Effect of sintering temperature on microstructure and electrical properties of ZVMCDN ceramics

The microstructure and electrical properties of ZnO-V₂O₅-MnO₂-Co₃O₄-Dy₂O₃-Nb₂O₅ (ZVMCDN) ceramics were investigated in accordance with sintering temperature (850-950 °C). The microstructure of the samples consisted of mainly ZnO grain as a main phase, and Zn₃(VO₄)₂, ZnV₂O₄, and DyVO₄ as the minor secondary phases. The sintered density decreased from 5.69 to 5.52 g/cm³ due to the volatility of V₂O₅ in accordance with increasing sintering temperature. The maximum nonlinear coefficient (57) was obtained at 925 °C. The donor concentration increased from 1.15 × 10¹⁸/cm³ to 11.1 × 10¹⁸/cm³ in accordance with increasing sintering temperature and the barrier height exhibited the maximum value (1.03 eV) at 925 °C.     

Improvement of electrical properties of V2O5 modified ZnO ceramics by Mn-doping for varistor applications

The dependence of microstructure, electrical properties, dielectric characteristics, and stability of conduction characteristics in ternary ZnO–V₂O₅–Mn₃O₄ system on the amount of Mn₃O₄ present in them was investigated. For all compositions studied, the microstructure of the ternary ZnO–V₂O₅–Mn₃O₄ system consisted of mainly ZnO grains and Zn₃(VO₄)₂ as a secondary phase. The incorporation of Mn₃O₄ to the binary ZnO–V₂O₅ system was found to restrict abnormal grain growth of ZnO. The breakdown field in the electric field–current density characteristics increased from 175 to 4,635 V/cm with the increase of Mn₃O₄ amount. The ternary system doped with 0.5 mol% Mn₃O₄ exhibited the highest non-ohmic properties, in which the non-ohmic coefficient is 22.4 and the leakage current density is 0.22 mA/cm². Furthermore, the sample doped with 0.5 mol% Mn₃O₄ was found to possess 0.43 × 10¹⁸/cm³ in donor density and 2.66 eV in barrier height.     

Structures, varistor properties, and electrical stability of ZnO thin films

In this letter, we report the structures, varistor properties, and electrical stability of ZnO thin films deposited by the gas discharge activated reaction evaporation (GDARE) technique. The X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements showed that the thin films thus prepared have polycrystalline structures with the preferred orientation along the (002) plane whose surface consists of ZnO aggregates with sizes of 50-200 nm. The ZnO thin films deposited by GDARE and annealed at 250 °C for 2 h have strong nonlinear varistor-type I-V characteristics. The nonlinear coefficient (α) of a single-layered ZnO thin film sample was 33 and that of a triple-layered sample obtained by the many-time deposition was 62. The varistor voltages (V_1mA) of the two samples are found rather close each other. Under a DC bias of 0.75 V_1mA and a temperature of 150 °C these thin films exhibit good electrical stability with a degradation rate coefficient K_T of 0.05 mA/h^1/2.     

The effect of sintering temperature on varistor properties of (Pr, Co, Cr, Y, Al)-doped ZnO ceramics

The effect of sintering temperature on varistor properties of (Pr, Co, Cr, Y, Al)-doped ZnO ceramics was investigated in the range of 1280-1350 °C. The increase of sintering temperature increased the average grain size (4.8-12.9 μm), whereas the sintered density was not nearly affected by sintering temperature. The breakdown field decreased over a wide range from 4610 to 1513 V/cm with the increase of sintering temperature. The nonlinear coefficient of this system was nearly constant in the range of 44-47 regardless of sintering temperature. The donor density decreased in the range of 1.51-1.32 × 10¹⁸/cm³ and the barrier height decreased from 1.40 to 0.92 eV with the increase of sintering temperature.     

