(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.     

CuO对NKN基无铅压电陶瓷结构和性能的影响

采用传统陶瓷工艺制备了添加氧化铜的铌酸钠钾基无铅压电陶瓷[(Na0.5K0.5)1-2xCuxNbO3,0≤x≤0.05],研究了氧化铜(CuO)的引入对(Na0.5K0.5)NbO3(NKN)基陶瓷的晶体结构和压电、铁电等性能的影响.研究结果表明,讨论的所有样品的主晶相均为正交钙钛矿结构;随着x的增加,陶瓷出现了K4CuNb8O23杂相;与纯NKN陶瓷相比,掺入一定量的CuO后,样品的致密度显著提高;随着CuO含量的增加,陶瓷的机电耦合系数(kp)和机械品质因数(Qm)先增加后减小,并在x=0.01时达到最大值:kp=38.7%,Qm=1000,而陶瓷的压电常数(d33)无显著变化;当x≥0.01时,样品呈现出双电滞回线的特征.     

(K0.5Na0.5)NbO3-LiNbO3无铅压电陶瓷的烧结特性和压电性能研究

采用传统陶瓷烧结工艺制备了(1-x)(K0.5Na0.5)NbO3-xLiNbO3无铅压电陶瓷,研究了陶瓷的结构、烧结特性及电性能特征.制备的(K0.5Na0.5)NbO3-LiNbO3陶瓷为单一的钙钛矿结构,室温下其相结构随LiNbO3含量增加逐渐由正交相向四方相转变,显微结构也由于LiNbO3含量的不同而表现出很大差异.与(K0.5Na0.5)NbO3陶瓷相比,(K0.5Na0.5)NbO3-LiNbO3陶瓷的烧结温度降低,烧结特性得到改善. (K0.5Na0.5)NbO3-LiNbO3陶瓷表现出优越的压电性能,其中0.94(K0.5Na0.5)NbO3-0.06LiNbO3(x=0.06)陶瓷的压电常数d33达到205pC/N,机电耦合系数kp为40.3%,kt达到49.8%.     

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℃.     

Ba,Sr掺杂对K0.47Na0.47Li0.06NbO3基无铅压电陶瓷结构、介电及压电性能的影响

采用传统的固态反应法制备了(K0.47Na0.47 Li0.06 )1-x(Ba0.5Sr0.5)xNbO3无铅压电陶瓷,研究了Ba,Sr掺杂对K0.47Na0.47Li0.06NbO3陶瓷的晶体结构、电畴结构、介电及压电性能的影响.随着Ba,Sr掺杂量的增加,陶瓷样品逐渐由正交相向四方相转变,同时居里温度(Tc)降低,剩余极化率(Pr)、矫顽场(Ec)、介电常数(εr)增加;压电常数(d33)、机电耦合系数(kp)先增加后减小.x=0.5％时陶瓷的压电常数d33达到221 pC/N,机电耦合系数kp为43.1％.     

(K_(0.5)Na_(0.5))_(0.94-2x)Li_(0.06)Sr_xNb_(0.98)Sb_(0.02)O_3无铅压电陶瓷的制备及性能研究

采用传统陶瓷烧结工艺制备了(K0.5Na0.5)0.94-2xLi0.06SrxNb0.98Sb0.02O3无铅压电陶瓷,研究了陶瓷的结构、烧结特性及电性能特征.研究结果表明:制备的KNLSN-Srx陶瓷为单一的具有四方相的钙钛矿结构,SEM照片中可以看出材料的平均晶粒尺寸随着Sr掺入量的增加逐渐变大,陶瓷的烧结温度随Sr掺入量的增加而升高,Li,Sr和Sb掺杂(K0.5Na0.5)NbO3后,材料的压电系数d33、平面机电耦合系数kp得到提高,同时介电损耗tanδ和机械品质因子Qm降低,Sr掺入量在2mol%时各项性能最佳(d33=130pC/N,kp=34.5%,tanδ=4.2%).     

