制备工艺对0.95(K_(0.5)Na_(0.5))NbO_3-0.05CaZrO_3基无铅陶瓷压电性能的影响

采用传统陶瓷工艺制备了0.95(K0.5Na0.5)NbO3-0.05CaZrO3无铅压电陶瓷。研究了烧结温度和极化工艺对陶瓷压电性能的影响。结果表明:随着烧结温度的提高,0.95(K0.5Na0.5)NbO3-0.05CaZrO3陶瓷的体积密度增大,在1170℃时达到最大值,同时d33和kp,在此温度也分别达到他们的最大值210pC/N和0.40。极化工艺对0.95(K0.5Na0.5)NbO3-0.05CaZrO3陶瓷的压电性能有明显的影响,0.95(K0.5Na0.5)NbO3-0.05CaZrO3陶瓷的最佳极化温度是70℃,最佳极化电场是4kV/mm。     

低温烧结PZT–0.5%PbO·WO_3压电陶瓷

以固态氧化物为原料,采用一次合成工艺制备锆钛酸铅(leadzirconatetitanate,PZT)–0.5%PbOWO3压电陶瓷,研究摩尔比n(Zr)/n(Ti)、烧结温度对陶瓷性能的影响。结果发现:合成温度900℃保温2h可以得到钙钛矿结构压电陶瓷。n(Zr)/n(Ti)=1.08时,烧结温度为1100℃保温2h,压电陶瓷的综合性能在准同型相界处达最佳:介电常数ε3T3/ε0=1593,介电损耗tg?=0.019,压电系数d33=363.5×10-6C/N,机电耦合系数Kp=0.596,机械品质因数Qm=88.4。     

BiFeO_3-K_(0.5)Na_(0.5)NbO_3无铅压电陶瓷的烧结工艺

采用传统固相烧结法制备性能良好的铁酸铋(BiFeO3,BF)掺杂的铌酸钾钠(K0.5Na0.5NbO3,KNN)压电陶瓷(BF-KNN),着重研究BF摩尔(下同)掺量对KNN结构与压电性能的影响规律以及BF-KNN陶瓷的烧结工艺。结果表明:适量BF有利于提高BF-KNN的压电性能,当BF掺量≥1%后,压电性能急剧降低。与仅烧结一次的样品相比,二次烧结BF-KNN陶瓷形成更加稳定的正交晶系钙钛矿结构,陶瓷组织致密,压电性能大幅度提高,压电常数(d33)、平面机电耦合系数(kp)与机械品质因数(Qm)分别达134pC/N、46%和364,但介电性能明显降低,相对介电常数(εr)从退火前的554降至388。一次、二次烧结样品的体积密度分别为4.12g/cm3和4.36g/cm3,相对密度分别为91.35%和96.67%。在温度低于490℃、频率为100kHz时,二次烧结样品的介电损耗tanδ5%,其Curie温度高达420℃。     

低温烧结PZT-O.5%PbO·WO3压电陶瓷

以固态氧化物为原料,采用一次合成工艺制备锆钛酸铅(lead zirconate titanate,PZT)-0.5%PbO·WO3压电陶瓷,研究摩尔比n(Zr)/n(Ti)、烧结温度对陶瓷性能的影响.结果发现:合成温度900℃保温2 h可以得到钙钛矿结构压电陶瓷.n(Zr)/n(Ti)=1.08时,烧结温度为1 100℃保温2 h,压电陶瓷的综合性能在准同型相界处达最佳:介电常数εT33/ε0=1 593,介电损耗tgδ=0.019,压电系数d33=363.5×10-6C/N,机电耦合系数Kp=0.596,机械品质因数Qm=8 8.4.     

Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3系无铅压电陶瓷的制备工艺研究

利用XRD、SEM等分析技术 ,研究了Na0 .5Bi0 .5TiO3 -K0 .5Bi0 .5TiO3 系无铅压电陶瓷的合成温度 ,烧成工艺条件对陶瓷晶体结构、压电性能的影响。结果表明 ,合成温度提高有利于主晶相的形成 ,适当延长保温时间有利于材料的压电性能。该体系随着KBT含量的增加 ,烧结温度提高 ,烧结温度范围变窄。同时研究了极化工艺条件对材料压电性能的影响表明 ,提高极化电场和适当提高极化温度有利于压电性能的提高 ,但过高的温度由于受到材料高温下退极化的影响而导致材料压电性能变差     

