稀土氧化物Pr2O3掺杂对高压ZnO压敏电阻性能的影响

采用低温固相化学反应法制备了Pr₂O₃掺杂的ZnO纳米复合粉体, 并用此粉体在不同烧结温度下制备了高压ZnO压敏电阻。采用X射线衍射、 比表面测试、 透射电镜、 扫描电镜等手段对制备的ZnO纳米复合粉体及高压ZnO压敏电阻进行了表征, 并与未掺杂ZnO压敏电阻进行了对比研究, 探讨了稀土氧化物Pr₂O₃掺杂对高压ZnO压敏电阻电性能的影响机制。结果表明: 较低的烧结温度(1030～1130 ℃)时, 掺杂的稀土氧化物Pr₂O₃偏析于ZnO晶界中, 有活化晶界、 促使晶粒生长的作用; 同时, Pr₂O₃掺杂导致1080 ℃烧结的ZnO压敏陶瓷体中晶体相互交织形成晶界织构, 比未掺杂的更均匀和致密, 这有助于高压ZnO压敏电阻晶界性能的改善, 从而提高其综合电性能。当烧结温度为1080 ℃时, Pr₂O₃掺杂的高压ZnO压敏电阻的综合电性能最佳: 电位梯度为864.39 V/mm, 非线性系数为28.75, 漏电流为35 μA。     

掺杂ZnO-V2O5压敏电阻的低温烧结

对掺杂ZnO-V2O5压敏电阻的低温烧结特性及电性能进行了研究.研究结果表明通过添加硼酸铅锌玻璃"形成"氧化物PbO和B2O3使其在常规电烧结炉中的烧结温度降低到了800℃,并使非线性特性明显提高,添加6wt%(PbO+B2O3)的样品经800℃ 4h烧结后,其非线性系数和漏电流密度可分别达到22.5,7.2×10-6A/cm2.     

TiO2压敏电阻的研究与应用

为了更好地研制和应用压敏电阻元件,介绍了TiO2压敏电阻的基本性质,压敏机理以及研究现状,阐述了制备过程中掺杂物种、掺杂浓度、烧结温度、粉体材料等因素对二氧化钛压敏电阻性能的影响.研究表明,TiO2系列压敏电阻具有较低的压敏电压、较高的非线性系数、超高的介电常数,并且制备工艺简单.TiO2系列压敏电阻能有效弥补SrTiO3和ZnO系压敏电阻器所存在的不足之处,是低压压敏陶瓷的研发方向.     

Sm2O3掺杂(Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3无铅压电陶瓷的制备与性能

采用固相合成法制备了Sm2O3掺杂的(Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3(BCZT)无铅压电陶瓷.借助XRD、SEM等手段对该陶瓷的显微结构与电性能进行了研究.结果表明,Sm2O3的掺杂降低了BCZT无铅压电陶瓷的烧结温度并使居里温度点Tc从85℃提高到95℃.当Sm2O3掺杂量为0.02wt%～0.1wt%时,样品具有典型ABO3型钙钛矿结构.Sm2O3掺杂量为0.02wt%时,所得陶瓷样品具有最优综合电性能,其压电常数d33、机电耦合系数kp、机械品质因子Qm、介电损耗tanδ和介电常数εr分别为590 pC/N、0.52、43、1.3%和3372.     

TiO2和MgO掺杂的ZnO导电陶瓷材料

以ZnO为基添加Al2O3、TiO2和MgO制备了导电陶瓷;研究了TiO2、MgO掺杂含量对ZnO陶瓷相对密度、电阻率和电阻温度系数的影响;测试分析了ZnO导电陶瓷在小电流和脉冲大电流下的伏安特性.结果表明,掺Ti有利于致密烧结,TiO2含量为0.6%(质量分数)时,样品相对密度为96%,室温小电流下测试其电阻率为8.14Ω·cm;添加适量MgO能降低电阻率且可改善电阻温度系数,MgO含量为0.4%(质量分数)时,小电流电阻率为5.67Ω·cm;室温小电流下样品伏安特性接近线性,在脉冲大电流下呈现一定非线性特性.     