Optical and electrical properties of zinc oxide/indium/zinc oxide multilayer structures

Zinc oxide/indium/zinc oxide multilayer structures have been obtained on glass substrates by magnetron sputtering. The effects of indium thickness on optical and electrical properties of the multilayer structures are investigated. Compared to a single zinc oxide layer, the carrier concentration increases from 8 × 10¹⁸ cm⁻³ to 1.8 × 10²⁰ cm⁻³ and Hall mobility decreases from 10 cm²/v s to 2 cm²/v s for the multilayer structure at 8 nm of indium thickness. With the increase of indium thickness, the transmittance decreases and optical band gap shifts to lower energy in multilayer structures. Results are understood based on Schottky theory, interface scattering mechanism and the absorption of indium layer.     

Effects of annealing temperature on microstructure and electrical properties of Mn-Co-Ni-O thin films

Mn_1.85Co_0.3Ni_0.85O₄ (MCN) thin films were prepared on Al₂O₃ substrates by chemical solution deposition method at different annealing temperature (650, 700, 750 and 800 °C). Effects of annealing temperature on microstructure and electrical properties of MCN thin films were investigated. The MCN thin film annealed at 750 °C is of good crystallization and compact surface. It shows lower resistance (4.8 MΩ) and higher sensitivity (3720.6 K) than those of other prepared films. It also has small aging coefficient (3.7%) after aging at 150 °C for 360 h. The advantages of good properties make MCN thin film very promising for integrated devices.     

Effects of Ag particles on sintering and electrical properties of ZnO-based varistor

ZnO-based varistors containing Ag particles (abbreviated as Z-Ag) were prepared using the conventional solid-state reaction method. The sintering and electrical properties of Z-Ag composites show that the composites can be achieved at a lower sintering temperature (920 °C) relative to that of a commercial ZnO-based varistor. The composites possess non-ohmic behavior analogous to that of the ZnO-based varistor, and the nonlinear voltage can be easily controlled by the content of Ag particles in the ceramic matrix. Meanwhile, the dielectric constant and dissipation factor indicate that the composites have enhanced dielectric properties at room temperature with increasing content of Ag particles, especially at frequencies of 0.5-30 kHz. The mechanisms involved are discussed.     

Synthesis,structure and electrical studies of praseodymium doped barium zirconium titanate

Praseodymium (Pr) doped barium zirconium titanate with nominal composition (Ba_1−xPr_x)(Zr_0.52Ti_0.48)O₃ (x = 0.1 and 0.2) were synthesized using solid state reaction method. X-ray analysis conform the formation of cubic phase Pr-doped barium zirconium titanate along with minor pyrochloric phase. The increase in grain size after primary investigation reveals the influence of Pr ions on the domain structure and its microstructure. In order to correlate the effect of the chemical composition with the conduction mechanism, different AC electrical parameters have been addressed. The frequency dependant tangent loss of the sample was less for both the ceramics. The temperature dependence results show that the dielectric parameters and resistivity increases as Pr-content in the ceramic increases; this is attributed to the grain size and dipole dynamics. Complex impedance (Z*) plots show frequency dependent behavior as the response for the grain resistance mechanisms. This mechanism has been represented by an equivalent circuit. The temperature dependence of the electrical conductivity and Seebeck coefficient showed n-type non-degenerated semiconductor in the measured temperature range. The temperature dependent conductivity measurement suggests a novel negative temperature coefficient of resistance behavior of the samples. Furthermore, the frequency dependent conductivity plot shows increasing behavior.     

Effects of cobalt doping on nonlinearity of zinc oxide

The microstructures and electrical properties of ZnO–Bi₂O₃–CoO (ZBC), ZnO–Bi₂O₃ (ZB) and ZnO–CoO (ZC) ceramics were investigated. Cobalt oxide addition could reduce bismuth loss at high sintering temperature. The same amount of cobalt within ZnO grains was found in both specimens, ZBC and ZC, suggesting that bismuth had no effect on the dissolution of cobalt in ZnO and cobalt substitution for zinc in the ZnO structure. The highest nonlinear coefficient of about 19 was found in the ZBC varistor sintered at 1000–1100 °C. For the ZC specimens, nonlinear properties could also be obtained in this sintering temperature range.     

