PZN-PT单晶的压电特性

Pb(Zn1 / 3Nb2 / 3) O3单晶是 Bokov 196 1年发现的 ,196 9年由 Nom ura扩展到 PZN- Pb Ti O3(PZN- PT)系。 J.Kuwata 1982年发现 ,在 MPB组分附近的 0 .91PZN- 0 .0 9PT菱面体单晶的 [0 0 1]方向施加电场时 ,可获得 d33=15 0 0 p C/N ,k33=0 .92的高值。从而引起了人们的注意。东芝公司的 M.Izumi等人着眼于该单晶较大的机电耦合系数 ,率先进行了 PZN- PT单晶的生长及其在医用超声探头上的应用研究。他们于 1997年用熔融法生长了 40 m m× 40 mm× 40 mm PZN- PT单晶 ,1998年又以批量生产为目标 ,用布里兹曼法成功地生长…     

熔剂法生长PZN-PT单晶的电性能研究

以55%PbO(摩尔分数)作熔剂,BaTiO3为成核剂,采用高温熔剂法加底部冷却技术成功生长了PZNT91/9单晶,其最大晶体尺寸达15 mm×13 mm。X-射线衍射(XRD)分析表明晶体为纯钙钛矿相,其显露面为立方晶形(100)面族。热释电研究表明单晶在69℃发生三方-四方相变,在174℃发生四方-立方相变。单晶的压电性能测试结果为:平面和厚度机电耦合系数分别为0.69、0.49;压电常数d33为1 330 pC/N;在13.6 kV/cm电场下应变达0.312%。     

Pb(Mg_(1/3)Nb_(2/3))O_3弛豫铁电晶体的生长形貌和生长机理

以PbO作助熔剂采用高温溶液法生长出Pb(Mg1/3Nb2/3)O3弛豫铁电晶体,利用X线衍射仪(XRD)和扫描电子显微镜(SEM)分析了晶体相结构和生长形貌。研究结果表明,采用高温溶液法生长出纯钙钛矿相结构的Pb(Mg1/3Nb2/3)O3弛豫铁电晶体,晶体多为淡黄色,较小的呈赝立方形态,较大晶体逐渐趋于不规则形态,最大尺寸达4mm×4mm×3mm。晶体中存在位错蚀坑和PbO包裹等生长缺陷,生长过程中的温度波动和成分起伏等因素导致这些缺陷的出现。晶体{100}面生长速率最慢能成为热力学上稳定存在的自然显露晶面,晶体的生长机制为二维成核层状生长。     

Pb(Mg_(1/3)Nb_(2/3))O_3弛豫铁电晶体的生长形貌和生长机理

以PbO作助熔剂采用高温溶液法生长出Pb(Mg1/3Nb2/3)O3弛豫铁电晶体,利用X线衍射仪(XRD)和扫描电子显微镜(SEM)分析了晶体相结构和生长形貌。研究结果表明,采用高温溶液法生长出纯钙钛矿相结构的Pb(Mg1/3Nb2/3)O3弛豫铁电晶体,晶体多为淡黄色,较小的呈赝立方形态,较大晶体逐渐趋于不规则形态,最大尺寸达4mm×4mm×3mm。晶体中存在位错蚀坑和PbO包裹等生长缺陷,生长过程中的温度波动和成分起伏等因素导致这些缺陷的出现。晶体{100}面生长速率最慢能成为热力学上稳定存在的自然显露晶面,晶体的生长机制为二维成核层状生长。     

物理气相法制备AlN晶体

研究了物理气相法制备AlN晶体的过程中生长条件的改变对晶体生长的影响.实验中,采用带石墨环的坩埚组件可以避免高温下钨坩埚体和盖的粘结问题.随着生长温度的升高,AlN晶体的形态从晶须过渡到棱形晶粒.温度高于1950℃时,才能制备出颗粒状.AlN晶体.同时,研究了过饱和压对晶体生长的影响.目前,已经制备出直径为1mm的高质量的六棱柱形的.AlN单晶,最大的单晶体的直径达2mm.     

物理气相法制备AlN晶体

研究了物理气相法制备AlN晶体的过程中生长条件的改变对晶体生长的影响.实验中,采用带石墨环的坩埚组件可以避免高温下钨坩埚体和盖的粘结问题.随着生长温度的升高,AlN晶体的形态从晶须过渡到棱形晶粒.温度高于1950℃时,才能制备出颗粒状.AlN晶体.同时,研究了过饱和压对晶体生长的影响.目前,已经制备出直径为1mm的高质量的六棱柱形的.AlN单晶,最大的单晶体的直径达2mm.     

