Titania doped YSZ for SOFC anode Ni-cermet

The influence of doping YSZ (8 mol%YttriaStabilizedZirconia) with 5 and 10 mol% TiO₂ on the electrical conductivity and the microstructure was examined for different YSZ-Ni cermets as a function of Ni-content. For the 5 mol%TiO₂-doped cermets the electrical conductivity was always better than that of the undoped, exhibiting a lower degradation rate at 1000 °C. Microstructure examination of the samples showed a lower tendency for agglomeration of the Ni-particles of the doped cermets compared to the Ni/YSZ cermet. The 10 mol%TiO₂-doped cermets exhibited lower conductivity values and this was attributed to the significantly higher porosity which resulted from a reaction taking place during sintering between the insoluble TiO₂ in YSZ and NiO. This reaction results in the formation of a NiO-TiO₂ spinel phase, which leads to the expansion of the samples causing microstructural defects. Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999.     

Optical characterization of gallium antimonide highly doped with manganese

Gallium antimonide crystals highly doped with Mn were prepared by a liquid-phase-electroepitaxy growth method. The crystals exhibited high hole concentrations up to 6×10¹⁸ cm⁻³. Photoluminescence (PL) and transmission techniques were used for their investigation. Spectral line-shapes typical for highly doped semiconductors were observed. The lines revealed the features corresponding to band gap narrowing and valence-band filling phenomena. Values of the band-gap narrowing ΔE_g and the degree of the valence-band filling ΔE_F were estimated from the PL spectra. The ionization energy of the Mn acceptor E_i was estimated to be approximately 15.1-15.6 meV. At low temperatures, the PL maxima shifted relatively strongly towards higher energy with temperature. The shifts most probably resulted from a dramatic change in the electron density of states near the bottom of the conduction band. The extent of low-energy tails of the PL bands correlates with the doping levels. The transmission spectra exhibited an absorption band centred at around 774-780 meV. The band most probably originated in electron transitions from the level of spin-orbit splitting to the top of the valence band.     

Synthesis and characterization of highly triboluminescent doped europium tetrakis compounds

One of the most intriguing properties involving crystals is their ability to emit light when fractured. While this property was discovered over 200 years ago, no one has ever been able to come up with a complete theory that can predict the physical principles associated with triboluminescence. However, this has not stopped scientists from coming up with various uses for these materials. One such application is to use these materials as the active element for smart impact sensors that can warn of catastrophic impacts. If these sensors are to become a reality however, the material must emit a bright light when fractured. One of the brightest triboluminescent materials found thus far is europium dibenzoylmethide triethylammonium (EuD₄TEA). This material was discovered by Hurt in 1966 and is bright enough to be seen in daylight. In 2011, the authors discovered that synthesizing EuD₄TEA using europium nitrate instead of chloride significantly increased the triboluminescence yield and made the synthesis much easier and more consistent. However, to date, there are few investigations into the effects of dopants on the triboluminescence of EuD₄TEA. This paper reports the investigation of the effects of various dopants on: (1) The triboluminescent light yield, (2) Crystal size and structure, (3) Synthesis time, and (4) Prompt decay time. Results show that inclusion of dopants during synthesis increases the triboluminescence emission of EuD₄TEA by 55%, significantly reduces the synthesis time, and controls the decay time. All of these properties can be useful for constructing the first prototype of a customized impact sensor.     

Electrical conductivity of thick film YSZ

When yttria-stabilized zirconia (YSZ) electrolyte is coated and co-sintered on top of Ni–YSZ anode support, the measured conductivities of YSZ thick films (10–30 μm thick) are often lower than that of bulk YSZ. In this study, we found the observation by fabricating free-standing YSZ thick films and measuring and comparing in-plain and across-plain conductivities. The in-plane conductivity of free-standing YSZ film matched very well with the conductivity of mm-thick bulk sample. It was further shown that the conductivity decrease can be minimized by using better electrode morphology.Another factor that decreases the film conductivity was identified when the thick film was reduced. The conductivity decrease, ∼26% after reduction for 1h in humidified hydrogen gas, was due to Ni-doping into YSZ during sintering process.In order to minimize the conductivity drop of thick film YSZ during SOFC (solid oxide fuel cell) operation, an intermediate layer may be used between YSZ and anode support to prevent Ni-doping during co-sintering process in addition to the well-designed electrode morphology.     

