Microstructure Of ZnO Research Articles

Influence of TiO2 doping on the grain growth and electrical properties of ZnO–Cr2O3-based varistor ceramics

The influence of TiO2 doping in the range 0–1 mol% on the microstructure and electrical characteristics of ZnO–Cr2O3-based varistor ceramics was studied. Exaggerated grain growth is observed owing to the presence of TiO2, which triggers the formation of inversion boundaries (IBs) in only a limited number of grains. TiO2 acts as the controller of ZnO grain growth, adjusting the grain size of the ZnO from 5.6 to 9.3 μm, and thus controlling the breakdown voltage. Meanwhile, the TiO2 doping decreased the height of the Schottky barrier, resulting in a lower nonlinear coefficient and a higher leakage current. The results are important for the control of the ZnO grain size with ZnO–Cr2O3-based varistors (having different nominal breakdown voltages) to obtain a suitable thickness for applications.

Effects of In2O3 doping on the microstructure and electrical properties of ZnO–V2O5–Nb2O5 varistor ceramics

To understand the effects of In2O3 on the microstructure, grain size dispersion, density and nonlinear electrical characteristics, ZnO–V2O5–Nb2O5 varistor ceramics with 0.02, 0.05 and 0.1 mol.% In2O3 were fabricated via sintering at 950–975 °C for 1 h. The sintered samples were evaluated by x-ray diffraction, scanning electron microscopy, density measurements and electrical measurements through a voltage source meter. In2O3 addition improves relative density to ≥99 % and acts as an efficient grain growth inhibitor, resulting in a narrower grain dispersion and finer ZnO grains due to the formation of In–V–O intergranular phases. The breakdown potential (E1mA) increases sharply to 7.49 ± 0.3 kV/cm (from 1.66 ± 0.1 kV/cm) as a result of grain size reduction to 2.1 ± 0.1 μm (from 3.89 ± 0.2 μm) with In concentration of 0.1 mol.% (from 0.02 mol.%). Doping of In2O3 improves the nonlinear exponent and reduces the leakage current density as a direct consequence of enhanced Schottky barrier height.

The Effect of Sintering Temperature on the Microstructure and Electrical Properties of ZnO–Bi2O3 Varistor Ceramics

The Effect of Sintering Temperature on the Microstructure and Electrical Properties of ZnO–Bi2O3 Varistor Ceramics

Bond characteristics, microstructure, and microwave dielectric properties of Bi2O3–ZnO–B2O3 glass-ceramics with Li2O substitution

The effect of Li2O substitution on the sintering behavior, lattice structure, microstructure, and microwave dielectric properties of ZnO–B2O3–Bi2O3 glass-ceramics was studied by various amounts of Li2O to substitute ZnO. The substitution of Li2O decreases the glass network connectivity and thus decreases the sintering temperature of the glass. In the sintered glass-ceramics, the substitution of 0.2 mol% Li2O leads to the most significant lattice activation resulting in the glass-ceramic exhibiting the smallest cell volume of Zn3B2O6 crystal and the microstructure with fine and uniform grains. The P–V-L theory is innovatively applied to glass-ceramic materials to characterize the variation in bond characteristics caused by lattice activation and it indicates that the 0.2 mol% Li2O substitution decreases the Zn–O bond ionicity and increases the lattice energy of the B–O bond, in the Zn3B2O6 crystalline phase. The refinement of microstructure and the optimization of bond characteristics improve the microwave dielectric properties of glass-ceramics. The glass-ceramic with 0.2 mol% Li2O substitution sintered at 620 °C for 5 h exhibits excellent microwave dielectric properties of εr ∼5.05, Q×f ∼15,383 GHz, τf ∼ −6 ppm/°C and good chemical compatibility with Ag or Al electrodes, which is a favorable candidate for application in ULTCC substrate materials.

