钛酸铋钠基无铅铁电陶瓷场致应变性能研究

钛酸铋钠(Bi_0.5Na_0.5)TiO₃(BNT)作为典型的钙钛矿型弛豫铁电体, 具有超高的场致应变, 是最有希望代替铅基体系的无铅压电体系之一。与铅基陶瓷相比, BNT基陶瓷具有驱动电压较高、迟滞较大以及温度稳定性差等劣势。为了优化无铅驱动器的应变性能, 本研究采用固相反应法制备(1-x){0.76(Bi_0.5Na_0.5)TiO₃-0.24SrTiO₃}-xNaNbO₃(BNT- ST-xNN, x=0~0.03)无铅铁电陶瓷。结果表明, 当x=0.01时, 该陶瓷在较低电场(E=4 kV/mm)下的应变值可达到0.278%, 等效压电系数d^*₃₃高达695 pm/V。此时, 陶瓷处于非遍历/遍历弛豫相界处, 电场诱导弛豫-铁电相变导致大场致应变。与x=0.01相比, x=0.02时应变值为0.249%, 略微下降, 但迟滞却降低至43%。此外, 该应变在25~100 ℃温度范围内维持稳定。本研究表明, 在BNT基陶瓷中固溶SrTiO₃和NaNbO₃组元可以提高场致应变值, 同时维持较低的驱动电场和良好的温度稳定性, 可用于压电驱动器研制。     

LiF掺杂对BiFeO3-BaTiO3陶瓷结构、铁电和压电性能的影响

采用固相反应法制备0.7BiFeO₃-0.3BaTiO₃+0.35%(摩尔分数，下同)MnO₂+x%LiF(BF-BT-MN-xLF)压电陶瓷。采用XRD,SEM,铁电测试系统和精密阻抗分析仪测试陶瓷的物相组成、显微结构和铁电、压电性能。结果表明：LiF掺杂加强晶格畸变，促进烧结和晶粒生长，改善压电性能的温度稳定性。Li⁺和F^-不等价取代A/B位产生的复合缺陷偶极子，转向速度滞后于外加电场的变化，导致电滞回线呈现夹持现象。同时，对BF-BT-MN-xLF陶瓷的退极化行为以及居里温度变化的研究表明，LiF掺杂显著提高陶瓷的居里温度T_c和退极化温度T_d,T_c和T_d分别由500℃和410℃(x=0)升高到550℃和505℃(x=0.50)。当LiF掺杂量为0.50%时，在860～1020℃温度范围内烧结的陶瓷始终保持较高的压电系数，d₃₃=176～202 pC/N。x=0.5...     

(Ba0.85Ca0.15)(Ti0.9Zr0.1-xSnx)O3无铅压电陶瓷的相结构与压电性能

钙锆共掺钛酸钡陶瓷(BCZT)具有优异的介电性能和压电性能, 是一类具有发展潜力的无铅压电陶瓷, 但其压电性能仍无法与铅基陶瓷媲美。为提高压电性能, 本研究对陶瓷材料进行Sn元素掺杂改性((Ba_0.85Ca_0.15)- (Ti_0.9Zr_0.1-xSn_x)O₃, x=0.02~0.07))。晶体结构分析证实所有组分的陶瓷无杂相, 处于正交相与四方相两相共存状态, 并具有较大的c/a; 显微结构分析发现所有陶瓷都很致密, 且平均晶粒尺寸随着Sn含量的增加而增大。当x=0.04时, 陶瓷最致密, 且室温处于准同型相界附近, 因此拥有最佳的电学性能: d₃₃=590 pC•N ^-1, k_p=52.2%, tanδ=0.016, ε ^T₃₃=5372, d ^*₃₃=734 pm•V ^-1, IR=57.8 GΩ•cm。本研究表明: Sn掺杂的BCZT基无铅压电陶瓷具有优异的压电性能, 有望在换能器、机电传感器和驱动器等方面得到应用。     