稀土氧化物Pr2O3掺杂对高压ZnO压敏电阻性能的影响

采用低温固相化学反应法制备了Pr2O3掺杂的ZnO纳米复合粉体,并用此粉体在不同烧结温度下制备了高压ZnO压敏电阻.采用X射线衍射、比表面测试、透射电镜、扫描电镜等手段对制备的ZnO纳米复合粉体及高压ZnO压敏电阻进行了表征,并与未掺杂ZnO压敏电阻进行了对比研究,探讨了稀土氧化物Pr2O3掺杂对高压ZnO压敏电阻电性能的影响机制.结果表明:较低的烧结温度(1030～1130℃)时,掺杂的稀土氧化物Pr2O3偏析于ZnO晶界中,有活化晶界、促使晶粒生长的作用;同时,Pr2O3掺杂导致1080℃烧结的ZnO压敏陶瓷体中晶体相互交织形成晶界织构,比未掺杂的更均匀和致密,这有助于高压ZnO压敏电阻晶界性能的改善,从而提高其综合电性能.当烧结温度为1080℃时,Pr2O3掺杂的高压ZnO压敏电阻的综合电性能最佳:电位梯度为864.39 V/mm,非线性系数为28.75,漏电流为35 μA.     

B2O3和Al2O3共同掺杂ZnO压敏陶瓷的性能

研究了B₂O₃(B)和Al₂O₃(Al)共掺杂对ZnO压敏陶瓷电学性能和微观结构的影响。结果表明,共掺杂B和Al的ZnO压敏陶瓷,具有低泄漏电流、高非线性和低剩余电压等优良电性能。B和Al的掺杂率为3.0%(摩尔分数)和0.015%(摩尔分数)的ZnO压敏陶瓷,其最佳样品的电参数为：击穿电压E_{1 mA}＝475 V/mm;泄漏电流J_L=0.16 μA/cm²;非线性系数α=106;剩余电压比K = 1.57。     

TiO2压敏陶瓷的研究进展

TiO2压敏陶瓷的压敏电压低、非线性系数高、介电常数大、制备工艺简单,在电子、通信、航天航空等高新技术产业的低压保护中具有广阔的应用前景。主要从粉体制备工艺、叠层方式烧结、烧结氛围、烧结温度及保温时间、掺杂物质及浓度等方面归纳总结了TiO2压敏陶瓷的研究状况,并展望了其今后的研究趋势。     

B_2O_3掺杂氧化锌压敏电阻烧结工艺的微观结构和电气特性

研究了在不同烧结温度下制备的直流ZnO压敏陶瓷的微观结构和电气特性。通过扫描电子显微镜,电流-电压的伏安特性,电容-电压和从小电流到大电流范围的X射线衍射图测量不同烧结温度下样品的电气参数和微观结构。实验结果表明在1150℃下烧结的样品晶粒尺寸比较均匀,非线性系数和泄漏电流分别为66和0.96μA/cm~2,电压梯度为381 V/mm,直流氧化锌压敏电阻的综合性能达到最优。随着烧结温度的升高,ZnO晶粒尺寸(d)会变大,导致单位长度内晶界数量减少使氧化锌压敏电阻的电压梯度减少。晶粒的尺寸的增加可以阻断三角区的互联互通,使泄漏电流减小。当烧结温度高于1 150℃时,会造成Bi_2O_3的挥发使非线性系数降低。获得电压梯度为381 V/mm的直流氧化锌压敏电阻有利于优化超高压避雷器结构、电阻柱上的电位分布更加均匀。综上所述,制备B_2O_3掺杂的氧化锌压敏电阻配方最佳的烧结温度为1 150℃。     

V~(5+)-Sr~(2+)共掺杂对TiO_2基压敏陶瓷性能的影响

研究了V~(5+)-Sr~(2+)共掺杂对TiO_2基压敏陶瓷电学性能的影响。采用固相烧结方法制备V~(5+)-Sr~(2+)共掺杂TiO_2样品。利用XRD衍射仪检测物相和SEM测定显微结构。用压敏电阻直流参数仪测定V~(5+)-Sr~(2+)共掺杂TiO_2样品在不同烧结温度和掺杂量下的电学性能。结果表明:掺杂0.35mol%的V_2O_5,XRD衍射仪没有检测到第二相的产生。随着SrCO_3掺杂量以及烧结温度的增加,样品压敏电压和非线性系数都有不同的变化趋势。当烧结温度为1 300℃、Sr~(2+)掺杂量为0.5mol%时,样品的各项电学性能最优:V~(5+)-Sr~(2+)共掺杂TiO_2样品压敏电压达到16.3V/mm,非线性系数α达到5.6。     