Microstructure, AC conductivity and complex modulus analysis of Ca-ZnO nanoparticles for potential optoelectronic applications

In the present work, we investigate the conductivity characteristics and microstructure of Ca-doped ZnO (ZO_Ca) nanoparticles. ZO_Ca nanoparticles were created using a straightforward sol-gel manufacturing method and annealed at various temperatures. Powder X-ray diffraction analysis provided proof of the ZO_Ca nanoparticles' purity, crystalline nature, and hexagonal structure. Meanwhile, the transmission electron microscopy (TEM) was used to establish the morphology and shape of the ZO_Ca nanoparticles, and energy dispersive X-ray spectroscopy analysis was used to discover the components that make up the particles' makeup. Moreover, AC conductivity measurements have been used to examine the electrical characteristics of ZO_Ca nanoparticles. Reduced activation energy values demonstrate the material's appropriateness for photonics devices, and the small proportion of activation energy derived from AC conductivity and complex modulus measurements is an added benefit for the construction of optoelectronic devices.

Optical properties, singlet oxygen, and free radical production ability with different UV irradiations and antimicrobial inhibitors against various bacterial species of ZnO: Eu nanoparticles

In this study, ZnO: Eu nanoparticles were produced by the co-precipitation method. In this context, X-ray diffraction (XRD) was analyzed to characterized the produced nanoparticles. Moreover, the approximate crystallite size of the nanoparticles was calculated using Scherrer's formula and Williamson-Hall's equation of 27 nm with a strain of 0.002. The crystalline size and the microstructure of ZnO: Eu nanoparticles were obtained by the scanning electron microscope (SEM) and its results were consistent with the analysis of (XRD). The optical properties of the prepared nanostructure were studied by applying photoluminescence spectroscopy (PL), which was observed in the spectrum obtained with an excitation wavelength of 325 nm in the ultraviolet range and visible zone of the peaks. The energy band gap was reached through ultraviolet-visible spectroscopy for ZnO: Eu nanoparticles. The connection between the produced nanostructure elements was defined by the Fourier transform infrared spectroscopy (FTIR). Methylene blue and anthracene reagents were used to detect the hydroxyl radical and singlet oxygen. The reduction in anthracene and methylene blue absorption emphasizes the production of singlet oxygen and radical hydroxyl. ZnO: Eu nanoparticles were used as an antimicrobial inhibitor against various bacterial species. Taken together, our results confirmed that the growth of bacteria can be inhibited by ZnO: Eu nanoparticles. The maximum diameter of the halo was not increased, due to the effect of 26 mm nanoparticles that is related to P.aeruginosa bacteria.

Effect of Powder Processing and Sintering Conditions on the Microstructural, Thermal, and Mechanical Properties of Reticulated Zinc Oxide Ceramic Foams

Ceramic foams are made of zinc oxide using different amounts of Sb2O3 and Bi2O3 as sintering aids. The effect of a ball milling processing of the starting powders and the sintering temperature on the microstructure and the properties of the ZnO foams is investigated. The focus is set on the evolution of the secondary phases formed within the microstructure of ZnO. A determining effect is identified in the amount of an Al2O3 impurity which is introduced by abrasion of the milling vessels during ball milling. Alumina is partially dissolved in a spinel α–Zn7Sb2O12 secondary phase which is stabilized by a reduction of the unit cell volume. Remaining Al2O3 is incorporated into zinc oxide under formation of a defect wurtzite phase. The phase evolution is a complex function of the content of sintering aids, the Al2O3 impurity level and the sintering temperature. The shrinkage during sintering and the porosity evolution are correlated to the phase composition within the ZnO material. The thermal conductivity and the compressive strength of the foams are determined, normalized with respect to their porosity, and correlated to the microstructure and phase composition of the ZnO strut material.

Effect of Co3O4-doping on the microstructure and electrical properties of novel ZnO–Cr2O3-based varistor ceramics

Novel ZnO–Cr2O3-based varistor ceramics have superior current-voltage (I–V) characteristics and, do not contain volatile, rare or toxic dopants. The results showed that doping with Co3O4 greatly affected the nonlinearity of the ZnO–Cr2O3-based ceramics, with the highest coefficient of nonlinearity α equal to 73, while the leakage current was lower than 0.2 μA/cm2. Such a varistor performance enhancement was explained by the substitution of Co2+ into the Zn sites leading to the formation of Zn interstitials and free charge carriers of ZnO grains as well as an increased concentration of electron-trapping interface states like adsorbed oxygen and consequently substantially increased electrostatic barriers at the grain boundaries. The optimal amount of added Co3O4 for high-performance ZnO–Cr2O3-based varistor ceramics was about 0.5 mol.%.