0.94[(Na0.96-xKxLi0.04)0.5Bi0.5]TiO3-0.06Ba(Zr0.055Ti0.945)O3无铅压电陶瓷的压电介电特性

对无铅压电陶瓷0.94[(Na0.96-xKxLi0.04)0.5Bi0.5]TiO3-0.06Ba(Zr0.055Ti0.945)O3的性质随K含量的变化进行了系统研究,获得压电应变常数d33高达185pC/N的0.94[(Na0.80K0.16Li0.04)0.5-Bi0.5]TiO3-0.06Ba(Zr0.055Ti0.945)O3压电陶瓷.随着K掺杂量的增加,该陶瓷材料的介电温谱峰值向右明显移动,其介电峰温度明显升高.     

(Na0.5K0.5)NbO3基无铅压电陶瓷的研究

由于钙钛矿结构无铅压电陶瓷具有高的压电性能，已成为无铅压电陶瓷研究的热点．本文综述了钙钛矿结构无铅压电陶瓷（Na0．5K0.5）NbO3的研究进展和趋势．重点从添加第二组元、添加助烧剂、取代改性和制备方法四个方面，归纳和分析了（Na0．5K0.5）NbO3基无铅压电陶瓷的研究开发进展，并对（Na0.5K0.5）NbO3基无铅压电陶瓷今后的研究和发展提出一些建议．     

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.     

Sb_2O_3掺杂对(Na_(1-x)K_x)_(0.5)Bi_(0.5)TiO_3无铅压电陶瓷性能的影响

采用传统工艺制备了(Na0.84K0.16)0.5Bi0.5TiO3压电陶瓷,研究掺杂离子Sb3+对(Na0.84K0.16)0.5Bi0.5TiO3微观结构和电性能的影响。结果表明烧结温度在1160℃时,样品密度达到最大值5.85g/cm3;X射线衍射(XRD)分析所有陶瓷样品均为钙钛矿相,Sb2O3的掺杂只改变晶胞体积或产生铋离子空位或钠离子空位,不形成异相;掺杂量在0.4%~0.6%时介电常数先增加后减小,介电损耗呈现增大趋势;掺杂0.5%的Sb2O3时,d33最大为142pC/N。     

The effect of CuO doping on the microstructures and dielectric properties of BaTiO3 ceramics

(1 − x) BaTiO₃/xCuO ceramic pellets with x = 0, 0.2, 0.4, 0.6, and 0.8% respectively were prepared by the traditional solid-state reaction method. The effect of CuO doping on the microstructure and dielectric properties of BaTiO₃ ceramics has been investigated. SEM and XRD results at room temperature show that the grain size grows with the increase of CuO content under the same sintering conditions and the crystal structure undergoes the mixed phases (pseudocubic/tetragonal) to tetragonal phase transition with the growth of grain size. Regular shape grains with average grain size ~2 μm are detectable in the specimens as CuO dopant content adds up to 0.8% and the crystal structure has completely changed into tetragonal phase. The permittivity increases markedly for CuO dopant content x = 0.2 ~ 0.4% and the dielectric loss decreases significantly after being doped by CuO and down to a minimum value for x = 0.8%. In addition, the permittivity and dielectric loss display a good stability in a broad frequency range comparing that of pure BaTiO₃ ceramics.     

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.     

Studies of structural,optical, and electrical properties associated with defects in sodium-doped copper oxide (CuO/Na) nanostructures

In the present paper, we report a detailed study on the sodium (Na) doping-induced modifications in the copper oxide (CuO) nanostructure and its properties. A facile and sustainable sol–gel synthesis approach was employed for the preparation of high-quality pristine CuO- and Na-doped CuO nanostructures(1.0, 3.0, 5.0 and 7.0 mol% doping levels, CuO/Na) with controlled shape and composition. Due to the remarkable difference in the ionic radii of Cu²⁺ (0.73 Å) and Na⁺ (1.02 Å), Na⁺ substitution in place of Cu²⁺ generates strain/distortions in CuO lattice. The XRD analysis reveal the structural alteration from monoclinic to cubic symmetry with increase in doping level and also reveal the phase purity up to 3% doping level, and beyond this (i.e., for 5 and 7% doping level) small amount of impurity phase corresponding to Na₂O was observed. The FTIR results further confirmed the presence of the Na–Cu–O stretching vibrations at higher Na-doped samples. Morphology of the samples indicates that the Na-doped CuO nanostructures exhibit less agglomeration compared to pristine CuO nanoparticles. The presence of Na in CuO lattice were found to greatly enhances optical and electrical properties owing to the formation of defects like copper vacancies and oxygen vacancies at the grain boundaries of the nanoparticles with increased doping of Na.     

