Ba（Ti0．91Zr0．09）0．99Al0．01O3陶瓷的介电弛豫特性

采用固相反应法制备了Ba1-xBi（Ti0.09Zr0.09）0.99Al0.01O3陶瓷,借助XRD、Agilent4284A、ZT-I电滞回线测量仪,研究了Bi^3＋和Al^3＋共掺杂后对陶瓷的相结构和介电特性的影响。研究结果表明,掺杂后Ba（Ti0．91Zr0．09）0．99Al0．01O3陶瓷的体积密度在x=0．03时,可达5．859g／cm^3,XRD结果显示,在x≤0．01时,衍射峰具有单一的四方BaTiO3结构,观察介电温谱（-30℃≤T≤130℃,10^-1kHz≤f≤10^3kHz,其中f为频率）可发现陶瓷从正常铁电体转变成弛豫铁电体,电滞回线显示矫顽场（Ec）和剩余极化强度（Pt）小,即Ec=0．93kV／cm,Pc=2．63μC／cm^2。     

Ba(Ti_(0.91)Zr_(0.09))_(1-3x/2)Mo_xO_3铁电陶瓷的相变弥散

采用固相反应法制备了MoO3施主掺杂的Ba(Ti0.91Zr0.09)O3陶瓷,借助Agilent4284A、ZT—I电滞回线和d33测量仪,研究了MoO3含量对Ba(Ti0.91Zr0.09)O3陶瓷介电性能的影响。结果表明:掺杂MoO3能降低Ba(Ti0.91Zr0.09)O3陶瓷的烧结温度。当x(MoO3)为0.05时,ρv达到最佳值5.682g·cm–3;tanδ最小为0.0157;εr为2510,相变温度向高温方向移动。在所研究的组分范围内,样品表现出扩散相变铁电体的特征,但未观察到典型的介电弛豫行为。     

CuO-BaO掺杂对Ba(Ti_(0.91)Zr_(0.09))O_3介电性能的影响

采用固相反应法制备了添加1%(质量分数)CuO-BaO混合物的Ba(Ti0.91Zr0.09)O3铁电陶瓷,研究了r(Cu∶Ba)对Ba(Ti0.91Zr0.09)O3铁电陶瓷烧结特性及介电性能的影响。结果表明:随着r(Cu∶Ba)的增加,Cu开始进入晶格,Ba(Ti0.91Zr0.09)O3陶瓷的密度先增加后减小,r(Cu∶Ba)为1.5时,ρ达最大值5.85g/cm3,斜方-四方相变峰出现介电弛豫现象,居里温度向低温方向移动,电滞回线呈现典型弛豫型铁电体的特征。     

Sb_2O_3掺杂Ba(Ti_(0.91)Zr_(0.09))O_3陶瓷的结构与性能

采用固相反应法制备了Sb2O3掺杂的Ba(Ti0.91Zr0.09)O3陶瓷,研究了Sb2O3掺杂量(x(Sb2O3)为0.5%～5.0%)对陶瓷晶相结构及介电性能的影响,分析了陶瓷电滞回线变化的原因。结果表明:Sb3+进入了Ba(Ti0.91Zr0.09)O3陶瓷晶格,引起晶格畸变,且无第二相出现。随着Sb2O3掺杂量的增加,陶瓷晶粒逐渐变小变均匀,tanδ减小。Sb2O3掺杂的Ba(Ti0.91Zr0.09)O3陶瓷为弥散相变铁电体,在x(Sb2O3)为3.0%处弥散程度最小。     

Ba(Ti_(0.91)Zr_(0.09_)O_3陶瓷介电弛豫现象的研究

采用固相反应法制备了CuO-BaO掺杂的Ba(Ti0.91Zr0.09)O3陶瓷,研究了掺杂量对陶瓷介电性能的影响。结果表明:随着CuO-BaO混合物掺杂量从0.3%增加到1.0%时,Ba(Ti0.91Zr0.09)O3陶瓷的斜方-四方相变峰出现介电弛豫现象并且弛豫程度Δtm′从2.9增加到5.5,相变温度从+5℃移动到–21℃,室温εr从2841增加到3372,并且高于四方-立方相变点的εr。电滞回线变窄,矫顽场变小,呈现典型弛豫型铁电体的特征。     

