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The moisture resistance of 5 mol% Nd2BaCuO5-added Nd1+xBa2−xCu3Oy (x = 0–0.8) ceramics was investigated. The samples were prepared by a solid-state reaction at 980 °C and exposed to a humid atmosphere at 40 °C and 93 %RH. The microstructure observation and X-ray diffraction measurement of the exposed samples revealed that the surface morphology and the crystal structure tended to be more stable when the amount of x was increased. The crystal structure was orthorhombic for x = 0 and tetragonal for x = 0.2–0.8. By comparing the lattice constants calculated by the bond valence to those determined by X-ray diffraction, it was suggested that a gap around the Ba site increased with the increasing x. The gap around the substituted Nd3+ for Ba2+ was considered to act as a trap site for OH−.

The enhancement of photoluminescence of alkali metal sulfate-doped zinc tungstate was investigated. All samples were prepared by solid-state reaction at 800 °C using ZnO, WO3, and alkali metal sulfates as starting powders. The zinc tungstate phase was confirmed from the samples by X-ray diffraction. The emission peak of the samples excited at 275 nm was observed at 465 nm. Rb2SO4 > K2SO4 > Cs2SO4 > undoped > Na2SO4 > Li2SO4 was the order of peak emission intensity of alkali metal sulfate-doped samples. Alkali metals with a large ionic radius (K, Rb, Cs) enhanced the emission of intrinsic luminescence in the blue wavelength region. Moreover, sulfates had the potential to change the luminescence activities of the samples.

In this work, we found the significant improvement of photoluminescence of zinc tungstate doped with potassium salts. The samples were prepared by solid-state reaction using ZnO, WO 3 , KNO 3 , K 2 SO 4 , and KCl as starting powders. The powders were mixed with the molar ratios of ZnO: WO 3 : potassium salts = 1: 1: x and sintered at 800 °C for 3 h in air. The emission peak of photoluminescence excited at 275 nm was observed at 465 nm. With increasing potassium salts content, the intensity increased reached its maximum at x = 0.02 and decreased. The tendency of the luminescence intensity for KCl doping was almost the same as KNO 3 doping, whereas, for K 2 SO 4 doping, the tendency of the decrease was less steep than other doping. The order of each maximum intensity was KNO 3 >K 2 SO 4 >KCl. It was considered that K replacing Zn in the crystal lattice enhanced the intrinsic luminescence in the blue wavelength region. Moreover, different anions doping had the different effect of the enhancement of the luminescence.

The effect of Sr substitution on the luminescence of Pr-activated Ca2-xSrxLaNbO6 was investigated. The samples were prepared by solid-state reaction. The Ca2LaNbO6 phase was confirmed in the samples with x = 0–1.5 by the X-ray diffraction. With increasing x, lattice constant β which is an angle between a and c axes in monoclinic structure decreased from 89.69°, reached its minimum value of 89.06° at x = 0.9, and increased. The emission peak of the samples excited at 450 nm was observed at 500 nm, 544 nm, 622 nm and 655 nm. The emission intensity at 655 nm showed a negative correlation with β. It was found that the decrease in lattice constant β had a significant effect in the improvement of the emission intensity.

Cu(In,Ga)Se2 (CIGS) crystals were synthesized by a mechanochemical (MC) process using a crank ball mill. The molar ratios of starting materials were Cu:In:Ga:Se=1:1-x:x:2 (0≤x≤1) and Cu:In:Ga:Se=1:0.7:0.3:y (2≤y≤3). The reaction time reduced with decreasing Se and Ga molar ratios. The collection rate decreased with longer reaction times. From XRD patterns, we confirmed that the CuInSe2 and/or CuGaSe2crystals were successfully grown when the powders reacted. Although the crystals grown with a selenium molar ration of 2 were Se-poor, those grown at a molar ratio of 3 were Se-rich. When Se increasing molar ratio, Cu, In, and Ga were away from the stoichiometric. With a molar ratio of Cu:In:Ga:Se=1:0.7:0.3:2.5∼2.7, their composition became stoichiometric. Crystal morphology was varied. CIGS crystals were thus successfully synthesized using a crank ball mill. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Nickel wire was used as a starting material to fabricate Ni nanoparticles. A glass substrate was placed above the wire to deposit the particles. The wire was heated by applying a d. c. voltage in the range of 2.2 ~ 4.0 V in oxygen atmosphere until the wire broke. White deposits were observed on the substrate after the heating. The TEM observation revealed that the deposits consisted of cubic nanoparticles with the edge lengths of 2 ~ 200 nm. The size of the particle tended to decrease with decreasing voltage. The particles were covered with films of approximately 4 nm in thickness. After reducing in hydrogen at 250°C for 30 min, the thickness of the films on the cubic particles decreased and the XRD peak intensity attributed to NiO decreased. Consequently the particles were found to be cubic Ni nanoparticles covered with NiO thin films.

