had only a-c monodomain without an 'a' domain in the as-synthesized state.

A methodology is presented to extract the relevant quantities of a Schottky contact, in the specific case of metal-ferroelectric-metal structures, by using the metal-ferroelectric interface. The models are applied to Pb(Zr, Ti)O3 thin films with different Zr/Ti ratios, fabricated by different deposition methods and having different Schottky contacts.

A study of fabrication and characterization results of piezoelectric micromachined ultrasonic transducers (pMUTs) based on 2-micrometer thick Pb(Zro.53Tio.47O3) (PZT) thin films is described. A transmit-receive experiment with two quasi-identical pMUTs showed significant signal transmission up to a distance of 20cm in air and 2 cm in the test liquid.

A diaphragm-type piezoelectric micromachined ultrasonic transducer (pMUT), a composite coating technique based on chemical solution deposition and high-energy ball milled powder used to fabricate thick PZT films, and micromachining of the pMUTs using thick films is investigated. Results suggested that the fabricated pMUT has very good ultrasound-radiating performance and can be used to compose pMUT arrays for generating ultrasound beam with high directivity in numerous applications.

Usage of light diffraction tomography to measure the acoustic field of micromachined ultrasonic transducers (MUT) in cases in which standard methods like hydrophone and microphone measurements fail is demonstrated. The results reveal that the air-coupled MUTs in the frequency range of about 1MHz as well as the extreme near field of a miniaturized continuous wave 10 MHz water-loaded transducer were successfully characterized with light diffraction tomography.

Phases and domains in a (110)-cut Pb(Mg1/3Nb2/3)(sub 0.74)Ti(sub 0.26)O3 single crystal are investigated as functions of temperature and dc electric (E) field by dielectric permittivity, polarizing microscopy and electric polarization. The unpoled sample has a dominant rhobohedral (R) phase, which coexists with monoclinic (M) phase domains at room temperature.

The time-dependent effects of a commercial soft lead zirconate titanate material are investigated at room temperature. The results help in understanding the mechanism of creep effects that might provide contributions to improve the performance and reliability of ultrahigh-precision positioning piezoactuators.

The nanocrystalline Pb(sub 0.92)Nd(sub 0.08)(Zr(sub 0.53)Ti(sub 0.47))(sub 0.98)O(sub 3)(PNZT) is synthesized by high-energy ball milling (mechanical alloying). The analysis of impedance and dielectric properties of PNZT as a function of temperature has showed the high permittivity of 10626 at 10 kHz at the Curie temperature (Tc), broadening of permittivity peak, lowering of Tc, decrease in conductivity and increase in relaxation time with the decrease in crystalline size.

The effect of oxygen content in the sputtered Pt oxide (Pt(sub x), x = 0.4 to 1) top electrode suppressing the hydrogen degradation of ferroelectric capacitors of PbZr(sub 0.4)Ti(sub 0.6)O3 (PZT) and also the role of hydrogen in degradation of ferroelectric capacitors are investigated. The results show that the high oxygen content in PtO(sub x) electrode interrupts the catalytic reaction of Pt in dissociation of hydrogen molecules and suppresses the interfacial segregation of hydrogen and its incorporation with PZT.

Conduction in thin films of PbSe nanocrystals doped by electrochemical gating was studied. Charging the film, with electrons or holes, increases the conductance by order of magnitude and the temperature and electric field dependence of conductance in the film measured between 4.3 and 135 K, were both well described by a variable range hopping model.

Manganese modified (1-x)BiScO3-(x)PbTiO3 (BSPT) compositions near the morphotrophic phase boundary are investigated and the electrical behavior is characterized at high temperatures, and a full set of material constants is determined using the resonance method. Studies revealed that these data should provide a basis to perform future theoretical analysis as well as device design, the temperature of the properties and very high RC modifying BSPT as a new material for high temperature actuation and sensing applications.

A study is conducted to investigate the length extensional (33-mode) electromechanical properties and their stability for morphotropic (001) oriented and poled multidomain PMN-PT single crystals when driven by a large electric field under a combined DC bias field and compressive mechanical stress. It is found that the remarkable small signal length extensional coupling (K33 > 0.99) and other electromechanical properties of morphotropic PMN-PT single crystals prevail under large drive.

A systematic study of the optoelectronic processes occurring in composites made of near-infrared (IR) emitting nanocrystals and conjugated polymers are reported. Results reveal that the process responsible for quenching the visible luminescence of the polymer by the nanocrystal varies depending on the nanocrystal composite.

Temperature dependences of the optic phonons in PbSc1/2Ta1/2O3 (PST) sol-gel films deposited on sapphire substrate are studied by means of Fourier transform far-infrared transmission spectroscopy in the temperature range of 20-900 K. In all the four films displaying different B-site order, the transverse-optic (TO) mode near 80 cm(super -1) at 10 K softens on heating to approximately 45 cm(super -1).

The synthesis and characterization of photonucleases N,N'-bis[2-[bis(1H-imidazol-4-ylmethyl)amino]ethyl]-3,6-arcidinediamine and N-[2-[bis(1H-imidazol-4-ylmethyl)amino]-3,6-acridinediamine, consisting of a central 3,6-acridinediamine chromophore attached to 4 and 2 metal-coordinating imidazole rings, respectively, are reported. The data indicates that buffer, pH, Hg(II), Fe(III), Cd(II), Zn(II), V(V), Pb(II), and light can be used to tune DNA cleavage by N,N'-bis[2-[bis(1H-imidazol-4-ylmethyl)amino]ethyl]-3,6-arcidinediamine under physiologically relevant conditions.

The calculation of electronic spectra of lead(II) complexes of some hydroxyflavone molecules by the time dependent density functional theory methodology is reported. The results obtained by taking into account the solvent effect are in very good agreement with the experimental features and lead to a complete assignment of the spectral changes observed upon complexation of these compounds.

The dielectric behavior of Pb0.5Ca0.5TiO3 thin films with different thickness is measured using capacitance versus voltage (C-V) technique. The feasibility of the films for fabrication of voltage tunable capacitors and charge storage devices (DRAMs) is confirmed.