Electronic structure and formation mechanism of complex Ti-Nb oxide

Two-layer thin film specimens of Nb₂O₅ and TiO₂ were deposited on optical-grade quartz and n-type single crystalline silicon substrates with (100) crystallographic orientation by a magnetron deposition source under high vacuum. All samples were subjected to 1-5 h of resistive heating at ultra high vacuum, and in situ X-ray diffraction measurements (XRD) were made in the temperature range of 300-1373 K. Analysis of the XRD data confirmed the growth of TiNbO₄ during cooling of the two-layered specimens which had been previously heated to 1373 K. Optical measurements revealed a band gap value of 3.78 eV for the direct transition and 3.29 eV for the indirect one. The samples had a transmittance of 85% in the visible range. Electrophysical measurements in high vacuum established the electroresistivity vs. temperature dependence in the range of 300-773 K, from 7.3 ? 10^− 1 to 3.9 ? 10^− 2 Ω cm, respectively. X-ray photoelectron spectroscopy measurements were used to examine the chemical shift for Nb 3d, with a value of − 1.1 eV in comparison with Nb⁵⁺ and matched to Nb⁴⁺[1], while the Ti lines correspond to Ti⁴⁺[2].     

Facile Synthesis of SnO2 Nanotube Arrays by Using ZnO Nanorod Arrays as Sacrificial Templates

SnO2 nanotube arrays have been synthesized by means of a simple and low-cost method. The ZnO nanorod arrays prepared by aqueous chemical growth method were used as templates. By liquid phase deposition, SnO2 nanotubes were obtained with proper deposition time. Scanning electron microscopy, transmission electron microscopy and X-ray diffraction were used to characterize the morphologies and structures of the products, and the formation mechanism was discussed according to the experimental results.     

Optical properties of thin films of mixed Ni-W oxide made by reactive DC magnetron sputtering

Thin films of Ni_xW_1 − x oxides with x = 0.05, 0.19, 0.43 and 0.90 were studied. Films with thicknesses in the range 125-250 nm were deposited on silicon wafers at room temperature by reactive DC magnetron co-sputtering from targets of Ni and W. The films were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), and spectroscopic ellipsometry (SE). XRD spectra and SEM micrographs showed that all films were amorphous and possessed a columnar structure. The ellipsometric angles Ψ and Δ of as-deposited films were measured by a rotating analyzer ellipsometer in the UV-visible-near infrared range (0.63-6.18 eV) and by an infrared Fourier transform rotating compensator ellipsometer in the 500-5200 cm⁻¹ wavenumber range. SE measurements were performed at angles of incidence of from 50 ° to 70 °. Parametric models were used to extract thicknesses of the thin films and overlayers of Ni_xW_1 − x oxide at different compositions, band gaps and optical constants. Features in the optical spectra of the Ni_xW_1 − x oxides were compared with previous data on tungsten oxide, nickel oxide and nickel tungstate.     

High k dielectrics for low temperature electronics

In this work the electrical and structural properties of two high k materials as hafnium oxide (HfO₂) and tantalum oxide (Ta₂O₅) produced at room temperature are exploited. Aiming low temperature processing two techniques were employed: r.f. sputtering and electron beam evaporation.The sputtered HfO₂ films present a nanocrystalline structure when deposited at room temperature. The same does not happen for the evaporated films, which are essentially amorphous. The density and the electrical performance of both sputtered and evaporated films are improved after annealing them at 200 °C. On the other hand, the Ta₂O₅ samples deposited at room temperature are always amorphous, independently of the technique used. The density and electrical performance are not so sensitive to the annealing process. The set of data obtained show that these dielectrics processed at temperatures below 200 °C present promising properties aiming to produce devices at low temperature with improved interface properties and reduced leakage currents.     