In this study, we report the growth of ZnO nanowire on quartz glass substrates with Au-catalyst assistance by electric current heating of ZnO ceramic bar. The effect of substrate temperature on the properties of ZnO nanostructures has been investigated systematically. Structural analysis indicates that the grown ZnO crystals belong to hexagonal phase with preferential growth along (0 0 2) orientation. Scanning electron microscopic studies reveal the aligned ZnO nanowires were grown at 800 °C. The typical length and diameter of nanowires are in the uniform ranges of 4–20 μm and 20–100 nm, respectively, showing their high aspect ratio of about 1000. We have made an attempt to discuss about the change in ZnO nanostructures with different substrate temperatures and the possible mechanism for the growth of nanowires. Optical reflectance studies show the infrared reflectivity was controlled through the substrate temperature.

The I–V characterisation of Ho(Ba2−xSrx)Cu3O7−δ (x = 0, 0·2 and 0·8) ceramic sensor rod with hot spot in flowing oxygen between 0 and 100% pO2 revealed good oxygen response with output current observed to strongly depend on pO2. All the samples showed higher sensitivity to pO2 below 20% with reduced electrical power consumption in Sr substituted rods. The x = 0·2 rod showed improvement in output current stability, reproducibility and transition of output current response between 20 and 100% pO2 compared to the x = 0 rod. Conductivity was found to be proportional to above 60% for x = 0 rod and above 40% for Sr substituted rods, while lower pO2 conductivity was proportional to , in agreement with the mass action law indicating difference in oxygen ionisation. The results are also discussed in terms of the possible influence of hot spot temperature on the structure of Ho123 and changes in oxygen activation energy as a result of the difference in ionic sizes between Ba2+ and Sr2+.

Zn wire was used as starting material in the fabrication of ZnO crystals in which a glass substrate was placed above the wire to grow ZnO crystals. The wire was heated by electric current in air. When the wire broke because of Joule heating, smoke arose from the wire and ZnO crystals were observed on the broken point, in the vicinity of the broken point, and on the glass substrate. The morphology and cathodoluminescence of the crystals were investigated. The crystals on the wire were 0.2–5 μm in size. The peak intensity ratio of ultraviolet (UV) emission to green emission increased with decreasing crystal size. The crystals on the substrate were tetrapod-like; the length and diameter of the tetrapod legs were 100–500 nm and 10–30 nm, respectively. The tetrapod-like nanocrystals produced only UV emissions.

In this study, Glass wool which is mainly applied to heat and acoustic insulation was used as reinforcement materials. The composite material samples consisting of glass wool, polypropylene, and maleic anhydride grafted polypropylene were synthesized and the tensile strengths were evaluated. The treatment of glass wool with 3-amino propyl triethoxy silane coupling agent together with epoxy film former enhanced the tensile strength of the composite samples including the glass wool and the tensile strength reached to the same level of the conventional composite samples including chopping continuous glass fiber. Therefore, we concluded that glass wool has a good potential as a reinforcing material in thermoplastic composites.

A ceramic rod of GdBa2Cu3O7-δ with Gd2BaCuO5 core was prepared using a dip coater and sintered at 950oC. A hot spot appeared when a certain voltage was applied to the rod. Oxygen sensing characteristics of the rod were investigated. It was found that the response time of the oxygen sensor using the rod with the core was shorter than that without the core, because the length of the oxygen diffusion in GdBa2Cu3O7-δ part in the rod with the core was shorter than that without the core.

