Grain size effects and structure origin in high-performance BaTiO3-based piezoceramics with large grains

Grain size shows significant influence on electrical properties of piezoceramics. However, there are few works to investigate the grain size effects in high-performance and large-grain piezoceramics and uncover the structure origin. In this work, large grain size from ~53 to ~92 µm was achieved in a high-performance BaTiO₃ (BT)-based ceramic via tuning sintering conditions. With grain size increasing, the ceramics exhibit same multiphase coexistence state, similar phase transition temperature, upward T_C dielectric peaks and reduced diffuseness degree. Because of the larger and more complex non-180° domains within bigger grains, the improvement in remnant polarization (P_r), coercive field and negative strain were observed in bigger-grain ceramics. The elevated P_r finally leads to the piezoelectric coefficient d₃₃ increasing from 500 to 650 pC/N. However, too large grains may cause the reduced strain due to the high remnant strain in first cycle. Therefore, big grain size is conducive to achieve high piezoelectricity while moderate grain size can facilitate strain response in high-performance ceramics with large grains, which is quite different with pure BT ceramic. This work presents insights into the grain size effects and affords guides to further optimize electrical properties in high-performance piezoceramics with large grains.     

PMN-PT系陶瓷的熔盐法合成及其压电性能研究

采用熔盐法合成在多晶相界附近的ＰＭＮ－ＰＴ系陶瓷样品,对其压电性能进行了研究,并与传统陶瓷工艺进行了比较．结果表明：熔盐法得到的样品的压电性能较好,Ｋｐ＝５８％,ｄ３３＝５２０ｐＣ／Ｎ;而传统陶瓷工艺得到的陶瓷样品的Ｋｐ＝４６％,ｄ３３＝３６７ｐＣ／Ｎ．采用ＳＥＭ和ＸＲＤ等手段对结果进行了分析和讨论．     

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。     

Preparation and Properties of Fine-Grain (1−x)BiScO3−xPbTiO3 Ceramics by Two-Step Sintering

(1− x )BiScO₃− x PbTiO₃ (BSPT) nanopowder with an average grain size of 10 nm with the composition of x =0.64, which has been reported to be close to the MPB in the bulk BSPT ceramics, was successfully synthesized. Subsequently, the techniques of preparation of high-performance fine-grain MPB–BSPT ceramics by two-step sintering were investigated, providing a feasible approach to produce a high-density fine-grain MPB–BSPT ceramic using pressureless means without any sintering aids at a low temperature of 800°C. The results have shown that the fine-grain ceramic possesses a higher piezoelectric constant and electromechanical coupling factor than the coarse-grain ceramic. The influences of the grain size on the piezoelectric and dielectric properties were also discussed. Within the scale of the grain sizes of our specimens, the piezoelectric constant increases up to 520 pC/N at the finest grain size of 200 nm, indicating a promising path for the improvement of the piezoelectric coefficient.     

含Pt金属芯压电陶瓷纤维的微观结构和电学性能

以传统固相法制备的0．55Pb（Ni1/3Nb2／3）O3-0．45Pb（Zr0.3Ti0.7）03（PNN-PZT）压电陶瓷粉体为原料,采用挤压成型工艺制备含Pt金属芯压电陶瓷纤维。以PbTi03作为保护粉体,对纤维坯体进行1200℃不同时间（0．5、1．0h和2．0h）的烧结处理。利用X射线衍射仪、扫描电子显微镜、阻抗分析仪和铁电分析仪等研究了烧结时间对纤维微观结构、压电性能和铁电性能的影响。结果表明：在烧结时间范围内制备的压电陶瓷纤维为单一钙钛矿结构,未发现焦绿石相或其他杂相;随烧结时间增加,陶瓷纤维晶粒尺寸增大,压电和铁电性能明显提高。在1200℃保温2．0h制备的压电陶瓷纤维电学性能较好,压电常数（西1）、相对介电常数（曲、介电损耗（tanδ）和矫顽场（＆）分别为-145pC／N、3313、2．6％和0．27kV／mm。介电温谱结果表明：该陶瓷纤维的特征Curie温度为125℃,峰值相对介电常数为8093。     

Fine-grained relaxor ferroelectric PMN-PT ceramics prepared using hot-press sintering method

