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1.
The microstructure, electrical properties, and dc-accelerated aging characteristics of Tb 4O 7-doped ZnO-based varistors were investigated for different Tb 4O 7 amounts and sintering temperatures. The sintered density increased with increasing Tb 4O 7 amount and sintering temperature. The average grain size decreased with increasing Tb 4O 7 amount and increased with increasing sintering temperature. The varistor voltage and nonlinear coefficient increased with
increasing Tb 4O 7 amount and decreased with increasing sintering temperature. The stability was worse with increasing Tb 4O 7 amount for the varistors sintered at 1,300 °C. The 0.5 mol% Tb 4O 7-doped varistors sintered at 1,350 °C exhibited a good stability for dc-accelerated aging stress of 0.95 V
1 mA/150 °C/24 h. 相似文献
2.
Conditions for the elaboration of varistors by spark plasma sintering (SPS) are investigated, using 70 nm zinc oxide nano-particles. For this purpose, the system constituted of zinc oxide, bismuth oxide and other metal oxide is used. Material sintering has been performed by SPS at various temperatures and dwell times. Determination of the microstructure and chemical composition of the as-prepared ceramics are characterized by scanning electron microscopy and X-ray diffraction analysis. Micro-structural analysis revealed the presence of ZnO, spinel and bismuth rich phases. ZnO based Varistor samples sintered within climb speeds 100 and 400 °C/min are compared. The nonlinear electrical characteristics, current–voltage, are measured. The breakdown voltage of the varistors strongly depends on grain sizes. The results show that the best varistors are obtained by SPS at sintering temperatures ranging from 900 to 1200 °C. 相似文献
3.
The Al doping effect on the microstructure, electrical properties, dielectric characteristics, and aging behaviors of ZPCCY-based
varistors was investigated in the range of 0.0–0.1 mol%. The breakdown electric field in the E-J characteristics decreased
in a wide range from 4,921 to 475 V/cm with increasing amounts of Al 2O 3. The nonlinear properties were improved by increasing amounts of Al 2O 3 up to 0.005 mol%, whereas the further additions caused it to decrease. The highest nonlinear coefficient (α = 45.2) was obtained
when Al 2O 3 concentration is 0.005 mol%. The Al 2O 3 acted as a donor due to the increase of electron concentration in the small range of 0.0–0.1 mol%. On the other hand, an
appropriate addition of Al 2O 3 in the range of 0.001–0.005 mol% was found to significantly improve the electrical stability against DC accelerated aging
stress. 相似文献
5.
The textured multilayer (ML) thin films of bismuth layered ferroelectric (FE) compounds, Bi 2VO 5.5 (BVO) and Bi 4Ti 3O 12 (BTO) with different individual layer thicknesses were fabricated via pulsed laser deposition technique on Pt(111)/TiO 2/SiO 2/Si substrates. X-ray diffraction studies confirmed that BVO and BTO retained their respective crystal structures in these multilayer (ML) thin films. The atomic force microscopy and scanning electron microscopy studies showed smooth and dense microstructures. The polarization hysteresis (P?CE) studies on a representative (BVBT30) ML thin film at 300 K confirmed the remnant polarization ( 2P r ) and coercive field ( E c ) to be ~20 ??C/cm 2 and 250 kV/cm, respectively. The value of P r obtained was greater than that of the single layer thin film of BVO ( P r ~ 5.6 ??C/cm 2). The room temperature dielectric constant (?? r??) and the loss (D) for BVBT30 ML measured at 100 kHz were 170 and 0.01, respectively. The frequency and temperature dependent dielectric constant, impedance, modulus and ac conductivity of these ML thin films were studied as a function of frequency (100 Hz?C1 MHz) in the 25?C300 °C temperature range. Two distinct electrical responses were observed in these films, which were attributed to the grain effects at low temperatures and grain boundary effects at higher temperatures. The frequency dependent electrical conductivity was fitted well with the double power law which evidenced two different types of contributions to the conductivity; the low frequency conductivity being due to the short range translational hopping and the high frequency conductivity was due to the localized or reorientational hopping. 相似文献
6.
用传统固相烧结工艺,制备了纯相的Bi4Ti3O12 (BTO)陶瓷,A位掺杂的Bi3.25La0.75Ti3O12(BLT),Bi3.15Nd0.85Ti3O12(BNdT)铁电陶瓷.X射线衍射结果表明,所有样品均为单一的层状钙钛矿结构,La、Nd掺杂未改变BTO的晶体结构.铁电测试结果表明,BTO、BLT和BNdT陶瓷的剩余极化2Pr值分别为12.4、23.8和39.4μC/cm2.A位掺杂后,BLT、BNdT的2Pr值比未掺杂的BTO分别提高了1.92和3.18倍.漏电流测试表明,BLT、BNdT陶瓷的漏电流密度比BTO明显降低.A位掺杂显著提高了BTO陶瓷的铁电性能. 相似文献
7.
