67 Pb(Mg1/3Nb2/3)O3-33PbTiO_3单晶90°铁电畴光学研究

采用偏光显微镜观察了67Pb(Mg1/3Nb2/3)O3-33PbTiO3固溶体铁电单晶在室温时90铁电畴结构.铁电畴结构与晶体质量有关,在正交偏光显微镜下光学透明晶体中存在着尺寸为23mm的均匀大畴,不同极化方向的大畴重叠形成雾状区,使晶体表现出光学质量宏观不均匀.在光学质量差的雾状晶体中则存在着0.1mm宽的110型带状孪生畴,使晶体形成表面浮凸,带状畴内还存在着90°     

67 Pb(Mg_(1/3)Nb_(2/3))O_3-33PbTiO_3单晶90°铁电畴光学研究

采用偏光显微镜观察了６７Ｐｂ（Ｍｇ_（１／３）Ｎｂ_（２／３））Ｏ_３－３３ＰｂＴｉＯ_３固溶体铁电单晶在室温时 ９０°铁电畴结构．铁电畴结构与晶体质量有关,在正交偏光显微镜下光学透明晶体中存在着尺 寸为２～３ｍｍ的均匀大畴,不同极化方向的大畴重叠形成雾状区,使晶体表现出光学质量宏观 不均匀．在光学质量差的雾状晶体中则存在着 ０．１ｍｍ宽的｛１１０｝型带状孪生畴,使晶体形成 表面浮凸,带状畴内还存在着９０°亚畴．并对这些畴的形成作了讨论．     

67Pb(Mg1/3Nb2/3)O3-33PbTiO3单晶的微结构与铁电畴

用偏光显微镜(PLM)和透射电镜(TEM)观察了67Pb(Mg1/3Nb2/3)O3-33PbTiO3单晶的畴结构.在PLM下,光学质量不同的晶体具有不同的畴结构,透明晶体具有毫米尺度的大畴,透明性差的晶体的带状孪生畴宽约为0.1mm;在TEM下,雾状晶体中存在着复杂的微米尺度的孪生畴,而均匀晶体中存在着不规则的微米尺度的180°畴.原位EDS分析表明,在孪生晶体中存在Nb-Ti-Mg-Pb-O非晶相.透明晶体的介电和压电常数显著地高于雾状晶体.讨论了化学不均性对畴结构的影响.     

热键合制作Yb:Y3Al5O12/Y3Al5O12复合晶体

采用热键合技术制备了Yb:Y3Al5O12/Y3Al5O12(Yb:YAG/YAG)复合晶体,对复合晶体进行了结构表征和键合质量检测.利用光学显微镜和扫描电镜观察了复合晶体横截面的形貌;在偏光显微镜下观察键合区域的应力,利用干涉条纹来表征复合晶体的光学均匀性;通过红外透过光谱的测量来检测复合晶体的键合质量.实验结果表明:热键合技术制备的Yb:YAG/YAG复合晶体键合界面处无界面缺陷,不存在复合界面空间过渡层,光学均匀性良好.     

Pb(Mg1/3Nb2/3)O3-PbTiO3晶体组分对结构与性能的影响

用熔体Modified Brdgman法生长出尺寸直径40 mm长度80 mm的弛豫铁电单晶PMNT90/10,表明该方法不仅适合在准同型相界(MPB)附近生长PMNT单晶,也适合生长PT含量很低的PMNT单晶.在生长出的PMNT90/10晶体中,铁电相与顺电相两相共存,并呈现亚微畴结构特征.随着晶体组分由PMN组元变化到MPB组分附近,PMNT的电畴结构呈现微畴-亚微畴-不规则宏畴-规则宏畴演化系列,而介电弛豫特性则逐步弱化.PMNT固熔体的电学性能依赖于晶体组分,(001)切型PMNT90/10晶体的压电常数d33约80 pC/N,显著低于MPB附近组分,但其介电常数ε达到12600,明显高于后者.     

Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3压电单晶的弛豫反常

对用改进的Bridgman法生长的Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3(PZNT91/9)单晶用Laue衍射法和XRD衍射曲线定向,取(001)晶片研究材料的电学性能.结果表明,材料的介电性能呈现出明显的频率色散现象,随着测试频率的升高,介电常数的峰值温度出现反常,峰的位置向低温方向移动.用扫描电子显微镜和正交偏光显微镜研究了PZNT91/9单晶的电畴结构,发现规则排列的带状畴与杂乱分布的细畴并存.X射线荧光分析结果表明,在PZNT91/9单晶中存在着由成分分凝引起的组分变化.成分分凝引起的组分波动和电畴结构的复杂性导致了材料性能的不均匀性,并与材料铁电相变的弥散性特征相关.     

