Search

ZnO linear resistors, due to its excellent performance, are widely used in numerous industries and gradually replacing traditional conductive resistors, presenting a broad prospect for application. To study the effects of lanthanide oxides on the microstructure and electrical properties of ZnO-based linear resistors, this paper prepared Dy 2 O 3 -doped ZnO-Al 2 O 3 -TiO 2 -NiO based linear resistors using a solid-state sintering method. The results showed that proper doping of Dy 2 O 3 could inhibit the growth of ZnO grains, leading to more uniform grain growth. Additionally, doped with appropriate amount of Dy 2 O 3 could enhance the linear performance of ZnO linear resistors, reduce the grain boundary barrier height (φ b), and decrease dielectric loss. Linear resistors with nonlinearity coefficient (α) of 1.07, grain boundary barrier height (φ b) of 0.0934 eV and resistance-temperature coefficient (α T) of −5.39 × 10−3/°C were obtained. The doping of Dy 2 O 3 could improve the comprehensive performance of ZnO linear resistors, making the fabricated ZnO linear resistors are more suitable for working in high frequency electric fields. The study and analysis of Dy 2 O 3 doped ZnO linear resistors are of significant importance for the preparation of high performance ZnO linear resistors. [ABSTRACT FROM AUTHOR]

ZnO-Pr 6 O 11 -based ZnO nonlinear ceramics are well studied for their stability. Improving the electrical properties and stability of varistors has been an important part of the research and development of ZnO ceramics. The doping of rare-earth oxides in previous studies did not result in better performance of ceramics. In this study, the doping of rare earth element europium oxide is carried out by the traditional solid phase sintering method using metal oxides ZnO-Pr 6 O 11 –CoO–La 2 O 3 (ZPCL) as the substrate, and the microstructure and electrical properties of the samples are tested. It is found that the doping of Eu 2 O 3 helps to increase the grain boundary barrier, effectively improves the nonlinear coefficient of varistors, which is a very important electrical parameter, and reduces the leakage current. The best performance of the varistors is obtained at 1.5 mol% Eu 2 O 3 doping, with the nonlinear coefficient of 18.7, the leakage current of 0.04 mA/cm2, the highest barrier height φ b of 0.45 eV and the breakdown field of 1283 V/mm. This study provides a reasonable theoretical basis and experimental support for the improvement of the electrical properties of ZnO-Pr 6 O 11 -based ZnO ceramics, and lays a certain foundation for the doping of rare earth oxides in ceramics in the future. [ABSTRACT FROM AUTHOR]

• Y 2 O 3 plays a limiting role on the growth of ZnO grains. • The doping of Y 2 O 3 affects the grain resistivity ρ g and grain boundary resistivity ρ gb of ZnO linear resistors. • The electrical properties of ZnO linear resistors were enhanced by Y 2 O 3 doping. ZnO-TiO 2 − MgO-Al 2 O 3 linear resistors with various Y 2 O 3 dopant concentrations were fabricated using the conventional solid-state reaction method. The comprehensive investigation of the impact of Y 2 O 3 addition on the microstructure and electrical characteristics of the resistors was carried out. The results indicated that the Y 2 O 3 phase hindered the growth of zinc oxide particles. Additionally, the incorporation of yttrium oxide increased the linearity of the resistors and affected the height of the grain boundary barrier (φ b). Subsequently, a Y 2 O 3 -doped ZnO linear resistor with a nonlinearity constant (α) of 1.09 and a resistance-temperature constant (α T) of -2.51 × 10−3/ °C was effectively produced. The comprehensive evaluation of the microstructure and relevant electrical characteristics enables the efficient production of linear resistors with excellent electrical properties. [Display omitted] [ABSTRACT FROM AUTHOR]

NbN/Cu composite films with different copper contents were synthesized by pulsed bias ion plating and the influence of copper contents on the crystal structure, toughness and tribological properties at room temperature was investigated. The results showed that three-phase of face-centered cubic (fcc) NbN, hexagonal close-packed (hcp) NbN and fcc-copper coexisted in the films. Addition of copper enhanced toughness from 0.14 MPa m 1/2 at 0 at.% copper to 0.73 MPa m 1/2 at 25.1 at.% copper due to the appearance a large volume of grain boundaries, while the hardness decreased gradually with the increase of copper contents. The average friction coefficient dropped from 0.81 at 0 at.% copper to 0.58 at 25.1 at.% copper, and the wear rate (WR) first decreased until a minimum, but a further increase in copper content led to the increase of the WR. The minimum value of WR was 1.2 × 10 −8 mm 3 /N·mm at 5.2 at.% copper. [ABSTRACT FROM AUTHOR]

