Doping of polyaniline by corona discharge

In the present article it is shown that a corona discharge can be employed to dope thin films of polyaniline (PANI) coated on poly(ethylene terephthalate) films, allowing the electrical conductivity to be tuned within the range 10(-10) to 0.3 S cm(-1). A study of the effect of different corona conditions, namely corona treatment for positive and negative polarities, air humidity, treatment time, corona current, and the geometry of the corona triode, on the electrical conductivity of the polyaniline is presented. The results indicate that the corona discharge leads to protonic doping of polyaniline similar to that which occurs in conventional protonic acid solution doping. Atomic force microscopic analysis shows that, as the PANI is exposed to the corona discharge, its globular morphology is disrupted leading to the appearance of droplet-like features and a significant decrease in the average height and surface roughness. Doping by corona discharge presents several advantages over the conventional solution method namely that it is a dry process which does not require use of chemicals reagents, and which is both rapid and avoids dopant migration. The latter can be important for applications of PANI in microelectronic devices. (C) 2000 American Institute of Physics. [S0021-8979(00)01608-X].

Ferroelectric and piezoelectric properties of bismuth titanate thin films grown on different bottom electrodes by soft chemical solution and microwave annealing

Bismuth titanate (Bi4Ti3O12, BIT) films were evaluated for use as lead-free piezoelectric thin films in micro-electromechanical systems. The films were grown by the polymeric precursor method on LaNiO3/SiO2/Si (1 0 0) (LNO), RuO2/SiO2/Si (1 0 0) (RuO2) and Pt/Ti/SiO2/Si (1 0 0) (Pt) bottom electrodes in a microwave furnace at 700 degrees C for 10 min. The domain structure was investigated by piezoresponse force microscopy (PFM). Although the converse piezoelectric coefficient, d(33), regardless of bottom electrode is around (similar to 40 pm/V), those over RuO2 and LNO exhibit better ferroelectric properties, higher remanent polarization (15 and 10 mu C/cm(2)), lower drive voltages (2.6 and 1.3 V) and are fatigue-free. The experimental results demonstrated that the combination of the polymeric precursor method assisted with a microwave furnace is a promising technique to obtain films with good qualities for applications in ferroelectric and piezoelectric devices. (c) 2006 Elsevier Ltd. All rights reserved.

Effect of Ta2O5 doping on the electrical properties of 0.99SnO(2)center dot 0.01CoO ceramic

The effect of Ta2O5 doping in 0.99SnO(2). 0.01CoO on the microstructure and electrical properties of this ceramic were analyzed in this study. The grain size was found to decrease from 6.87 mu m to 5.68 mu m when the Ta2O5 concentration increased from 0.050 to 0.075 mol%. DC electrical characterization showed a dramatic increase in the current loss and decrease in the non-linear coefficient with the increase of the Ta2O5 concentration. The conduction mechanism is by thermionic emission and the potential barriers are of Schottky type, separated by a thin film. (C) 2000 Kluwer Academic Publishers.

Effect of Fe2O3 doping on the electrical properties of a SnO2 based varistor

The effect of Fe2O3 addition on the densification and electrical properties of the (0.9895 - x) SnO2 + 0.01CoO + 0.005Nb(2)O(5) + xFe(2)O(3) system, where x = 0.005 or 0.01, was considered in this study. The samples were sintered at 1300degreesC for 2 h. Microstructure analysis by scanning electron microscopy showed that the effect of Fe2O3 addition is to decrease the SnO2 grain size. J x E curves indicated that the system exhibit a varistor behavior and the effect of Fe2O3 is to increase both, the non-linear coefficient (alpha) and the breakdown voltage (E-r). Considering the Schottky thermionic emission model the potential height and width were estimated. Small amount addition of Fe2O3 to the basic system increases both the potential barrier height and width. (C) 2002 Kluwer Academic Publishers.

The effect of EU3+ ion doping concentration in Gd2O3 fine spherical particles

This work reports on the preparation of Gd2O3, cubic system, with spherical particles, narrow size distribution, whether or not doped with 1-5 at.% of Eu3+ and the influence of Eu3+ concentration on optical and morphological properties. Average diameter and size distribution particle analyses were performed for all samples from SEM results. Doped samples were also investigated by luminescence spectroscopy and emission kinetic measurements. All oxide samples present a particle average diameter distribution range from 110 to 150 nm and a decrease of particle average diameter with the presence of Eu3+. The particle size decrease is almost the same for all samples with different doping ion concentration. Therefore, the presence of doping ion may be inhibiting particle growth after the nucleation process. From spectroscopic studies, the doping ion distribution in the surface of oxide samples can be considered homogeneous because concentration quenching is not observed, as well as a significant difference among the calculated lifetime for each sample. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Influence of Zn2+ co-doping ion on Eu3+-O2- associate luminescence in Sr2SiO4