近化学计量比LiNbO3晶体电畴结构观察和机理探讨

采用双坩埚提拉法(DCCZ)生长了各种不同成分的近化学计量比LiNbO₃晶体, 并用腐蚀法观察了其电畴结构. 结果表明, 化学成分对未经极化处理晶体的电畴结构起决定性作用, 当Li₂O 含量处于49.4mol%附近时, 晶体z面电畴呈现特殊的三次对称反畴; 当晶体中Li₂O含量为49.7mol%时, 晶体为完全单畴. 本文对其形成机理进行了探讨, 认为在由顺电相向铁电相转变 时, 局部铁电畴的极性方向与该处沿z轴方向的温度梯度正负密切相关, z轴生长晶体时, 由于相变发生所处位置离生长界面的距离受LiNbO₃晶体计量比影响, 所处温场固有温梯也 随之不同, 在此基础上解释了不同成分晶体的电畴结构形成原因. 最后讨论了控制铁电畴结构的工艺措施.     

高均匀性高掺镁铌酸锂晶体的生长与表征

采用提拉法生长了高掺镁铌酸锂晶体,并采用高温极化法使晶体单畴化.为研究晶体的成分均匀性、光学均匀性及铁电畴均匀件,采用光谱、激光干涉、电子探针、显微观察等表征手段测定与观察了晶体的紫外吸收边、OH吸收峰、折射率梯度△n、晶体径向上的微观成分及晶体的铁电畴结构.结果表明:通过采用合适的生长组分和改进提拉法生长工艺获得了高质量的高掺镁铌酸锂晶体.晶体的紫外吸收边位于308 nm附近,OH吸收峰位于高抗光损伤阈值特征峰2828 nm处,光学均匀性达△n5.11×10~(-5).在1200℃下通过外加电场极化获得了高均匀性且完全单畴的铁电畴结构.     

近化学计量比LiNbO3晶体电畴结构观察和机理探讨

采用双坩埚提拉法(DCCZ)生长了各种不同成分的近化学计量比LiNbO3晶体,并用腐蚀法观察了其电畴结构.结果表明,化学成分对未经极化处理晶体的电畴结构起决定性作用,当Li2O含量处于49.4mol%附近时,晶体z面电畴呈现特殊的三次对称反畴;当晶体中Li2O含量为49.7mol%时,晶体为完全单畴.本文对其形成机理进行了探讨,认为在由顺电相向铁电相转变时,局部铁电畴的极性方向与该处沿z轴方向的温度梯度正负密切相关,z轴生长晶体时,由于相变发生所处位置离生长界面的距离受LiNbO3晶体计量比影响,所处温场固有温梯也随之不同,在此基础上解释了不同成分晶体的电畴结构形成原因.最后讨论了控制铁电畴结构的工艺措施.     

BaTiO3晶体的电畴结构和单畴化方法

BaTiO3晶体的光折变应用之前，必须对晶体进行单畴化处理．根据BaTiO3晶体中90°电畴结构和包裹体之间的关系，我们找到一种在晶体极化之前就能有效地检查出BaTiO3晶体中包裹体的方法．根据BaTiO3晶体中90°电畴和180°电畴的形成特点，既可以让晶体以缓慢速度降温通过顺电-铁电相交点（1℃／15min），消去BaTiO3晶体的90°电畴，也可以用在α轴方向上施加一定的压力消去BaTiO3晶体的90°电畴．180°电畴可以在晶体的温度接近居里点时，通过在（001）面上施加1～3×105V／m的电场来消除     

Domain patterns on ferroelectric Rh:BaTiO3 single crystals

Single crystal growth and domain structure of Rh:Barium titanate (BaTiO₃) have been investigated. Rh doping in BaTiO₃ is effective for the growth of bulk crystals without twin formation. Atomic force microscope (AFM) and optical microscope studies reveal the formation 180° and 90° domains on the grown crystals. It has been observed that the complex 180° domain structure with typical size of around 20 μm exists in the c-domain of {0 0 1} face of Rh doped BaTiO₃ crystals.     

Complementary characterization techniques for identification of ferroelectric domains in KNbO3 single crystals

KNbO₃ single crystals are often utilized for their piezoelectric and optical properties. In this study the domain configurations in as-grown single crystals were investigated using reflected light microscopy, scanning electron microscopy and atomic force microscopy. Using atomic force microscopy it was possible to image the distortion induced on the crystal surface by the domain walls and to quantify the predicted angle between (001)_pc planes across these walls for the cases of both 90° domain walls and S walls. These features can also be imaged using the other two techniques. This direct measurement of surface distortion verifies the geometrical model of domain structures, and suggests that any possible strain energy considerations are minor in predicting the surface topography in the material after phase changes from the growth temperature.     

Investigation of the Effect of the Annealing Process on the Domain Structure of 0.65Pb(Mg1/3Nb2/3)O3–0.35 PbTiO3 Single Crystal Using Scanning Electron Acoustic Microscopy

Scanning electron acoustic microscopy has been used to reveal the ferroelectric and ferroelastic domain structures in a 0.65 Pb(Mg_1/3Nb_2/3)O₃–0.35 PbTiO₃ single crystal without any sample pretreatment. The investigation revealed the presence of the ferroelectric tetragonal 90° domain structure in the original material. The formation of twofold symmetrical butterfly-shaped ferroelastic domains was observed after the sample had been annealed at 300°C for 3 h and then slowly cooled. The origin of the butterfly-shaped domains is discussed.     