Tungsten trioxide films were deposited on the glass substrate by electric current heating method using tungsten wire in air. Applied voltages to the tungsten wire were increased at rates of 0.05, 0.5, 5 and 50 V/min. The resultant films consisted of particles. A particle size of the crystals increased with increasing voltage applying rate. The effects of an ultraviolet (UV) irradiation on the reflectance of the films were investigated. The reflectance in the wavelength range of 500 - 2500 nm decreased by the irradiation. When the films were left in dark after the irradiation, the reflectance returned to the initial. With increasing voltage applying rate, absorption peak shifted toward longer wavelength in the region of 1250 - 1500 nm and the peak intensity decreased.

A glass substrate was sputter-etched by R. F. magnetron sputtering at the powers of 100 or 200 W for 60 min in Ar gas. Pd thin film as a sensing agent of hydrogen (H2) was deposited on the glass substrate. The durability of the sensor was evaluated during hydrogen absorption-desorption cycles. The Pd thin film on the glass substrate without sputter etching peeled off after dozens of the cycles. However, the Pd thin film on sputter-etched glass substrate didn’t peel off. The contact angle of water on the glass substrate with sputter etching was smaller than that without sputter etching, suggesting that the surface energy of the substrate was increased by employing the sputter etching process. The improvement of durability for the optical hydrogen sensor using sputter etched substrate was related to the increase of surface energy induced by the sputter etching.

Aluminum nitride ceramics were sintered with 1.0 and 4.8 mass% Ca3Al2O6 (C3A) as a sintering additive. Temperature dependence of cathodoluminescence (CL) for the ceramics was investigated in order to obtain information on lattice defects. The CL peak intensity at 3.5 eV in the ceramics sintered with 1.0 mass% C3A decreased with increasing temperature, so called thermal quenching. The maximum CL peak intensity of the ceramics sintered with 4.8 mass% C3A was much lower than that with 1.0 mass% C3A, reflecting that the oxygen-induced defect density dramatically decreased with increasing amount of C3A. In case of the ceramics sintered with 4.8 mass% C3A, the CL peak intensity at 3.4 eV showed the thermal quenching in the range of 130 - 350 K, whereas in the range of 80 - 130 K and 350 - 475 K, it increased with increasing temperature, so called “negative” thermal quenching. From the results, we suggest a presence of at least two trapping levels in the ceramics sintered with C3A.

Aluminum nitride ceramics were prepared by sintering with 0–4.8 mass% of Ca 3 Al 2 O 6 (C 3 A) as a sintering additive. The transmittance in the range of 260–550 nm increased with increasing amount of C 3 A. The cathodoluminescence intensity attributed to oxygen-induced defects decreased with increasing amount of C 3 A. From the results, the increase of the transmittance in the range of 260–550 nm was considered to be related to the decrease of the oxygen-induced defect density.

Zinc oxide (ZnO) ceramics was coupled and reacted with alpha aluminum oxide (α-Al2O3) ceramics at 1200oC for 24 h. SEM observation and energy dispersive X-ray spectroscopy (EDS) analysis revealed the existence of diffusion layer of 10 μm thickness on the α-Al2O3 side of interface between ZnO and α-Al2O3. The diffusion layer is considered to consist of a ZnAl2O4, from the result of XRD. The cathodoluminescence of the diffusion layer was compared with that of zinc aluminate (ZnAl2O4) ceramics synthesized by conventional solid state reaction method. The single phase ZnAl2O4 showed weak emission peaked at 4.6 eV. On the other hand, the diffusion layer showed intense emission peaked at 3.75 eV. The ZnAl2O4 on the α-Al2O3 side of the interface synthesized by coupling of ZnO and α-Al2O3 is considered to be a excellent material as an ultraviolet light emitter.

Beta gallium oxide (β-Ga2O3) ceramics was coupled and reacted with zinc oxide (ZnO) ceramics at 1200oC for 24 h. Energy dispersive X-ray spectroscopy (EDS) analysis revealed the existence of diffusion layer near the interface between β-Ga2O3 and ZnO. Furthermore, the layer showed monochromatic and intense cathodoluminescence (CL) at 3.5 eV. On the other hand, very weak emissions were observed from the out of the layer. The compound in the layer is considered to be an attractive material for ultraviolet optoelectronics.

