Nb,Ti微合金钢热变形的动态模拟变形抗力模型

本报道Ｎｂ，Ｔｉ微合金钢的热变形动态模拟变形抗力模型。在试验中用热加工模拟试验机进行高温压缩试验，其变形温度为１１２３－１４２３Ｋ，变形速率为０．１－６０ｓ＾－１。结果表明，在峰值以前该钢种的流变应力数学模型为：σ＝５．９９．ε＾０．１６７·ε＾（６．４７×１０＾－５·Ｔ）·ｅｘｐ（４０６４／Ｔ）。形变激活能（Ｑ）为４４４ｋｊ／ｍｏｌ，０β系数为０．０８０。峰值应力（σｐ），临界应变（εｃ）和…     

PMN-BT陶瓷的介电性能和相变温度

制备了一系列ＰＭＮ－ＢＴ陶瓷,系统地研究了ＢＴ含量的变化对介电性能和相变温度的影响．ＰＭＮ－ＢＴ陶瓷的相变温度与组成呈“Ｕ”型变化曲线．相变温度的异常变化是由于系统中存在Ｂａ（Ｍｇ１／３Ｎｂ２／３）Ｏ３顺电微区所致．ＰＭＮ－ＢＴ陶瓷的介电弛豫特性随ＢＴ的增加经历了一个由弱变强,再由强变弱的过程．对由两种钙钛矿化合物构成的铁电固溶体相变温度的变化规律进行了讨论．     

Na1/2Bi1/2TiO3-BaTiO3系陶瓷压电性?及弛豫相变研究

系统研究了（１－ｘ）Ｎａ１／２Ｂｉ１／２ＴｉＯ３－ｘＢａＴｉＯ３（ｘ＝０．０２、０．０４、０．０６、０．０８、０．１０）无铅压电陶瓷系统的相界、材料压电性能,弛豫特性及相变．这个系统的陶瓷材料具有Ｋｔ／Ｋｐ较大,频率常数比较高等特点．Ｘ－ｒａｙ衍射结构分析发现此系统的相界在０．０４＜ｘ＜０．０６之间;材料的一些主要性能在相界附近达到极值．利用介电系数－温度曲线,并结合热激电流曲线对此系统的弛豫性进行研究和分析;初步研究了各配方组成的铁电－顺电的相变过程,发现在一定的组成范围内,材料在由铁电相向顺电相的转变过程中经历了一个过渡相区．     

多组份复合的热释电陶瓷材料

制备了具有不同组成分布的ＰＺＴ复合热释电陶瓷材料．复合材料从低温铁电相（ＦＲＬ）到高温铁电相之间的相变区域比较宽．对三组份复合材料而言，在３０～４６℃之间，其热释电系数达到１４×ｌ０－７Ｃ／Ｋ·ｃｍ２，比同一系统中线性热释电效应的数值高三倍．     

Pb（Mg1／2W1／2）O3—PbTiO3—PbZrO3l陶瓷的化学不均匀性和介电行为的…

研究了Ｐｂ（Ｍｇ１／２Ｗ１／２）Ｏ３－ＰｂＴｉＯ３－ＰｂＺｒＯ３陶瓷的化学不均匀性和介电行为。ＥＤＳ分析得到：体系中存在富Ｗ和富Ｚｒ、Ｔｉ的两相，平均分子式为：Ｉ相（富Ｗ相）：Ｐｂ（Ｍｇ０．２７０Ｗ０．３６７Ｚｒ０．１８２）Ｏ３．０９１；Ⅱ相（富Ｚｒ、Ｔｉ相）：Ｐｂ（Ｍｇ０．１０９Ｗ０．１８７Ｔｉ０．２０４Ｚｒ０．３４０）Ｏ２．７５８。两种居里点分别为：ＴＣＩ〈－６５℃，ＴＣＩ＝１０５℃，图像处理     