CuO掺杂对Ba(Ti_(0.91)Zr_(0.09))O_3陶瓷介电性能的影响

采用固相反应法制备了CuO掺杂的Ba(Ti0.91Zr0.09)O3陶瓷,借助XRD、SEM、Agilent4284A测试仪,研究了CuO掺杂对Ba(Ti0.91Zr0.09)O3陶瓷的结构及介电性能的影响.结果表明,CuO具有细化陶瓷晶粒的作用.随着CuO掺杂量的增加,Ba(Ti0.91Zr0.09)O3陶瓷的斜方-四方相变峰出现介电弛豫现象,相变点处的介电常数增加,并且居里峰出现相变弥散现象.当w(CuO)=0.38%时,斜方-四方相变峰的弛豫程度最大.     

Li-Mo共掺杂Ba(Ti_(0.91)Zr_(0.09))O_3陶瓷的介电弛豫

采用固相反应法制备了Ba1-xLix(Ti0.91Zr0.09)1-yMoyO3陶瓷,并研究了Li-Mo共掺杂对其相结构和介电性能的影响。结果表明:当x>0,y=0时,陶瓷为单一的四方钙钛矿结构;当x=0,y>0或x=y>0时,陶瓷出现第二相BaMoO4。在–30～+130℃,Li-Mo共掺杂时,陶瓷具有铁电–顺电弥散相变特征,随着频率的增加,介电常数峰值对应的温度tm移向高温,陶瓷由正常铁电体变成弛豫铁电体。     

氧化物掺杂Ba(Ti0.91Zr0.09)O3陶瓷的介电弛豫行为

采用固相反应法分别制备了CuO、Bi2O3、MoO3和Li2O氧化物掺杂的Ba(Ti0.91Zr0.09)O3陶瓷.研究A位和B位施-受主掺杂对介电弛豫行为的影响.不同频率下陶瓷样品的介电温谱显示适量的掺杂可以诱发弛豫行为.根据A位和B位的替代离子类型,讨论了弛豫特性产生的机理.     

Zr与稀土Nd复合掺杂对钛酸钡陶瓷结构及介电性能的影响

在1 270℃的烧结温度下,采用固相反应法对BaTiO3粉体进行Nd2O3和ZrO2双施主复合掺杂,合成(Ba0.98Nd0.02)(Ti1–xZrx)O3(BTNZ)陶瓷,研究了Zr掺杂量对BTNZ陶瓷的显微结构及介电性能的影响。结果表明:随着Zr掺杂量的增加,BTNZ陶瓷的介电峰移向室温;加入适量的Zr离子替代BaTiO3中的Ti离子能很好地改善BTNZ陶瓷的介电性能,当Zr掺杂量为x=0.01时,BTNZ陶瓷的相对介电常数可达7 200。     

Nb掺杂对BaTi_(0.96)Al_(0.04)O_3陶瓷介电性能的影响

为探究Al-Nb共掺对BaTiO_3介电性能的影响及其掺杂机制,以Ba Ti_(0.96)Al_(0.04)O_3为基础配方,通过传统的固相反应法制得BaAl_(0.04)Ti_(0.96-x)Nb_xO_3(0≤x≤0.08)陶瓷样品,并通过XRD、LCR分析仪和Gulp软件来对样品的结构、介电性能进行分析。结果表明:当x≥0.03时陶瓷样品中出现第二相;随着Nb~(5+)含量的增加,陶瓷从传统的铁电体转变成弛豫铁电体,介电峰值温度(Tm)向低温方向移动,且当x≤0.01时介电常数增大,当x≥0.02时介电常数减小;通过Gulp模拟分析得出晶体中钡空位补偿机制优先发生,可能伴有少量钛空位补偿,主要存在的缺陷簇是[2Nb_(Ti)~·-V_(Ba)~"]。     