We developed a new zinc oxide (ZnO) crystal growth method using Au combined with electric current heating. Au paste was placed on a ZnO ceramic bar. When a certain current flowed through the bar, the paste melted on the bar. Then crystals grew on the molten Au surface immediately. The shape of the crystals depended on the atmosphere during the growth. The whiskers with spherical top and the crystals consisting of a hexangular pyramidal base and needle head were grown on Au in air and Ar atmosphere, respectively. From cathodoluminescence at room temperature, the weak ultraviolet (UV) emission at approximately 3.2 eV and the strong visible emission at approximately 2.3 eV were observed from the whisker grown in air. The UV emission at approximately 3.3 eV dominated a spectrum from the pyramidal crystal grown in Ar atmosphere.

High-resolution photoluminescence (PL) measurement was carried out for copper aluminum disulfide (CuAlS2) powder at 12 K. Several sharp PL lines were observed in the range from 3.580 to 3.320 eV. The emission peaks at photon energies from 3.566 to 3.459 eV were attributed to free-exciton (FE) and bound-excitons (BE). The several weak emissions at below 3.476 eV were clarified to be phonon replicas (PR) by Raman scattering and in the viewpoint of exciton-phonon interaction. We observed the one, two and three-phonon replicas related to E(LO, TO) and B2(LO, TO) vibrational modes in chalcopyrite structure. It was suggested that the strong interaction between excitons and optical phonons took place in obtained CuAlS2 powder.

Aluminum nitride (AlN) ceramics with various amounts of Ca3Al2O6 (C3A) as a sintering additive were sintered at 1880°C for 50 h in N2 atmosphere. The thermal conductivity of AlN ceramics increased with increasing amount of C3A in the range from 0.5 to 4.8 mass%. Cathodoluminescence (CL) intensity attributed to oxygen-induced defects decreased with increasing amount of C3A. From the results, the increase of the thermal conductivity was considered to relate to the decrease of the oxygen-induced defects by increasing amount of C3A.

Alpha aluminum oxide (α-Al2O3) ceramics was coupled and reacted with zinc oxide (ZnO) ceramics at 1200°C for 24 h. Energy dispersive X-ray spectroscopy (EDS) analysis revealed the existence of step-shaped distribution of Al and Zn near the interface between α-Al2O3 and ZnO. Intense ultraviolet (3.75 eV) emission was clearly observed from the layer. On the other hand, very weak emissions were observed outside the layer near the interface. The compound in the layer is considered to be an attractive material for ultraviolet optoelectronics.

Beta gallium oxide (β-Ga2O3) crystals were grown on β-Ga2O3 ceramics heated by electric current under vacuum at various ambient temperatures. From cathodoluminescence at room temperature, emission peaks at 2.9 and 3.5 eV were clearly observed. With increasing ambient temperature, the relative intensity of ultraviolet emission (3.5 eV) to blue emission (2.9 eV) showed a peak at 400oC. These results suggest that the ambient temperature during the electric current heating of β-Ga2O3 ceramics in vacuum is one of the most effective factors for the ultraviolet emissive β-Ga2O3 crystal.

Copper aluminum disulfide (CuAlS2) powders were synthesized in an evacuated ampoule at elevated temperatures. X-ray diffraction analysis revealed that the powders heated at temperatures higher than 800oC were single-phase CuAlS2. In the cathodoluminescence (CL) spectra measured at room temperature, the powders heated at temperatures higher than 600oC exhibited a visible emission peak at approximately 1.8 eV and a distinct ultraviolet emission peak at 3.45 eV. The powder heated at 700oC showed the maximum intensity of ultraviolet emission which is considered to be associated with excitons.

A hot spot, which is a local area glowing orange, appears in a GdBa2Cu3O7−δ ceramic rod when a voltage exceeding a certain value is applied to the rod at room temperature. The rod with the hot spot shows various functional characteristics that give rise to applications in devices. We found that the hot spot created a sponge-like structure in the rod. The elemental map revealed that the sponge-like structure was composed of Gd2BaCuO5 grains. The hot spot is considered to decompose GdBa2Cu3O7−δ into Gd2BaCuO5 and liquid phase, and the liquid phase moves toward the periphery of the rod, leaving sponge-like structure composed of Gd2BaCuO5 grains. The novel sponge-like structure created in the GdBa2Cu3O7−δ rod by the hot spot may bring about new applications for magnetic separations of fluids.