A/B位双取代钛酸铋钠基压电陶瓷性能研究

采用固相烧结方法制备了Bi、Co同时取代化学计量比钛酸铋钠基(Bi_0.5+x/2Na_0.5-x/2)_0.94Ba_0.06Ti_1-xCo_xO₃无铅压电陶瓷, 研究了材料中A/B位缺陷对其电滞回线和电致应变的影响。结果表明陶瓷具有均一的赝立方结构, 随着掺杂量的增加, 材料铁电-弛豫相转变温度降低, 应变增加。同时材料在疲劳过程中伴随着弛豫相的增多, 在较低电场下产生较大的应变(0.458%), 逆压电常数d₃₃^*达到770 pm/V。介电温谱和电滞回线上反常变化与化学计量比陶瓷中产生的A/B位缺陷偶极子密切相关, 并表明这种缺陷偶极子是以氧空位为媒介形成的。     

Bi过量以及冷却方式对BiFeO3-BaTiO3陶瓷的相结构及电学性能的影响

采用传统固相烧结法制备了0.7BiFeO₃-0.3BaTiO₃-xBi₂O₃(0≤x≤0.05)无铅压电陶瓷, 研究了Bi补偿量x和冷却方式对其相结构、微观形貌和综合电学性能的影响。结果表明：所有样品均为菱方相(R)和伪立方相(PC)两相共存, 0≤x≤0.01样品为纯的钙钛矿结构, 且x=0.01样品的两相比例C_R/C_PC接近1; x>0.01样品中出现富Bi杂相Bi₂₅FeO₄₀。与冷却方式相比, 优化Bi补偿量更有利于提升BFBT-xBi₂O₃陶瓷的压电性能。随着x增大, d₃₃先增大后减小, 在x=0.01时获得最优值。由于较小的晶粒、较合适的C_R/C_PC以及较大的残余应变, 水冷BFBT-0.01Bi₂O₃陶瓷获得了最优的压电性能(d_33水冷=141 pC/N、k_p=27%)和高T_C=507℃。研究结果表明, BFBT基陶瓷有希望成为兼具高压电性能和高T_C的无铅压电材料体系之一。     

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℃。     

0.94Na1/2Bi1/2TiO3-0.06BaTiO3:TiO2无铅复合陶瓷的结构及退极化温度研究

采用固相法将纳米TiO₂引入0.94Na_1/2Bi_1/2TiO₃-0.06BaTiO₃ (简称NBT-6BT)钙钛矿结构压电陶瓷晶界中, 成功制备出NBT-6BT: xTiO₂ (x=0, 0.05, 0.1, 0.2, 0.3) 0-3型复合结构陶瓷, 并系统地研究了掺杂TiO₂对陶瓷的结构及压电性能的影响。实验结果表明, 部分TiO₂进入晶格内部造成陶瓷单斜相Cc含量减少, 晶体对称性提高; 随着TiO₂的掺杂量的增加, 明显提高了NBT-6BT陶瓷的退极化温度。对NBT-6BT:0.1TiO₂样品, 在保持一定压电常数(69 pC/N)的前提下, 陶瓷的退极化温度相比纯NBT-6BT提升约88%, 此时介电损耗tanδ=0.044, 表明该材料是一种适用于更高温区间的新型无铅压电材料。     

(Bi0.5Na0.5)0.935Ba0.065TiO3-xBiScO3陶瓷储能及应变性能研究

本研究采用BiScO₃组分对固相烧结工艺制备的(1-x)(Bi_0.5Na_0.5)_0.935Ba_0.065TiO₃-xBiScO₃(BNBT-xBS)无铅陶瓷进行改性, 考察了BiScO₃掺杂含量对陶瓷的微观结构、储能、场致应变和介电等性能的影响。结果表明: 随着BiScO₃掺杂含量的增加, BNBT-xBS陶瓷的相结构由三方相与四方相共存演变为伪立方相, 无杂相形成, 且平均晶粒尺寸略有增大; BiScO₃组分的引入破坏了BNBT陶瓷铁电畴的长程有序, 表现出弱极化, 且伴随有铁电相到弛豫铁电相的相变过程。BiScO₃组分提高了储能和应变性能, 在70 kV/cm电场下其最大储能密度为0.46 J/cm³, 电致应变达到0.25%。介电常数随着掺杂含量的增加逐渐降低, 其介电行为也表明陶瓷具有弛豫铁电体特征; BNBT-xBS陶瓷表现出负温度系数效应, 且在450℃以下具有较好的绝缘性。     

