(K,Na)NbO3基无铅压电陶瓷的研究现状与进展

综述了近年来(K,Na)NbO3基无铅压电陶瓷在掺杂改性以及晶粒定向技术制备织构化陶瓷研究的新进展,重点分析了(K,Na)NbO3基无铅压电陶瓷的K/Na比为0.5和非0.5时,陶瓷压电性能上的差异,发现K/Na比偏离0.5时,具有更为优异的压电、介电性能,最后展望了(K,Na)NbO3基无铅压电陶瓷的掺杂改性及晶粒定向技术的研究趋势.     

(Bi0.5Na0.5)TiO3(BNT)基无铅压电陶瓷研究进展

(Bi0.5Na0.5)TiO3(BNT)基无铅压电陶瓷体系是目前研究最广泛的功能陶瓷材料之一.综述了BNT基无铅压电陶瓷的研究现状,讨论了相关体系的设计方法、铁电性、压电性以及BNT体系的制备方法.分析比较了BNT系压电陶瓷与Pb(Zr,Ti)O3(PZT)压电陶瓷的性能差异以及存在的问题,对BNT基无铅压电陶瓷进行了展望.     

(Na0.5Bi0.5)TiO3-BaTiO3的合成与压电性能

合成了具有单一钙钛矿结构的(Nao.5Bi0.5)1-xBaxTiO3超细粉料,研究其陶瓷的压电性能.结果表明,柠檬酸与金属离子的摩尔比(C/Mn )和前驱体溶液的pH值是影响溶胶与凝胶形成的主要因素,凝胶在600℃下热处理1 h后可形成单一钙钛矿结构的(Nao.5Bi0.5)1-xBaxTiO3超细粉料.用柠檬酸盐法合成粉料的颗粒细小、化学成分均匀,有利于提高(Na0 5Bi0.5)1-xBaxTiO3陶瓷的压电性能.在准同质相界附近的组分存在较多的自发极化取向,因而表现出优良的压电性能.x=0.06时,柠檬酸盐法制备陶瓷样品的压电常数d33达到180 pC/N.     

Vibrational measurements of Na/Ni(111) and (Na + CO)/Ni(111)

The vibrational properties of Na atoms and of Na coadsorbed with CO on Ni(111) have been studied by high-resolution electron energy loss spectroscopy. Loss measurements showed a significant weakening of the alkali–substrate bond as a function of the alkali coverage. Moreover, we found that coadsorbed CO molecules dramatically influence the vibrational properties of Na adatoms. The Na–Ni stretching frequency (22 meV) measured on the Na/Ni(111) system shifted down to 13 meV for the (Na + CO)/Ni(111) surface. This unexpected result was ascribed to a charge transfer from Na to CO. Present findings give new insights on the nature of the alkali–substrate and alkali–CO bond.     

(Na0.5Bi0.5)TiO3基无铅压电陶瓷研究进展

综述了（Na0.5Bi0.5)Tio3（简写为NBT）基无铅压电陶瓷的发展现状，特性及影响因素，用分子轨道理论解释了NBT强铁电性的成因，对研究较多的三个体系：NBT-ATiO3(A=Ca,Sr,Ba),NBT-BNbO3(B=Na,K)和NBT－Ln掺杂体系给予了概括介绍，内容包括成分配比，性能和应用，并提出了NBT基无铅压电陶瓷的设计原则。     

Ferroelectric and piezoelectric properties of (1 − x) (Bi0.5Na0.5)TiO3–xBaTiO3 ceramics

Lead-free ceramics based on bismuth sodium titanate (Bi_0.5Na_0.5TiO₃, BNT)–barium titanate (BaTiO₃,BT) have been prepared by solid state reaction process. The (1?x)BNT–(x)BT (x = 0.01,0.03,0.05,0.07) ceramics were sintered at 1,150 °C for 4 h in air, show a pure perovskite structure. X-ray diffraction analysis indicates that a solid solution is formed in (1?x)BNT–(x)BT ceramics with presence of a morphotropic phase boundary (MPB) between rhombohedral and tetragonal at x = 0.07. Raman spectroscopy shows the splitting of (TO₃) mode at x = 0.07 confirming the presence of MPB region. The temperature dependence dielectric study shows a diffuse phase transition with gradual decrease in phase transition temperature (T_m). The dielectric constant and diffusivity increases with increase in BT content and is maximum at the MPB region. With the increase in BT content the maximum breakdown field increases, accordingly the coercive field (E_c) and remnant polarization (P_r) increases. The piezoelectric constant of (1 ? x)BNT–(x)BT ceramics increases with increase in BT content and maximum at x = 0.07, which is the MPB region. The BNT–BT system is expected to be a new and promising candidate for lead-free dielectric and piezoelectric material.     