Strain relaxation in Ge0.09Si0.91 epitaxial thin films measured by wafer curvature

Strain relaxation in a 7200Å thick Ge_0.09Si_0.91 epitaxial film grown on (100) silicon has been investigated using wafer curvature measurements. The measurements were performed during heating and isothermal annealing in a vacuum furnace at temperatures up to 900° C. For as-deposited samples, strain relaxation was observed between 600 and 800° C and was governed by dislocation nucleation. For films whose surface had been lightly abraded in order to nucleate dislocations, strain relaxation occurred by dislocation motion in a temperature range between 500 and 650° C. Isothermal measurements of strain relief were obtained at various temperatures and used to test models for the dislocation velocity.     

Photoluminescence and photoreflectance study of Si/Si0.91Ge0.09 andSi9/Ge6 quantum dots

Nanometer-scale quantum dots based on a series of Si/Si_0.91Ge_0.09 strained layer superlattices and a Si₉/Ge₆ strain-symmetrized superlattice were fabricated using electron beam lithography and reactive ion etching. They were investigated by photoluminescence and photoreflectance. It was found for the first time that the quantum efficiency of optical emission from the quantum well layers increased by over two orders of magnitude when the quantum dot sizes were reduced to ≤100 nm.     

Phase transformation and paired-plate precipitate formation in Pb0.91La0.09Zr0.65Ti0.35O3 films grown on sapphire substrates

We report on the phase transformation behavior of Pb_0.91La_0.09Zr_0.65Ti_0.35O₃ (9/65/35) PLZT films grown on r-sapphire substrates via rf-magnetron sputtering. A complex microstructure results in these films depending on deposition and annealing conditions. A random equiaxed polycrystalline grain morphology was observed after rapid thermal annealing or furnace annealing when the as-deposited films were predominantly pyrochlore. Precipitate formation (100–150 nm) was observed in PLZT films that were deposited at temperatures in excess of 490°C with a perovskite structure, after furnace annealing at 700°C. We believe that this is related to internal stresses in the films due to both the lattice mismatch and the thermal expansion mismatch between the PLZT film and the sapphire substrate.     

On the Feasibility of Growing Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 Single Crystals

Pb[(Zn_1/3Nb_2/3)_0.91Ti_0.09]O₃ (PZNT91/9) single crystals were grown by two methods: from solution using PbO as a self‐fluxing agent (SC method) and directly from the melt without fluxing (MC method). In both growth methods, an allomeric Pb[(Mg_1/3‐Nb_2/3)_0.69Ti_0.31]O₃ (PMNT69/31) single crystal was used as a seed. X‐ray diffraction patterns of ground crystals showed that phase‐pure perovskite PZNT91/9 single crystals were successfully fabricated by the above two methods. The composition of the crystals obtained by both the SC and MC methods was analyzed using X‐ray fluorescence, which confirmed that the crystal composition is close to the nominal value, although volatilization of PbO and segregation during crystal growth are inevitable. The MC PZNT91/9 crystals exhibit excellent piezoelectric properties, with the piezoelectric constant, d₃₃, in the range of 1800–2200 pC N^–1. This value is comparable to that of the SC crystals. However, the MC crystals show an abnormal dielectric behavior. In contrast with the SC crystals, in the MC crystals a much broader dielectric peak appears in the dielectric response curves, accompanied by a much lower peak temperature of around 105 °C. Furthermore, frequency dispersion is apparent over a much wider temperature range (even more apparent than in pure relaxors), where a large, i.e., about 70 °C, full width at half maximum (FWHM) for the dielectric peaks is observed in the dielectric response. It is speculated that such an unusual phenomenon correlates with defects, microinhomogeneities, and polar regions in the as‐grown MC crystals. The origins of this abnormality have not been interpreted in detail until now. However, optical observation of the domain structure confirms that both the SC and MC crystals possess complex structural states.