Relaxor ferroelectric PbMg_1/3Nb_2/3O₃-PbTiO₃ (PMN-PT) ceramics are high-performance piezoelectric materials that are widely used in many electronic devices. However, it is extremely difficult to manufacture thin piezoelectric components dozens of micrometers in size using commercial coarse-grained PMN-PT ceramics. This limits the application of PMN-PT ceramics to high-frequency ultrasonic devices. In this work, we prepared a dense, fine-grained PMN-PT ceramic at low temperature using a hot-press sintering (HPS) method. The HPS ceramic had small grains with an average size of 1 μm and maintained high performance with a large permittivity (ε_r = 4500), piezoelectricity (d₃₃ = 650 pC/N), and electrostrain (S_E = 0.14% at 20 kV/cm). The large volume fraction of grain boundaries led to stronger relaxor behavior of the fine-grained PMN-PT ceramic than of the normal coarse-grained one. Owing to its small grains and high piezoelectric performance, this fine-grained PMN-PT ceramic meets the strict requirements of manufacturing thin piezoelectric components. Our results demonstrate that PMN-PT ceramics have great potential for developing low-cost, high-frequency ultrasonic devices by replacing expensive piezoelectric single crystals.     

PLZT驰豫铁电陶瓷偏压压电效应的研究

本文研究了铌掺杂的ＰＬＺＴ驰豫铁电陶瓷在不同直流偏压及温度下的介电常数ε３３,平面机电耦合系数ｋ和等效横向压电常数ｄ３１。实验表明,铌掺杂的ＰＬＺＴ驰豫铁电陶瓷ｄ３１值可由直流偏压控制及ｄ３１值的温度系数远小于ＰＭＮ－ＰＴ系陶瓷。室温上２ｍｏｌ％和３ｍｏｌ％的铌掺杂的ＰＬＺＴ１０／６５／３５驰豫铁电陶瓷在１０ＫＶ／ｃｍ的偏压下│ｄ３１│分别为２０５ｐＣ／Ｎ和１６０Ｃ／Ｎ。     

Effect of the slurry composition on the piezoelectric properties of PZT ceramics fabricated via materials extrusion 3D printing

Herein, the effect of the binder content in lead zirconate titanate (PZT) slurry has been systematically studied to improve the piezoelectric properties of PZT ceramics prepared via material extrusion 3D printing. For smooth printing, a slurry with a binder concentration ranging from 6 to 12 wt% was proposed. The porosity of the green body first decreased and then increased with an increase in the binder concentration, and the minimum porosity was obtained when the binder concentration reached 10 wt%. Samples with increased density were obtained after debinding and lead-rich atmosphere sintering. PZT piezoceramics fabricated using a binder content of 10 wt% exhibit the maximum relative density (96.9%), largest piezoelectric constant (342.6 pC/N) and dielectric constant (1621). Based on the above process, the wood pile structure and helical twentytetrahedral structural components were successfully fabricated using the material extrusion process. This research lays the foundation for the engineering application of 3D printing to fabricate high-performance piezoceramics with complex shapes.     

Li2CO3掺杂对0.2PMN-0.8PZT陶瓷的影响

利用铌铁矿预产物合成法,研究不同温度烧结下Li2CO3掺杂对0.2 PMN-0.8PZT压电陶瓷(简称PLC)的相结构和电性能的影响。X射线衍射(XRD)和扫描电镜(SEM)的分析结果表明,掺杂LiCO3的0.2PMN-0.8PZT压电陶瓷经不同温度煅烧后,所有陶瓷样品的相组成均为纯钙钛矿相,并随着烧结温度的升高,PLC的相结构有由四方相向菱方相转变的趋势。通过0.2PMN-0.8PZT压电陶瓷掺杂LiCO3煅烧后的微观形貌、介电常数、压电性能、铁电性能的分析,发现经1200℃烧结的样品的介电和压电性能最佳:介电常数(εr)为38512,室温压电常数(d33)为300 pC/N,剩余极化强度(Pr)为31.3 C/cm2,矫顽电场(Ec)为7.5 kV/cm。     

Low‐temperature sintering and enhanced piezoelectric properties of random and textured PIN–PMN–PT ceramics with Li2CO3

Low‐temperature sintered random and textured 36PIN–30PMN–34PT piezoelectric ceramics were successfully synthesized at a temperature as low as 950°C using Li₂CO₃ as sintering aids. The effects of Li₂CO₃ addition on microstructure, dielectric, ferroelectric, and piezoelectric properties in 36PIN–30PMN–34PT ternary system were systematically investigated. The results showed that the grain size of the specimens increased with the addition of sintering aids. The optimum properties for the random samples were obtained at 0.5 wt% Li₂CO₃ addition, with piezoelectric constant d₃₃ of 450 pC/N, planar electromechanical coupling coefficient k_p of 49%, peak permittivity ε_max of 25 612, remanent polarization P_r of 36.3 μC/cm². Moreover, the low‐temperature‐sintered textured samples at 0.5 wt% Li₂CO₃ addition exhibited a higher piezoelectric constant d₃₃ of 560 pC/N. These results indicated that the low‐temperature‐sintered 36PIN–30PMN–34PT piezoelectric ceramics were very promising candidates for the multilayer piezoelectric applications.     

