Study of polarization phenomena in Schottky CdTe diodes using infrared light illumination

Schottky CdTe diode detectors suffer from a polarization phenomenon, which is characterized by degradation of the spectral properties over time following exposure to high bias voltage. This is considered attributable to charge accumulation at deep acceptor levels. A Schottky CdTe diode was illuminated with an infrared light for a certain period during a bias operation, and two opposite behaviors emerged. The detector showed a recovery when illuminated after the bias-induced polarization had completely progressed. Conversely, when the detector was illuminated before the emergence of bias-induced polarization, the degradation of the spectral properties was accelerated. Interpretation of these effects and discussion on the energy level of deep acceptors are presented.     

Effect of heating temperature on dielectric properties of Pb(Zr,Ti)O3 [PZT] fibers

Ferroelectric Pb(Zr_0.53Ti_0.47)O₃ fibers were reproducibly fabricated by sol-gel technique using triethanolamine (TEA) complexed alkoxide. The phase transition from pyrochlore to perovskite took place about 400°C and a stable single perovskite phase was obtained at 550°C. PZT gel fibers spun through nozzle were heat-treated at 700°C, and at 1000°C for 1 h to certify the effect of heat-treatment temperature on the electrical properties. The PZT fibers had elliptical cross sections with diameter of 72 m–92 m, and dense microstructure was obtained by heating at 1000°C. In the PZT fibers heat-treated at 1000°C, a distinguishable relative permittivity peak and a pyroelectric current peak were observed at their Curie temperature. The P-E hysteresis loops of the crystalline PZT fibers were also observed.     

Sol-gel synthesis of high-humidity-sensitive amorphous P2O5-TiO2 films

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Ion exchange of intercalation compounds from WOP2O7 and intercalation ofn-alkylamines

Ion exchange of Na _x WOP₂O₇ ·nH₂O (x 1.4) prepared from WOP₂O₇ was attempted, using alkaline and alkaline earth ions. The degree of exchange was observed to be >50% at 90° C except for Mg²⁺. The basal spacing of ion-exchanged materials for the hydrated phase were dependent on the number of water molecules in the interlayer spaces, while those for the dehydrated phase increased with the size of ions in the interlayer spaces. The network of water molecules linked by the hydrogen bond in the interlayer spaces seems to determine the basal spacing. By the ion-exchange reaction,n-alkylammonium ions were intercalated into the interlayer spaces of Na _x WOP₂O₇ ·nH₂O (x 1.4) and Sn _x H _y WOP₂O₇ ·nH₂O (2x +y 0.5). In spite of the difference in the charge density of the host layer, a similar arrangement of alkyl chains in the interlayer spaces resulted, and neutral amines were considered to be intercalated as well as ammonium ions. Direct reaction ofn-alkylamine with WOP₂O₇ produced an intercalation compound without reduction of tungsten. The arrangement of the amines in the interlayer spaces is similar to that supposed to the ion-exchanged derivatives when heated at 140° Cin vacuo.     

Interphase transfer of tackifier between poly(butadiene) and poly(styrene-co-butadiene)

The interphase transfer behavior of poly(styrene-co-α-methyl styrene), which is known as a tackifier in rubber industry, is investigated using poly(butadiene) rubber (BR) and poly(styrene-co-butadiene) rubber (SBR). The films of pure rubbers and the blends with the tackifier were prepared by a solution-cast method using toluene as a solvent. Two sheets composed of different rubbers, in which the tackifier was mixed at least in one rubber sheet, were piled together and annealed beyond the glass transition temperature T _g of the tackifier. The transfer phenomenon of the tackifier between the sheets was evaluated by the peak shift in the tensile loss modulus E″ curve, ascribed to T _g of the rubbers, which was measured by the dynamic mechanical analysis. Moreover, crystallization temperature of BR was also employed as a measure of the transfer, because the tackifier retards the crystallization of BR. It is found that the tackifier moves from one rubber to another during annealing procedure to reduce severe localization. When the content is the same in each rubber, the tackifier immigrates from BR to SBR, suggesting a better miscibility with SBR. This behavior is attributed to the small difference in the solubility parameter between SBR and the tackifier as compared to that between BR and the tackifier.     

Lead phthalocyanine incorporated in sol and gel

Lead phthalocyanine (PbPc) was first successfully doped in organic-inorganic matrix by choosing proper alkoxy-silane containing amino-group by sol-gel processing. The characteristics of PbPc in sol and gel were studied using optical absorption spectroscopy. The results show that the presence of PbPc monomer in the sol and gel is strongly controlled by the pH value of sol, and the action of amino-group is an important factor for PbPc monomer able to exist in gel.     

Identification of characterization factor for power system oscillation based on multiple synchronized phasor measurements

Electric power systems in Japan are composed of remote and distributed location of generators and loads mainly concentrated in large‐demand areas. The structures having long‐distance transmission tend to produce heavy power flow with increasing electric power demand. In addition, some independent power producers (IPP) and power producer and suppliers (PPS) are participating in the power generation business, which makes power system dynamics more complex. However, there was little observation as a whole power system. In this paper the authors present a global monitoring system of power system dynamics by using the synchronized phasor measurement of demand‐side outlets. Phasor Measurement Units (PMU) are synchronized based on the global positioning system (GPS). The purpose of this paper is to show oscillation characteristics and methods for processing original data obtained from PMU after certain power system disturbances triggered by accidents. This analysis resulted in the observation of the lowest and the second lowest frequency mode. The derivation of eigenvalue with the two‐degree‐of‐freedom model brings a monitoring of two oscillation modes. Signal processing based on wavelet analysis and simulation studies to illustrate the obtained phenomena are presented in detail. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(3): 10– 18, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20316