Polycrystalline ferroelectric Bi 4Ti 3O 12 ceramics have been prepared by the method of reactive liquid phase sintering. The sintering behaviour of the Bi 2O 3-TiO 2 composite was examined by plotting the isothermal densification curves. The results indicate that the starting oxides are involved in the reaction even at temperatures lower than or equal to 800°C, but the reaction advances at a very slow rate. Above solidus, the liquid phase promotes an extended reaction. Saturation observed in two densification curves, at 875 and 1100°C demonstrate that the reaction proceeds by two steps. A completion of the Bi 4Ti 3O 12 formation occurs after 60 min of sintering at 1100°C. Optical micrographs of sintered bismuth titanate ceramics show randomly oriented ferroelectric grains separated by a paraelectric intergranular layer. The Bi 4Ti 3O 12 crystallites exhibit a platelike morphology, similar in the appearance to mica, as evidenced by scanning electron micrographs. Isothermal annealing (750 to 950°C) does not affect the microstructure and electric properties of sintered bismuth titanate. The considerable value of dielectric permittivity and the appearance of hysteresis have been correlated to the presence of oxygen vacancies within the pseudotetragonal structure of Bi 4Ti 3O 12. The oxygen vacancies are preferentially sited in the vicinity of bismuth ions as evidenced by X-ray photoemission data. XPS and AES measurements confirm that the surface concentration of cations comprising the Bi 4Ti 3O 12 ceramics does not deviate from the nominal bulk composition. 相似文献
8.
以五水硝酸铋为铋源、钛酸四丁酯为钛源,通过水热法制备了Bi4Ti3O12,再以硝酸银为银源、盐酸为氯源,采用光照还原Bi4Ti3O12得到Ag@AgCl/Bi4Ti3O12复合材料.利用XRD、UV-Vis DRS、SEM、TEM、BET和XPS等方法对所制备材料的组成和结构进行表征和分析,并以甲基橙(MO)溶液的脱色... 相似文献
9.
In this study, xLaMnO3-(1???x)CaCu3Ti4O12 (0?≤?x?≤?0.7) composite ceramics have been prepared by the conventional solid-state method. XRD results show that the composite ceramics are mainly composed of LaMnO3 and CaCu3Ti4O12 phases. Electrical property analysis shows that the resistivity ρ25 gradually decreases from 2.17?×?108 to 1.74?×?105 Ω·cm with increasing LaMnO3 content. The relationship between lnρ and 1000/T is not linear and changes around 350 °C. In the temperature range of 0–350 °C, the activation energy Ea0–350 °C decreases gradually with the increase of the LaMnO3 content. In the temperature range of 350–500 °C, the activation energy Ea350–500 °C increases first and then decreases, which is related to the variation of oxygen vacancy. The compounding of LaMnO3 gives rise to the decrease in B value, thus, providing the potential for the applications of wide temperature range thermistors. After annealing, the coefficient of aging (ΔR/R) of the composites decreases from 23.73 to 3.01%. 相似文献
10.
Spark plasma sintering (SPS) combined with heat treatment was investigated to prepare laminated ceramics from compositions having quite different sintering temperatures. Although the optimal sintering temperature of BaNd 2Ti 4O 12 (BNT) ceramics was much higher than that of Bi 4Ti 3O 12 (BIT) ceramics, sandwiched BaNd 2Ti 4O 12/Bi 4Ti 3O 12/BaNd 2Ti 4O 12 (BNT/BIT/BNT) composite ceramics were successfully prepared with this new method. The results of scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) showed that the BNT layers and the BIT layer were well bonded and no significant diffusion between them was observed. The temperature coefficient of dielectric constant of the laminated ceramic was found to be much smaller than that of BNT ceramic. 相似文献
12.
ZnO-based varistor ceramics doped with fixed Y 2O 3 and different Sm 2O 3 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 Sm 2O 3 decrease the leakage current and enhance nonlinearity characteristics of ZnO-based varistor ceramics markedly. The varistor ceramics with 0.25 mol% Sm 2O 3 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/cm 2. The results illustrate that doping Y 2O 3 and Sm 2O 3 may be a promising route for the production of ZnO-based varistor ceramics with good electrical properties. 相似文献
13.
Journal of Materials Science: Materials in Electronics - Bi7Ti4.5-xTaxW0.5O21 (BTW-BIT-xTa, x?=?0.00, 0.05, 0.10, 0.15, 0.20, 0.30) intergrowth bismuth-layered ceramics were fabricated... 相似文献
14.
