ZnO-MgO-TiO_2-SnO_2系高频介电陶瓷的制备与介电性能

在ZnO-TiO2-SnO2陶瓷基础上,掺杂MgO得到(1-x)ZnO-xMgO-0.88TiO2-0.12SnO2系新型介电陶瓷。对其相转变、微观组织结构和高频介电性能进行了研究,结果表明,在不加入任何烧结助剂情况下,试样可于1 080℃达到烧结,其相对密度为94.4%;当x=0.05时,陶瓷为纯相尖晶石结构(Zn0.95,Mg0.05)2(Ti0.88,Sn0.12)O4,其介电性能优良,1 MHz时ε=18.88,tanδ=5×10-4,τε=2.89×10-6/℃,可用作高频电容器材料的优秀候选材料。

Resistive Switching Behavior of Ag/Mg0.2Zn0.8O/ZnMn2O4/p^+-Si Heterostructure Devices for Nonvolatile Memory Applications

The Ag/Mg0.2Zn0.8O/ZnMn2O4/p^＋-Si heterostructure devices were fabricated by sol-gel spin coating technique and the resistive switching behavior,conduction mechanism,endurance characteristic,and retention properties were investigated.A distinct bipolar resistive switching behavior of the devices was observed at room temperature.The resistance ratio R_（HRS）/RLRS of high resistance state and low resistance state is as large as four orders of magnitude with a readout voltage of 2.0 V.The dominant conduction mechanism of the device is trap-controlled space charge limited current（SCLC）.The devices exhibit good durability under 1×10^3cycles and the degradation is invisible for more than 10^6 s.

The Electrical and Optical Properties of Zn0.5Li2xMg0.5-xFe2O4 Lithium Doped Nanoparticle Prepared by Coprecipitation Method

In this study, nano ferrite materials were produced to replace costive industrial materials [1]. Ferrite nanoparticles are the interesting material due to their rich and unique physical and chemical properties. They find applications in catalysis, bio-processing, medicine, magnetic recording, adsorption, devices etc. Using co-participation method, five nano ferrite samples Zn0.5Mg0.5-xLi2xFe2O4 (x = 0.00, 0.10, 0.20, 0.30 and 0.40) were prepared. The electrical and optical properties of the Zn0.5Mg0.5-xLi2xFe2O4 samples were studied using the Ultraviolet-visible (UV-Vis) spectroscopy. The results verified that the formation of the absorption coefficient of the five samples of Zn0.5Mg0.5-xLi2xFe2O4 increased with the increase of Lithium (Li2x). The energy band gap of the Zn0.5Mg0.5-xLi2xFe2O4 samples ranged from 3.28 to 3.12 eV [1]. The extinction coefficient (K) for five samples of Zn0.5Li2xMg0.5-xFe2O4 increased with the increase of Lithium (Li2x) at 338 nm from 0.074 to 0.207. The high magnitude of optical conductivity is (1.34 × 1012 sec-1) and the maximum value of electrical conductivity is 42 (Ω.cm)-1. This may due to the electrical and optical properties of lithium.

Synthesis and electrochemical properties of Zn_2SnO_4 and Zn_2Sn_(0.8)Ti_(0.2)O_4/C

Compound Zn2Sn0.8Ti0.2O4 was synthesized by a hydrothermal method in which SnCl4-5H2O,TiCl4,ZnCl2 and N2H4-H2O were used as reactants.The composite Zn2Sn0.8Ti0.2O4/C was then prepared through a carbothermic reduction process using the as-prepared Zn2Sn0.8Ti0.2O4 and glucose as reactants.The structure,morphology and electrochemical properties of the as-prepared products were investigated by XRD,XPS,TEM and electrochemical measurements.In addition,electrochemical Li insertion/extraction in composite Zn2Sn0.8Ti0.2O4/C were examined by ex situ XRD and SEM.The first discharge capacity of Zn2SnO4 is about 1670.8 mA-h/g,with a capacity retain of 342.7 mA-h/g in the 40th cycle at a constant current density of 100 mA/g in the voltage range of 0.05-3.0 V.Comparing with the Zn2SnO4,some improved electrochemical properties are obtained for Zn2Sn0.8Ti0.2O4,Zn2SnO4/C and Zn2Sn0.8Ti0.2O4/C.The composite Zn2Sn0.8Ti0.2O4/C shows the best electrochemical properties,and its first discharge capacity is about 1530.0 mA-h/g,with a capacity retain of 479.1 mA-h/g the 100th cycle.