All-solid-state reflectance-type electrochromic devices using iridium tin oxide film as counter electrode

We prepared an all-solid-state reflectance-type electrochromic device (ECD), consisting of the following five layers: Al/WO₃/Ta₂O₅/Ir_xSn_1 − xO₂/ITO. Using RF ion plating, we prepared a film containing dispersed iridium oxide in a tin oxide matrix; this film acts as the counter electrode in the all-solid-state ECD. Protons were used as coloration ions in the ECD. The size of the ECD was 150 cm², and the reflectance changed between more than 60% from 15%. The coloration and bleaching response times were less than a few seconds. We analyze the optical characteristics of the ECD, and report the results of a consecutive drive test and a high-temperature heat resistance test.     

Comparative study on early stages of film growth for transparent conductive oxide films deposited by dc magnetron sputtering

Early stages of film growth were investigated on three different kinds of representative transparent conductive oxide films including tin doped indium oxide (ITO), indium zinc oxide (IZO) and gallium doped zinc oxide (GZO) films deposited on unheated alkali free glass substrates by dc magnetron sputtering. The variations in sheet resistance, film coverage and average surface roughness showed clearly that ITO and GZO films possessed Volmer-Weber growth mode. In contrast, the evolution of islands is not clearly observed for IZO film. The nucleation density of IZO film is considered to be much higher than that of ITO and GZO films.     

纳米氧化物的合成新方法

以草酸和醋酸盐为原料,用低热固相化学反应合成出前驱配合物ＮｉＣ２Ｏ４·２Ｈ２Ｏ,ＣｕＣ２Ｏ４ 和ＺｎＣ２Ｏ４·２Ｈ２Ｏ,再分别在３５０℃,３００ ℃和４６０℃热分解２ｈ,得到纳米ＮｉＯ,ＣｕＯ和ＺｎＯ。用Ｘ－ 射线粉末衍射、透射电镜对产物的组成、大小、形貌进行表征。结果表明,纳米ＮｉＯ为球形立方晶系结构,平均粒径约为４０ｎｍ 左右;纳米ＣｕＯ为球形单斜晶系结构,平均粒径约为３０ｎｍ 左右;ＺｎＯ为粒度分布均匀的球形六角晶系结构,平均粒径约为２０ｎｍ 。     

Stability of indium-oxide thin-film transistors by reactive ion beam assisted deposition

This work reports on the performance and stability of bottom-gate In₂O₃-TFTs with PECVD silicon dioxide gate dielectric. A highly-resistive amorphous In₂O₃ channel layer was deposited at room temperature by reactive ion beam assisted evaporation (IBAE). The field-effect mobility of the n-channel TFT is 33 cm²/V-s, along with an ON/OFF current ratio of 10⁹, and threshold voltage of 2 V. Device stability was demonstrated through measurement of the threshold voltage shift during long-term gate bias-stress and current stress experiments. Device performance, including stability, together with low-temperature processing, makes the indium-oxide TFT an attractive candidate for flexible transparent electronics, and display applications.     

Highly conductive, undoped ZnO thin films deposited by electron-cyclotron-resonance plasma sputtering on silica glass substrate

The electrical and optical properties of undoped ZnO films deposited by electron cyclotron resonance (ECR) plasma sputtering at room temperature were characterized. The lowest resistivity we achieved was 2.6 × 10^− 3 Ωcm with optical transmittance at visible wavelengths higher than 85%. The X-ray diffraction (002) peak was weak and the rocking curve was asymmetrical, indicating that oxygen vacancies prevented large crystalline domains from forming. At low argon-sputtering-gas pressure, carrier concentration and Hall mobility increased with increasing argon pressure. When the optimum pressure (40 mPa) was exceeded, however, Hall mobility and optical transmittance were severely reduced, which indicated that excess Zn atoms were populated at the interstitials of the network. Admitting only 0.67 mPa of O₂ gas during deposition deteriorated resistivity over 1 MΩcm due to high excitation efficiency in the ECR plasma. Deposition under a higher magnetic field produced lower resistivities.