Influence of Gd2O3 on phase,microstructure, and electrical properties of ZnO varistor ceramics

Journal of Materials Science: Materials in Electronics - Gd2O3-doped ZnO varistor ceramics were successfully prepared through the solid reaction sintering route. The influence of Gd2O3 additive on...     

Effect of the interface on the electrical properties of an indium zinc oxide/SiOx multilayer

In this work, indium zinc oxide (IZO) films have been deposited on a polyethylene terephthalate substrate coated with an SiO_x film. Based on a comparative investigation of an IZO monolayer and an IZO/SiO_x multilayer, it is shown that oxygen has a great effect on the electrical properties of the thin films. A mechanism is described to explain the influence of the introduced SiO_x buffer layer. It is considered that an interfacial layer has come into being at the interface between the SiO_x layer and IZO layer, and the properties of this layer have been evaluated. Moreover, the electrical properties of the IZO/SiO_x multilayer have been successfully improved by controlling the oxygen content of the interfacial layer.     

Grain size-dependent Mg/Si ratio effect on the microstructure and mechanical/electrical properties of Al-Mg-Si-Sc alloys

Al-Mg-Si-Sc alloys with different Mg/Si ratio (<1.73 in wt.% vs>1.73 in wt.%) and different grain size (coarse grains vs ultrafine grains) were prepared, which allowed to investigate the grain size-dependent Mg/Si ratio effect on the microstructural evolution and concomitantly on the hardness and electrical conductivity when subjected to aging at 200 °C. In the coarse-grained Al-Mg-Sc-Sc alloys, the β″ precipitation within the grain interior and also the precipitation hardening were highly dependent on the Mg/Si ratio, while the electrical conductivity was slightly affected by the Mg/Si ratio. A promoted β″ precipitation was found in the case of Si excess (Mg/Si ratio <1.73), much greater than in the case of Mg excess (Mg/Si ratio>1.73). While in the ultrafine-grained Al-Mg-Si-Sc alloys, the electrical conductivity rather than the hardness was more sensitive to the Mg/Si ratio. The alloy with Si excess displayed electrical conductivity much higher than its counterpart with Mg excess. This is rationalized by the grain boundary precipitation promoted by Si, which reduced the solute atoms and precipitates within the grain interior. Age softening was found in the ultrafine-grained alloy with Si excess, but the ultrafine-grained alloy with Mg excess held the hardness almost unchanged during the aging. The hardness-conductivity correlation is comprehensively discussed by considering the coupling effect of Mg/Si ratio and grain size. A strategy to simultaneously increase the hardness/strength and electrical conductivity is proposed for the Al-Mg-Si-Sc alloys, based on present understanding of the predominant factors on strengthening and conductivity, respectively.     

多元施主掺杂对直流ZnO压敏陶瓷结构与电气性能的影响EI北大核心CSCD

采用传统的陶瓷烧结工艺制备B_(2)O_(3),In_(2)O_(3),Al_(2)O_(3)多元施主掺杂的直流ZnO压敏陶瓷样品,考察不同掺杂比(0.1%~0.4%,摩尔分数)的B_(2)O_(3)对直流ZnO压敏陶瓷样品微观结构和电气性能的影响。利用X射线衍射仪、扫描电子显微镜、能量色散X射线光谱及数字源表等分别对样品的物相、微观形貌、成分及电性能进行表征。结果表明,多元施主掺杂剂(Al_(2)O_(3),In_(2)O_(3)和B_(2)O_(3))的共掺杂明显改善直流ZnO压敏陶瓷的综合性能,其中,Al_(3)+提高样品的电导率,降低样品的残压比;In^(3+)通过钉扎效应限制晶粒的生长,改善样品的电压梯度;B^(3+)的掺杂增加样品的表面态密度,提高势垒高度并有效抑制泄漏电流的增加。B_(2)O_(3)掺杂量为0.3%时,样品的综合性能最优:电压梯度为486 V/mm,泄漏电流密度为0.58μA/cm^(2),非线性系数为85,残压比为1.55。     