Pb(Ni1/3Nb2/3)O3-PbTiO3系统准同型相界附近的介电异常

用两步合成法制备了（１－ｘ）Ｐｂ（Ｎｉ１／３Ｎｂ２／３）Ｏ３－ｘＰｂＴｉＯ３（ｘ＝０．３０－０．４０）陶瓷,对其相结构和介电性能进行了研究。ＸＲＤ分析表明,准同型相界在ＰＴ含量ｘ＝０．３４－０．３８范围内。介电性能研究结果表明,组成在准同型相界处的试样,其介电常数呈现最大值,同时还发现,准同型相界处的陶瓷出现介电双峰,其中一个为驰豫型铁电相向顺电相转变的相变峰;另一个介电峰处于１３０－１５０℃的高     

溶胶凝胶法制备掺铅钛酸钡纳米晶及其结构相变

采用溶胶－凝胶工艺制备了不同晶粒大小的、掺铅（５ｍｏｌ％）钛酸钡（ＢＰＴ）纳米晶．用ＴＥＭ、ＸＲＤ和ＤＳＣ研究了ＢＰＴ样品的晶粒大小、结构及其相变特性．结果表明,纳米晶ＢＰＴ随着晶粒尺寸的减小,由铁电四方相向顺电立方相过度,并且相变变得弥散．其顺电－铁电相变随着晶粒尺寸的减小而消失．另一方面,随着晶粒尺寸的增加,其铁电四方－铁电正交相交消失,即抑制了其正交相的形成．     

串联2—2复合材料的介电击穿

串联２－２型压电复合材料结构较为简单,它是研究具有复杂连通性压电复合材料的基础。本文从能量的角度推导出串联２－２复合材料中压电陶瓷层上的电场强度Ｅｃ＝εｐＶｃεｐ＋εｃ（１－Ｖｃ）Ｅｏ和聚合物层上的电场强度Ｅｐ＝εｃＶｃεｐ＋εｃ（１－Ｖｃ）Ｅｏ。由于压电陶瓷的介电常数εｃ（≈１６００ε０）远远大于聚合物的介电常数εｐ（≈１２ε０）,因此Ｅｐ远远大于Ｅｃ。尽管聚合物的介电强度高于压电陶瓷的介电强度,但由于Ｅｐ远远大于Ｅｃ,所以串联２－２型压电复合材料的介电击穿往往是从聚合物层开始的,最后导致复合材料整体被击穿。     

铌锌酸铅基陶瓷的铁电行为研究

采用具有改进ＳａｗｙｅｒＴｏｗｅｒ电路的全自动铁电体电滞回线测试系统，对（０．９ｘ）Ｐｂ（Ｚｎ１／２Ｎｂ２／３Ｏ３０．１ＢａＴｉＯ３ｘＰｂＴｉＯ３［（ｘ＝０．０５，０．１０，０．１５，简称ＰＺＮＢＴＰＴ（０．１／ｘ）］系列铁电陶瓷样品在０℃～１９０℃温度范围内强场下的极化强度进行了详细测试，并与其弱场介电行为对比，探讨了铁电宏畴微畴不同的强场极化特性，发现ＰＺＮＢＴＰＴ（１０／１５）铁电陶瓷样品的极化强度在自发正常铁电体弛豫型铁电体转变温度Ｔｎｒ下有一个增大过程。     

前驱体制备途径对PFN-PMN二元铅基铁电陶瓷性能的影响

综合运用 ＸＲＤ、ＳＥＭ、ＴＥＭ、ＥＤＳ和介电测量等方法,考察了一步预煅烧法和二步预煅烧法等前驱体制备途径对Ｐｂ（Ｆｅ_１／２Ｎｂ_１／２）Ｏ_３（ＰＦＮ）－Ｐｂ（Ｍｇ_１／３Ｎｂ_２／３）Ｏ_３（ＰＭＮ）二元系铁电陶瓷显微结构和介电性能的影响．研究结果表明,对（１－Ｘ）ＰＦＮ－ＸＰＭＮ二元系而言,在所考查的组成范围内（Ｘ＝０～０.５）;其居里温度与ＰＭＮ的含量近似成线性关系,且随Ｘ的增加,居里温度向低温方向移动.峰值介电常数随Ｘ的增加而降低．（预）煅烧和烧结条件对显微结构和介电性能都有不可忽视的影响．对用一步预煅烧法和二步预煅烧法得到的样品的介电性能和其他性能进行了比较,并对其差异产生的可能机制进行了讨论．     