La2O3-B2O3玻璃添加对Zn0.5Ti0.5NbO4微波介质陶瓷结构及性能影响

利用X射线衍射、扫描电子显微镜等手段研究了添加La2O3-B2O3玻璃作为烧结助剂的Zn0.5Ti0.5NbO4微波介质陶瓷在低温烧结过程中的结构及微波介电性能变化。实验结果表明,适当的La2O3-B2O3玻璃添加不会影响Zn0.5Ti0.5NbO4陶瓷的相组成。添加质量分数2%的La2O3-B2O3烧结助剂有助于在烧结过程中形成液相,液相能有效加速Zn0.5Ti0.5NbO4陶瓷的低温烧结过程,实现Zn0.5Ti0.5NbO4陶瓷的致密化。在875℃烧结时,添加质量分数2%La2O3-B2O3玻璃的Zn0.5Ti0.5NbO4陶瓷具有优异的微波介电性能:εr=33.91,Q×f=16579 GHz(f=6.1 GHz),τf=-68.54×10-6/℃。

复合添加ZnO/V_2O_5对(Zr_(0.8)Sn_(0.2))TiO_4陶瓷性能的影响

讨论了复合添加Zn O/V2O5对(Zr0.8Sn0.2)Ti O4介质陶瓷烧结机制和微波介电性能的影响。结果表明:Zn O/V2O5对(Zr0.8Sn0.2)Ti O4的烧结有一定的促进作用,但Zn O/V2O5添加量的增大会造成晶格缺陷和残留气孔增多,从而导致材料的密度和Q×f降低。在1 320℃保温4 h并添加了0.6 wt%Zn O/V2O5的试样具有相对较好的介电性能:εr=36.48,Q×f=16 800 GHz。

Influences of Dopants on Microstructure and Magnetic Properties of (Mg_(0.476)Mn_(0.448)Zn_(0.007))(Fe_(1.997)Ti_(0.002))O_4 Ferrites

Influences of addition of CaO, CoO and V2O5 on the microstructure and magnetic properties of （Mg0.476Mn0.448Zn0.007）（Fe1.997Ti0.002）O4 ferrites were investigated. The powders of （Mg0.476Mn0.448Zn0.007） （Fe1.997Ti0.002）O4 composition were prepared by using a conventional ceramic powder processing technique. The experimental results showed that the average grain size of the sintered ferrites codoped with 0.03wt% CaO, 0.04wt% CoO and 0.06wt% V2O5 was about 15 μm; the saturation magnetization of ferrites was 68.78 emu/g. The addition of V2O5 in the ferrites can not only increase value of the saturation magnetization, but also decrease the average grain size of （Mg0.476Mn0.448Zn0.007）（Fe1.997Ti0.002）O4 ferrites. Simultaneous incorporation of CoO, CaO and V2O5 dopants into （Mg0.476Mn0.448Zn0.007）（Fe1.997Ti0.002）O4 ferrites can not only improve the saturation magnetization of the materials, but also inhibit abnormal grain growth.

MnO2对(Zr0.8Sn0.2)Ti1+δO4+2δ微波介质陶瓷的结构与介电性能的影响

研究掺杂0-0.2wt.%Mn O2的(Zr0.8Sn0.2)Ti1+δO4+2δ(δ=-0.2-0.2)微波介质陶瓷(ZST)的结构和介电性能。固相法制备陶瓷粉料,采用XRD和SEM手段分析陶瓷的晶相和显微结构,并用平行板谐振器法测试样品的微波介电性能。结果表明,未掺杂Mn O2的(Zr0.8Sn0.2)Ti1+δO4+2δ(δ≠0)存在第二相,且(Zr0.8Sn0.2)Ti1.2O4.8陶瓷的微波介电性能最差;掺杂0.2wt.%Mn O2极大地改善了(Zr0.8Sn0.2)Ti1.2O4.8陶瓷的介电性能,Q×f从25.40 THz升高至43.63 THz,频率温度系数从39.0 ppm/℃降至16.8 ppm/℃。

