铌酸钾钠基无铅压电陶瓷的制备工艺技术研究进展

基于对人类生存环境的保护和发展环境友好型材料与电子产品的要求,铌酸钾钠(K0.5Na0.5NbO3,简写为KNN)基无铅压电陶瓷由于其具有优越的电学性能和较高的居里温度而成为目前世界范围内压电铁电材料研究的热点之一。材料制备工艺技术在材料科学技术中占有极其重要的地位。结合国际无铅压电陶瓷的研究情况,综述了近年来铌酸钾钠基无铅压电陶瓷在粉体制备、陶瓷烧结以及陶瓷织构化等制备工艺技术上研究的新进展并展望了其发展趋势。     

Structure and piezoelectric properties of Cu-doped potassium sodium tantalate niobate ceramics

The Cu-doped (K_0.5Na_0.5)(Nb_0.95Ta_0.05)O₃ (KNNT) ceramics were prepared by the solid state reaction ceramic technique. The phase structure and the micro-morphology were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). There exhibits a single phase in perovskite structure, even the grain sizes increase with copper addition. The dielectric constant (ε), the planar mode electromechanical coupling factor (k_p), the piezoelectric coefficient (d₃₃), and the mechanical quality factor (Q_m) of KNNT ceramics with copper additive are 320–450, 0.21–0.41, 70–110 pC/N, 105–979, respectively.     

一种改性铌酸盐系无铅压电陶瓷的合成与特性研究

K0.5Na0.5NbO3(KNN)系铌酸盐是一类可能替代铅基压电陶瓷的无铅压电陶瓷.利用Ta和Sb掺杂或者取代KNN中的相关离子,在陶瓷的准同型相界(MPB)处显现出高的压电和介电性能.利用传统技术制作出一种新的致密度较高的无铅压电陶瓷(1-x)(K0.5Na0.5)(Nb0.96Sb0.04)O3-xLiTaO3(简记为KNNS-LT).所有的组分在MPB处都存在纯的钙钛矿结构,主要压电性能在MPB处达极大值,其机电耦合系数kp为40%,压电常数d33为225pC/N,居里温度Tc为355℃.     

Lead-free piezoelectric ceramics manufactured from tantalum-substituted potassium sodium niobate nanopowders

Nanopowders of lead-free (K_0.5Na_0.5)(Nb_0.9Ta_0.1)O₃ (KNNT) system were prepared by high-energy ball milling at different milling times keeping the milling speed fixed at 250 rpm. The particle size first decreases from 35 nm to 3 nm and then increases to 98 nm as the milling time increases in steps of 5 h from 10 h to 30 h. Without using any sintering aid, dense ceramics were formed by sintering the powders at 1050 °C for 1 h. With decreasing particle size of the starting nanopowders, the ceramics exhibit gradual increase in density from 93.1% to 95.8%, coercive field (E_c) from 10.9 kV/cm to 15.1 kV/cm, electromechanical coupling factor (k_p) from 35% to 48%, and piezoelectric charge constant (d₃₃) from 80 pC/N to 128 pC/N. The systematic changes observed in these parameters corroborate the observed increase in particle size as the milling time increases from 25 h to 30 h.     

Effects of sintering aid CuTa2O6 on piezoelectric and dielectric properties of sodium potassium niobate ceramics

In this study, the effects of a sintering aid CuTa₂O₆ (CT) on (Na_0.5K_0.5)NbO₃ (NKN) ceramics were investigated. The diffracted angles in XRD profiles decreased because the Nb-sites were replaced by Cu and Ta ions, causing the expansion of lattice volume. SEM images showed smaller grain sizes at a low concentration of CuTa₂O₆, and grain sizes increased as the concentration of CuTa₂O₆ doping increased because of a liquid phase formed. When CuTa₂O₆ dopants were doped into NKN ceramics, the T_O–T and T_c phase transitions decreased because the replacement of Ta⁵⁺ ions in the B-site. A high bulk density (4.595 g/cm³) and electromechanical coupling factor (k_p, k_t) were enhanced when CT dopants were doped into NKN ceramics. Moreover, the mechanical quality factor (Q_m) also increased from 67 to 1550. NKN ceramics with sintering aid CuTa₂O₆ doping showed excellent piezoelectric properties: k_p: 42.5%; k_t: 49.1%; Q_m: 1550; and d₃₃: 96 pC/N.     

