离子对(Nb5+-Cr3+)掺杂对0.93Bi0.5Na0.5TiO3-0.07BaTiO3陶瓷微观结构和电学性能的影响

采用固相烧结法制备(Bi_0.5Na_0.5)_0.93Ba_0.07Ti_1-x(Nb_0.5Cr_0.5)_xO₃(摩尔分数x=0%、0.5%、1%、2%、2.5%、5%)(简称BNBT-xNC)无铅压电陶瓷,研究离子对(Nb⁵⁺-Cr³⁺)对0.93Bi_0.5Na_0.5TiO₃-0.07BaTiO₃(简称BNT-7BT)陶瓷微观结构、介电、铁电和应变性能的影响。结果表明,所有组分为伪立方相。随着离子对(Nb⁵⁺-Cr³⁺)含量增加,BNBT-xNC陶瓷的铁电弛豫特性明显改变,在较低掺杂浓度下(0%≤x≤1%)为非遍历弛豫态,随含量增加(1%≤x≤2%),出现非遍历-遍历弛豫态共存,最后转变为遍历弛豫态(2.5%≤x≤5%);陶瓷从铁电态向弛豫态转变,应变性能先增加后降低,最大应变S_max和逆压电常数d^*₃₃在x=2%时达到最大,分别为0.22%和431 pm/V。     

Co、Sm共掺杂PZN-PZT压电陶瓷的低温烧结与电性能研究

试验采用传统固相法，成功制备出Co、Sm共掺杂的Pb_0.95Ba_0.05(Zn_1/3Nb_2/3)_0.2(Zr_0.52Ti_0.48)_0.8O₃+0.6mol%Co₂O₃+0.04mol%Sm₂O₃三元系压电陶瓷。研究分析了不同烧成温度下PZN-PZT压电陶瓷材料的压电性能、介电性能、相组成及其微观结构。结果显示，Co、Sm共掺杂不仅改善了PZN-PZT的压电、介电综合性能：d₃₃=301 p C/N,K_p=0.72,ε_r=1486.46,tanδ=0.11%,Q_m=515，而且将材料的烧成温度降低到950℃。     

Sm掺杂Pb(Mg1/3Nb2/3)O3-PZT压电陶瓷的研究

本文通过一步反应合成法制备了铌镁-锆钛酸铅(Pb(Mg_1/3Nb_2/3)O₃-Pb(Zr,Ti)O₃,PMN-PZT)压电陶瓷,研究了稀土元素钐(Sm)掺杂对PMN-PZT(x%(摩尔分数)Sm-PMN-PZT)结构与电学性能的影响规律,得到了具有高压电性、高机电耦合系数和高居里温度的压电陶瓷。当x=2.0时,压电常数d₃₃=611 pC/N,机电耦合系数k_p=0.68,介电损耗tan δ=1.65%,相对介电常数ε_r=2 650,居里温度T_C=283 ℃。测试压电陶瓷电致应变性能,在3 kV/mm下单极电致应变达到0.20%,显示出其大应变材料的特征。结果表明,Sm掺杂PMN-PZT压电陶瓷具有优异的综合电学性能,有望在换能器、传感器以及致动器等领域广泛应用。     

富铈Ce1-xLaxO2催化甲烷氧氯化性能

以硝酸铈、硝酸镧为前体,用氨水共沉淀法制备了一系列Ce_1-xLa_xO₂(x≤0.5)催化剂,利用XRD、N₂吸附-脱附、SEM、Raman、H₂-TPR和OSC对催化剂的物理化学性质进行了表征,并考察其在甲烷氧氯化反应中的催化性能。结果表明:Ce_1-xLa_xO₂催化剂的氧化还原性质随着镧含量的变化发生显著改变,并且这一性质的变化与反应的转化率及产物分布具有较强的联系。Ce_1-xLa_xO₂表面氧物种的活泼性对催化剂活性影响显著,而体相氧物种容易将生成的甲烷氯化物深度氧化。在Ce_1-xLa_xO₂(x<0.3)催化剂上表面氧物种起主导作用,氯甲烷为主要反应产物,Ce_0.8La_0.2O₂催化剂上氯甲烷选择性最高为52%。在体相氧物种更活泼的Ce_0.7La_0.3O₂和Ce_0.5La_0.5O₂上产物中CO的选择性显著上升,Ce_0.5La_0.5O₂催化剂上CO选择性高达48%。稳定性测试表明Ce_0.8La_0.2O₂催化剂具有良好的稳定性。     