The complex evaluation of functional properties of nearly dense BCZT ceramics and their dependence on the grain size

In this article, the effect of dwell time (2–48?h) during isothermal sintering at 1520?°C on the grain size, density and crystal structure of (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ is demonstrated. All ceramics exhibited the phase transition from orthorhombic to mixed orthorhombic and tetragonal phases between 12 and 24?h dwell time. The piezoelectric, dielectric and ferroelectric properties of these ceramics show a strong correlation with grain size in the range of 16.5–44.5?µm. Nearly dense microstructure (93.1–94.3% t.d.) was maintained during entire dwell time range without sacrificing much of its functional properties. Increasing grain size caused a little decrease in d₃₃* piezoelectric constant from 480 pC/N to 460 pC/N while mechanical quality factor (Q_m) increased from 62 to 136. Diffusivity coefficient (γ) ranges between 1.46 and 1.55 which indicates a normal ferroelectric behavior.     

Building submicron crystalline piezoceramics: One-step pressureless sintering partially amorphized nanopowder

The key to miniaturization of piezoelectric devices is to build high-performance fine-grained piezoceramics. Although the preparation of fine-grained ceramics can be achieved by hot press sintering or spark plasma sintering, complex processes, and high costs hinder the popularization of such technologies. In this work, a one-step conventional pressureless sintering technique based on partially amorphized nano-precursors has been proposed for low-cost preparation of submicron-structured ceramics. Using this technology, 0.36BiScO₃–0.64PbTiO₃ ceramics with an average particle size of 170 nm and a relative density of 95% can be prepared at temperature as low as 900°C, while the samples still have excellent piezoelectric properties (d₃₃ = 220 pC/N, g₃₃ = 40 × 10⁻³ Vm/N). In the process of sintering partially amorphized nano-precursors, the initial densification rate is faster than the grain growth rate, which can be attributed to two effects promoting low temperature densification, one is the liquid phase sintering mechanism associated with the amorphous phase, and the other is the filling effect of small particles deposited at the grain boundaries. This work is simple and easy to implement, and it is expected to be extended to the preparation of other types of fine-grained ceramics.     

(Ba,Ca)(Ti,Zr)O3–CeO2 translucent and opaque ceramics — Optical and electromechanical characteristics

This work demonstrates promising approaches to synthesize multifunctional-translucent BCZT-CeO₂ ceramic for electro-mechanical/optical conversion. Nearly fully dense BCZT-CeO₂ electroceramics were fabricated by spark plasma sintering (SPS) showing high dielectric permittivity of 5875 and low dielectric loss of 2.1%. Altogether, an extraordinary optical transmittance was attained as ～ 40% at 750 nm wavelength and ～ 46% in the infrared region. The fine grains restricted piezoelectric constant, d₃₃, to a moderate value of ～ 145 pC/N but with an enhanced Curie temperature, T_C ～ 135 °C. Post rapid pressure-less sintering on SPSed samples led to a fast grain growth within an extra hour of sintering and a major improvement of piezoelectric properties (d₃₃ = 532 pC/N and k_p = 43%) was achieved. A substantial amount of energy can be saved by both approaches owing to rapid heating/cooling rates and short dwell-times, at least when compared to conventional sintering. This success highlights ingenious avenues for further studies on BCZT-CeO₂ electro-optical ceramics.     

Investigation of dielectric and piezoelectric properties in aliovalent Eu3+-modified Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics

Rare earth (Eu³⁺)-modified Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT) polycrystalline ferroelectric ceramics were fabricated by high-temperature solid-state sintering, the phase structure, dielectric and piezoelectric properties were investigated. Eu³⁺ addition was found to significantly improve dielectric and piezoelectric properties of PMN-PT, where the optimized properties were achieved for the composition of 2.5 mol%Eu: 0.72PMN-0.28PT, with the piezoelectric d₃₃ = 1420 pC/N, dielectric ε_r = 12 200 and electromechanical k₃₃ = 0.78, respectively. All these results indicate that the Eu³⁺-doped PMN-PT ceramics are promising candidates for high-performance room-temperature piezoelectric devices.     