CaxSr1-xBi2Nb2O9无铅压电陶瓷制备及其高温稳定性研究

采用传统固相法制备了Ca_xSr_1-xBi₂Nb₂O₉ (x=0、0.10、0.25、0.40)无铅压电陶瓷, 研究了Ca²⁺掺杂量对其微观结构、电学性能及其高温稳定性的影响。掺入Ca²⁺并未改变SrBi₂Nb₂O₉陶瓷的晶体结构; 随着Ca²⁺掺杂量的增加, 陶瓷晶粒由片状向长条状转变; 陶瓷的矫顽场(E_c)下降, 剩余极化强度(P_r)先增大后减小; 陶瓷的居里温度由450℃升高到672℃。当x=0.10时, 陶瓷具有较好的综合性能: 2P_r=14.8 μC/cm², d₃₃=22 pC/N, T_c=488℃; 当退火温度达到400℃时, 压电常数d₃₃仍达到20 pC/N, 说明该材料具有较好的温度稳定性, 可以在400℃的高温环境中应用。     

(0.96NaNbO3-0.04CaZrO3)-xFe2O3反铁电陶瓷的介电及储能性能研究

0.96NaNbO₃-0.04CaZrO₃(简称NNCZ)陶瓷在室温下展现出稳定的双电滞回线, 但是其储能密度、储能效率和击穿强度都比较低, 限制其成为储能材料。本工作通过掺杂Fe₂O₃, 利用Fe ³⁺离子变价的特点, 实现NNCZ储能性能的优化。采用传统固相法制备了(0.96NaNbO₃-0.04CaZrO₃)-xFe₂O₃(简称NNCZ-xFe)反铁电储能陶瓷, 并对样品的相结构、微观形貌、电学性能和储能性能进行了表征, 重点研究了Fe₂O₃掺杂量对NNCZ陶瓷介电和储能性能的影响规律。结果表明, 样品均具有单一的钙钛矿结构, 掺杂Fe₂O₃能明显降低NNCZ陶瓷的烧结温度, 晶粒平均尺寸随着掺杂量增大先减小后增大, 掺杂量x=0.02时, 晶粒平均尺寸最小(5.04 mm), 且具有较好的储能性能。室温下, NNCZ-0.02Fe击穿强度为230 kV/cm, 击穿前的有效储能密度和储能效率分别为1.57 J/cm ³和55.74%。在125 ℃和外加电场为180 kV/cm下, NNCZ-0.02Fe的储能密度为4.53 J/cm ³。掺杂Fe₂O₃使NNCZ陶瓷的烧成温度降低, 氧空位的迁移速率下降, 抑制晶粒的长大, 同时降低了介电损耗, 使得击穿强度增加; 适量氧空位钉扎使得反铁电相向铁电相相翻转变得困难, 避免出现哑铃状双电滞回线, 从而提高储能效率。本研究结果表明NNCZ-xFe在电介质储能领域具有潜在应用价值。     

Piezoelectric and dielectric properties of PZT–PZN–PMS ceramics prepared by molten salt synthesis method

Piezoelectric powders and ceramics with the composition of Pb_0.95Sr_0.05(Zr_0.52Ti_0.48)O₃–Pb(Zn_1/3Nb_2/3)O₃–Pb(Mn_1/3Sb_2/3)O₃ (PZT–PZN–PMS) were prepared by molten salt synthesis (MSS) and conventional mixed-oxide (CMO) methods, respectively. The influence of synthesis process on the properties of powders and ceramics were investigated in detail. The results show that the MSS method significantly improved the sinterability of PZT–PZN–PMS ceramics, resulting in an improvement of dielectric and piezoelectric properties compared to the CMO method. The optimum values of MSS samples are as follows: _r = 1773; tan δ = 0.0040; T_c = 280 °C; d₃₃ = 455 pC/N; k_p = 0.70; Q_m = 888; E_c = 10.3 kV/cm; and P_r = 28.2 μC/cm², at calcination of 800 °C and sintering of 1120 °C temperature.     