铌镁酸铅-钛酸铅陶瓷介电与压电性能的研究

用二步合成法制备了（１－ｘ）Ｐｂ（Ｍｇ１／３Ｎｂ２／３）Ｏ３－ｘＰｂＴｉＯ３原料,并制成了纯钙钛矿结构压电陶瓷。研究三方－四主相界附近组份及工艺与性能的关系。材料以１２００℃附近保温１５０ｍｉｎ为佳。材料性能表明,有希望成为新型压电陶瓷。     

Measurements along the growth direction of PMN-PT crystals: dielectric, piezoelectric, and elastic properties

Property measurements are reported for Pb(Mg1/3Nb2/3)03-PbTiO3 (PMN-PT) single crystals grown along (001) by a seeded-melt method. Chemical segregation occurs during crystal growth, leading to property changes along the growth direction. Variations in dielectric, piezoelectric, and elastic properties were evaluated for specimens selected from the crystals. Room-temperature data are correlated with Tc and composition that ranged from 27 to 32% PT, i.e., in the vicinity of the morphotropic phase boundary (MPB). While there was little change in the high electromechanical coupling factor k33 (0.87-0.92), both the piezoelectric charge coefficient d33 (1100-1800 pC/N) and the free dielectric constant K3 (4400-7000) were found to vary significantly with position. Increases in d33 and KT33 were relatively offsetting in that the ratio yielded a relatively stable piezoelectric voltage coefficient g33 (27-31 x 10(-3) Vm/N). Values are also reported for the elastic compliance (3.3-6.3 x 10(-11) m2/N) determined from resonance measurements. Enhancements in d33 and K(T)33 were associated with lattice softening (increasing sE33) as the composition approached the MPB. Details are reported for the piezoelectric, dielectric, and elastic properties as a function of growth direction, Tc, and composition. The results are useful for an understanding of properties in PMN-PT crystals and for the design of piezoelectric devices.     

Characterization of flux-grown PZN-PT single crystals for high-performance piezo devices

Relaxor ferroelectric Pb(Zn(1/3)Nb(2/3))O(3-x)PbTiO(3) (PZN-PT) and Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3)(PMN-PT) single crystals are the potential candidates for future high-performance piezoelectric devices due to their exceptionally high dielectric and piezoelectric properties. Characterization on flux-grown PZN-PT single crystals of different orientations revealed that PZN-(6-7)%PT single crystals show good homogeneity in dielectric and electromechanical properties and composition. When poled in [001] direction, these crystals exhibit high longitudinal-mode properties with dielectric constant (K(T)) approximately equal to 7000, piezoelectric coefficients (d(33)) approximately equal to 2800 pC/N, and electromechanical coupling factors (k(33)) > or = 0.92. For [011]-cut crystals, optimally poled PZN-7%PT single crystal exhibits very high transverse-mode dielectric and piezoelectric properties with K(T) > or = 5000, d(32) approximately equal to -3800 pC/N and k(32) > or = 0.90. [011]- poled PZN 6%PT has d(32) approximately equal to -3000 pC/N and comparable k(32) and K(T) values. In comparison with melt-grown PMNPT single crystals, flux-grown PZN-PT single crystals show good compositional homogeneity, superior and consistent dielectric and electromechanical properties, and higher depolarization temperatures (TDP).     