When a Zn wire was heated by electric current, ZnO whiskers grew on the wire surface. The average diameters of the whiskers grown under O 2 , 20% O 2 and Ar atmospheres were 0.12, 0.17 and 0.4 μm, respectively. The well-known visible emission was observed from the whiskers grown under O 2 and 20% O 2 atmospheres. The whiskers grown under Ar atmosphere showed strong ultraviolet (UV) emission. X-ray diffraction measurements revealed that the crystalline quality of the whiskers increased with decreasing O 2 concentration in the growth atmosphere. It was found that residual O 2 of less than 10 ppm in Ar atmosphere is used for the synthesis of the whiskers with UV emission. Monitoring O 2 concentration during the electric current heating of Zn wire in Ar atmosphere was effective in estimating the yields of the whiskers.

A hot spot, which is a local area glowing orange, appears in LnBa 2 Cu 3 O 7− δ (Ln: rare earth element) ceramic rod when a voltage exceeding a certain value is applied to the rod at room temperature. The rod with the hot spot shows various functional characteristics that give rise to applications in devices such as a constant-current generator, an oxygen sensor. The durability of the rod during a sustained presence of the hot spot is improved upon adding BaAl 2 O 4 into the GdBa 2 Cu 3 O 7− δ . In this paper, GdBa 2 Cu 3 O 7− δ -based composite ceramic rod with various BaAl 2 O 4 contents were prepared by solid-state reaction, and current–voltage characteristics and temperature dependences of resistivity were measured. The minimum electric power required for the hot spot to appear increased with increasing BaAl 2 O 4 content. From the temperature dependence of the resistivity, temperature just before the hot spot appearance could be successfully estimated. The minimum electric power required for the hot spot to appear can be expected from the temperature dependence of the resistivity of the ceramics, which is useful to design the functional devices exploiting the hot spot.

Copper doped hydronium alunite; (H 3 O)Al 3 (SO 4 ) 2 (OH) 6 :Cu was successfully synthesized under hydrothermal conditions. The blue cathodoluminescence (peak at about 414 nm) was observed from the (H 3 O)Al 3 (SO 4 ) 2 (OH) 6 :Cu when the copper ratio x was 1 and above, where x was the molar ratio of Cu:Al:S = x :3:2 (0 ≤ x ≤ 15) in the starting materials. The luminescence intensity increased with increasing x up to 3, and then decreased. The monovalent copper ion (Cu + ) was detected by XPS measurements for all the doped samples. In addition, the divalent copper (Cu 2+ ) was detected for the samples with x ≥ 6. Therefore, the origin of the blue luminescence is considered to be monovalent Cu + ion. Excess doping of Cu + ( x ≥ 6) is thought to cause a concentration quenching of the luminescence. The obtained (H 3 O)Al 3 (SO 4 ) 2 (OH) 6 :Cu is expected to find use in the blue luminescent phosphor under electron beam irradiation.

Glass wool is discontinuous glass fiber with the average diameters of 3-4 μm produced by means of centrifugal process, and mainly applied to heat and acoustic insulation. But, there are few reports on glass wool applied to reinforcement of plastic materials in which chopped strand made by chopping continuous glass fiber is used primarily. In this study, the polyamide 66-based composite material samples containing glass wool were prepared and its wear property as a mechanical property was evaluated. It was found that the composite has an advantage on the wear property compared with a conventional glass fiber reinforced plastic, and the result suggests that glass wool has a possibility as a reinforcement material applied to plastic parts required wear resistance.

Cu wires were heated by electric currents to fabricate Cu2O thin films. The films were successfully deposited on glass substrates placed above the wires at air pressures in the range of 100 - 40 Pa. Then the films were annealed in a controlled atmosphere and investigated the crystallinity, morphology and the time response to illumination of the films. After annealing at 800 °C at atmospheric pressure with oxygen partial pressure of 12 Pa, the crystallinity was increased and the time response of photoconduction was successfully improved.