Crystallization in the Three-Component Systems Rb₂SO_4-MSO_4-H₂O (M = Mg, Co, Ni, Cu, Zn) at 298 K

The crystallization in the three-component systems Rb2SO4-MSO4-H2O (M = Mg, Co, Ni, Cu, Zn) is studied by the method of isothermal decrease of supersaturation. It has been established that isostructural double compounds, Rb2M(SO4)2·6H2O (M = Mg, Co, Ni, Cu, Zn), , crystallize from the ternary solutions within wide concentration ranges. The infrared spectra are discussed with respect to the normal vibrations of the sulfate ions and water molecules. The unit-cell group theoretical treatment of the double salts is presented. The extent of energetic distortions of guest ions (about 2 mol%) matrix-isolated in the respective selenates, (M' = K, Rb,;M" = Mg, Co, Ni, Cu, Zn), is commented.

Theoretical Study of Electron Paramagnetic Resonance Spectra and Local Lattice Distortion for Mn^(2+) in Zn(ClO_4)_2·6(H_2O)Mg(ClO_4)_2·6(H_2O)

The electron paramagnetic resonance（EPR） spectra of trigonal Mn^（2＋） centers in Zn（ClO4）2·6（H2O） and Mg（ClO4）2·6（H2O） crystals were studied on the basis of the complete energy matrices for a d^5 configuration ion in a trigonal ligand field. It was demonstrated that the local lattice structure around a trigonal Mn^（2＋） center has an compressed distortion along the crystalline c3 axis, and when Mn^（2＋） is doped in the Zn（ClO4）2·6（H2O） and Mg（ClO4）2·6（H2O） crystals, there is a similar local distortion. From the EPR calculation, the local lattice structure parameters R=2.183 2 ？, for Zn（ClO4）2·6（H2O）, R=2.130 2 ？, for Mg（ClO4）2·6（H2O） have been determined.

红色长余辉发光材料Ca_2Zn_4Ti_(15)O_(36)∶Pr^(3+)的合成和发光性质

分别采用高温固相法和溶胶 凝胶法合成了新型红色长余辉发光材料Ca2Zn4Ti15O36∶Pr。高温固相法合成Ca2Zn4Ti15O36需要在1200℃灼烧96h才能形成纯物相。热重分析曲线和X射线衍射分析结果表明:溶胶 凝胶法制得的前驱体在700℃灼烧12h开始形成Ca2Zn4Ti15O36物相;在1000℃灼烧24h得到Ca2Zn4Ti15O36纯物相;最佳反应温度为1000℃,激活剂Pr3+的最佳浓度为0.6mol%,发光强度比高温固相法增强了510%。

Li_2Mg_2Si_4O_(10)F_2、H_2Mn_8O_(16)·1.4H_2O和Li_(1.3)Ti_(1.7)Al_(0.3)(PO_4)_3在高浓度LiCl水溶液中的离子交换行为

研究了用功能材料Li_2Mg_2Si_4O_(10)F_2(LHT)、H_2Mn_8O_(16)·1.4H_2O(CRYMO)和Li_(1.3)Ti_(1.7)Al_(0.3)(PO_4)_3(LTAP)分别去除高浓度氯化锂水溶液中的杂质Fe^(3+)、K^+和Na^+.实验结果表明,这几种功能材料分别对溶液中的杂质Fe^(3+)、K^+和Na^+有很高的选择性,除杂效果明显.分析和研究了这几种功能材料在高浓度氯化锂水溶液中分别与Fe^(3+)、K^+和Na^+的交换行为.结果表明,在高浓度氯化锂溶液中这几种功能材料与杂质交换的动力学行为可近似用JMAK方程描述.