铌镁酸铋-钛酸铅压电陶瓷准同型相界附近的性能和相变温度研究

利用传统固相烧结法制备了Bi(Mg_2/3Nb_1/3)O₃-PbTiO₃(BMN-PT)压电陶瓷, 分析了不同PbTiO₃含量对BMN-PT压电陶瓷的晶体结构、介电、压电及铁电性能的影响. XRD结果表明: 合成的BMN-PT陶瓷具有纯钙钛矿结构, 并且在PbTiO₃含量为x=0.60时, 其组分的XRD图谱在衍射角2θ=45°出现明显的分峰, 说明该组分相结构中存在三方和四方相的共存. 压电铁电性能显示, BMN-0.60PT有最大的压电常数d₃₃(~170pC/N)和平面机电耦合系数k_p(0.35), 最小的矫顽场E_c(29.4 kV/cm)及最大的剩余极化P_r(31.4 μC/cm²). 确定了BMN-PT压电陶瓷的准同型相界(MPB)为PbTiO₃含量x=0.60的组分. 介电系数温谱表明介电系数峰值温度(Tm)随着PbTiO₃含量的增大而升高, MPB组分的Tm约为276℃.     

PMN-PT驰豫铁电单晶及其超声换能器性能研究

测试了PMN－PT（67／33）切型铁电单晶的机电性能,分析了该晶体与常用压电材料在微观结构和机电性能上差异。对该压电单晶未调末调制下纵向长度伸缩振动模超声换能器性能进行了理论分析。讨论了压电单晶的机械和介电损耗对超声换能器性能的规律。     

BaZrO3掺杂对(K0.49Na0.51)0.98Li0.02(Nb0.77Ta0.18Sb0.05)O3无铅压电陶瓷的结构与电性能的影响

采用固相反应法制备了(K_0.49Na_0.51)_0.98Li_0.02(Nb_0.77Ta_0.18Sb_0.05)O₃-xBaZrO₃ (NKNLST-xBZ, x = 0~0.020 mol)无铅压电陶瓷, 系统研究了BaZrO₃的掺杂量对陶瓷的压电、介电、机电和铁电性能的影响。结果表明: 随着BaZrO₃掺杂量x的增加, 陶瓷的晶体结构由正交相向四方相转变, 在x=0.005~0.008区间出现正交相与四方相两相共存的区域, 在此区域内陶瓷的晶粒变得细小且均匀, 介电损耗tanδ大幅降低, 压电常数d₃₃和平面机电耦合系数k_p增加。该体系陶瓷的介电常数ε T 33 /ε0则随着BaZrO₃的增加持续增加, 相变温度则向低温方向移动。当x=0.005时, 该组成陶瓷具有最佳的综合性能: 压电常数d33=372 pC/N, 平面机电耦合系数kp=47.2%, 介电损耗tanδ=3.1%, 以及较高的介电常数ε^T₃₃ /ε₀=1470和居里温度T_c=208℃。     

Phase-transition temperatures and piezoelectric properties of (Bi1/2Na1/2)TiO3-(Bi1/2Li1/2)TiO3-(Bi1/2K1/2)TiO3 lead-free ferroelectric ceramics.

The phase-transition temperatures and piezoelectric properties of x(Bi(1/2)Na(1/2))TiO3-y(Bi(1/2)Li(1/2))TiO3-z(Bi(1/2)K(1/2))TiO3 [x + y + z = 1] (abbreviated as BNLKT100(y)-100(z)) ceramics were investigated. These ceramics were prepared using a conventional ceramic fabrication process. The phase-transition temperatures such as depolarization temperatures T(d), rhombohedraltetragonal phase transition temperature T(R-T), and dielectric-maximum temperature T(m) were determined using electrical measurements such as dielectric and piezoelectric properties. The X-ray powder diffraction patterns of BNLKT100(y)-100(z)) show the morphotropic phase boundary (MPB) between rhombohedral and tetragonal at approximately z = 0.20, and the piezoelectric properties show the maximum at the MPB. The electromechanical coupling factor k(33), piezoelectric constant d(33) and T(d) of BNLKT4-20 and BNLKT8-20 were 0.603, 176 pC/N, and 171 degrees C, and 0.590, 190 pC/N, and 115 degrees C, respectively. In addition, the relationship between d33 and Td of tetragonal side and rhombohedral side for BNLKT4-100z and BNLKT8-100z were presented. Considering both high Td and high d(33), the tetragonal side of BNLKT4-100z is thought to be the superior composition. The d(33) and T(d) of BNLKT4-28 were 135 pC/N and 218 degrees C, respectively. Moreover, this study revealed that the variation of T(d) is related to the variation of lattice distortion such as rhombohedrality 90-alpha and tetragonality c/a.     