Herein, to improve the electrical characteristics, ZnO linear resistors mixed with MgO, TiO 2 , Al 2 O 3 , and various concentrations of Sc 2 O 3 (with 0, 0.35, 0.7, and 1.05 wt %) were obtained using the conventional solid-state sintering technique, while the influences of Sc 2 O 3 doping on the micro-morphology and electrical characteristics was investigated in detail. The crystalline phases and microstructure were investigated by X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and scanning electron microscopy (SEM). The dielectric properties and electrical characteristics were evaluated using a precision inductance-capacitance-resistance meter and a high-voltage source meter. Results from SEM micrographs, XRD patterns, and EDS mappings illustrated that the doping of Sc 2 O 3 hinders the growth of ZnO grains. Electric field-current density and resistivity-frequency measurements illustrated that the doping of Sc 2 O 3 improves the linear performance of ZnO linear resistors and increases its grain resistivity and grain boundary resistivity. With Sc 2 O 3 doping, the dielectric properties of the samples are significantly affected, while the resistance-temperature features reveal the negative temperature constant function. By appropriate Sc 2 O 3 doping, the ZnO linear resistors exhibited excellent performance with grain boundary barrier height φ b of 0.0106 eV, nonlinear coefficient α of 1.03, and resistance temperature constant α T of −2.88 × 10−3. It is beneficial to investigate the influence of Sc 2 O 3 doping on the micro-morphology and electrical performances in detail for the preparation of zinc oxide linear resistors with superior performance. • With Sc 2 O 3 doping, the ZnO grain size d is decreasing. • Sc 2 O 3 as a donor additive, enhances the linear characteristics of ZnO linear resistors. • With Sc 2 O 3 doping, the ε r and tanδ of the ZnO linear resistors decrease. [ABSTRACT FROM AUTHOR]

In this work, the microstructure (for instance grain size and elemental distribution) and comprehensive electrical performances of ZnO–Bi 2 O 3 –Cr 2 O 3 –MnO 2 varistors, with various amounts of Co 2 O 3 prepared via the traditional solid-state sintering method were investigated. The influences of Co 2 O 3 doping on the microstructure of the ZnO varistors were evaluated via X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectrometer (EDS), while the effects on the electrical performance of the ZnO varistors were analyzed via voltage source meter and inductance-capacitance-resistance meter. The experimental results indicate that Co 2 O 3 doping can contribute to improve the electrical characteristics of ZnO varistors. The double Schottky barrier height φ b and nonlinearity coefficient α was enhanced significantly. Meanwhile, Co 2 O 3 doping can effectively reduce ZnO grain resistivity ρ g and increase grain boundary resistivity ρ gb. In this research, there was an optimal content of Co 2 O 3 (0.5 mol%), the α of the ZnO varistors reaches the maximum value of 46.7 and the φ b reaches the maximum value of 0.63 eV with the optimal content. [ABSTRACT FROM AUTHOR]

Abstract: Formic acid is the main breakdown product of mild hydrothermal treatment of carbohydrates. Further conversion to methanol was achieved using Cu as catalyst and Zn as reductant under hydrothermal conditions of 250–325°C for 3–12h. Both Cu and Zn used were commercial Cu and Zn powders with particle sizes of 200mesh. A methanol yield of 32% was achieved at 300°C for 5h with 6.5mmol of Cu, 12mmol of Zn and a filling rate of 44%. Thus, this process may provide a promising solution to producing methanol from biomass by converting carbohydrates into formic acid. [Copyright &y& Elsevier]

Cr3+-doped near-infrared (NIR) luminescent materials have become a research hotspot in luminescence functional materials. However, developing NIR phosphors with emission wavelengths exceeding 1000 nm, suitable for organic compound non-destructive analysis, remains a significant challenge. In this study, LiSc(WO 4) 2 :Cr3+ NIR phosphors were synthesized using a simple solid-state reaction method. Low temperature photoluminescence emission spectrum, electron paramagnetic resonance spectrum, and fluorescence decay curve confirmed that Cr3+ ions occupied both LiO 6 and ScO 6 octahedron sites, forming two luminescence centers. The sample exhibited an emission wavelength of 1082 nm under 523 nm excitation, with a full width at half maximum (FWHM) of 290 nm. As the Cr3+ concentration increased, the emission peak showed a blue shift. The sample LiSc(WO 4) 2 :0.3Cr3+ with optimal optical performance exhibited an emission wavelength of 1023 nm and an FWHM of 228 nm. Its luminescence intensity retained 38.4 % of room temperature value at 380 K, and the internal and external quantum efficiency were 33.2 % and 18.9 %, respectively. When packaged with a 525 nm green LED, the device as a NIR light source is capable of accurately identifying water, ethanol, ammonia, and silicone oil. This work demonstrates that tungstate materials have great potential in the field of optical materials and offers a new perspective for selecting matrix materials in the development of Cr3+-doped long-wavelength broadband NIR phosphors. [ABSTRACT FROM AUTHOR]