(Pb0.97La0.02)(Zr0.6Sn0.4)O3反铁电陶瓷的介电储能性能

电介质电容器具有超高的功率密度和超快的充放电速率,因而在脉冲功率技术中具有应用前景。利用固相法制备了(Pb_0.97La_0.02)(Zr_0.6Sn_0.4)O₃(PLZS)反铁电陶瓷,研究了不同烧结温度下PLZS陶瓷的晶体结构、微观形貌、介电性能、反铁电及储能性能。结果表明,不同温度烧结的样品均具有正交钙钛矿结构,且随着烧结温度的升高,陶瓷的致密度逐渐提高、晶粒尺寸也逐渐增大。因此,最佳温度下(1 225℃)烧结的陶瓷具有最佳的储能性能,可回收能量密度密度约13.3 J/cm³,储能效率约83.6%。     

铈掺杂PZN-PZT三元系压电陶瓷的烧结特性研究

采用传统的固相反应法制备了掺杂0.2 wt.%CeO₂的0.3Pb(Zn_1/3Nb_2/3)O₃-0.7Pb(Zr_0.52Ti_0.48)O₃(0.3PZN-0.7PZT-0.2Ce)三元系压电陶瓷,并研究了烧结温度(1190～1260℃)对其相结构、微观形貌以及电学性能的影响。XRD和SEM分析发现:所有烧结样品均呈纯的钙钛矿相结构,随着烧结温度的升高,陶瓷样品的相结构从三方相逐渐转变为四方相,1230℃烧结得到的样品由三方相和四方相共存;当烧结温度高于1230℃过后,晶粒开始显著长大,直至液相始出现。介电温谱研究证实:随着烧结温度的升高,0.3PZN-0.7PZT-0.2Ce陶瓷的居里温度(Tc)逐渐升高而介电损耗因子(tan δ)逐渐降低,1230℃烧结得到的样品介电常数(ε_r)最大而温度系数(TK_ε)最小。压电性能以及谐振-反谐振测试表明:提高烧结温度有助于提升陶瓷的压电性能(d     

ZnO-B2O3玻璃对Li2Zn3Ti4O12-CaTiO3复合陶瓷低温烧结及性能的影响

采用传统固相反应法制备0.94Li₂Zn₃Ti₄O₁₂-0.06CaTiO₃(LZT-CT)复合陶瓷,采用高温熔融法制备ZnO-B₂O₃(ZB)玻璃;以ZB玻璃为烧结助剂,研究了添加不同质量分数(x=0.5%、1.0%、1.5%、2.0%和2.5%)的ZB玻璃对LZT-CT复合陶瓷的烧结特性、物相组成、微观结构以及微波介电性能的影响。结果表明:ZB玻璃能有效地将LZT-CT复合陶瓷的烧结温度从1 175 ℃降低到875 ℃,并促进了LZT-CT复合陶瓷的致密化。当ZB玻璃掺量x≤2.5%时,LZT-CT复合陶瓷中除了LZT、CT相,没有出现其他新相。随着ZB玻璃添加量增加,复合陶瓷的体积密度、介电常数(ε_r)、品质因数(Q×f)均先增加后减小,谐振频率温度系数(τ_f)变化不大,在(-2.25~4.51)×10^-6/℃波动。当ZB玻璃掺量为2.0%时,LZT-CT复合陶瓷在875 ℃烧结2 h,获得最大体积密度(4.22 g/cm³)以及优异的微波介电性能,ε_r=23.9,Q×f=58 595 GHz,τ_f=-0.14×10^-6/℃。     

Sm掺杂PMN–PT弛豫铁电陶瓷的大信号径向谐振响应

弛豫铁电材料因具有高的介电常数和压电系数而广泛应用于致动器、换能器等领域。实际使用中往往需要施加大信号激励驱动谐振，因此了解掌握大信号激励下的谐振特性变化极为重要。然而，目前这方面的研究却少有文献报道。针对这一问题，以二步氧化物固相反应法制备了高压电性Pb_0.9625Sm_0.025[(Mg_1/3Nb_2/3)_0.71Ti_0.29]O₃陶瓷材料，用本人搭建的大信号谐振响应测试系统研究了驱动场幅值和温度对径向谐振特性的影响。结果表明：低驱动场下谐振响应能保持单一谐振峰直至完全退极化，但随着驱动场的增大谐振响应变得复杂，即使在低温也呈现多个谐振峰。谐振特性的变化与机械品质因子Q_m、铁电宏畴尺寸及相组成密切相关，低Q_m材料在大驱动场下产生的内热加速了宏畴裂解并引发了二级铁电相变。谐振特性的不稳定及较大谐振频率温度系数限制了Sm改性PMN–PT弛豫铁电陶瓷的应用，尤其是在大信号下。     