Electrical and structural characterization of inhomogeneously doped semiconductors by infrared spectroscopy

An optical method is presented for thenon-destructive electrical and structural characterisation of multilayer structures. The presented concept yields the complex refractive index profiles within an arbitrary composed layer system by using the symmetrical transmission and the asymmetrical reflectivity caused by the optical inhomogeneity of a material. This method includes the superimposition of coherent multiple reflections within the refractive index profile as well as incoherent multiple reflections within the whole wafer. This analysis yields the spacial distribution of free carrier density profiles within the sample as well as the transitions between different crystal phases by using the least squares fit procedures. The results of the optical analysis are compared with other methods used to quantitatively determine density profiles and phase transitions such as SIMS, spreading resistance, stripping Hall and RBS.     

Surface characterization of Ag/Titania adsorbents

The Ag/Titania adsorbent for selective removal of the desulfurization-refractive polycyclic aromatic sulfur heterocycles (PASHs) from liquid hydrocarbon fuels was prepared, its total and the Ag specific surface area were determined and the surface reaction sites in the sorbent that may be active in the adsorptive selective desulfurization were characterized by several spectroscopic and surface science techniques. The sorbent contains Ag, Ti, O and spurious C on its surface, as by the XPS measurements. Silver is present as an oxide, as judged by the XPS Auger parameter (AP). The complementary electron spin resonance (ESR) spectroscopy confirms that the majority of Ag is present in the diamagnetic Ag¹⁺ form, with the minor concentration (∼0.1% of total Ag) present as Ag²⁺. The findings by XPS and ESR are confirmed by the XRD, UV-vis spectroscopy and thermodynamic considerations. The supported Ag is highly dispersed on the surface of the titania support, with the particle size of ∼30-60 Å depending on Ag content, with an Ag specific surface area of ∼7-14 m²/g, vs. the total surface area of ∼114-58 m²/g.     

Electrical characterization of PVA-based nanocomposite electrolyte nanofibre mats doped with a multiwalled carbon nanotube

An attempt has been made to prepare and characterise ammonium thiocyanate (NH₄SCN) salt and a multiwall carbon nanotube (MWNT)-doped polyvinyl alcohol-based nanofibre mats using an electrospinning process. The X-ray diffraction result shows an improvement in the amorphous nature of composite electrolyte fibre mats with increasing concentrations of the MWNT filler. The DSC behaviour of these nanofibre mat exhibits better thermal response upon dispersal of the filler. Composite electrolyte nanofibre mat doped with 6 wt% MWNT shows optimum conductivity, viz., 5.8?×?10^?4 Scm^?1. The temperature dependence of the bulk electrical conductivity displays a combination of Arrhenius and Vogel–Tammam–Fulcher nature. Dielectric loss studies have also been used to understand the conduction process in the system. Jonscher power law seems to be obeyed during ac conductivity measurements of the fibre mats.     

Electrical conductivity of YSZ film grown by pulsed laser deposition

Yttria-stabilized zirconia (YSZ) thin films, 0.6–1.5 μm, were deposited on Pt and sapphire substrates by a pulsed laser deposition (PLD) method. Their structural and transport properties have been studied by means of X-ray diffraction and electrical conductivity measurements. The in-plane and the perpendicular-to-plane conductivities (hereafter, “across-plane” conductivity) of thin films were measured and compared to that of bulk sample. X-ray diffraction and electron microscopy results showed that the films on Pt and sapphire were polycrystalline cubic with a columnar structure. Both the across-plane and the in-plane conductivities of YSZ thin film were close to that of bulk specimens. Thus no conductivity enhancement was found for the present nano-crystalline YSZ films (grain or column size, 60∼100 nm).     