Sintering, microstructure and piezoelectric properties of CuO and SnO2 co-modified sodium potassium niobate ceramics

The CuO and SnO₂ co-modified Na_0.52K_0.48NbO₃ ceramics were prepared by a conventional mixed oxide method. Densification can be further improved but the grain growth is inhibited as a small amount of SnO₂ is added into 1% CuO doped Na_0.52K_0.48NbO₃. The results indicate that the physical and various electrical properties of CuO and SnO₂ doped Na_0.52K_0.48NbO₃ ceramics significantly depend on sintering conditions and the content of dopants. The ceramics doped with 1 mol% CuO and 1 mol% SnO₂ sintered at 1070 °C for 3 h show improved dielectric and piezoelectric properties: d₃₃ = 120 pC/N, k_p = 0.38, Q_m = 1040, ?_r = 710 and tanδ = 0.013 (1 kHz), in comparison with un-doped or CuO doped compositions.     

常压烧结制备透明铌酸钾钠陶瓷

在铌酸钾钠(KNN)陶瓷中掺杂锂和铋的氧化物作为晶粒生长抑制剂,用常压烧结工艺制备了铌酸钾钠透明陶瓷(K0.48-0.5xNa0.52-0.5xLixNb1-xBixO3,x=0.04～0.15)材料。研究了掺杂量、烧结工艺条件对陶瓷透明性、光电系数、晶相结构和微观形貌的影响。当x=0.09时,厚度为0.5mm陶瓷样品的红外透光率达到82%,光电系数为6.06×1011m/V。     

钛酸铋钠基无铅压电陶瓷研究近期进展

钛酸铋钠(分子式是Bi0.5Na0.5TiO3,简写为BNT)基无铅压电陶瓷性能优良,但与铅基陶瓷相比还有相当的差距,其性能有待进一步提高.从BNT基陶瓷改性、陶瓷新体系以及陶瓷制备技术等多方面,分析了提高BNT基陶瓷性能的原理、途径和方法,指出了发明陶瓷新体系的有关思路,讨论了陶瓷制备技术与陶瓷性能的关系.同时,列举了近期在BNT基陶瓷性能改善研究中的若干新进展和新结果、性能良好的BNT基陶瓷新体系及制备工艺和制备新技术对陶瓷性能的影响,并对今后的相关研究进行了展望.     

Enhancement of Q(m) by co-doping of Li and Cu to potassium sodium niobate lead-free ceramics.

Lead-free piezoelectric ceramics KNN modified by Li-substitution and CuO addition have been synthesized, and the piezoelectric and dielectric properties were measured. A morphotropic phase boundary (MPB) between orthorhombic and tetragonal phases was formed with Li-substitution. The co doping of Li and Cu markedly enhanced the mechanical quality factor (Q(m)) in comparison with the sole doping of Li and Cu. Anomalous anti ferroelectric-like hysteresis curves were observed in 2 mol% CuO-doped ceramics. The anti-ferroelectric-like curves were changed to that of normal ferroelectrics following poling. A model based on the formation of the internal bias field (Ei) due to the movements of space charges was proposed to explain these phenomena. It was considered that the Ei stabilized the spontaneous polarization (Ps) and suppressed the domain wall motion to enhance the Q(m). The highest Qm obtained in this study was 742. The [(Na0(0.5)K0(0.5))(0.96)Li0(0.04) ] NbO(3) + 0.45 mol% CuO ceramics showed a high Q(m) value of 414 with a high piezoelectric constant d(33) of 100 pC/N.     