弛豫型铁电体在准同型相界的压电性能

ＰＭＮ、ＰＺＮ、ＰＮＮ 等弛豫型铁电体与ＰＴ 形成的固溶体在准同型相界附近具有良好的压电性能。在ＰＭＮ、ＰＺＮ 的单晶材料中,ｋｐ 高达９２ ％ ,ｄ３３ 达到１５００ｐＣ／ Ｎ, 在以ＰＭＮ、ＰＺＮ、ＰＮＮ 为基的陶瓷材料中,ｄ３３ 分别达到６９０ｐＣ／ Ｎ、６８０ｐＣ／Ｎ 和５４０ｐＣ／ Ｎ,Ｑｍ 在１００ 左右。这类材料的共同特点是机电耦合系数和压电系数较大,而品质因数较小,在压电换能器和致动器领域具有很好的应用前景。     

Dielectric and electromechanical properties of barium titanate single crystals grown by templated grain growth

Single crystals of BaTiO(3) were grown by templated grain growth (TGG). TGG involves contacting a single crystal "template" to a sintered polycrystalline matrix, then heating the assemblage to a temperature that promotes the migration of the single crystal boundary through the matrix. In this investigation the properties of millimeter-sized, plate-shaped and bar-shaped, single crystals of BaTiO(3) grown by TGG were examined in order to compare the results to single crystals grown by conventional methods. A dielectric constant, epsilon(33)(T)/epsilon(0), of 260, polarizations of P(R)~16 muC/cm(2) and P(sat)~21.5 muC/cm(2), electromechanical coupling coefficients of k(33)~0.51 and k(31)~0.18, and a piezoelectric coefficient of d(33)~140 pC/N were achieved. Entrapped porosity in the crystals made fully poling the crystals difficult.     

Intrinsic polarization and resistive leakage analyses in high performance piezo-/pyroelectric Ho-doped 0.64PMN-0.36PT binary ceramic

This paper presents in detail the ferroelectric properties of Ho-doped 0.64Pb(Mg_1/3Nb_2/3)O₃-0.36PbTiO₃ ceramic including determination of intrinsic polarization and investigation of resistive leakage. The effect of Ho³⁺ doping on the structure, dielectric, piezoelectric and ferroelectric properties of PMN-PT ceramics was studied. Perovskite phase of pure and Ho-doped 0.64Pb(Mg_1/3Nb_2/3)O₃-0.36PbTiO₃ ceramics were synthesized using solid state reaction method. Powder XRD confirmed the incorporation of Ho³⁺ ions in PMN-PT lattice. EDX spectra confirmed the existence of Ho and its homogeneity in doped-sample. The average grain size, transition temperature and dielectric loss factor (tan δ) decreased while the density and the dielectric constant of the PMN-PT ceramic increased by Ho doping. Furthermore, an increase in the ferroelectric properties and the piezoelectric coefficient (d₃₃¹, from 547 to 610?pm/V) were observed for doped sample. The ‘Remanent Hysteresis Task’ revealed that a major portion (80.42%) of the remanent polarization (P_r) is switchable in the sample which makes Ho-doped PMN-PT a potential material for memory switching devices. Time-dependent compensated (TDC) hysteresis task and fatigue test were carried out which revealed resistive leakage and fatigue free nature of Ho-doped PMN-PT ceramic. These results demonstrate that Ho-doped PMN-PT ceramic possesses excellent properties to achieve a variety of applications.