Microstructure of ZnO:Er Films Prepared by Magnetron Sputtering

Microstructure of ZnO:Er Films Prepared by Magnetron Sputtering

Effect of Sc2O3 doping on microstructure and electrical properties of ZnO–Bi2O3-based varistors

ZnO varistors are widely used in electrical systems. In this study, the effects of different contents of Sc2O3 doping on the microstructure and electrical properties of ZnO varistors were systematically analyzed. The results show that the doping of Sc2O3 is conducive to the uniform growth of the ZnO grains and improves the breakdown field strength of varistors. At the same time, Sc2O3 doping improves the barrier height of the varistors, resulting in a significant increase in nonlinear coefficient and a decrease in leakage current density. The sample doped with 0.15 mol% Sc2O3 exhibited excellent electrical properties with breakdown field strength of 696.13 V/mm, a leakage current density of 1.26 μA cm−2, and a nonlinear coefficient of 55.00. The Sc2O3 doped samples have good performance, which is of guiding significance for the study of other trivalent and tetravalent ion doping with a radius similar to that of Zn2+.

Effect of ZnBi2O4 and Bi2O3 addition on the microstructure and electrical properties of ZnO–Co3O4–Mn3O4 varistors

Effect of ZnBi2O4 and Bi2O3 addition on the microstructure and electrical properties of ZnO–Co3O4–Mn3O4 varistors

Mg doping effects on the microstructure and piezoelectric characteristics of ZnO:Li films deposited at room temperature using an RF sputtering deposition method

In this work, Density functional theory (DFT + U) was used to simulate Mg doped LZO (ZnO:Li 3 mol%) based on an atomic substitution concept. The calculation results indicate the piezoelectric constants e33, e31 and lattice constant a have a tendency to increase significantly due to Mg doping effects. Also, an RF magnetron sputtering system was used to prepare Mg-doped LZO films (ZnO: Li 3 mol%) with Mg doping concentrations of 0, 3, 6, 9 mol% at room temperature. A further analysis shows that when the proposed films are deposited at room temperature, Li atoms will bond with oxygen atoms to form Li2O2 to help to enhance the piezoelectric properties of the films. This is also found to be one of the reasons for the error in the simulated lattice constants.In addition, the doping of Mg induces lateral tensile stress in the ZnO structure. This phenomenon can produce lattice distortion and change the asymmetry of the ZnO atomic center at room temperature, thus improving the piezoelectric properties (piezoelectric coefficient d33 is increased from 4.5 to 26.3 pm/V). The reported d33 value is the highest compared to other reports on ZnO-based films deposited at room temperature.

Influence of Co2O3 doping on the microstructure and electrical properties of ZnO–Bi2O3-based varistors

In this work, the microstructure (for instance grain size and elemental distribution) and comprehensive electrical performances of ZnO–Bi2O3–Cr2O3–MnO2 varistors, with various amounts of Co2O3 prepared via the traditional solid-state sintering method were investigated. The influences of Co2O3 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 Co2O3 doping can contribute to improve the electrical characteristics of ZnO varistors. The double Schottky barrier height φb and nonlinearity coefficient α was enhanced significantly. Meanwhile, Co2O3 doping can effectively reduce ZnO grain resistivity ρg and increase grain boundary resistivity ρgb. In this research, there was an optimal content of Co2O3 (0.5 mol%), the α of the ZnO varistors reaches the maximum value of 46.7 and the φb reaches the maximum value of 0.63 eV with the optimal content.

Effect of Ho2O3 doping on the microstructure and electrical properties of ZnO–Bi2O3–Sb2O3–Cr2O3–Co2O3–MnO2-based varistors

Ho2O3 doped ZnO–Bi2O3–Sb2O3–Cr2O3–Co2O3–MnO2-based varistors (ZBSCCM based varistors) was fabricated by solid-state reaction and subsequent sintering process. Microstructure characterization by X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicated the Ho2O3 phase with the doping content no more than 0.8 mol% was distributed along the grain boundaries of ZnO grains and could restrain the growth of ZnO grain. However, excessive Ho2O3 doping (>1.0%) delayed the full densification of the green pellets, leading to the decrease in relative density of the sample. The electrical properties were investigated by means of direct current measurement. It was found that proper amount of Ho2O3 doped in the ZBSCCM based varistors was able to improve the electrical properties. Particularly, the varistor doped with 0.8 mol% of Ho2O3 possessed the highest breakdown field (1578.5 V/mm), an excellent nonlinear coefficient α (86.3) and a small leakage current density (1.06 μA/cm2).