Electrical degradation of porous and dense LSM/YSZ interface

Electrochemical cells formed by the interface between dense and porous lanthanum strontium manganate (LSM) and yttria stabilized zirconia (YSZ) were submitted to annealing temperatures varying from 1373 K to 1673 K for 200 h and studied by Impedance Spectroscopy (IS) in order to investigate how the high annealing temperature can modify the contact between LSM/YSZ and to which extension these changes influence the electrical behavior of dense and porous LSM electrodes before and after the formation of insulating phases. Up to 1473 K the annealing process did not lead to substantial electrical behavior modifications at the LSM/YSZ interfaces for both porous and dense electrodes. IS measurements show two capacitive semicircles, the best fitting of impedance data brings to an equivalent circuit constituted by a serial combination of the electrolyte resistance and two parallel combinations of a resistance and a constant phase element, CPE. The higher frequency semicircles, HF, were attributed to the diffusion of oxide ions from the interface LSM/YSZ to the oxide ion vacancies located at the electrolyte surface. The semicircle at lower frequency, LF, will be ascribed to the oxygen species adsorption and diffusion in the LSM. At 1473 K the only changes recorded are related with the sinterization process of the porous electrodes. Over of 1473 K, the resistance contributions increased largely, especially for porous electrodes, and one additional semicircle was observed. This semicircle was associated to the oxygen diffusion process at the new insulating phases formed from YSZ and LSM solid state reactions. Porous and dense electrodes exhibited different rates for the degradation process. The porous electrode degraded faster than the dense one, probably because of the morphological effects as grain growth and their coalescence during annealing at higher temperatures.     

Electrical and spectroscopic characterization of polyaniline-polyvinyl chloride (PANI-PVC) blends doped with sodium thiosulphate

Polyaniline is doped with sodium thiosulphate in aqueous tetrahydrofuran (THF) and the blended films have been prepared by changing the amount of doped polyaniline (PANI) in the fixed amount of polyvinyl chloride (PVC). The electrical conductivity of various samples of polyaniline-polyvinyl chloride (PANI-PVC) blends has been studied to see the effect of dopant in the temperature range 300-400 K. Mott's parameters are used to explain the conduction mechanism. Different parameters such as pre-exponential factor (σ₀), activation energy (ΔE) and T₀ have also been calculated to see the effect of chemical doping. The crystallinity of the blends is explained on the basis of T₀. The calculated values of T₀ show that crystallinity increases with an increase of doped PANI in PANI-PVC blends. Fourier transform-infrared (FTIR) spectroscopy is done to explore the nature and interaction of dopant into the polymeric chain.     

Electrical conductivity of Co doped cuprous oxide

The solubility limit of metals in cuprous oxide is very low and it is therefore difficult to form solid solutions of metal oxides with cuprous oxide. In an on going research looking for such solid solutions and their properties we have prepared Co doped Cu₂O. We report here on measurements of the electrical conductivity of Co doped Cu₂O as a function of the oxygen partial pressure. It is found that Co doped material is an n-type semiconductor in the low oxygen partial pressure regime and p-type at higher oxygen pressures (while undoped Cu₂O is a p-type material throughout the whole existence regime). A point defect model is discussed. The ionic transference number is also measured and is found to be less than 2⋅10⁻⁴. Paper presented at the 2nd Euroconference on Solid State Ionics, Funchal, Madeira, Portugal, Sept. 10–16, 1995     

Electrical properties of heterovalently doped apatite-like oxosilicates

Oxygen-ion-conductive apatite-like oxosilicate and silicophosphate ceramics has been prepared by sintering sol-gel synthesis products at temperatures 200°C below those of solid-phase synthesis. The electrical properties of the ceramics obtained have been studied by impedance spectroscopy in the range 400–1000°C. A positive effect of heterovalent substitutions in the silicon sublattice on the bulk and intergrain conductivities is established. The increase in the oxygen-ion conductivity in La_9.6Si_5.7Mg_0.3O_26.1 in comparison with the other studied oxosilicates by more than two orders of magnitude is related to the formation of additional interstitial positions for oxygen ions as a result of partial substitution of the silicon ion, tetrahedrally coordinated by oxygen, with the Mg ion having a characteristic octahedral coordinatio     

Preparation and characterization of highly conducting and transparent Al doped CdO thin films by pulsed laser deposition

Highly conducting and transparent aluminum doped CdO thin films were deposited using pulsed laser deposition technique. The effect of growth temperature on structural, electrical, and optical properties was studied. It is observed that the film orientation changes from preferred (1 1 1) plane to (2 0 0) plane with increase in growth temperature. The electrical resistivity of the films was found to increase with increase in growth temperature. The low resistivity of 4.3 × 10⁻⁵ Ω cm and high transparency (∼85%) was obtained for the film grown at 150 °C. The band gap of the films varies from 2.74 eV to 2.84 eV.     