基于CTGS的高温压电加速度传感器研究

近年来,航空航天领域的飞速发展要求振动测量技术能耐受更高温度,因此高温压电加速度传感器备受关注。通过优化压电晶体切型和设计质量块结构,该文设计并制备了基于硅酸镓钽钙（CTGS）压电单晶材料的压电加速度传感器。实验结果表明,该传感器的谐振频率约为2.2 kHz。在振动频率为100 Hz~1.1 kHz下,常温时传感器的电荷灵敏度基本稳定,平均值为2.44 pC/g（g=9.8 m/s2）。在常温~600 ℃内,传感器的电荷灵敏度基本保持不变,1.1 kHz振动频率下传感器的电荷灵敏度平均值为2.56 pC/g。该传感器能在600 ℃高温下稳定工作。     

用SEM研究Y系超导单晶的生长习性

本文报道用SEM观察研究R-Ba-Cu-O(R为Y、Gd、Tm)超导单晶的形貌、生长习性、生长台阶,并讨论了单晶生长过程。这些结果对超导单晶生长研究具有重要意义。高温氧化物超导单晶RBa_2Cu_3O_x是用自助溶剂法生长的,Tc(zero)为91K。图1为充分发育的超导单晶的形貌照片。(a)为YBa_2Cu_3Ox(b)为GdBa_2Cu_3O_x,(c)为TmBa_2Cu_3O_x。可见,发育良好的Y系超导单晶外形的矩形片状,具有相交为90°的方角。晶体外形反映了晶体的对称性——正交结构。显露的晶面为(100),(010),(001)等。其中(001)面最大,说明晶体沿C轴方向生长速度最慢。图2为发育初期的晶体,     

溶菌酶晶体形貌的原子力显微成像观测

为研究蛋白质晶体的生长机理,采用气相扩散法制备溶菌酶晶体,使用原子力显微成像技术观测了溶菌酶晶体(101)生长面的形貌.发现溶菌酶晶体(101)面生长呈现螺旋住错的特征,其台阶平均高度为2.9 nm,相当于单分子层的厚度.而以前在高过饱和度条件下得到的溶菌酶晶体的AFM图像显示为二维成核生长机理,其台阶高度为双分子层的厚度5.6 nm.这说明气相扩散法制备蛋白质晶体时,由于溶液的过饱和度较小,溶菌酶在溶液中可能不形成多聚物而是以单个分子的形式结合到晶体上,即(101)面的主要生长单元并非具有43螺旋结构的四聚体,而是溶菌酶单分子.这一结果为蛋白质晶体生长机理的探索提供了实验依据,是对溶菌酶晶体生长单元认识的补充.     

单晶LN BAW谐振器有限元仿真研究

利用离子注入剥离法(CIS)制备的铌酸锂(LN)压电薄膜可用于制备体声波(BAW)器件,近年来备受关注。滤波器的指标与谐振器的性能密切相关,但基于LN单晶薄膜的BAW谐振器,对其结构的仿真优化还未有较深入的报道。该文以LN单晶薄膜为核心压电层材料,构建了固态反射型(SMR)单晶薄膜谐振器有限元仿真模型,对其压电层厚度和布喇格反射层厚度进行了设计,并重点针对谐振器上电极的台阶结构进行了二维模型仿真,为高频LN BAW滤波器的制备提供了理论依据。     

Ag掺杂PZN-PZT微观结构及电学性能影响

采用常规陶瓷工艺制备了0.2Pb(Zn1/3Nb2/3)O3-0.8Pb(Zr0.5Ti0.5)O3(0.2PZN-0.8PZT)三元系陶瓷,系统研究了Ag掺杂对体系微观结构及电学性能的影响。结果表明,Ag在钙钛矿中的溶解限约为0.1%(质量分数)。低于溶解限,Ag以离子掺杂形式进入钙钛矿晶格置换A位的Pb2+,以受主掺杂机制影响体系电学性能;高于溶解限,过量的Ag以单质形式沉积在晶界,弥散分布在0.2PZN-0.8PZT相中。Ag单质使陶瓷体系形成复相结构,在烧结降温阶段产生内应力,改变了材料的电畴结构,并影响陶瓷的直流电阻率和压电性能。     

铟掺杂ZnO体单晶的生长及其性质

研究了In掺杂n型zno体单晶的化学气相传输法生长和材料性质.利用霍尔效应、x射线光电子能谱、光吸收谱、喇曼散射、阴极荧光谱等手段对晶体的特性和缺陷进行r分析.掺In后容易获得浓度为1018～lO19cm-3的n型ZnO单晶,掺人杂质的激活效率很高.随着掺杂浓度的提高,znO单晶的带边吸收和电学性质等发生明显的变化.分析了掺In-ZnO单晶的缺陷及其对材料性质的影响.     