Porous Li-Na-K niobate bone-substitute ceramics: Microstructure and piezoelectric properties

Disc specimens of a porous ceramic, lithium sodium potassium niobate (Li_0.06Na_0.5K_0.44)NbO₃, were prepared using ammonium oxalate monohydrate or poly(methyl methacrylate) as pore-forming agent, and made piezoelectric using a modified polarizing method to preserve biocompatibility. Scanning electron microscopy showed a bicontinuous 3-3 structure of interconnected pores 150-250 µm in size. The piezoelectric constant (d₃₃) and electromechanical coupling coefficient (Kp) are discussed as a function of porosity and pore shape: d₃₃ fitted the theoretical expectation for shape factor K_s = 1, while Kp was approximately constant (~ 0.23) for porosity of 15-45 vol.%. 50 vol.% AOM gave the highest porosity (~ 45%) without decline of the value of Kp whilst maintaining mechanical integrity. Such materials show promise for use as a piezoelectric composite bone substitute.     

Examination of selectivity of templates for the textured potassium sodium niobate ceramics

To achieve the surface-orientation-controlled microstructure of K_0.5Na_0.5NbO₃, not only the template must exhibit the high anisotropy like a plate-shape but the reactive stability as well as the crystallographic coherency between the template and the K_0.5Na_0.5NbO₃ must be carefully considered. In this work, we focused on what kinds of ceramics are suitable for the fabrication of the surface-orientation-controlled K_0.5Na_0.5NbO₃. First of all, BaTiO₃, SrTiO₃, Ba(Zr_0.1Ti_0.9)O₃, KNbO₃, NaNbO₃, KTaO₃ and NaTaO₃ were chosen as the candidates in the regard of the crystallographic coherency. To verify the chemical stability between candidate ceramics and K_0.5Na_0.5NbO₃, the prepared candidate ceramic bulks were embedded by the K_0.5Na_0.5NbO₃ powder, they were annealed at 1100 °C, and then the interface regions between candidate ceramics and K_0.5Na_0.5NbO₃ were investigated using Secondary Electron Microscopy (SEM) equipped with Energy Dispersive Spectrometer (EDS). From these experimental results, BaTiO₃, SrTiO₃, Ba(Zr_0.1Ti_0.9)O₃, KNbO₃ and NaTaO₃ were found to be not appropriate for the templates for the tailoring of K_0.5Na_0.5NbO₃, while the NaNbO₃ and KTaO₃ showed a good crystallographic coherency and a chemical stability with K_0.5Na_0.5NbO₃.     

Coupling effects of the A-site ions on high-performance potassium sodium niobate ceramics

Although vast efforts have been given to the phase boundary engineering(PBE) of potassium sodium niobate(KNN) ceramics by using chemical dopants,the inherent issues like the K/Na ratio were not paid enough attention,hindering the further understanding of physical mechanisms.Herein,we investigated the effect of the K/Na ratio on PBE-featured KNN-based ceramics.The K/Na ratio significantly influences the local A-site environment and thereby alters mesoscopic ferroelectric domains and macroscopic s...     

Growth of lithium doped silver niobate single crystals and their piezoelectric properties

Lithium doped silver niobate (Ag_1−xLi_xNbO₃, 0 < x < 0.1) is one of the candidate materials for lead-free piezoelectric materials. In this study, Ag_1−xLi_xNbO₃ single crystals were successfully grown by a slow cooling method. Crystal structure was assigned to perovskite-type orthorhombic (monoclinic) phase. Dielectric properties were measured as a function of temperature. As a result, with increasing lithium contents, the phase transition at around 60 °C was shifted to lower temperature while the phase transition at around 400 °C was shifted to higher temperature. On the basis of these peak shifts, the lithium contents in Ag_1−xLi_xNbO₃ single crystals were determined. Moreover, P–E hysteresis measurement revealed that pure silver niobate crystal was weak ferroelectrics with P_r of 0.095 μC/cm² while Ag_0.9Li_0.1NbO₃ (ALN10) crystal was normal ferroelectrics with P_r of 10.68 μC/cm². About this ALN10 crystal, polling treatment was performed and finally piezoelectric properties were measured. As a result, high electromechanical coupling coefficient k₃₁ over 70% was observed.     