Minority carrier lifetime in highly doped Ge

The minority carrier lifetime is measured in p-type Ge up to a majority carrier concentration of 10¹⁹ cm⁻³ using the photoconductive effect and the photo-magneto-electric effect. A stronger than linear dependence of the reciprocal lifetime on the carrier density is observed. Therefrom, from the weak temperature-dependence, from previous work and from the comparison with Si-data, we conclude that the dominant recombination mechanism at high carrier concentrations is the phonon-assisted band to band Auger-recombination. A transition coefficient of about 10⁻³¹ cm⁶ sec⁻¹ is estimated.     

Electrical properties of doped single crystals of ZnSb

The conductivity , thermo-emf , and Hall constant R are reported for the range 100 °-490 ° K for ZnSb crystals doped with Ag, Au, Ga, In, Sn, Pb, and Te. Ag, Au, sn, and Pb act as acceptors, while In and Te increase the hole concentration, increase , and leduce . This occuis at relatively high concentrations by foimation of InSb and ZnTe molecules. Ga in ZnSb acts as a donor (compensating) component.     

Electrical conductivity-measurements on doped VO2 single-crystals

The doping effect of 0.05–.05 atom % W or 0.05% Mo on the electrical conductivity of VO₂ was investigated. An impurity-conduction with activation-energies of 0.22 eV for W resp. 0.1 eV for Mo is observed. The temperature of the semiconduction to metaltransition in VO₂ is reduced proportionally by only 24°K/%-W-concentration, which indicates a negligible action of free carried concentration on lattice-transition.     

铂掺杂扶手椅型石墨烯纳米带的电学特性研究

本文采用基于密度泛函理论(DFT)的第一性原理计算了铂原子填充扶手椅型石墨烯纳米带(AGNR)中双空位结构的电学性能.计算结果表明: 通过控制铂原子的掺杂位置, 可以实现纳米带循环经历小带隙半导体—金属—大带隙半导体的相变过程; 纳米带边缘位置是铂原子掺杂的最稳定位置, 边缘掺杂纳米带的带隙值随宽度的变化与本征AGNR一样可用三簇曲线表示, 但在较大宽度时简并成两条曲线, 一定程度上抑制了带隙值的振荡; 并且铂原子边缘掺杂导致宽度系数N_a = 3p和3p + 1(p是一个整数)的几个较窄纳米带的带隙中出现杂质能级, 有效地降低了其过大的带隙值. 此外, 铂掺杂AGNR的能带结构对掺杂浓度不是很敏感, 从而降低了对实验精度的挑战. 本文的计算有利于推动石墨烯纳米带在纳米电子学方面的应用.     

Electrical conductivity of doped and undoped calcium tartrate

The electrical conductivity of polycrystalline samples of calcium tartrate tetrahydrate ([CaC₄H₄O₆ 2H₂O] 2H₂O) in pure form and doped with barium and with strontium were studied in the temperature range (65<T<95°C). According to these results, it seems that two types of conduction exist in these compounds, one at low temperature and the other at high temperature, by the way of extrinsic and intrinsic conduction, respectively. This behavior may be attributed to the rotation of the tartrate ions by thermal energy.     

Electrical characterization of Schottky diodes based on boron doped homoepitaxial diamond films by conducting probe atomic force microscopy

A large planar tungsten carbide (WC) Schottky diode on p-type homoepitaxial diamond was mainly investigated on a microscopic level by atomic force microscopy (AFM) and conducting probe atomic force microscopy (CP-AFM), allowing simultaneous topographic and local electrical resistance imaging measurements. These techniques revealed the existence of a specific microstructure on the WC Schottky contact consisting of electrically insulating islands surrounded by conductive paths. The islands are found to be insulating in the whole range of explored bias [−5 V, +5 V], whereas the current flowing between the islands is 1000 times lower at a reverse bias of −5 V than at a forward bias of +5 V, in agreement with the rectifying ratio found from macroscopic current–voltage (I–V) measurements. CP-AFM provides a prospective imaging tool which is well suited for analyzing the local electrical properties and instabilities of Schottky junctions.     

Electron-phonon coupling in highly doped n type silicon

The effect of free electrons on the optical phonon of silicon at the center of the Brillouin zone is studied using the Raman scattering technique. Heavy doping gives rise to a continuous electronic Raman scattering and makes the phonon line shape assymetric. The profile factor which is related to the disymetry, is shown to have the signes of the matrix elements of the electron-phonon interaction.