Composite ceramic rods of GdBa 2 Cu 3 O 7− δ with various contents of CuO were prepared as oxygen sensors by solid state reaction. A hot spot appeared in the rod when a certain voltage was applied to the rod at room temperature. The current running through the rod with the hot spot decreased with decreasing oxygen partial pressure (Po 2 ). For the rods containing 0–11 vol% CuO, the currents decreased to almost zero at Po 2 2 2 were improved by adding 15–52 vol% CuO to GdBa 2 Cu 3 O 7− δ .

A novel oxygen sensor using hot spot on ceramic rod of high-T c superconductor RBa2Cu3O7−δ (R: rare earth element) has been developed. The hot spot appears by the self-heating of the local part on the RBa2Cu3O7−δ ceramic rod when a voltage above threshold is applied at room temperature. This sensor operates without any separate heater by taking advantage of the high temperature of the hot spot wherein oxide ions can diffuse easily. The oxygen concentration is determined from the value of the current flowing through the rod by utilizing the change in the resistivity of the hot spot depending on oxygen partial pressure in atmosphere. Oxygen concentration of 0∼100% can be detected with high sensitivity and the response time is several seconds. The response performance of this oxygen sensor is almost the same as that of limiting-current-type zirconia sensor operating at 500°C.

Copper aluminum disulfide (CuAlS2) powders were synthesized in the evacuated ampoule. The luminescence properties of obtained powders were evaluated by photoluminescence (PL) at various temperatures. The visible emission peaks at 2.16 and 1.90 eV, and weak ultraviolet emission peak at 3.47 eV were obtained in the room temperature PL. The temperature dependence of the PL revealed that the ultraviolet emission at room temperature was considered to be free-exciton. Several emission peaks related to free-exciton, bound-exciton and phonons were observed in the high-resolution PL at 12 K, reflecting that the obtained powders had high crystallinity. Emission peaks at 3.459 and 3.300 eV for CuAlS2 were observed for the first time. The former emission might be originated from the bound exciton and the latter from the donor–acceptor pair recombination.

When a dc voltage above 5 V was applied to wire-like GdBa2Cu3O7-δ samples, a glowing hot spot appeared and moved to the negative electrode. The direction of movement could be reversed time after time by switching the polarity of the applied voltage. The samples were annealed by letting this glowing hot spot travel back and forth in the sample. The velocity of the hot spot depended on the direction of movement, however, for one direction the velocity of the hot spot decreased with annealing. After the hot spot moved back and forth 5 times, as well the density as the critical current density increased.

Publisher Summary The functions inherent in nanoparticles can be maintained while lowering their reactivity by fabricating nanoparticles into nanostructures. Stable nanostructured materials, fully utilizing the functions of nanoparticles, can be created by fabricating composite and bulk materials from nanoparticles, depending on their intended use. This chapter deals with such nanostructured materials and their various functions and the characteristic evaluation by function. It summarizes the nature of nanostructures, relevant examples of the relations between nanostructures and their characteristics, and the functionality and the evaluation of the characteristics of nanostructures. The chapter describes an electrode of a solid oxide fuel cell (SOFC), the structure of which is controlled using surface-coating type composite particles and the inner-dispersion type composite particles, as an example to explain the relation between nanostructures and their functional performance. In fabricating nanostructures in the application of nanoparticles, new functionalities are expected to produce many applications ranging over almost all fields in the coming years, with the advancement of technology. The chapter discusses the functional characteristics that are expected to be implemented in nanostructures in the coming future, including mechanical characteristics, thermal characteristics, electrical characteristics, electrochemical characteristics, electromagnetic characteristics, optical characteristics, catalytic characteristics, and gas permeability and separation characteristics.

We report here on the appearance of a hysteresis in the current-voltage characteristic, when a voltage is applied to a GdBa2Cu3O7−δ rod at room temperature. This hysteresis was caused by the appearance and disappearance of a hot spot. When a gradually increasing dc voltage (0–8 V) was applied to a GdBa2Cu3O7−δ rod, a hot spot appeared at a given voltage, Va. Further increasing of the voltage increased the spot size, while the current stayed constant. When a voltage of 8 V was reached, the voltage was gradually decreased. The spot did not disappear at Va, but at a voltage 0.2 to 1.3 V lower than Va. The current remained constant until the spot disappeared. By the authors' best knowledge, this is the first report of a hysteresis in the current-voltage characteristic at room temperature for a high Tc superconductor.