Effects of BiAlO3 on structure and electrical properties of K0.5Na0.5NbO3-LiSbO3 lead-free piezoceramics

(1−x)(0.948 K_0.5Na_0.5NbO₃-0.052LiSbO₃)-xBiAlO₃ (KNNLS-xBA) lead-free piezoceramics were synthesized by conventional solid state reaction method. The compositional dependence of phase structure and electrical properties of the ceramics was systemically studied. XRD patterns revealed that all the ceramic samples possessed pure perovskite structure. In addition, polymorphic phase transition (PPT) for the ceramics with BA doping could not be observed in the measuring range from room temperature to 500 °C. Within the studied range of BA addition, the ceramics with x = 0.002 represented a relatively desirable balance between the degradation of the piezoelectric properties, improvement in temperature stability and mechanical quality factor. It was found that the KNNLS-0.002BA ceramics exhibited optimum overall properties (d₃₃ = 233 pC/N, k_p = 35%, tanδ = 0.047, P_r = 27.3 μC/cm², Q_m = 56 and T_c = 349 °C), suggesting that this material should be a promising lead-free piezoelectric candidate for piezoelectric applications.     

Structure and electrical properties of strontium barium niobate ceramics

SBN, x=0.25, 0.35, 0.50, 0.60 and 0.75 series of ceramics prepared by traditional sintering method have been studied systematically. The impact of composition and sintering temperature on structures, microstructures, and electrical properties of SBN ceramics was characterized of X-ray diffraction, scanning electron microscopy, and electrical measurements. It is found that the composition and temperature play an important role on the fabrication of single phase tetragonal TTB SBN ceramics. At x=0.5, TTB SBN ceramics can be obtained at 1200°C. For x<0.5, it consists of a mixture of TTB structure SBN and orthorhombic phase BaNb₂O₆ even at 1300°C; TTB structure SBN and orthorhombic phase SrNb₂O₆ for x>0.5. The complete TTB phase is produced at 1350°C. With Sr content increasing, the electrical performances show a regular change, strongly conforming to the reducing of the Curie temperature. SBN with the Sr composition of x=0.60-0.75 is a promising candidate for electro-optics device applications.     

Effect of Sm2O3 dopant on microstructure and electrical properties of ZnO-based varistor ceramics

ZnO-based varistor ceramics doped with fixed Y₂O₃ and different Sm₂O₃ have been prepared by the conventional solid-state reaction route, and the phase composition, microstructure and electrical properties have been investigated by XRD, SEM and a V–I source/measure unit. The XRD analyses show the presence of primary phase ZnO and some minor secondary phases. Doping appropriate contents of Sm₂O₃ decrease the leakage current and enhance nonlinearity characteristics of ZnO-based varistor ceramics markedly. The varistor ceramics with 0.25 mol% Sm₂O₃ sintered at 1,125 °C for 1 h exhibit reasonable electrical properties with the breakdown field of 446.4 V/mm, the nonlinear coefficient of 65.8 and the leakage current of 2.36 μA/cm². The results illustrate that doping Y₂O₃ and Sm₂O₃ may be a promising route for the production of ZnO-based varistor ceramics with good electrical properties.     

Sintering behavior and electrical properties of the (Li, Ta, Sb) modified (K, Na)NbO3 lead-free ceramics with KNbO3 as sintering aid

Highly dense KNbO₃ (KN) doped (Li, Ta, Sb) modified (K, Na)NbO₃ ceramics (NKLNST) were prepared by normal sintering at reduced temperature of 1060 °C. The XRD study indicates that KN diffuses into the NKLNST lattice to form a new homogenous solid solution. It was found that the presence of KNbO₃ greatly enhances the densification of the ceramic, providing a dense ceramic at a lower sintering temperature due to the formation of a suitable amount of liquid phase around the optimal temperature. The 0.95(Na_0.52 K_0.44Li_0.04)(Nb_0.88Sb_0.08Ta_0.04)O₃ − 0.05KNbO₃ ceramics show a dense microstructure of ρ = 4.56 g/cm³, with a high piezoelectric d₃₃ up to 350 pC/N and k_p up to 0.49.     