EDTA络合溶胶-凝胶法制备Y_2O_2S:Eu^(3+),Mg^(2+),Ti^(4+)红色长余辉材料

采用EDTA(乙二胺四乙酸)络合溶胶-凝胶法制备了Y2O2S:Eu3+,Mg2+,Ti4+粉体。采用X射线衍射仪、扫描电子显微镜和荧光分光光度计对不同温度合成的样品性能进行测试与表征。结果表明:当硫化温度低于1 000℃时,样品为Y2O3与Y2O2S的混合相;当温度在1 050～1 100℃时,样品为纯相的Y2O2S;当温度升高到1 150℃时,再次出现Y2O3的相。硫化温度在950～1 100℃时,产物的粒径为50～300 nm。用波长为330 nm的紫外光激发样品时,626 nm处的发射对应于Eu3+的5D0-7F2跃迁。硫化温度为1 100℃时,样品的余辉时间最佳,为95 min(≥1 mcd/m2)。相比于以乙酰丙酮为络合剂的溶胶-凝胶法,EDTA络合溶胶-凝胶法制备的样品的发光性能具有较大提高。

Li_2Zn_(3(1-x))Ca_(3x)Ti_4O_(12)微波陶瓷介电性能研究

本文以Li2CO3,ZnO,CaCO3,TiO2为原料,采用固相反应法制备了Li2Zn3(1-x)Ca3x Ti4O12(x=0,0.05,0.1,0.15)陶瓷,并研究了CaTiO3固溶量对其显微结构和微波介电性能的影响。结果表明:Li2Zn3Ti4O12晶相中固溶CaTiO3相,晶胞参数会增大;少量CaTiO3相固溶于Li2Zn3Ti4O12陶瓷后,提高了Li2Zn3Ti4O12陶瓷的烧结温度及其介电常数,但降低了其品质因素,可增大其温频系数。在1100℃/2 h烧结条件下,Li2Zn2.7Ca0.3Ti4O12陶瓷微波介电性能达到:εr=24,Q×f=50000 GHz,τf=-25×10-6/℃。

前驱溶液的pH值对制备Ca_2Zn_4Ti_(16)O_(38)∶Pr^(3+),Na^+发光粉物相、形貌和发光性质的影响

以钛酸丁酯、醋酸钙、醋酸锌、柠檬酸和乙二醇为原料,采用溶胶-凝胶法制备Ca2Zn4Ti16O38∶Pr3+,Na+发光粉。研究了前驱溶液的pH值对溶胶-凝胶转变过程、发光粉物相组成、样品形貌和发光性质的影响。通过热重-差热分析(TG/DTA)、X射线衍射(XRD)分析、扫描电子显微镜(SEM)对前驱物分解、发光粉物相和颗粒大小进行了研究。采用荧光光谱对材料的光谱性质进行了表征。研究发现前驱溶液pH≤3时,所得发光粉样品为蓬松的、颗粒均匀的单相Ca2Zn4Ti16O38粉末,红色余辉时间较长;随着pH值增大,逐渐有杂质相TiO2、CaTiO3和Zn2TiO4生成,并且样品颗粒逐渐变大,颗粒团聚呈现不规则形状,余辉时间变短。结果表明,只有在pH≤3条件下以溶胶-凝胶法制备Ca2Zn4Ti16O38∶Pr3+,Na+发光粉下才能获得被日光有效激发,并呈现余辉衰减慢的红色长余辉(644 nm)发光。

新型荧光粉Ca2Zn4Ti16O38：Pr^3＋Na^＋的合成和红色长余辉性质

采用溶胶-凝胶法合成了Ca2Zn4Ti16O38∶Pr3+,Na+荧光粉。通过X-射线衍射和荧光光谱表征样品的物相组成和发光性质。X射线衍射(XRD)分析表明添加适量的H3BO3作助熔剂有利于形成良好的Ca2Zn4Ti16O38晶体结构。荧光光谱表明Ca2Zn4Ti16O38∶Pr3+,Na+在可见光区(450～495nm)呈现Pr3+离子的4f→4f特征激发光谱以及613nm(1D2→3H4)和644nm(3P0→3F2)特征发射。Ca2Zn4Ti16O38∶Pr3+,Na+被可见光(475nm)激发产生的3P0→3F2(644nm)红色发射呈现出极慢的衰减特性。Ca2Zn4Ti16O38∶Pr3+,Na+是一种新型的可见光激发红色长余辉荧光粉。