Structure and dielectric properties of potassium niobate nano glass–ceramics

Glasses in the composition of 25K₂O-25Nb₂O₅-50SiO₂ (mol %) have been prepared by melt quenching technique and isothermally heat-treated at 800 °C for different duration (0–200 h). The formed nanocrystalline KNbO₃ phase, crystallite size and morphology are examined by X-ray diffraction, Fourier transform infrared reflection spectroscopy, field emission scanning and transmission electron microscopes. The frequency and temperature dependent dielectric constant and loss tangent are measured in the frequency and temperature ranges 0.1–1000 kHz and 200–500 °C respectively. The dielectric constant and loss tangent are found to decrease with increasing frequency and increase with increasing temperature. The dielectric constant and loss tangent versus temperature curve at different frequency revealed the phase transition of KNbO₃ from paraelectric cubic to ferroelectric tetragonal around 425 and 397 °C (Curie temperature) for nano glass–ceramics obtained after 1 and 200 h heat-treatment respectively.     

Effects of sintering temperature on dielectric and piezoelectric properties of KNN-LS-BF-0.4mol%CuO lead-free piezoelectric ceramics

KNN-LS-BF-0.4mol%CuO piezoelectric ceramics were prepared by the traditional sintering method. The effects of sintering temperature on the dielectric and piezoelectric properties of KNN-LS-BF-0.4mol%CuO ceramics were studied. The results reveal that the sintering temperature has significant influence on the microstructure and the properties of KNN-LS-BF-0.4mol%CuO ceramics. With the increase of sintering temperature from 1,040 to 1,080 °C, the grains become more homogeneous and more tight-arrangement, resulting in the higher relative density as well as the best dielectric and piezoelectric properties. However, the properties of the samples would be deteriorated as they are sintered over 1,080 °C.     

Dielectric and pyroelectric properties of monovalent-lithium modified trivalent-samarium doped barium strontium sodium niobate tungsten bronze structured ceramics

The dielectric and pyroelectric properties of trivalent-samarium doped barium strontium sodium niobate tungsten bronze structured ceramics are further modified with monovalent-Lithium. Ba_1.6−(3/2)y Sr_2.4Sm _y Li _x Na_(2−x)Nb₁₀O₃₀ was studied for y = 0.1 and x in the range of 0 ≤ x ≤ 1. The BSSLNN ceramics can be indexed by typical orthorhombic structure and these orthorhombic (mm2) peaks are assigned to standard file No. C73-1214. Tolerance factor and average electronegativity difference has been determined for BSSLNN ceramics. Pyroelectric and DC resistivity properties of BSSLNN ceramics are reported. x = 1 composition was found to be optimum among the series for possible pyroelectric applications.     

Phase transition and domain variation contributions to piezoelectric properties of alkaline niobate based lead-free systems

The intrinsic correlation and mechanism between electrical properties and phase transitions in alkaline niobate based lead-free piezoelectric ceramics were explored by taking typical (Na_0.52K_0.48−x )(Nb_0.95−x Ta_0.05)O₃-xLiSbO₃ compositions as a case study. The diffuseness of the phase transition leads to two-phase coexistence promoting piezoelectric activity and simultaneously induces remarkable temperature sensitivity, based on the variation of orthorhombic and tetragonal domains. The polymorphism, not a morphotropism of the phase boundary was considered as a structural root for these kinds of compositions. The refinement of compositions within two-phase coexistence zone compromises two opposite effects, although the composition range is narrow, suggesting the property sensitivity to the composition and a processing solution to the property optimization as well.     

BNT基无铅压电陶瓷的研究与进展--无铅压电陶瓷20年发明专利分析之二

Bi0．5Na0．5TiO3(BNT)基无铅压电陶瓷是目前研究最广泛、最具吸引力的无铅压电陶瓷体系。本文分析了BNT基无铅压电陶瓷近20年的发明专利，着重讨论了相关体系的压电铁电性能，并展望了BNT基压电陶瓷今后的发展趋势。     

铌酸盐系无铅压电陶瓷的研究与进展--无铅压电陶瓷20年专利分析之四

综合分析和评述了近20年的铌酸盐系无铅压电陶瓷发明专利，着重介绍了主要的铌酸盐系无铅压电陶瓷相关体系及其压电铁电性能和制备工艺技术，并展望了铌酸盐系无铅压电陶瓷今后研究和发展的几个方面。特别是对NaNbO3、Sr2NaNb5O15体系以及相关钨青铜结构体系的改性、复合和理论研究，提出了具体的建议。