a) J. Kim, a) B. Wilkens, b) N. Newman, a),b),g) J.M. Rowell, a) A.V. Pogrebnyakov, c),d),e) X.X. Xi, c),d),e) J.M. Redwing, d),e) S.Y. Xu, c),e) Qi Li, c),e) and B.H. Moeckly f)

Microwave-hydrothermal processing has so far been used only to dissolve inorganic solids for chemical analysis. We report herein the use of microwave-hydrothermal processing to synthesize various ceramic powders in binary and polynary systems. We describe the synthesis of some electroceramic powders such as BaTiO3, SrTiO3, Sr0.5Ba0.5TiO3, PbTiO3, BaZrO3, SrZrO3, Pb(Zr0.52Ti0.48)O3, and pyrochlore phases with the Pb(Mg1/3Nb2/3)O3 and Pb(Zn1/3Nb2/3)O3 compositions by this novel microwave-hydrothermal processing technique.

In this paper, we report the synthesis, structure and electrical conductivity of Mo‐doped compounds with a nominal chemical formula of Ce1–xMoxO2+δ (x = 0.05, 0.07, 0.1) (CMO). The formation of fluorite‐like structure with a small amount of Ce8Mo12O49 impurity (JCPDS Card No. 31‐0330) was confirmed using a powder X‐ray diffraction (PXRD). The fluoride‐type structure was retained under wet H2 and CH4 atmospheres at 700 and 800 °C, while diffraction peaks due to metal Mo were observed in dry H2 under the same condition. AC impedance measurements showed that the total conductivity increases with increasing Mo content in CMO, and among the investigated samples, Ce0.9Mo0.1O2+δ exhibited the highest electrical conductivity with a value of 2.8 × 10–4 and 5.08 × 10–2 S cm–1 at 550 °C in air and wet H2, respectively. The electrical conductivity was found to be nearly the same, especially at high temperatures, in air, O2 and N2. Chemical compatibility of Ce0.9Mo0.1O2+δ with 10 mol‐% Y2O3 stabilised ZrO2 (YSZ) and Ce0.9Gd0.1O1.95 (CGO) oxide ion electrolytes in wet H2 was evaluated at 800–1,000 °C, using PXRD and EDX analyses. PXRD showed that CMO was found to react with YSZ electrolyte at 1,000 °C. The area specific polarisation resistance (ASPR) of Ce0.9Mo0.1O2+δ on YSZ was found to be 8.58 ohm cm2 at 800 °C in wet H2.

No abstract

No abstract

The superconductor-insulator transition (SIT), one of the most fascinating quantum phase transitions, is closely related to the competition between superconductivity and carrier localization in disordered thin films. Here, superconducting TiO x films with different oxygen contents were grown on Al 2 O 3 substrates by a pulsed laser deposition technique. The increasing oxygen content leads to an increase of disorder, a reduction of carrier density, an enhancement of carrier localization, and therefore a decrease of superconducting transition temperature. A fascinating SIT emerges in cubic TiO x films with increasing oxygen content and its critical sheet resistance is close to the quantum resistance h/(2e) 2 ~6.45 kΩ. The scaling analyses of magnetic field-tuned SIT exhibit that the critical exponent products zν increase from 1.02 to 1.31 with increasing disorder. Based on the results, the SIT can be described by the "dirty boson" model, and a schematic phase diagram for TiO x films was constructed.

No abstract

Tunnel junctions composed of two ferromagnetic electrodes separated by a ferroelectric barrier were fabricated from epitaxial La0.7Sr0.3MnO3/Ba0.95Sr0.05TiO3/La0.7Sr0.3MnO3 trilayers. Typical R−H curves with sharp-switched resistance states (magnetic parallel and antiparallel) of magnetic tunnel junctions have been observed up to room temperature. After applying a poling voltage, which reverses the barrier polarization, both the parallel and antiparallel resistance states will switch to different values. Clear tunneling magnetoresistance and tunneling electroresistance, hence the four resistance states have been observed at room temperature.