掺杂对(Na_(1/2)K_(1/2))NbO_3-CaTiO_3无铅陶瓷烧结温度和电学性能的影响

通过传统固相反应法、利用两步合成工艺,在常压、960～1160℃烧结制备0.95(Na1/2K1/2)NbO3-0.05CaTiO3(0.95NKN-0.05CT)及WO3、CuO掺杂0.95NKN-0.05CT无铅压电陶瓷。X射线衍射分析表明:960℃和1020℃烧结制备的掺杂前后的0.95NKN-0.05CT陶瓷均为纯钙钛矿结构。随着CuO掺杂量的增加及烧结温度的升高,CuO掺杂0.95NKN-0.05CT陶瓷中出现杂相,并伴随着压电性能的下降。添加第二组元CaTiO3和氧化物掺杂可增加(Na1/2K1/2)NbO3(NKN)陶瓷的致密度,同时烧成陶瓷的介电、铁电和压电性能也有明显改善。摩尔分数分别为1%和2%CuO掺杂0.95NKN-0.05CT陶瓷的压电常数分别达到165pC/N和140pC/N。     

(K_(0.5)Na_(0.5))NbO_3-CaZrO_3基无铅压电陶瓷的相结构和压电性能研究

采用传统陶瓷工艺制备了(1-x)(K0.5Na0.5)NbO3-xCaZrO3(简称KNN-CZ)无铅压电陶瓷。分析了陶瓷样品的相结构组成。测试结果表明:所有陶瓷样品均为钙钛矿相,未发现其它晶相。随着CaZrO3含量的增加,(1-x)KNNxCZ陶瓷的相结构由正交相转变为四方相,最后变为立方相。研究了不同CaZrO3含量对压电性能的影响,实验表明:当CaZrO3含量为0.05mol时,压电常数d33和径向机电耦合系数kp分别达到了最大值196pC/N和0.35。(1-x)KNNxCZ(x=0.05)陶瓷的压电性能展现了良好的温度稳定性和经时稳定性,这些结果表明(1-x)KNN-xCZ(x=0.05)陶瓷是一种优良的无铅压电备选材料。     

Bi0.5Na0.5TiO3基无铅压电陶瓷设计与制备研究的新进展

综述了Bi0.5Na0.5TiO3(BNW)基无铅压电陶瓷体系研究的最新进展,介绍了BNT基无铅压电陶瓷的设计方法及其制备技术.用自洽场离散变分法(self-consult charge-discrete variation-Xa,SCC-DV-Xa)等计算方法可为设计新型BNT基陶瓷提供重要的理论指导.用湿化学法,包括:溶胶-凝胶法、柠檬酸盐法、水热法等,可以合成BNT基纳米粉体,该类方法制备的BNT基粉体具有良好烧结活性,利于致密化烧结,使材料电性能得到改善.用模板晶粒生长技术可获得晶粒生长定向程度很高的BNT基压电陶瓷材料,进而提高材料在特定方向的压电性能.     

超快速高温烧结钛酸钡压电陶瓷的制备及性能

烧结工艺直接影响陶瓷的显微结构及性能。利用超快速高温工艺制备钛酸钡压电陶瓷,并与常规烧结工艺制备的钛酸钡陶瓷进行对比。研究了超快速高温烧结电流对钛酸钡陶瓷组成、结构以及性能的影响。结果表明：超快速高温烧结可以抑制晶粒的生长,采用超快速高温烧结工艺在电流为180 A保温5 min后,钛酸钡陶瓷的室温相对介电常数为3 450、介电损耗为1.89%、压电常数为283 p C·N^–1,这些性能均与常规烧结钛酸钡性能相当,超快速高温整个烧结时间较常规工艺缩短了196倍,是一种新型高效功能陶瓷烧结方法。     

抗还原型PZT压电陶瓷的制备与性能

采用固相法制备出可在低氧压和还原性气氛中烧结的压电陶瓷材料。材料最佳组成为:Pb0.95Sr0.05(Zr0.54Ti0.46)O3+0.03%(质量分数)CuO+0.05%Nd2O3+1.00%Sb2O3。通过施主和受主共掺杂,既抑制了烧结过程中氧空位扩散,又避免了Ti4+与自由电子结合转变成为Ti3+,使陶瓷保持了压电性能。结果表明:添加半径合适的稀土元素,是使陶瓷具有抗还原性能的关键之一。当烧结温度为1050℃时,陶瓷压电应变常数d33=294 pC/N,平面机电耦合系数kp=43.56%,相对介电常数εT33/ε0=1 333,介电损耗tanδ=0.019 7。该材料可应用于与Ni、Cu等贱金属低温共烧的叠层压电器件中,能够大大降低器件的成本。     

Piezoelectric K0.5Na0.5NbO3 Ceramics Textured Using Needlelike K0.5Na0.5NbO3 Templates