Preparations and properties of low loss Sr1−xBaxNb2O6 ferroelectric single crystals

The growth parameters and ferroelectric properties of SBN and lead-modified SBN single crystals grown by the Czochralski method have been investigated. All crystals were grown in the [001] direction in air. It was observed that the degree of difficulty of growth increased as the diameter and Ba content of the crystal increased. Crack-free single crystals ~ 1. cm in diameter have been grown. The temperature dependence of pyroelectric properties have been studied. Poled SBN (x=0.5) with the very low loss factor of 0.003 has been obtained. High detectivity pyroelectric infrared detectors have been made from these low loss crystals.     

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.     

活性真皮基质的研制及生物学活性检测

目的构建含有成纤维细胞（Fb）-胶原-猪去细胞真皮基质（PADM）的活性真皮基质。研究培养液中转化生长因子-β1（TGF-β1）和碱性成纤维细胞生长因子（bFGF）的分泌情况。方法将Fb与胶原混合种植于PADM的表面，收集第2、4、6、8、10d培养液样本，双抗体夹心ELISA法测定其中TGF-β1、bFGF的含量。结果Fb在胶原内结构完整，与PADM形成复合真皮基质。TGF-β1和bFGF浓度培养第4天与第2天比较显著上升（P〈0．01），并达到稳定水平。结论Fb-胶原-PADM真皮替代物可作为构建组织工程全层皮肤的真皮支架。     

Ba_(0.99)Nd_(0.01)TiO_3纳米颗粒的合成及其光学性能研究

用熔盐法合成了掺Nd钛酸钡(Ba0.99Nd0.01TiO3)纳米颗粒,用X射线衍射、透射电镜和拉曼光谱研究了所制Ba0.99Nd0.01TiO3纳米颗粒的晶体结构,讨论了Nd掺杂对BaTiO3结构的影响,并分析了纳米颗粒的紫外–可见光吸收和光致发光性能。结果表明:合成的纳米颗粒是单晶的四方结构,平均粒径约为200 nm,光学带隙为3.23 eV。在近红外波段900 nm和1 060 nm附近有强烈发光,其分别是由Nd3+的4F3/2→4I11/2和4F3/2→4I13/2跃迁辐射导致。     

退火处理对0.5PZN-0.5PZT陶瓷弛豫性的影响

采用常规陶瓷工艺制备了Pb(Zn_(1/3)Nb_(2/3))_(0.5)(Zr_(0.5)Ti_(0.5))_(0.5)O_3 (0.5PZN-0.5PZT)铁电陶瓷,并在氧气氛下进行退火.运用XRD、直流电导率和介电温度谱测试氧气氛退火前后陶瓷相结构与电性能的变化,并对弛豫性与微结构的关系进行探讨.结果表明,氧气氛退火可有效补偿体系中的氧空位,降低四方相含量,材料的弛豫性显著增强.     

Selective Nucleation of Organic Single Crystals from Vapor Phase on Nanoscopically Rough Surfaces

Organic field‐effect transistors (OFETs) are attractive for microelectronic applications such as sensor arrays or flexible displays, due to their adequate performance and relatively low production costs. Organic single‐crystal transistors have emerged as benchmark devices for studying the intrinsic charge‐transport properties in organic semiconductor materials. Conventional approaches for growing organic single crystals result in uncontrollable dimensions and the formation of extremely fragile crystals. In addition, the hand‐selection and placement of individual crystals on a device structure represents a severe limitation for producing arrays of single‐crystal transistors with high density and reasonable throughput. As a result, the application of organic single‐crystal transistors has been restricted to fundamental charge transport studies, with their commercial application not yet realizable. We recently reported a materials‐general method of fabricating large‐area arrays of patterned organic single crystals. Microcontact‐printed octadecyltriethoxysilane (OTS) film domains on smooth, inert substrates were found to act as preferential nucleation sites for single crystals for a broad range of organic semiconductor materials, such as pentacene, tetracene, rubrene and C₆₀. In order to understand the underlying mechanism of preferential nucleation, the stamped OTS domains and the contact plane between the OTS domains and the organic crystals were inspected by atomic force microscopy (AFM) and optical microscopy. Our analysis suggests that crystals nucleate at the base of tall OTS pillars that form the significantly rough surface in the stamped domains. The selective nucleation inside the rough surface regions is discussed by means of a rate‐equation model of the growth process.     

Growth and characterization of 2-inch high quality β-Ga2O3 single crystals grown by EFG method

β-Ga2O3 is an ultra-wide band-gap semiconductor with promising applications in UV optical detectors,Schottky barrier diodes,field-effect transistors and substrates for light-emitting diodes.However,the preparation of large β-Ga2O3 crystals is undeveloped and many properties of this material have not been discovered yet.In this work,2-inch β-Ga2O3 single crystals were grown by using an edge-defined film-fed growth method.The high quality of the crystal has been proved by high-resolution X-ray diffraction with 19.06 arcsec of the full width at half maximum.The electrical properties and optical properties of both the unintentionally doped and Si-doped β-Ga2O3 crystals were investigated systematically.