The content of free oxygen O ad at the ZnO grain boundaries has an important impact on the double Schottky barrier and electrical properties of ZnO varistors. In this work, Bi–Er–O pre-synthesized (BE) phase (Bi 1- x Er x) 2 O 3 (0.25 < x < 0.455) with high conductivity of O ad was prepared using Bi 2 O 3 and Er 2 O 3 as raw materials, and the effects of the BE phase doping on the phase, grain boundary properties, and electrical properties of ZnO–Bi 2 O 3 –Sb 2 O 3 –Co 2 O 3 –MnO 2 –Cr 2 O 3 –SiO 2 varistors were studied. XRD analysis shows that the lattice constant of the BE phase (Bi 1- x Er x) 2 O 3 is between (Bi 0.75 Er 0.25) 2 O 3 and BiErO 3. With increasing doping content of the BE phase from 0 to 0.75 wt%, part of Er3+ still exists in the form of the BE phase (Bi 1- x Er x) 2 O 3 at the ZnO grain boundaries, and its content increases with increasing doping content of the BE phase. The conductivity of O ad in (Bi 1- x Er x) 2 O 3 is much higher than that in Bi 2 O 3 , resulting in the generation of a large number of negative O′ and O″ at the ZnO grain boundaries, and decreasing concentration of the intrinsic point defect zinc interstice Zn i. So the donor concentration N d decreases, the height of the grain boundary barrier increases, the depletion layer widens, and the electrical properties are improved. By analyzing the low-temperature permittivity spectra, it was calculated that with increasing doping content of the BE phase from 0 to 0.75 wt%, the concentration of oxygen vacancy V O • decreases inappreciably, but the concentration of zinc interstice Zn i • • decreases by about 23%. When the doping amount of the BE phase is 0.75 wt%, the nonlinear coefficient α of the obtained ZnO varistors is 73.9 ± 0.6, and the leakage current density J L is only 0.3 ± 0.1 μA/cm2. This study provides an important reference for improving the electrical properties of ZnO varistors by manipulating the Bi-rich phase structure to improve the double Schottky barrier characteristics. [ABSTRACT FROM AUTHOR]

Abstract: We describe a simple experiment on the interference of refraction light by ultraweak liquid surface wave at low frequency. The surface wave profile is generated by electrically driven vertical oscillations exciters. The high visibility and stable laser interference fringes were gathered experimentally. The theoretical light intensity distribution agrees well with the observations. In particular, we show the relation between the light intensity distribution and the characteristic features of the surface wave. In addition, we can measure the amplitude and wavelength of the ultraweak liquid surface wave at low frequency by this means. [Copyright &y& Elsevier]

ZnO-Pr 6 O 11 based varistors have anticipated application prospect in electrical system, but the study of the detailed microstructure is still poor. In this paper, the effect of Pr 6 O 11 doping on the microstructure (such as element distributions and grain boundary characteristics) and electrical properties of the ZnO-Pr 6 O 11 –Co 2 O 3 –Cr 2 O 3 –Y 2 O 3 varistors manufactured by the conventional solid-state sintering procedure was studied detailedly. Without Pr 6 O 11 doping, the elements have the similar distributions in the interior and grain boundaries of ZnO phase, and the double Schottky barrier cannot be formed. With Pr 6 O 11 doping, Pr 6 O 11 liquid phase dissolving a large number of Zn, Cr, and Y forms during sintering and Pr 6 O 11 solid phase forms in the ZnO grain boundaries during cooling, so the double Schottky barriers form. The voltage gradients E 1 mA and nonlinearity coefficients α of the samples with Pr 6 O 11 contents of 0.25–1 mol% are much larger than those of the sample without Pr 6 O 11 doping, and the values of α and E 1 mA increase with Pr 6 O 11 content increasing from 0 to 1 mol%. The values of α and E 1 mA simultaneously depend on the double Schottky barrier height ϕ b and the CPE exponent α CPE. Finally, the ZnO varistor with a voltage gradient of 333.6 V/mm and a nonlinearity coefficient of 24.4 was obtained by Pr 6 O 11 doping of 1 mol%. The detailed study of the microstructure and related mechanism is of great importance for preparing ZnO-Pr 6 O 11 based varistors with excellent electrical properties. [ABSTRACT FROM AUTHOR]