PLZST陶瓷衬底上La0.7Sr0.3MnO3薄膜生长及其磁性能和电输运特性研究

采用磁控溅射法在PLZST陶瓷衬底上制备了不同厚度的LSMO薄膜, 并对其微结构、磁性能及电输运特性进行了研究。结果表明, LSMO薄膜具有单一钙钛矿结构, 晶粒均匀, 表面平整, 其中20 nm厚LSMO薄膜粗糙度仅为2.93 nm。在10~300 K温度范围内, LSMO薄膜均具有大的磁电阻效应, 20 nm厚的LSMO薄膜磁电阻温度稳定性优异。随着薄膜厚度的增加, 薄膜的居里温度、金属绝缘体转变温度、磁化强度和导电性能降低。这可能是由于Pb、Sn、Zr等离子扩散进入LSMO薄膜中, 导致MnO₆八面体畸变造成的。     

Contribution to the comprehension of dissipation phenomena in lead zirconate titanate: aliovalent doping effect

By the solid reaction method, undoped, potassium doped and niobium doped lead zirconate titanate (PZT) are elaborated. The mechanical losses measured in the range of the Hz as a function of temperature shows two peaks R₁ and R₂, and a ferroelectric transition peak P₁ between ferroelectric and para-electric states on the undoped PZT—Pb(Zr_0.54Ti_0.46)O₃—noted PZT54/46. Potassium doped PZT—Pb_1−xK_x(Zr_0.54Ti_0.46)O₃—shortly called PKZT 100x/54/46 shows an increase in the height of both the peaks at a doping content, x, less than 0.5 at.% but an opposite effect is observed above this value. Niobium doped PZT—Pb[(Zr_0.54Ti_0.46)_1−yNb_y]O₃—shortly called PNZT 100y/54/46, shows the vanish of the R₂ peak and the decrease of the height of the R₁ peak when the doping content increases.     

Dielectric Properties of Ba0.6Sr0.4TiO3-La(B0.5Ti0.5)O3 (B=Mg, Zn) Ceramics

Ba_0.6Sr_0.4TiO₃-La(B_0.5Ti_0.5)O₃ (B = Mg, Zn) ceramics were prepared by a solid-state reaction method, and their microwave dielectric characteristics and tunability were investigated. The ferroelectric-dielectric solid solutions with cubic perovskite structures were obtained for compositions of 10 to 60 mol% La(Mg_0.5Ti_0.5)O₃ and 10 to 50 mol% La(Zn_0.5Ti_0.5)O₃. With the increase of linear oxide dielectric content, the dielectric constant and tunability were decreased and Qf was increased. Ba_0.6Sr_0.4TiO₃-La(Mg_0.5Ti_0.5)O₃ has better dielectric properties than Ba_0.6Sr_0.4TiO₃-La(Zn_0.5Ti_0.5)O₃. 0.9Ba_0.6Sr_0.4TiO₃-0.1La(Mg_0.5Ti_0.5)O₃ has a dielectric constant ε = 338.2, Qf = 979 GHz and a tunability of was 3.7% at 100 kHz under 1.67 kV/mm. The Qf value of 0.5Ba_0.6Sr_0.4TiO₃- 0.5La(Mg_0.5Ti_0.5)O₃ reached 9367 GHz, but the tunable properties were lost.     

High electrical properties of W-additive Mn-modified PZT–PMS–PZN ceramics for high power piezoelectric transformers

The ceramics were prepared successfully by the addition of WO₃ to the Mn-modified Pb(Zr_0.52Ti_0.48)O₃–Pb(Mn_1/3Sb_2/3)O₃–Pb(Zn_1/3Nb_2/3)O₃ (PZT–PMS–PZN) for high power piezoelectric transformers application. XRD analysis indicated that the ceramics were mainly composed of a tetragonal phase in the range of 0–1.0 wt.% WO₃ addition. The grain size of the ceramics significantly decreased from 10.0 to 2.9 μm by addition of WO₃. Moreover, the addition of WO₃ promoted densification of the ceramics and increased mechanical quality factor (Q_m), planar coupling factor (K_p) and piezoelectric constant (d₃₃) kept high values, whereas, dielectric loss (tan δ) was low. Δf (=f_a − f_r) slightly changed when WO₃ addition was above 0.5 wt.%. The ceramics with 0.6 wt.% WO₃ addition, sintered at 1150 °C showed the optimized piezoelectric and dielectric properties with Q_m of 1852, K_p of 0.58, d₃₃ of 243 pC/N and tan δ of 0.0050. The ceramics are promising candidates for high power piezoelectric transformers application.     