The effect of CuO on the grain growth of ZnO

The grain growth kinetics in the 1, 2, 3 and 4 wt.% CuO doped ZnO was studied using the simplified phenomenological grain growth kinetics equation Gⁿ – G₀ⁿ = K₀ t exp (– Q/RT) together with microstructure properties of the sintered samples. The grain growth exponent value (n) was found to be 3 for 1, 2 and 3 wt.% CuO doped ZnO and 5.5 for 4 wt.% CuO doped ZnO. The apparent activation energy was decreased with CuO doping up to 3 wt.% from 250 kJ/mol to 150 kJ/mol but it was not changed significantly (155 kJ/mol) by 4 wt.% CuO doping. CuO doping up to 3 wt.% promoted the grain growth of ZnO whereas 4 wt.% CuO doping inhibited the grain growth of ZnO because of formation of Cu-rich secondary phase in the grain boundaries.     

Low temperature sintering and microwave dielectric properties of SmAlO3 ceramics

The effects of sintering aids on the microstructures and microwave dielectric properties of SmAlO₃ ceramics were investigated. CuO and ZnO were selected as sintering aids to lower the sintering temperature of SmAlO₃ ceramics. With the additions, the sintering temperature of SmAlO₃ can be effectively reduced from 1650 to 1430°C. The crystalline phase exhibited no phase differences at low addition level while Sm₄Al₂O₉ appeared as a second phase as the doping level was over 0.5 wt.%. In spite of the additions, the dielectric constants showed no significant change and ranged 19-21. However, the quality factor Q×f was strongly dependent upon the type and amount of additions. The Q×f values of 51,000 and 41,000 GHz could be obtained at 1430°C with 0.25 wt.% CuO and ZnO additions, respectively. The temperature coefficients depended on the additions and varied from −40 to −65 ppm/°C. Results of X-ray diffractions, EDS analysis and scanning electron microscopy were also presented.     

Microstructure and dielectric properties of Ca1–3/2xBixCu3Ti4O12 (x = 0, 0.05, 0.10, 0.15 and 0.20) ceramics

Influence of bismuth substitution on calcium site in CaCu₃Ti₄O₁₂ has been investigated. Compositions of Ca_1-3/2xBi_xCu₃Ti₄O₁₂ (x = 0, 0.05, 0.10, 0.15 and 0.20) were fabricated by solid-state sintering method. Crystal structure is remained cubic. X-ray diffraction indicates the presence of secondary phase of CuO in CCTO ceramics. Bismuth doping restrains the formation of CuO phase apparently. The grain size of CaCu₃Ti₄O₁₂ ceramics was greatly decreased by Bi³⁺ doping, resulting from the ability of bismuth to inhibit the grain growth. The dielectric and electric properties of CCTO ceramics were found to be influenced by bismuth doping. The fitting results of the complex impedance spectra showed an increase of the resistance of grain and grain boundary by bismuth substitution. Ca_0.70Bi_0.20Cu₃Ti₄O₁₂ showed the highest dielectric constant in the low frequency range. A modest composition such as Ca_0.85Bi_0.10Cu₃Ti₄O₁₂ expressed the optimized dielectric properties of higher dielectric constant (1.3 × 10⁴) and lower dielectric loss (0.06) than pure CCTO. The low and high temperature dielectric loss spectra demonstrate the interfacial polarization of the initial and secondary oxygen ionization, relating with the grain and grain boundary (the electrode contact for Ca_0.70Bi_0.20Cu₃Ti₄O₁₂) respectively.     