Improved performance by texturing has become attractive in the field of lead‐free ferroelectrics, but the effect depends heavily on the degree of texture, type of preferred orientation, and whether the material is a rotator or extender ferroelectric. Here, we report on successful texturing of K_0.5Na_0.5NbO₃ (KNN) ceramics by alignment of needlelike KNN templates in a matrix of KNN powder using tape casting. Homotemplated grain growth of the needles was confirmed during sintering, resulting in a high degree of texture parallel to the tape casting direction (TCD) and the aligned needles. The texture significantly improved the piezoelectric response parallel to the tape cast direction, corresponding to the direction of the strongest <001>_pc orientation, while the response normal to the tape cast plane was lower than for a nontextured KNN. In situ X‐ray diffraction during electric field application revealed that non‐180° domain reorientation was enhanced by an order of magnitude in the TCD, compared to the direction normal to the tape cast plane and in the nontextured ceramic. The effect of texture in KNN is discussed with respect to possible rotator ferroelectric properties of KNN.     

Thermally-stable large strain in Bi(Mn0.5Ti0.5)O3 modified 0.8Bi0.5Na0.5TiO3-0.2Bi0.5K0.5TiO3 ceramics

(1-x)[0.8Bi_0.5Na_0.5TiO₃-0.2Bi_0.5K_0.5TiO₃]-xBi(Mn_0.5Ti_0.5)O₃ (x = 0–0.06, BNKMT100x) lead-free ferroelectric ceramics were prepared via solid state reaction method. Bi(Mn_0.5Ti_0.5)O₃ induces a structure transition from rhombohedral-tetragonal morphotropic phases to pseudo-cubic phase. Moreover, the wide range of compositions within x = 0.03–0.055 exhibit large strain of 0.31%–0.41% and electrostrictive coefficient of 0.027–0.041 m⁴/C². Especially, at x = 0.04, the large strain and electrostrictive coefficient are nearly temperature-independent in the range of 25–100 °C. The impedance analysis shows the large strain and electrostrictive coefficient originate from polar nanoregions response due to the addition of Bi(Mn_0.5Ti_0.5)O₃.     

K0.5Na0.5NbO3-BaCu0.5W0.5O3无铅压电陶瓷的结构与性能

以传统固相法工艺制备(1-x)K0.5Na0.5NbO3-xBaCu0.5W0.5O3[(1-x)KNN-xBCW]无铅压电陶瓷,研究不同BCW掺量(x=0％,0.1％,0.25％,0.5％,1.0％,摩尔分数,下同)对KNN陶瓷的晶体结构和电性能的影响,结果表明:x＜0.5％时,KNN陶瓷的相结构没有改变,仍为正交相...     

Dielectric properties of some low-lead or lead-free perovskite-derived materials: Na0.5Bi0.5TiO3–PbZrO3, Na0.5Bi0.5TiO3–BiScO3 and Na0.5Bi0.5TiO3–BiFeO3 ceramics

Na_0.5Bi_0.5TiO₃ (NBT) and its modifications are known to be new lead-free ferroelectric materials and are promising for environment friendly devices. The systems under investigation were (i) NBT (trigonal/ferroelectric)–PbZrO₃ (orthorhombic/antiferroelectric); (ii) NBT (trigonal/ferroelectric)–BiScO₃ (trigonal/paraelectric); and (iii) NBT (trigonal/ferroelectric)–BiFeO₃ (trigonal/antiferromagnetic).The lattice parameters change as expected from the respective ionic radii values. For NBT–PZ, the dielectric permittivity shows a large frequency and temperature dispersion suggesting a relaxor-like behaviour dependent on the thermal annealing of the samples. For NBT–BS, the Curie temperature increases with BS content as well as the diffuseness of the phase transition, connected with the introduced disorder. For NBT–BF, the overall behaviour of the permittivity of NBT is maintained up to 50% BF but anomalies of the permittivity appeared close to 600 °C, which might be connected with the onset of magnetic influence for high BF content.     

Electrical properties and relaxor phase evolution of Nb-Modified Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3-SrTiO3 lead-free ceramics

In this work, the crystalline phase, domain structure, and electrical properties of [Bi_0.5(Na_0.84K_0.16)_0.5]_0.96Sr_0.04Ti_1-xNb_xO₃ (x = 0.010–0.030) ceramics are investigated. Increasing the Nb content induces the phase transition from coexistent rhombohedral and tetragonal phases to a single pseudo-cubic phase, and the lamellar ferroelectric domains evolve into polar nanoregions. Decreased ferroelectric-to-relaxor transition temperature and enhanced frequency dispersion are found in the temperature-dependent dielectric constant and loss, implying a transition from the non-ergodic to ergodic relaxor state. The Nb substitution significantly degrades the long-range ferroelectric order with sharply decreased piezoelectric coefficients from ? 140 to ? 1 pC/N. However, a large strain of 0.32% at 5 kV/mm (normalized strain of 640 pm/V) is obtained around the critical composition of x = 0.0225. The composition of x = 0.030 shows good temperature insensitivity of the strain response, characterized by 308 pm/V with less than 15% reduction from 25 °C to 125 °C.     