锆锡钛酸镧铅反铁电体陶瓷的低温烧结和储能特性

随着风电、光电等绿色能源的利用和对大功率电力电子装备需求的增加,大功率储能器件受到了广泛的关注,而具有高储能密度和高储能效率的(Pb,La)(Zr,Sn,Ti)O₃ (PLZST)反铁电体陶瓷用于超级介电储能电容器具有明显的优势。但是,受到陶瓷本身高烧结温度(1 200～1 300℃)的限制,难以适应贱金属内电极多层陶瓷电容器的应用。为了适应贱金属铜(Cu)内电极的烧结,将玻璃粉MgO–Al₂O₃–ZnO–B₂O₃–SiO₂(MAZBS)添加到(Pb_0.97La_0.02)(Zr_0.55Sn_0.41Ti_0.04)O₃(PLZST)反铁电体陶瓷中,使烧结温度低于铜内电极的熔点。研究结果表明：当添加了玻璃粉MAZBS的质量分数为0.75%时,PLZST陶瓷在较低的温度(930℃)下可以实现致密烧结,且陶瓷在室温和外加电场300 kV...     

Ba 2+和In 3+共掺杂硅酸镧固体电解质的制备及性能

采用高温固相法制备磷灰石型硅酸镧陶瓷La_9.4Ba_0.6Si_6-xIn_xO_27-δ（x=0,0.1,0.2,0.3,0.4）。采用XRD、SEM和拉曼光谱等测试分析手段表征了La_9.4Ba_0.6Si_6-xIn_xO_27-δ固体电解质掺杂体系的相组成和微观形貌特征;采用交流阻抗谱测试研究了La_9.4Ba_0.6Si_6-xIn_xO_27-δ掺杂体系在不同温度下的电导率变化规律。研究发现,所有La_9.4Ba_0.6Si_6-xIn_xO_27-δ陶瓷试样的结晶度良好且均具有氧基磷灰石结构;仅在La位掺杂Ba ²⁺时,La_9.4Ba_0.6Si₆O_27-δ试样晶粒形貌不规则,In ³⁺掺杂后晶粒呈等轴状均匀生长。各个试样的总电导率与测试温度之间符合Arrhenius关系。In ³⁺最佳掺杂量x为0.2,此时La_9.4Ba_0.6Si_5.8In_0.2O_27-δ陶瓷具有最高的电导率,其电导率（1 073 K）、活化能和指前因子分别为5.08×10 ^-3 S/cm、0.86 eV和2.91×10 ¹¹ S·K/cm。     

Dielectric, Ferroelectric and Piezoelectric Studies of PMN Modified PLZT Ceramics

Dielectric, ferroelectric and piezoelectric properties of xPb(Mg_1/3Nb_2/3)O₃-(1-x)(Pb_0.988 La_0.012)(Zr_0.535Ti_0.465)O₃ ceramic system synthesized through columbite precursor method are investigated. X-ray diffraction patterns of ceramics indicated pseudocubic phase formation with pyrochlore phase. Grain growth (4.47 μ m) and apparent density (7.68 gm/cm³) enhanced remarkably in 0.8PMN-0.2PLZT composition, respectively. Increasing PMN content remarkably increased both room temperature dielectric permittivity (ε_RT = 2316) and dielectric maximum (ε_Tc = 24747) in 0.6PMN-0.4PLZT composition, respectively. PMN substitution in PLZT system enhanced the ferroelectric remanent (P_r = 28.4 μ C/cm²) and spontaneous (P_s = 31.2 μ C/cm²) polarization while coercive field (E_c) continuously decreased in xPMN-(1-x)PLZT system. PMN modification in PLZT system influenced piezoelectric properties (d₃₃, k_p and k_t) throughout the PMN-PLZT system.     

Effect of Microstructure on Ferroelectric and Piezoelectric Properties of A-Site and B-Site Modified PLZT

Ba modified (Pb,La,Ag)(Zr,Ti)O₃ ceramics synthesized by conventional mixed-oxide method with chemical formula [Pb_{0.983 - z}La_0.012Ag_0.005Ba_z] [(Zr_0.52Ti_0.48)_0.99825]O₃ were investigated for ferroelectric and piezoelectric properties. XRD studies indicate that increment of Ba concentration resulted in strong tetragonality in the ceramics. Grain growth (3.08 μ m) inhibited and apparent density (7.54 gm/cm³) enhanced up to 1.5 mole% Ba respectively. As Ba content increased dielectric properties showed maximum values (ε_RT = 2347, ε_Tc = 23449) while T_c constantly decreased. The remanent (P_r = 34.72 μ C/cm²) and spontaneous polarization (P_s = 41.84 μ C/cm²) were optimum in 1 mole% Ba respectively while E_c showed increasing trend throughout the series. Piezoelectric properties attained maximum values of d₃₃ = 438 pC/N in 1.5 mole% Ba while k_p = 0.533 and k_t = 0.412 in 1 mole% Ba doped (Pb,La,Ag)(Zr,Ti)O₃ ceramics respectively.     