Mn^5＋：Ba3（VO4）2可调谐激光晶体的生长

报导了用中频感应引上法生长Ｍｎ＾５＋；Ｂａ３（ＶＯ４）２晶体的实验呼结果，晶体主要解理面为（０００１）面，常见缺陷是沿生长中心轴的散射颗粒“芯”，指出了生长高质量高浓度Ｍｎ＾５＋：Ｂａ３（ＶＯ４）２单晶的有效途径、优质尺寸大于直径３０ｍｍ×４５ｍｍ测定了该晶体的吸收光谱和荧光光谱。     

Large electric-field-induced strain in ferroelectric crystals by point-defect-mediated reversible domain switching

Ferroelectric crystals are characterized by their asymmetric or polar structures. In an electric field, ions undergo asymmetric displacement and result in a small change in crystal dimension, which is proportional to the applied field. Such electric-field-induced strain (or piezoelectricity) has found extensive applications in actuators and sensors. However, the effect is generally very small and thus limits its usefulness. Here I show that with a different mechanism, an aged BaTiO(3) single crystal can generate a large recoverable nonlinear strain of 0.75% at a low field of 200 V mm(-1). At the same field this value is about 40 times higher than piezoelectric Pb(Zr, Ti)O(3) (PZT) ceramics and more than 10 times higher than the high-strain Pb(Zn(1/3)Nb(2/3))O(3)-PbTiO(3) (PZN-PT) single crystals. This large electro-strain stems from an unusual reversible domain switching (most importantly the switching of non-180 degrees domains) in which the restoring force is provided by a general symmetry-conforming property of point defects. This mechanism provides a general method to achieve large electro-strain effect in a wide range of ferroelectric systems and the effect may lead to novel applications in ultra-large stroke and nonlinear actuators.     

Electric-field and stress effects on depoling and overpoling phenomena in [001]-poled transverse mode Pb(Zn1/3Nb2/3)O3-(6-7)%PbTiO3 single crystal of [110] length cut

Solid-solution Pb(Zn(1/3)Nb(2/3))O(3)-PbTiO(3) (PZN-PT) single crystals, touted as next-generation piezoelectric materials, have been studied extensively in the past decade. This work addresses the advantages and limitations of transducers made of transverse mode PZN-(6-7)%PT single crystals of [110](L) X [001](T)(P) cut. This cut exhibits superior electromechanical properties, with k(31) ≈ 0.85 and d(31) ≈-1450 pC/N, and an extremely high d(31)/S(E)(11) value of >35 C/m(2). It also has relatively high overpoling, i.e., rhombohedralto- tetragonal phase transformation, field of ≈2 kV/mm. This overpoling field further decreases with increase in axial compressive stress. Despite these good attributes, this crystal cut has a low depoling field of ≤ 0.3 kV/mm, a result of low coercive fields of [001]-poled relaxor-based single crystals, which decreases further with increasing axial compressive stress, limiting its bipolar drive capability. The axial compressive stress required to cause overpoling via rhombohedral-to-tetragonal phase transformation of relevant domain variants in the crystal is found to be >90 MPa. In contrast, this crystal cut depolarizes at comparatively low axial tensile stress of ≈15 MPa, the magnitude of which is not significantly affected by the moderate forward field applied.     

Ferroelectric domain in PMN-xPT single crystal studied by piezoresponse force microscopy and finite-element analysis

Ferroelectric domain structures in (001)-cut Pb(Mg(1/3)Nb(2/3))O(3)-38%PbTiO(3) and (011)-cut Pb(Mg(1/3) Nb(2/3))O(3)-60%PbTiO(3) single crystals are studied by means of piezoresponse force microscopy (PFM). The out-of-plane- polarization (OPP) and in-plane-polarization (IPP) domain piezoresponse imaging reveals the domain and domain boundary configurations in these two different PbTiO(3)-content crystals. Finite-element analysis is carried out to illustrate the OPP and IPP-PFM imagings mechanism and interpret the domains superposition phenomenon during PFM imaging.     

Pb[（Zn1／3Nb2／3）0.91Ti0.09]O3压电单晶的驰豫反常

对用改进的Bridgman法生长的Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3（PZNT91／9）单晶用Laue衍射法和XRD衍射曲线定向，取（001）晶片研究材料的电学性能，结果表明，材料的介电性能呈现出明显的频率色散现象，随着测试频率的升高，介电常数的峰值温度出现反常，峰的位置向低温方向移动。用扫描电子显微镜和正交偏光显微镜研究了PZNT91／9单晶的电畴结构，发现规则排列的带状畴与杂乱分布的细畴并存，X射线荧光分析结果表明，在PZNT91／9单晶中存在着由成分分凝引起的组分变化。成分发凝引起的组分波动和电畴结构的复杂性导致了材料性能的不均匀性，并与材料铁电相变的弥散性特征相关。