Search

CaBi2Nb2O9 ceramics were fabricated via the solid-state reaction method by the addition of B2O3 as a sintering aid at lower sintering temperatures than that prepared without B2O3. Ferroelectricity, piezoelectricity, and resistivity can be still greatly enhanced when the sintering temperature is decreased from 1075 °C for CaBi2Nb2O9 to 975 °C for CaBi2Nb2O9–0.25 wt. % B2O3. The high resistivity and weak c-axis texture ensure that the ceramics can be fully polarized in a high enough electric field. The increased spontaneous ferroelectric and remanent polarization result in a significant enhancement in the piezoelectric properties of CaBi2Nb2O9–0.25 wt. % B2O3. The sample sintered at 975 °C possesses a high piezoelectric coefficient d33 of ∼15.0 pC/N and resistivity of 1.4 × 106 Ω cm (at 600 °C) along with a high ferroelectric Curie temperature TC of ∼954 °C. This work is beneficial for the preparation of high-temperature piezoelectric ceramics with excellent electrical properties at a low sintering temperature. [ABSTRACT FROM AUTHOR]

CaBi2Nb2O9 ceramics were fabricated via the solid-state reaction method by the addition of B2O3 as a sintering aid at lower sintering temperatures than that prepared without B2O3. Ferroelectricity, piezoelectricity, and resistivity can be still greatly enhanced when the sintering temperature is decreased from 1075 °C for CaBi2Nb2O9 to 975 °C for CaBi2Nb2O9–0.25 wt. % B2O3. The high resistivity and weak c-axis texture ensure that the ceramics can be fully polarized in a high enough electric field. The increased spontaneous ferroelectric and remanent polarization result in a significant enhancement in the piezoelectric properties of CaBi2Nb2O9–0.25 wt. % B2O3. The sample sintered at 975 °C possesses a high piezoelectric coefficient d33 of ∼15.0 pC/N and resistivity of 1.4 × 106 Ω cm (at 600 °C) along with a high ferroelectric Curie temperature TC of ∼954 °C. This work is beneficial for the preparation of high-temperature piezoelectric ceramics with excellent electrical properties at a low sintering temperature. [ABSTRACT FROM AUTHOR]

Room temperature ferromagnetism has been observed in hydrogenated N-doped amorphous carbon films (a-CNx:H) prepared by plasma enhanced chemical vapor deposition. The magnetization of the films changed depending on the ratio (R) of the flow rate of nitrogen to that of methane during deposition and on the annealing temperature. The highest magnetization of the as-deposited samples was obtained with R = 4. Annealing the films at 300 °C resulted in a significant increase in the magnetic moment compared to that of the as-deposited films. When the annealing temperature was above 500 °C, the magnetic moment of the samples decreased. No ferromagnetic impurities could be detected. The ferromagnetism of the a-CNx:H film is attributed mainly to spin-polarization of the p orbitals of the N adatoms on the surface or in the interlayers of irregular carbon. [ABSTRACT FROM AUTHOR]

We have investigated the InGaAs/GaAsSb/InAlGaAs/InAlAs type-II 'W' quantum wells (QWs) grown on InP substrates by molecular beam epitaxy. The photoluminescence (PL) emission wavelength longer than 2.56 μm at room temperature (RT) is demonstrated for the first time in this material system. The PL emission peaks of our designed samples can cover a wide range from 2 to 2.5 μm at cryogenic temperature. The samples show good optical quality that the reduction in integrated PL intensity is only around one order of magnitude from 35 K to RT. We found that the integrated PL intensity decreased as the emission wavelength increased, which is due to the reduction in the electron-hole wave function overlap. This is consistent with the calculated result. In the power dependent PL measurements, the emission peak of 'W' type QWs show blue shifts with the excitation power (Pex) but does not follow the Pex1/3 rule as predicted by type-II band bending model. The localized states filling effect gives reasonable explanations for the observed phenomena. [ABSTRACT FROM AUTHOR]

Photoluminescence (PL) and optically detected magnetic resonance are employed to study effects of nonstoichiometry during the growth on defect formation in ZnO epilayers grown by molecular-beam epitaxy (MBE). Several defects are revealed via monitoring the yellow PL emission (∼2.17 eV) and their magnetic resonance signatures are obtained. The defects are concluded to be common for the MBE growth and are facilitated during the off-stoichiometric growth conditions, especially under excess of oxygen. [ABSTRACT FROM AUTHOR]

Structural evolution along the edges of magnetic fluid microstrips under external magnetic fields is investigated in this article. It was found that when the external magnetic field increased the structure evolves from an originally monodispersed state to a disordered column state, and then to several levels of ordered structures. For the ordered structure state, a one-dimensional periodic structure resulted under lower field strengths, and with an increase in field strength, more columns formed. Hence, a two-dimensional ordered array of columns was achieved. Further experimental results showed that the ordered structure can be manipulated by adjusting control parameters, such as field strength, sweep rate, fluid concentration, strip width, and strip thickness. These results lay the groundwork for utilizing controllable ordered structures in magnetic fluid microstrips to develop potential applications, such as photonic crystals or waveguides. [ABSTRACT FROM AUTHOR]

An ultrafast time-resolved terahertz spectroscopy is utilized to study the carrier dynamics of indium nitride (InN) nanorod arrays and an epitaxial film. The results showed that the electrons confined in the narrow structure of nanorods are significantly affected by the carrier diffusion process near the surface, which caused the abnormally long relaxation time for nanorods.

Presents a study which examined the effect of germanium on the solubility of silicon in aluminum. Method of the study; Results and discusion; Conclusion.

Presents information on a study which analyzed the ground-state energy of the XY antiferromagnetic chains with spin-1/2 and spin-1, by a real space renormalization group method. Discussion of the lower bound of the ground state energy for spin-1/2; Examination of the alternating AXY chains; Concept of the quantum block renormalization group.

Presents a study which examined the giant magnetoresistance effect in ferromagnetically ordered thin film and bulk based on the Hund's rule coupling between the mobile electron and the core spin of manganese ions. Results; Discussion; Conclusion.

Focuses on a study which examined the band structure and magnetic properties of RFe[sub11]TiN[subx] rare-earth iron intermetallic compounds. Review of related literature; Computational approach considered; Results and discussion.

Provides information on a study which investigated the problem of the existence of long-range staggered magnetic order in the antiferromagnetic Heisenberg model on the square lattice by a renormalization group analysis. Methods; Results; Discussion.

Investigates the electronic structure and the related magnetic properties of R[sub2]Fe[sub17]Z[subx] compounds. Description of the cluster model; Information on the charge and magnetic moment distribution in the compounds.

Studies the standing waves in gallium arsenide coplanar waveguides. Advantages of the coplanar waveguide in monolithic millimeter-wave integrated circuits; Information on the electron-optic sampling technique; Measurements of the standing waves.