This work reports on the study about the luminescence behavior of Eu3+-O2- associates in Sr2SiO4 doped with Eu3+, or simultaneously doped with Eu3+ and Zn2+ ions, where the Zn2+ doping ion acts as a charge compensating agent. Both Sr2SiO4:Eu3+ and Sr2SiO4:Eu3+,Zn2+ emission spectra show two types D-5(0)-->F-7(0) type transitions, one type related to Eu3+ in the Sr2+ Site, at 577 and 580 nm and the other one related to Eu3+-O2- associates, at 574 nm. Excitation spectra present two CT bands at 275 and 324 nm related to each emission center, respectively. Comparing the relative intensities between the emission spectra, the 0-->0 transition at 574 nm assigned to Eu3+-O2- associates in the Sr2SiO4:Eu3+ emission spectrum is much more intense than the same transition in the Sr2SiO4:Eu3+,Zn2+ emission spectrum. Moreover, in the Sr2SiO4:Eu3+ excitation spectrum, the intensity ratio between the CT band related to the Eu3+-O2- emission center and Eu3+ F-7-->L-5(6) transition is also larger than in the Sr2SiO4:Eu3+,Zn2+ one. Therefore, the presence of Zn2+ species provides an extra charge compensating mechanism, which decreases the formation of Eu3+-O2- associates. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Enhanced electrical property of nanostructured Sb-doped SnO2 thin film processed by soft chemical method

The effect of the Sb addition on the microstructural and electrical conductivity of the SnO2 thin film was studied in this work. Experimental results show that the Sb addition allowed to control the grain size and electrical conductivity of the SnO2 thin film, resulting in a nanostructured material. The nanostructured Sb-doped SnO2 thin films present high electrical conductivity, even in the presence of high porosity, supporting the hypothesis that nanostructured material must possess strong electrical conductivity. This work involves important aspects that can be applied to the development of high performance transparent conducting thin film. (C) 2003 Elsevier B.V. All rights reserved.

Study of Ti-modified columbite route and the effect of lithium doping in 0.9PMN-0.1PT ceramics

The influence of lithium on the structural characteristics of PMN-PT ceramic was studied. The synthesis of PMN-PT powders using this precursor leads to the formation of high amount of perovskite phase. The insertion of Li(+) ions in B-site affects the microstructure because the rise in mass transport changes the mechanical characteristics of sintered ceramic. Higher values of K(m) and T(m) were gotten when lithium is inserted into perovskite phase. Secondary phase was found when lithium content increase beyond 1 mol%, besides the occurrence of transgranular fractures in sintered ceramic. Also, the additive acts increasing the relaxor behavior.

Magnetic doping in Zn7-xMxSb2O12 spinels (M = Ni and Co)

In this article we present a concise report on our studies on the magnetic behavior and structural arrangements of the inverse spinel Zn7-xMxSb2O12 system (M = Ni, Co). Studies on the temperature dependence of the magnetization (M) of several samples in this system showed the occurrence of a spin-glass-like state in temperatures around 10 K. The capability of this system to hold magnetic ions in either octahedral and/or tetrahedral positions is responsible for the occurrence of competing ferromagnetic and antiferromagnetic interactions. This condition is likely to cause the appearance of the observed spin-glass-like behavior. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Connective tissue graft to correct peri-implant soft tissue margin: A clinical report

This clinical report describes the use of a subepithelial connective tissue graft to recontour a soft tissue margin discrepancy for a single-implant crown in the anterior maxilla. This procedure demonstrates that the use of soft tissue grafts to correct an esthetic deficiency may be a feasible approach to establish new and stable peri-implant soft tissue contours. The patient presented was followed for 18 months.

Barium strontium titanate nanocrystalline thin films prepared by soft chemical method

Barium strontium titanate (Ba0.65Sr0.35TiO3) nanocrystalline thin films, which were produced by the soft chemical method, were crystallized at low temperature using a domestic microwave oven. A SiC susceptor were used to absorb the microwave energy and rapidly transfer the heat to the film. Low microwave power and short time have been used. The films obtained are crack-free, well-adhered, and fully crystallized. The microstructure displayed a polycrystalline nature with nanograin size. The metal-BST-metal structure of the thin films treated at 700 degrees C show food electric properties. The ferroelectric nature of the BST35 thin film was indicated by buttertly- shaped C-V curves. The capacitance-frequency curves reveal that the dielectric constant may reach a value up to 800 at 100kHz. The dissipation factor was 0.01 at 100kHz. The charge storage density as function of applied voltage graph showed that the charge storage densities are suitable for use in trench type 64 Mb ( 1-5 mu C/cm(2) and 265 Mb (2-11 mu C/cm(2)) DRAMs. (C) 2007 Elsevier Ltd. All rights reserved.