Optical quality inspection of PLZT ceramics by using CGH-element

Optical quality of surfaces of thin PLZT (Pb_0.9La_0.1(Zr_0.65Ti_0.35)O₃) ceramic plates were investigated with a computer-generated hologram. The surfaces of PLZT samples showed fluctuations in local curvature, and wedgeness for all the cases studied.     

高Q值(1-x)(Sr0.2Nd0.208Ca0.488)TiO3-xNd(Ti0.5Mg0.5)O3微波陶瓷的微结构及介电性能研究

采用固相法制备了(1-x)(Sr_0.2Nd_0.208Ca_0.488)TiO₃-xNd(Ti_0.5Mg_0.5)O₃(0.3≤x≤0.4, SNCT-NTMx)系微波介质陶瓷材料, 并研究了该体系的相组成、显微结构、烧结性能和微波介电性能之间的关系。结果表明: 在x = 0.3~0.35范围内, SNCT-NTMx陶瓷形成了正交钙钛矿固溶体, 并伴随有少量未知第二相; 当x增至0.4时, 第二相含量有所增加。介电性能研究结果显示: 随着x的增加, 体系介电常数(ε_r)减小, 但品质因子(Q×f)得到改善; 此外, 体系谐振频率温度系数(τ_f)随NTM含量的增加逐渐向负值方向移动。当x = 0.35, 陶瓷样品在1520℃烧结4 h 得到的微波介电性能较优: ε_r=50.1, Q×f =44910 GHz, τ_f= -1.7×10^-6/℃。     

In situ investigation of thermally influenced phase transformations in (pb0.92sr0.08) (zr0.65ti0.35)o3 thin films using micro-raman spectroscopy and x-ray diffraction

Thin films of ferroelectric strontium-doped lead zirconate titanate [PSZT, (Pb_0.92Sr_0.08)(Zr_0.65Ti_0.35)O₃] deposited by RF magnetron sputtering have been analyzed by in situ analysis techniques. The in situ techniques employed for this study include micro-Raman spectroscopy and X-ray diffraction (XRD), and variations in thin film structure and orientations for temperatures up to 350degC and 750degC for the respective techniques have been studied. The samples analyzed were PSZT thin films deposited on platinum-coated silicon substrates at either room temperature or at 750degC. In situ measurements using micro-Raman spectroscopy and XRD techniques have been used to identify the Curie point for poly-crystalline PSZT thin films and to determine the temperature-activating significant grain growth for room-temperature-deposited PSZT thin films. To study the presence of hysteresis, analysis was carried out during both temperature ramp-up and ramp-down cycles. Raman measurements showed expected bands (albeit weak), and the in situ measurements have detected variations in the crystal structure of the thin film samples, with negligible variations between the heating and cooling cycles. A combination of the Raman and XRD results has shown that the temperature activating significant grain growth for the room-temperature deposited films is about 275degC and the Curie point lies between 325 and 400degC. This relatively high Curie point makes these films suitable for wide temperature range applications.     

The influence of fabrication processing on domain structure and polarization switching in PZN-based ferroelectric ceramics

Lead zinc niobate (Pb(Zn_1/3Nb_2/3)O₃, PZN) based ceramics are prepared by using conventional mixing oxide and complex phase reaction-sintering ceramic techniques. From the results of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), it is clear that these two fabrication processing routes produce different microstructures and ferroelectric domains in the same Pb(Zn_1/3Nb_2/3)O₃–BaTiO₃–Pb(Zr_0.4Ti_0.6)O₃ composition. Furthermore, different phase transitions are observed for the temperature dependence of the dielectric permittivity that can be confirmed by differential scanning calorimetry (DSC). Different polarization switching characteristics are also examined by using high field-induced strain and ferroelectric hysteresis loop. It is suggested that the distribution of the inner stress and domain configuration should be related with the fabrication processing of ferroelectric ceramics.