Effect of sintering condition on microstructure and dielectric properties of BSTN composite ceramics

The effect of sintering condition on the phase composition, microstructure and dielectric properties of barium strontium titanate niobate (BSTN) composite ceramics, in which the perovskite phase and the tungsten bronze phase coexisted, was investigated by XRD, SEM and LCZ Meter. The results show that more Sr²⁺ ions dissolved from the grain boundaries into the crystal lattice of the pervoskite phase and the tungsten bronze phase, especially, into the lattice of the pervoskite phase with the increasing of sintering temperature and sintering time, respectively. So the Curie temperature point decreases with the increasing of sintering temperature. The crystal growth rate of the tungsten bronze phase is higher than that of the perovskite phase in BSTN composite ceramics as the sintering temperature increases. The reasonable sintering temperature is about 1275 °C for BSTN composite ceramics. The activation energy to setting up polarization in BSTN composite ceramics increases with the increase of the applied frequency.     

Effects of Cr2O3 doping on the electrical properties and the temperature stabilities of PNW-PMN-PZT ceramics

The ceramics with 0.90Pb(Zr_0.50Ti_0.50)O₃-0.07Pb(Mn_1/3Nb_2/3)O₃-0.03Pb(Ni_1/2W_1/2)O₃ were prepared by adding Cr₂O₃. The effects of Cr₂O₃ doping on the phase structure, the microstructure and the electrical properties of ceramics were investigated. Meanwhile, the temperature stabilities of the resonant frequency (f_r) and the electromechanical coupling factor (K_p) were studied. The results showed that the better temperature stability could be obtained at x = 0.2 wt.% when the calcining temperature was 800 °C and the sintering temperature was 1150 °C. The parameters were Δf_r/f_r25 °C = −0.17% and ΔK_p/K_p25 °C = −1.39%. Moreover, the optimized electrical properties were also achieved, which were K_P = 0.54, Q_m = 1730, d₃₃ = 330 pC/N, ?_r = 2078 and tan δ = 0.0052. The optimized properties make the ceramics with this composition to be a good candidate for high power piezoelectric transformers applications.     

Effects of thermal treatment on the electrical and optical properties of silver-based indium tin oxide/metal/indium tin oxide structures

In this article, we report the results of the study of thermal treatment effects on the electrical and optical properties of silver-based indium tin oxide/metal/indium tin oxide (IMI) multilayer films. Heat treatment conditions such as temperature and gaseous atmosphere was varied to obtain better electrical and optical properties. We obtained improved electrical properties and observed considerable shift in the transmittance curves after heat treatment. Several analytical tools such as X-ray diffraction, spectroscopic ellipsometer and spectrophotometer were used to explore the causes of the changes in electrical and optical properties. The sheet resistance of the structure was severely influenced by deposition conditions of the indium tin oxide (ITO) layer at the top. Moreover, the shift of optical transmittance could be explained on the basis of the change in refractive indices of ITO layers during heat treatment. The properties of Ag-alloy-based IMI films were compared with those of pure Ag-based ones. Some defects originating from Ag layer corrosion were observed on the surface of ITO-pure Ag–ITO structures, however, their number decreased significantly in the cases of Ag-alloys containing Pd, Au and Cu, though the resistivity values of Ag-alloys were slightly higher than those of silver. Atomic force microscopy measurement results revealed that the surface of the IMI multilayer was so smooth that it meets the required qualifications as the bottom electrode of organic light emitting diodes.