ZnFe2O4 Nanoparticles on ZIF-8-Derived ZnO for Enhanced Acetone Sensing

The development of uniform heterostructures for gas-sensing materials is promising to achieve both a fast response and recovery time at low gas levels and good selectivity at significantly high interference gas levels. Here we report the preparation of a ZIF-8-derived metal oxide semiconductor nanocomposite with a heterojunction structure and its application as acetone gas sensor. This heterojunction composite was fabricated through in situ growth of ZnFe2O4 nanoparticles (10–20 nm) on the outer surface of rhombic dodecahedral-shaped ZnO. Through the derivative strategy, the ZnFe2O4/ZnO heterojunction sensor had a high response value of 225 ± 15 and a fast response time of 6 s to 100 ppm of acetone at the optimum working temperature of 260 °C. Furthermore, the response value reached 5.1 for only 1.8 ppm of acetone even under extremely high humidity (85%). To obtain a demonstration of the concept, an in-depth investigation of the sensing performances and the microstructure and surface state of ZnO and ZnFe2O4/ZnO heterojunction materials was carried out. We found that the excellent acetone sensitivity enhancement could largely be attributed to the ultrahigh number of free electrons and the abundant active sites generated by the tightly bound n–n heterojunction structure of ZnFe2O4/ZnO and the morphological characteristics. The large specific surface area of every sensing domain was the secondary factor in enhancing the gas-sensing properties. It suggests that this design for fabricating uniform and sensitive gas sensors may facilitate potential applications in detecting acetone gas.

Effects of the electric field on microstructure and electrical properties of ZnO–Bi2O3–Co2O3 varistor by flash sintering

Effects of the electric field on microstructure and electrical properties of ZnO–Bi2O3–Co2O3 varistor by flash sintering

Investigation of the Effect of (Nd, Al) Co-doping on the Microstructure and Electrical Conductivity of ZnO

Investigation of the Effect of (Nd, Al) Co-doping on the Microstructure and Electrical Conductivity of ZnO

Microstructure and Red Luminescence of ZnO Nanoparticles/Nanofibers Synthesized by Electrospinning Followed by Thermal Annealing

Microstructure and Red Luminescence of ZnO Nanoparticles/Nanofibers Synthesized by Electrospinning Followed by Thermal Annealing

Effects of the Er2O3 doping on the microstructure and electrical properties of ZnO–Bi2O3 based varistor ceramics

In the present study, the effects of Er2O3 doping on the phase, microstructure, and electrical properties of ZnO–Bi2O3 based varistors were systematically investigated. In particular, a correlation between the microstructure and electrical properties was established based on the quantitative analyses of grain size, grain size distribution, and porosity. It was found that appropriate Er2O3 content of 0.4 mol% effectively decreased the grain size and improved the homogeneity of grain size distribution, contributing to a well-connected Bi2O3 intergranular network. Thus, simultaneously enhanced voltage gradient of 280 V/mm and relatively high nonlinear coefficient of 46 were achieved in varistors. However, with further increasing Er2O3 content, the excess Er2O3 phases were generated and agglomerated at grain boundaries. This further caused coarse pores and seriously undermined the connectivity of Bi2O3 networks, leading to the decrease in nonlinearity of varistors. Furthermore, such a correlation revealed in this study may provide valuable guidelines for developing high-performance ZnO–Bi2O3 based varistors.

Synthesis of ZnO Nanoparticles/Nanofibers and Their Luminescence via Electrospinning

This article reports on the synthesis procedure of ZnO nanoparticles/nanofibers structure by electrospinning method using Zinc acetate and polyvinylpyrrolidone (PVP) surfactant as reagents and evaluates their luminescent properties. The microstructure of ZnO nanoparticles/nanofibers was observed by FE-SEM. The phase formation of ZnO nanoparticles/nanofibers was studied by XRD. ZnO nanoparticles/nanofibers structure shows strong luminescence centering at 660 nm, which has potential applications in solid-state lighting.