ZnO-based varistor ceramics were prepared at sintering temperatures ranging from 900 °C to 1,300 °C, by subjecting the mixed
oxide powders to high-energy ball milling (HEBM) for 0, 5, 10 and 20 h, respectively. Varistor ceramics prepared by HEBM featured
denser body, better electrical properties sintered at low-temperature than at traditional high-temperature. The high density
is due to the refinement of the crystalline grains, the enhanced stored energy in the powders coming from lattice distortion
and defects as well as the promotion of liquid-phase sintering. Good electrical properties is attributed to proper microstructure
formed at low-temperature and improved grain boundary characteristics resulting from HEBM. With increasing sintering temperatures,
the electrical properties and density became worse due to the decrease in amount of Bi-rich phase. Temperature increased up
to 1,200 °C or above, the Bi-rich phase vanished and the ceramics exhibited very low nonlinear coefficient. 相似文献
15.
Natural-superlattice-structured ferroelectric thin films, Bi 3TiNbO 9–Bi 4Ti 3O 12 (BTN–BIT), have been synthesized on Pt/Ti/SiO 2/Si by metal organic decomposition (MOD) using BTN–BIT (1 mol:1 mol) solution. BTN–BIT films show natural-superlattice peaks below 2 θ = 20° in X-ray diffraction patterns, which indicate that the BTN–BIT films annealed at 700–800 °C in O 2 ambient are consisted of iteration of two unit cells of Bi 3TiNbO 9 and one unit cell of Bi 4Ti 3O 12. As the annealing temperature increases from 600 to 750 °C, uniform and crack-free films, better crystallinity and ferroelectric properties can be obtained, but the pyrochlore phase in BTN–BIT films annealed over 800 °C would impair the ferroelectric properties. With the increase of O 2 flow rate from 0.5 to 1.5 L/min, both remanent polarization Pr and coercive electric field EC increase, which are mainly attributed to reduction of the vacanvies of Bi and oxide ions in the films. Natural-superlattice-structured BTN–BIT thin films having 2–1 superlattice annealed at 750 °C in O 2 ambient with a flow rate of 1.5 L/min exhibit superior ferroelectric properties of Pr = 23.5 μC/cm 2 and EC = 135 kV/cm. 相似文献
17.
研究了Bi4Ti3O12掺杂对(Bi1.5Zn0.5)(Zn0.5Nb1.5)O7(BZN)陶瓷烧结特性、相结构和介电性能的影响.采用传统的固相反应法制备样品,X射线衍射技术分析相结构,SEM观察表面形貌.结果表明,Bi4Ti3O12掺杂能有效地促进烧结,提高介电常数ε,降低介电损耗tgδ,优化介电频率温度系数αε.1000℃烧结8%(摩尔分数) Bi4Ti3O12掺杂的BZN陶瓷具有较好的介电性能ε=192,tgδ= 4.21×10-4,αε=-3.37×10-4/℃. 相似文献
18.
对硅衬底生长的Bi4Ti3O12和Bi3.25La0.75Ti3O12薄膜样品测量了慢正电子多普勒展宽谱,得到了S参数随正电子注入能量的变化。通过对S参数和W参数的分析,讨论了这类材料中的捕获态特征和结构特点,结果表明,薄膜与硅衬底界面的缺陷为空位-氧复合体,La的掺杂有助于阻止空位-氧复合体向界面的扩散。 相似文献
19.
Bi 1/2?xNa 1/2?xBa 2xCu 3Ti 4O 12 (x = 0, 0.025, 0.05, 0.075) polycrystalline ceramics are prepared by a modified Pechini method. Effect of Ba doping on the dielectric and nonlinear electrical behaviors are investigated in detail. All the samples exhibit giant dielectric effect and nonlinear electrical behavior. Compared with Bi 1/2Na 1/2Cu 3T i4O 12 ceramics, the permittivity drops down and the nonlinear electrical behavior shifts to low voltage area by Ba doping. The permittivity reduces from 20,004 to 7,006 at 1 kHz. The breakdown voltage and nonlinear coefficient values decrease to 10.8 V/mm and 1.5, respectively. Additionally, the electrostatic barrier height drops down to 0.66 eV. Giant dielectric response and nonlinear electrical behavior can be interpreted in terms of internal barrier layer capacitors model. These results imply that Ba substitution can adjust the dielectric and nonlinear electrical behaviors of Bi 1/2Na 1/2Cu 3T i4O 12 ceramics, which is a promising candidate for low voltage varistor materials. 相似文献
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