(K0.5Na0.5)NbO3–Bi(Mg0.5Ti0.5)O3 solid solution: phase evolution, microstructure and electrical properties

Lead-free piezoelectric ceramics with the composition of (1 ? x)(K_0.5Na_0.5)NbO₃–xBi(Mg_0.5Ti_0.5)O₃ [(1 ? x)KNN–xBMT, 0 ≤ x ≤ 0.04] were synthesized via solid-state reaction method. X-ray diffraction patterns revealed that the orthorhombic—tetragonal phase transition was present for (1 ? x)KNN–xBMT with increasing the content of BMT. The study of dielectric properties illustrated that both peaks of orthorhombic—tetragonal (T _O–T ) and tetragonal—cubic (T _T–C ) phase transitions shifted to lower temperature. Through adding BMT, the electrical properties of KNN ceramics were obviously improved. The optimized piezoelectric and ferroelectric properties with d ₃₃  = 127 pC/N, k _p  = 36.58 %, P _r  = 22.1 μC/cm² were obtained as x = 0.01.     

(Na,K)0.5Bi0.5TiO3无铅压电陶瓷的结构与性能研究

研究了K0.5Bi0.5TiO3(KBT)含量对Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3(BNKT)无铅压电陶瓷的显微组织结构及压电性能的影响规律,结果表明随KBT含量增加,BNKT无铅压电陶瓷的晶胞参数增大,密度减小,晶粒尺寸减小,居里温度从326℃升高到360℃,压电常数、介电常数和介电损耗增加,机械品质因数下降;KBT含量为0.15mol的(Na0.85K0.15)0.5Bi0.5TiO3无铅压电陶瓷位于准同型相界处,具有较佳的压电性能.     

(Na0.5Bi0.5)TiO3基弛豫铁电体相变的研究进展

钛酸铋钠((Na0.5Bi0.5)TiO3,NBT)是一种典型的A位复合钙钛矿结构弛豫铁电体,具有复杂的相变序列,介电温度峰呈现明显的弛豫性.总结了NBT弛豫铁电体的相变及NBT基复合铁电体准同型相界的研究进展;从晶体结构出发,通过与B位复合型钙钛矿结构弛豫铁电体类比,对A位复合型NBT的弛豫机理进行了探讨,提出NBT弛豫性来源于其A位离子有序-无序引起的B位离子位移的变化.     

Crystallization of salts M3[NpO4(OH)2]·nH2O (M = Na, K, Rb, Cs) from concentrated alkali solutions at low temperatures. Synthesis and structure of a new Np(VII) compound, Na3[NpO4(OH)2]·6H2O

Precipitation of salts M₃[NpO₄(OH)₂]·nH₂O (M = Na, K, Rb, Cs) from concentrated alkali solutions at low temperatures (about ?10°C) was studied. From solutions with [OH^?] > 9.5 M, these compounds are isolated as coarse black crystals in high yield without impurity of other phases. The K, Rb, and Cs salts crystallize in the form of the previously studied compounds K₃[NpO₄(OH)₂]·2H₂O and M₃[NpO₄(OH)₂]·3H₂O (M = Rb, Cs). In the case of Na, a new hydrate Na₃[NpO₄(OH)₂]·6H₂O was obtained, and its crystal structure was determined. Crystals of the hexahydrate consist of centrosymmetrical tetragonal-bipyramidal anions [NpO₄(OH)₂]^3?, crystallographically independent Na(1) and Na(2) cations, and water molecules. The coordination surrounding of the Np atom is characterized by noticeable difference (Δ = 0.0203 Å) in the Np-O bond lengths in the equatorial plane of the bipyramid. The [NpO₄(OH)₂]^3? anions are combined with the Na(2) cations to form infinite chains [Na(2)NpO₄(OH)₂(H₂O)₂]^2? in such a manner that the lateral edges of the anion are simultaneously the lateral edges of the Na(2) coordination polyhedron. Incorporation of one of the two crystallographically independent O atoms of the NpO₄ group into the Na(2) coordination surrounding is responsible for a noticeable difference in the Np-O bond lengths in the equator of the [NpO₄(OH)₂]^3? anion. The types of hydrogen bonding in the structures of Na3[NpO₄(OH)₂]·nH₂O (n = 0, 2, 4, 6) are compared.     