掺钾对PMN基陶瓷有序微区及介电和电致伸缩性能的影响

使用二次合成法制备了不同钾含量的0.80Pb(Mg1/3Nb2/3)O3-0.20PbTiO3陶瓷，首先研究了掺钾对PMN基预烧粉体和陶瓷试样相组成的影响，在此基础上详细研究了掺钾对PMN基陶瓷有序微区、介电和电致伸缩性能的影响规律。掺钾对PMN基预烧粉体和陶瓷的相组成影响很小；理论计算和Raman散射光谱分析都表明掺钾使PMN基陶瓷的有序微区的尺寸稍微减小；掺钾也小幅度地减小了PMN基陶瓷的介电和电致伸缩性能，最后分析了掺钾降低介电和电致伸缩性能的原因。     

Effects of CuO、MoO3 and WO3 dopping on magnetic properties of NiZn ferrites

研究了CuO、MoO3和WO3掺杂对NiZn铁氧体电磁性能的影响.研究表明,适量的CuO掺杂能提高材料烧结密度并降低磁晶各向异性常数,从而提高材料的起始磁导率,但居里温度也有一定程度的下降.当主配方中CuO含量(摩尔分数)为4%时能最好的兼顾材料高磁导率和高居里温度的要求.而MoO3和WO3掺杂则均能引起晶界附近阳离子空位增多,从而加速晶界移动,促进晶粒尺寸增大,进而提高材料的起始磁导率.同时,由于W离子具有较强的占据铁氧体A位替代Fe3 的趋势,需要更大的掺杂量才能达到磁导率的峰值,其居里温度和饱和磁感应强度也低于相应MoO3掺杂的材料.     

钴掺杂氧化铜/可见光协同活化PMS降解罗丹明B及其机理研究

元素掺杂是提升催化剂性能的重要方法。研究采用快速沉淀法制备了钴掺杂氧化铜(Co-doped CuO)纳米催化材料, 在可见光条件下, 20 min内其活化的过氧硫酸氢钾复合盐(PMS)对罗丹明B染料的降解率达到96%以上, 远优于同等条件制备的CuO。本研究还考察了溶液pH、染料初始浓度、催化剂用量等对降解效率影响。钴掺杂后氧化铜纳米颗粒由三维针梭状结构转变为近二维薄带状结构。同时钴掺杂提高了CuO的平带电位进而提升了电荷转移效率。XPS及EPR结果表明钴掺杂能够提高CuO的氧空位含量进而提升催化活性。捕获剂实验结果表明反应过程中的主要活性物种为空穴(h⁺_VB), 且羟基自由基(•OH)、单线态氧(¹O₂)、超氧自由基(•O₂^-)、硫酸根自由基(SO₄^-•)也参与了降解反应。最后, 本文初步阐明了Co-doped CuO协同可见光活化PMS降解有机污染物的反应机理。     

CaCu3Ti4-3/4zFezO12/偏聚氟乙烯和Ca1-3/2xLaxCu3-yMgyTi4O12/偏聚氟乙烯复合材料的制备及介电性能研究

以CaCu3Ti4O12为原料,采用溶胶-凝胶法制备CaCu3Ti4-3/4zFezO12 (CCTFO)和Ca1-3/2xLaxCu3-y MgyTi4O12(CLCMTO)前驱粉体,以聚偏氟乙烯(PVDF)为基体采用球磨共混法热压制备CaCu3Ti4-3/4zFezO12(CCTFO)/PVDF和Ca1-3/2xLaxCu3-yMgyTi4O12(CLCMTO)/PVDF复合材料,考察掺杂量和前驱粉体填充质量对复合材料微观结构和介电性能的影响。结果表明:当前驱粉体填充质量增加到50%时,复合材料出现团聚现象。复合材料的介电常数和介电损耗均随填料含量的增加而升高,Fe掺杂后虽然不能提高复合材料的介电常数,但能降低中到高频段的介电损耗,La、Mg双掺杂不仅可以提高介电常数还可以降低介电损耗。