Preparation of Pb(Zr,Ti)O-3 thin films by soft chemical route

Lead zirconate titanate, Pb(Zr0.3Ti0.7)O-3 (PZT) thin films were prepared with success by the polymeric precursor method. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), Micro-Raman spectroscopy and X-ray diffraction (XRD) were used to investigate the formation of the PZT perovskite phase. X-ray diffraction revealed that the film showed good crystallinity and no presence of secondary phases was identified. This indicates that the PZT thin films were crystallized in a single phase. PZT thin films showed a well-developed dense grain structure with uniform distribution, without the presence of rosette structure. The Raman spectra undoubtedly revealed these thin films in the tetragonal phase. For the thin films annealed at the 500-700 degreesC range, the vibration modes of the oxygen sublattice of the PZT perovskite phase were confirmed by FT-IR. The room temperature dielectric constant and dielectric loss of the PZT films, measured at 1 kHz were 646 and 0.090, respectively, for thin film with 365 nm thickness annealed at 700 degreesC for 2 h. A typical P-E hysteresis loop was observed and the measured values of P-s, P-r and E-c were 68 muC/cm(2), 44 muC/cm(2) and 123 kV/cm, respectively. The leakage current density was about 4.8 x 10(-7) A/cm(2) at 1.5 V. (C) 2003 Elsevier Ltd. All rights reserved.

Electronic structure of Pb1-xLaxTiO3 ferroelectric materials from Ti 2p and O 1s soft x-ray absorption spectroscopy

The electronic structure of Pb1-xLaxTiO3 (PLT) compounds for x ranging from 0 to 30 at. % of La is investigated by means of soft x-ray absorption near edge structure (XANES) at the Ti L-3,L-2 and O K edges. The greatest modification in the structure of the Ti 2p XANES spectra of the PLT compounds is observed in the region of the high energy peak of the L-3 edge (e(g) states), which exhibits a splitting in the undoped sample. As the amount of lanthanum increases, this splitting becomes less pronounced. This modification is interpreted as a decrease in the degree of disorder of titanium atoms, which is correlated to the substitution of Pb by La atoms. The structural changes observed at the low energy peaks of the O K-edge XANES spectra of the PLT compounds may be interpreted in terms of hybridization between O 2p, Ti 3d, and Pb 6p orbitals. A decrease in the degree of hybridization observed as Pb atoms are replaced by La atoms may be related to the differences in the ferroelectric properties observed between x=0.0 and x=0.30 compounds. (c) 2006 American Institute of Physics.

Does alveolar soft-part sarcoma exhibit skeletal muscle differentiation? An immunocytochemical and biochemical study of myogenic regulatory protein expression

There has been persistent controversy regarding the nature of cell differentiation in alveolar soft-part sarcoma (ASPS) since its first description in 1952. Some studies suggest that ASPS might represent an unusual variant of skeletal muscle tumor, Given the availability of new monoclonal antibodies to probe for skeletal muscle differentiation and the rapid advance in immunocytochemical techniques for deparaffinized, formalin-fixed tissue sections, we wished to test the proposed hypothesis that ASPS might represent a new type of rhabdomyosarcoma Twelve archival samples of ASPS were retrieved, and we investigated the expression of two myogenic regulatory proteins, MyoD1 and myogenin, as rvell as other muscle-associated proteins, using sensitive immunocytochemical techniques. Despite the presence of desmin immunostaining in six ASPSs, no tumors were positive for either muscle actin or myoglobin Most importantly, no specimen showed nuclear expression of MyoD1 or myogenin, In 11 tumors, however, there was considerable granular immunostaining in the tumor cell cytoplasm with the anti-MyoD1 monoclonal antibody 5.8A, a phenomenon observed in various nonmuscle normal and neoplastic tissues with this antibody, To analyze the exact nature of immunostaining of MyoD1 and desmin in ASPS, biochemical analyses using available fresh frozen tumor tissue were performed, Although a 53-kDa band was noted with antidesmin antibody on Western blot analysis, no specific protein band that corresponds to the 45-kDa MyoD1 was detected with antibody 5.8A. These results confirm the presence of desmin in ASPS but argue against authentic expression of MyoD1, They also suggest that the cytoplasmic immunostaining observed with anti-MyoD1 antibody 5.8A most likely represents a nonspecific cross-reaction with an unknown cytoplasmic antigen, Considering the master role that MyoD1 and myogenin play in skeletal muscle commitment and differentiation and the lack of expression of these two proteins in ASPS as determined immunocytochemically and biochemically, we think that the histogenesis of ASPS remains unknown.