含Ag0.16Na0.84Zr2(PO4)3抗菌喷雾剂

叙述了含Ag_(0.16)Na_(0.84)Zr_2(PO_4)_3抗菌喷雾剂的制法、性能与应用     

Nb2O5掺杂高温无铅(Ba,Bi,Na)TiO3基PTCR陶瓷结构与电性能研究

采用固相反应法制备了施主掺杂浓度不同的Nb₂O₅（分别为0.1mol%、 0.3mol%、 0.5mol%、 0.7mol%）掺杂(Ba, Bi,Na)TiO₃基PTCR陶瓷. 对其微观结构及电性能进行研究发现：随着Nb₂O₅掺杂浓度的增加,陶瓷晶粒尺寸先变大后变小,室温电阻率也随之先减小后增大,说明Nb₂O₅的掺杂量存在一个临界施主掺杂浓度. 当Nb₂O₅施主掺杂量为临界施主掺杂浓度0.5mol%时,获得了居里温度T_c为 183℃、室温电阻率ρ为1.06×10³Ω·cm、升阻比ρ_max/ρ_min为1.0×10⁴的高温无铅PTCR陶瓷. 通过交流复阻抗谱分析,探讨了Nb₂O₅施主掺杂在该PTCR陶瓷中的作用机理.     

(1-x)K0.48Na0.52NbO3-xBi0.45Nd0.05(Na0.92Li0.08)0.5ZrO3无铅压电陶瓷相结构及压电性能

为了在获得较高压电性能的同时又不大大降低陶瓷的居里温度(T_C), 设计和制备了Bi_0.45Nd_0.05(Na_0.92Li_0.08)_0.5ZrO₃改性的K_0.48Na_0.52NbO₃系无铅压电陶瓷((1-x)KNN-xBNNLZ), 研究了BNNLZ含量对KNN基无铅压电陶瓷相结构和电学性能的影响。研究结果表明, 所有陶瓷样品均具有较高的居里温度T_C(>300℃)。随着BNNLZ含量的增加, 陶瓷的正交-四方相变温度(T_O-T)不断向低温方向移动, 而三方-正交相变温度(T_R-O)不断向高温方向移动, 最终在陶瓷中形成了三方-四方(R-T)共存相, R-T共存相处于0.05<x<0.07范围。BNNLZ的加入引起陶瓷相结构的演化改变导致压电常数(d₃₃ )、介电常数(ε_r )、剩余极化强度 (P_r )和机电耦合系数(k_p )都先增大后减小, 当x=0.06时陶瓷具有最佳压电性能: d₃₃=313 pC/N, k_p=42%, P_r=25.48 μC/cm², ε_r=1353, tanδ=2.5%, T_C=327℃。     

烧结方式对(K,Na,Li)(Nb,Sb,Ta)O3压电陶瓷的微观结构和物理性能的影响

(K,Na)NbO₃基陶瓷(KNLNST陶瓷)是一类很有发展潜力的无铅压电材料, 目前对其进行两步烧结相关的研究还很少。本工作分别采用普通烧结(Conventional Sintering, CS)和两步烧结(Two-step Sintering, TSS)制备了(K_0.4425Na_0.52Li_0.0375)(Nb_0.8825Sb_0.08Ta_0.0375)O₃陶瓷, 并进行微观结构与物性的对比研究。TSS可将(K,Na)NbO₃基陶瓷的相对密度ρ°由CS时的95.0%提高至97.0%, 压电系数d₃₃由CS时的363 pC/N增大到387 pC/N。两种烧结方式制备的KNLNST陶瓷的微观组织结构和电畴结构有着很大的差异。KNLNST-CS陶瓷的晶粒尺寸较小而且分布较为均匀, 极化后多数晶粒的电畴图案为简单的平行条纹。KNLNST-TSS陶瓷的晶粒尺寸则大小分布不均匀, 极化后许多大晶粒中呈现带状条纹内部又存在着精细的平行条纹的电畴图案。     