Enhanced pyroelectric response from domain-engineered lead-free (K0.5Bi0.5TiO3-BaTiO3)-Na0.5Bi0.5TiO3 ferroelectric ceramics

Enhanced pyroelectric response is achieved via domain engineering from [001] grain-oriented, tetragonal-phase, lead-free 0.2(2/3K_0.5Bi_0.5TiO₃-1/3BaTiO₃)-0.8Na_0.5Bi_0.5TiO₃ (KBT-BT-NBT) ceramics prepared by a templated grain growth method. The [001] crystallographic orientation leads to large polarization in tetragonal symmetry; therefore, texturing along this direction is employed to enhance the pyroelectricity. X-ray diffraction analysis revealed a Lotgering factor (degree of texturing) of 93 % along the [001] crystallographic direction. The textured KBT-BT-NBT lead-free ceramics showed comparable pyroelectric figures of merit to those of lead-based ferroelectric materials at room temperature (RT). In addition to the enhanced pyroelectric response at RT, an enormous enhancement in the pyroelectric response (from 1750 to 90,900 μC m^?2 K^?1) was achieved at the depolarization temperature because of the sharp ferroelectric to antiferroelectric phase transition owing to coherent 180° domain switching. These results will motivate the development of a wide range of lead-free pyroelectric devices, such as thermal sensors and infra-red detectors.     

Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3系无铅压电陶瓷的极化工艺研究

主要研究了极化电场,极化时间和极化温度等工艺参数对Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3系无铅压电陶瓷介电和压电性能的影响。结果表明:极化电场和极化温度对压电陶瓷的介电、压电性能影响较大,而极化时间则影响较小。适宜的极化电场是3～3.5kV/mm,极化温度70～80℃,极化时间为10～15min。     

CeO2掺杂钛酸铋钠钾陶瓷的制备工艺与介电性能

为了进一步探索合成工艺对钛酸铋钠系无铅材料的结构及介电特性的影响,本文以甘氨酸为燃料,利用固相-燃烧法制备了CeO2掺杂的Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3 (BNKT)陶瓷.XRD表明,在固相合成工艺中引入燃烧法制备BNKT陶瓷,比传统固相法降低预烧温度150 ℃,掺杂的CeO2扩散进入了BNKT钙钛矿的晶格,且当掺杂量为0%~0.3%时,形成纯的钙钛矿相结构;SEM表明,CeO2掺杂使晶粒尺寸趋于平均,对晶粒生长有抑制作用;介电温谱表明,随着CeO2掺杂量增加,介电常数εr和退极化温度Td、相转变温度Tm降低,介电反常峰逐渐弱化,且室温至300 ℃,介电损耗tanδ始终在0.3%以下,并从微结构缺陷空位形成机制角度,结合铁电畴壁运动状态,分析讨论了对材料介电特性的作用规律.     

Characterization of multiferroic PbFe0.5Nb0.5O3 and PbFe0.5Ta0.5O3 ceramics derived from citrate polymeric precursors

Ceramics of the perovskite multiferroics PbFe_0.5Nb_0.5O₃ (PFN) and PbFe_0.5Ta_0.5O₃ (PFT) were synthesized from new citrate polymeric precursors. X-ray tests pointed to trace amounts of the pyrochlore phase. SEM studies revealed the heterogeneous grain size distribution for PFN and the homogeneous one for PFT. Dielectric studies pointed to one diffuse T-C phase transition at 378 K for PFN and two diffuse M-T and T-C phase transitions, at 200 and 235 K, for PFT, respectively. X-ray photoelectron spectroscopy studies of PFN reveal that all ions exist in one valence state, however, with two chemical shifts for Pb²⁺. Two valence states for the majority of ions of PFT seem to be connected with a higher volume fraction of the amorphous grain-boundary phase. The electronic energy band gap for both compounds is approximately 2.8 eV. Two magnetic transitions, ie, from the paramagnetic to the antiferromagnetic phase and then to the spin-glass phase, were observed at 156 and 10 K for PFN, and at 145 and 15 K for PFT, respectively.     

Raman spectroscopy of Na0.5Bi0.5TiO3

We have measured the Raman spectra of bismuth sodium titanate in its rhombohedral, tetragonal, and cubic phases, with special attention paid to the phase transitions at 584K and 837K (heating). Both transitions appear to be order-disorder and strongly first order, with large thermal hysteresis. The phonon spectra at temperature slightly below the tetragonal phase are remarkably similar to BaTiO₃ with A₁(To) modes at 130, 269, and 541 cm^-1 (compared with 170, 270, 520 cm^-1 in BaTiO₃) and an E(TO) at 52 cm^-1.