红色长余辉荧光粉Ca_2Zn_4Ti_(16)O_(38)∶Pr^(3+)的水热辅助合成及发光性质

采用水热法辅助合成了纯相Ca2Zn4Ti16O38∶Pr3+荧光粉,初始nCa∶nZn∶nTi=2∶4.1∶15,煅烧条件为1 050℃空气气氛烧结5 h。并以X射线衍射、扫描电镜、紫外可见漫反射光谱和荧光光谱表征了样品的物相组成、微观形貌和光谱性质。合成的荧光粉在高温煅烧后仍较好地保持了球形的微观形态,优化的Pr3+掺杂浓度为0.015。Ca2Zn4Ti16O38∶Pr3+荧光粉在471 nm波长激发下发射红光,发射谱通过高斯分峰拟合得到位于605、620和645 nm的3个发射峰,分别对应于Pr3+的1D2→3H4,3P0→3H6和3P0→3F2跃迁。在471 nm波长激发下,Ca2Zn4Ti16O38∶Pr3+的614 nm红光发射表现出超长余辉特性,表明该荧光粉是一种能被可见光有效激发的红色长余辉荧光粉。

碱土金属离子对红色长余辉材料Y2O2S∶Eu3+,M2+ (M=Mg,Ca,Sr,Ba),Ti4+纳米阵列发光性能的影响

采用溶胶凝胶模板法制备红色长余辉发光材料Y2O2S∶Eu3+,M2+(M=Mg,Ca,Sr,Ba),Ti4+纳米阵列,利用X射线衍射、扫描电子显微镜和荧光分光光度计、照度计分别研究了不同二价离子掺杂下所合成样品的物相、形貌及发光性能。结果表明:样品排列整齐有序,管径大小统一;不同的二价离子种类没有改变晶体结构和发射峰的位置,但对余辉性能有较大的影响。用324 nm波长光激发样品,由于Eu3+的5D0→7F2跃迁,最强的红色发射峰位于626 nm处;不同离子掺杂样品的余辉性能按Ba2+、Ca2+、Sr2+、Mg2+的顺序递加,其中二价离子为Mg2+时,余辉时间长达287 s(≥1 mcd/m2),表现出最佳的余辉性能。

氧扩散电极与Ti/SnO_2-Sb_2O_4电极协同降解水中苯酚

采用热压法制备多孔氧扩散电极,采用热解法制备Ti/SnO2-Sb2O4电极,并将两电极应用于光电催化降解水中苯酚的研究中。通过BET测试、X射线衍射(XRD)分析及扫描电镜分析(SEM)对电极进行了表征。考察了相同操作条件下吸附、光催化、电催化、光电催化等过程对苯酚降解效果的影响。结果表明:氧扩散电极的比表面积较大,主要晶相为石墨、Mn3O4,电极表面和内部的物料混合及气孔分布比较均匀;Ti/SnO2-Sb2O4电极的主要晶相是SnO2和Sb2O4,钛基表面的二氧化锡是四方相的金红石结构;在降解水中苯酚的过程中,氧扩散电极与Ti/SnO2-Sb2O4光阳极能产生良好的光电协同效应。

H_3BO_3对Li_2Zn_3Ti_4O_(12)微波介质陶瓷低温烧结与微波介电性能的影响

采用传统固相反应法制备了添加H_3BO_3助烧剂的Li_2Zn_3Ti_4O_(12)(LZT)陶瓷,分别通过XRD、SEM、排水法及网络分析仪等方法研究了不同H_3BO_3添加量对所得陶瓷的物相、微观形貌、烧结特性与微波介电性能的影响。结果表明在LZT陶瓷中添加3wt%H_3BO_3可有效降低烧结温度,在900℃/2 h烧结条件下可以获得高致密性及优异的微波介电性:ρ=4.15 g/cm^3,εr=17.916,Q×f=61200 GHz,τf=-52.87×10^(-6)/℃。