Mg~(2+)掺杂对PZT陶瓷材料介电性能的影响

系统地研究了Mg2+掺杂对PZT材料相结构及介电性能的影响,结果表明:Mg2+的添加阻止了陶瓷晶粒的过分长大,起到了细化晶粒的作用,改善其烧结性能,降低了烧结温度;由于晶格发生畸变,体系的相结构由三方相向四方相过渡;Mg2+的引入使PZT陶瓷材料的红外光谱图明显向高波数的方向移动,并且显著提高了材料的介电常数,有效降低了其介电损耗,使材料的介电性能得到了明显优化。     

Effects of sintering temperature and poling conditions on the electrical properties of Ba0.70Ca0.30TiO3 diphasic piezoelectric ceramics

The effects of sintering temperature and poling conditions on the electrical properties of tetragonal and orthorhombic diphasic Ba_0.70Ca_0.30TiO₃ (BCT) lead-free ceramics have been systematically investigated. On the one hand, with increasing sintering temperature from 1270 °C to 1400 °C, the bulk density increases monotonically and the Curie temperature keeps almost constant with the value of ∼120 °C, whereas the grain size, the maximum relative dielectric constant, room temperature polarization reach the maximum values for samples sintered at 1340 °C. On the other hand, it is found that the piezoelectric property depends on poling electric field and poling temperature significantly. An enhanced piezoelectric behavior of d₃₃=126 pC/N, k_p=0.29, and Q_m=588 is obtained for the BCT ceramics poled at 100 °C with 30 kV/cm field for 20 min. The aging behavior of the piezoelectric property is also investigated.     

半化学法制备工艺对PMN-PT陶瓷电性能的影响

以硝酸镁代替MgO,采用两种半化学法制备工艺分别制备了铌镁酸铅-钛酸铅陶瓷,并研究了陶瓷的相组成、显微结构和电性能。实验结果表明,采用两步半化学法(SCM-A)制备的陶瓷为纯钙钛矿相结构,晶粒大小约为5μm,结构致密,该陶瓷的介电常数峰值达45 000,剩余极化强度为31.8μC/cm2,压电常数为450 pC/N;而采用一步半化学法(SCM-B)制备的陶瓷则含有少量焦绿石相,晶粒大小约为2μm,该陶瓷的介电常数峰值为25 000,剩余极化强度约为26.9μC/cm2,压电常数为360 pC/N。     

Correlation between the grain size and phase structure,electrical properties in BiScO3-PbTiO3-based piezoelectric ceramics

As one of the most promising candidates of high-temperature piezoelectric sensors, BiScO₃-PbTiO₃ (BS-PT)-based ceramics are commonly modified by end-member substitution to modify the phase structures and electrical properties. In this work, BS-PT-based piezoelectric ceramics with various grain sizes (1.4-3.7 μm) of the composition 0.98(0.36BiScO₃-0.64PbTiO₃)-0.02Bi(Sn_1/3Nb_2/3)O₃ were prepared by conventional solid-state reaction method at different sintering temperatures from 1100℃ to 1180℃. X-Ray diffraction results show that the tetragonal phase content increases from 68.9% to 85.7% with the increasing sintering temperature. Transmission electron microscope characterizations reveal that micromorphology and domain morphology are sensitive to grain size. In addition, the dielectric and ferroelectric properties are almost independent on the sintering temperature, whereas an optimal piezoelectric constant d₃₃ of 450 pC/N is achieved when the sintering temperature is 1120℃, which can be due to the suitable coexistence of the rhombohedral and tetrahedral phase, as well as the coexistence of nanodomains and subsize strip-like domain. All of the results not only open a new window to improve d₃₃ of piezoelectric ceramics but also help to further understand microstructure-property relationships in piezoelectric ceramics.     

Improved ferroelectric,piezoelectric, and dielectric properties in pure KNN translucent ceramics by optimizing the normal sintering method

In this study, it is reported that various properties can be selectively derived in a pure (K_0.5Na_0.5)NbO₃, KNN ceramics through optimizing the sintering temperature by the conventional sintering method. High piezoelectric, ferroelectric, and dielectric properties such as d₃₃ = 127 pC/N, P_r = 31 μC/cm², and ε_r = 767 are obtained at the sintering temperature of 1100 °C. On the contrary, the specimen sintered at 1130 °C does not show high piezoelectric and ferroelectric properties, but it is translucent with a transmittance of 22% and 57% at the wavelength of 800 and 1600 nm respectively and shows a very high dielectric constant ε_r of 881. The origin of the high piezoelectric constant owes to large remanent polarization and dielectric constant, and dense microstructure with uniform distribution of large grains with the conjunction of relatively large crystal anisotropy. On the other hand, dense microstructure with almost no porosity, highly compacted grain boundaries, uniform distribution of grains, and relatively low crystalline anisotropy are responsible for the translucency and large dielectric constant of the ceramic specimens. This study demonstrates that the lead-free KNN ceramic has the potential to show multiple noteworthy properties such as piezoelectric, ferroelectric, dielectric, and transparent properties. This work provides a pure KNN ceramic simultaneously with high piezoelectric and transparent characteristics prepared only by using the conventional sintering method at a moderate sintering temperature for the first time in the literature.