水热-溶剂热法合成(K,Na)NbO_3无铅压电陶瓷及其性能测试

通过添加异丙醇利用水热溶剂热法合成了(K,Na)NbO3无铅压电陶瓷粉体.研究了矿化剂浓度、反应物浓度对产物晶相、粒径大小、形貌以及化学组成等的影响.利用X射线衍射仪、傅立叶变换红外吸收光谱以及扫描电子显微镜对所得粉体进行了表征.随后,利用合成的(K,Na)NbO3无铅压电陶瓷粉体,按照传统固相烧结工艺烧制压电陶瓷,并研究了其压电性能.实验结果表明:通过添加异丙醇有机溶剂,可以在矿化剂浓度为2mol/L的条件下合成出纯钙钛矿结构的(K,Na)NbO3粉体.随着反应溶液中K离子含量的增加,产物中离子K的含量也在增加.组成为K0.22Na0.78NbO3样品的压电常数d33高达120 pC/N,与传统固相合成法获得的(K0.5,Na0.5)NbO3常压烧结得到的陶瓷性能相当.由此可预见利用水热溶剂热法合成的(K0.5,Na0.5)NbO3粉体烧结的陶瓷可获得更高的电学性能.     

Dielectric,ferroelectric, and field-induced strain properties of Ta-doped 0.99Bi0.5(Na0.82K0.18)0.5TiO3–0.01LiSbO3 ceramics

Ta-doped 0.99Bi_0.5(Na_0.82K_0.18)_0.5TiO₃–0.01LiSbO₃ (BNKTT–LS) ceramics were prepared through a conventional mixed oxide solid-state sintering route. Partial substitution of Ta for Ti decreased the dielectric constant and depolarization temperature. The dielectric curves, polarization and strain hysteresis loops demonstrated that the incorporation of Ta stabilized the canonical relaxor phase of BNKT–LS ceramics leading to the degradation of piezoelectric and ferroelectric responses. The destabilization of field-induced ferroelectric order at x = 0.013 was accompanied by substantial enhancement in strain level. A unipolar field-induced strain of 0.39 % with a normalized strain (S _max/E _max =  $ d_{33}^{*} $ ) of 650 pm/V was achieved at a driving field of 6 kV/mm. The observed large strain can be attributed to the non-ergodic relaxor phase at zero electric field that transformed into an ergodic relaxor phase under the influence of the applied electric field.     

(Na1/2Bi1/2)TiO3(NBT)无铅压电陶瓷的研究进展

对(Na1/2Bi1/2)TiO3基无铅压电陶瓷的研究现状进行了综述.着重概括了通过元素替代/掺杂手段对NBT陶瓷性能的影响规律.该系统陶瓷具有的强铁电性质与Bi3 密切相关;材料压电性能可通过改性技术进行调节:如通过加入第二组元化合物降低其矫顽场而提高NBT基陶瓷压电性能.总结了(Na1/2Bi1/2)TiO3基无铅压电陶瓷组成的研究思路和方向.     

Phase structure and electrical properties of (Li,Ta)-doped (K,Na)NbO<Subscript>3</Subscript> lead-free piezoceramics in the vicinity of Na/K = 50/50

The phase structure and electrical properties of (K,Na)NbO₃ (KNN)-based lead-free piezoelectric ceramics with nominal composition Li_0.03 (Na _x K_1−x )_0.97Nb_0.8Ta_0.2O₃ (LKNNT, x = 0.50−0.55) were investigated with an emphasis on the influence of Na/K ratio. By XRD and Raman measurements, it was revealed that the phase transition from the co-existence of O ₁ and T ₁ to the co-existence of O ₂ and T ₂ occurs when x = 0.52. At this Na/K ratio, a peak of dielectric constants was obtained, which also corresponds to a morphotropic phase boundary between T ₁ and T ₂ besides that between O ₁ and O ₂ in LKNNT ceramics. All the Li_0.03 (Na _x K_1−x )_0.97Nb_0.8Ta_0.2O₃ ceramics with x = 0.50 − 0.55 show excellent piezoelectric performance, and the piezoelectric coefficient d*₃₃ can reach as high as 335 pm/V. The room-temperature piezoelectric properties in the present LKNNT ceramics are not sensitive to the change of Na/K ratio, indicating that the orthorhombic to tetragonal phase co-existence dominates the enhancement of piezoelectric properties. However, the results on the piezoelectricity measurement at elevated temperature showed possible to further enhance piezoelectric properties by adjusting Na/K ratio in the tetragonal LKNNT ceramics.