Microwave dielectric characteristics of ceramics in Mg2SiO4–Zn2SiO4 system

(Mg_1−xZn_x)₂SiO₄ ceramics were prepared and characterized. The densification temperatures of the present ceramics are much lower than those for Mg₂SiO₄ and Zn₂SiO₄ end-members. Small solid solution limits of Zn in Mg₂SiO₄ and Mg in Zn₂SiO₄ are observed, and the bi-phase structure is confirmed in (Mg_1−xZn_x)₂SiO₄ ceramics with x = 0.1–0.9. Even though, it is clear that the Qf value of Zn₂SiO₄ ceramics can be significantly improved together with a suppressed temperature coefficient of resonant frequency τ_f by substituting Mg for Zn. (Mg_0.4Zn_0.6)₂SiO₄ ceramics indicate a good combination of microwave dielectric characteristics: _r = 6.6 Qf = 95,650 GHz, and τ_f = −60 ppm/°C.     

Synthesis, sintering and characterization of PNZST ceramics from high-energy ball milling process

Pb_0.99Nb_0.02[(Zr_0.60Sn_0.40)_0.94Ti_0.06]_0.98O₃ powders were synthesized from oxide mixtures of Pb₃O₄, Nb₂O_5, ZrO₂, SnO_2, and TiO₂ using a Fritsch P4™ vario-planetary ball milling system. The perovskite structure of PNZST powder can be obtained well after 14 h milling and crystallite size of the powders greatly reduced to 20–30 nm. The resultant powders have better sinterability characteristics to obtain dense ceramic bodies at low temperature. The dielectric constant of samples shows a maximum at 1150 °C and the PE_MC to PE_SC transformation temperature shifts to higher temperature with an increase in grain size. The field-induced strain reaches maximum longitudinal strain of 0.32% and the P–E hysteresis loop shows much higher squareness at 1150 and 1200 °C. The measured dielectric and antiferroelectric properties of the PNZST ceramics were found to be comparable to those from other processing techniques.     

0.06BiYbO3-0.94Pb(Zr0.48Ti0.52)O3三元系压电陶瓷的氧化物掺杂改性研究

针对新一代声波测井仪器对其核心元件压电陶瓷兼具高居里温度、高压电系数以及高稳定性要求的迫切需求,本文采用传统的固相反应-无压烧结技术制备了一种0.06BiYbO₃-0.94Pb(Zr_0.48Ti_0.52)O₃(BY-PZT)三元系压电陶瓷,并研究了四种氧化物掺杂对其微观结构及电学性能的影响。由XRD和SEM表征可知所有样品均呈纯四方相钙钛矿结构,掺杂Cr₂O₃的样品平均晶粒尺寸最大。介电温谱和谐振频谱研究证实四种氧化物掺杂均能提高其介电性能的温度稳定性。掺杂La₂O₃的样品介电常数温度系数(Tk_ε)最低,掺杂MnO₂的样品机械品质因素(Q_m)最高,而掺杂CeO₂的样品抗热退极化性能最好。高温复阻抗(Cole-Cole图)分析表明,Cr₂O₃掺杂能够显著提高BY-PZT陶瓷的高温电阻率,陶瓷在高温下的电导行为主要由晶界响应控制。综合来看,掺杂La₂O₃的样品兼具高居里温度(T_C=397 ℃)和高压电系数(d₃₃=290 pC/N),并且在300 ℃退火4 h后d₃₃仍能保持在270 pC/N左右,有望在极限工作温度为300 ℃的高温压电器件中获得应用。     

Phase transitions and domain structures in relaxor-based ferroelectric (PbZn1/3Nb2/3O3)0.915(PbTiO3)0.085 single crystal

Polarization-electric field (P-E) hysteresis loops and domain structures have been measured as a function of temperature in relaxor-based ferroelectric single crystal (PbZn_1/3Nb_2/3O₃)_0.915(PbTiO₃)_0.085 (PZN-8.5%PT). In order of increasing temperature, PZN-8.5%PT undergoes successive phase transitions: rhombohedra1 phase (below ∼375 K) → coexistence of rhombohedral and tetragonal phases (between ∼375 and ∼390 K) → tetragonal phase (between ∼390 and ∼420 K) → coexistence of tetragonal and cubic phases (between ∼420 and ∼460 K) → cubic phase (above ∼460 K). Phase coexistence suggests an inhomogeneous distribution of Ti⁴⁺ concentration in the PZN-8.5%PT crystal.