Synthesis of platelike CaTiO3 particles by a topochemical microcrystal conversion method and fabrication of textured microwave dielectric ceramics

Platelike CaTiO₃ particles with an orthorhombic perovskite structure have been synthesized by topochemical microcrystal conversion (TMC) from platelike precursor particles of the layer-structured CaBi₄Ti₄O₁₅ at 950 °C. The CaTiO₃ particles inherited and retained the shape of the precursor particles with a thickness of approximately 0.3 μm, and a width of 2–6 μm. XRD analysis showed that in the TMC reaction, the crystallographic {0 0 1} plane of CaBi₄Ti₄O₁₅ is converted into the {1 0 0} plane of CaTiO₃. Using the platelike CaTiO₃ particles as templates in the templated grain growth method, dense {1 0 0} grain-oriented CaTiO₃ ceramics having a {1 0 0} orientation could be fabricated at sintering temperatures between 1350 and 1500 °C. The maximum orientation factor reached 99.7% at 10% of template. It was found that texturing improves microwave dielectric low-loss properties, providing a 1.55 times higher Q_f value of 9310 GHz in textured ceramics compared to that of 6005 GHz in non-textured ceramics.     

大功率多层压电陶瓷变压器的新进展

利用新开发成的大功率压电陶瓷材料 ,研制成功了输出功率大于10W以上的大功率多层压电陶瓷变压器 ,其输出效率大于94 % ,升压比为25～30     

Dielectric and piezoelectric properties of (1−x)(Bi,Na)TiO3–x(Bi,K)TiO3 lead-free ceramics for piezoelectric energy harvesters

The piezoelectric and dielectric properties of the (1−x)(Bi,Na)TiO₃–x(Bi,K)TiO₃ (x=0.12, 0.14, 0.18, 0.20 and 0.30) lead-free ceramics were investigated. Specimens were prepared by the conventional mixed oxide method and sintered at 1170 °C in air. Scanning electron microscopy indicated that increasing x from 0.12 to 0.30 causes a decrease in the grain size. The (1−x)(Bi,Na)TiO₃–x(Bi,K)TiO₃ ceramics shows a homogeneous microstructure and excellent dielectric and piezoelectric properties. Specimens with optimum composition showed a piezoelectric charge constant d₃₃ of 166 pC/N, an electromechanical coupling factor k_p of 0.5, a dielectric constant ε_r of 1591.32 at 1 kHz and generated power output of 37.49 nW/cm².     

电子陶瓷材料介电功能应用研究现状与前瞻

电子陶瓷如压电陶瓷、铁电陶瓷等作为一种广泛采用的敏感材料广泛应用于光电子等领域,本文对其当前应用的现状进行了回顾,介绍了压电陶瓷在超声马达、汽车陶瓷传感器、压电振动陀螺仪、压电陶瓷微位移器、扫描显微镜等中的应用,介绍了铁电陶瓷在微波通讯中的应用,并对未来的趋势提出了展望。     

焦绿石相对PMSN四元系压电陶瓷性能的影响

通过X射线衍射、扫描电镜及电性能测试 ,分析了PMSN系压电陶瓷中焦绿石相对材料性能的影响 ,讨论了解决的办法 ;研究发现 ,焦绿石相的存在造成了低介电常数、高损耗 ;采用预合成铌铁矿法能够有效地抑制焦绿石相的生成     

Formation mechanism of barium titanate single crystalline microplates based on topochemical transformation using bismuth-based precursors

Owing to their importance in applications related to textured ceramics engineering, two-dimensional perovskite single-crystal microplates are highly desirable. In this work, (001)-oriented perovskite-structured BaTiO₃ (BT) single-crystal microplatelets were fabricated from an Aurivillius-structured BaBi₄Ti₄O₁₅ precursor via topochemical transformation. XRD, SEM, DTA, and TEM characterizations were performed to investigate the crystallization behavior and morphology evolution of the product at different reaction stages, with a focus on the formation mechanism of BT single crystalline microplatelets. Our results indicate that secondary recrystallization repaired the significant micro-structural/crystalline damage that was caused, thereby preserving the single-crystal structure during structural conversion. The subsequent epitaxial growth and replenishment through Ostwald ripening resulted in more regular shapes and narrower distributions of BT microplatelets. This study not only suggests suitable BT template candidates for the application of textured ceramics, but also provides new insights into a simple topochemical transformation strategy for manufacturing two-dimensional perovskite microcrystals.     

Composition and poling condition-induced electrical behavior of (Ba0.85Ca0.15)(Ti1−xZrx)O3 lead-free piezoelectric ceramics

Lead-free (Ba_0.85Ca_0.15)(Ti_1−xZr_x)O₃ (BCTZ) piezoelectric ceramics were fabricated by normal sintering in air atmosphere. BCTZ ceramics with x = 0.10 possess a coexistence of tetragonal and rhombohedral phases at ∼40 °C. The Curie temperature of BCTZ ceramics decreases with increasing the Zr content. Piezoelectric properties of BCTZ ceramics are dependent on the poling conditions (i.e., the poling temperature and the poling electric field), and the underlying physical mechanism is illuminated by the phase angle. The BCTZ (x = 0.10) ceramic, which locates at the existence of two phases and is poled at E ∼ 4.0 kV/mm and T_p ∼ 40 °C, exhibits an optimum electrical behavior at a room temperature of ∼20 °C: d₃₃ ∼ 423 pC/N, k_p ∼ 51.2%, 2P_r ∼ 18.86 μC/cm², 2E_c ∼ 0.47 kV/mm, ?_r ∼ 2892, and tan δ ∼ 1.53%.     

提高点火用压电陶瓷元件性能的研究

本文从理论上对压电点火器的点燃率及使用寿命与压电材料性能的关系进行了讨论,并据此开发出点燃率和放电灵敏度高,使用寿命长达60万次的点火用压电陶瓷材料。     

Giant piezoelectric coefficient of PNN-PZT-based relaxor piezoelectric ceramics by constructing an R-T MPB

xTa-PNN-PZT piezoelectric ceramics with [0.55 Pb(Ni_1/3Nb_2/3)O₃ - 0.45 Pb(Zr_0.3Ti_0.7)O₃ - xwt%Ta₂O₅] + 1 wt% PbO composition (0 ≤ x ≤ 0.7) were prepared by conventional solid-state reaction method. Special attention was paid to the effect of Ta₂O₅ concentration on structural, dielectric, piezoelectric, and ferroelectric properties of these ceramics. In particular, rhombohedral-tetragonal morphotropic phase boundary was observed in PNN-PZT crystal structure near the composition of x = 0.5. At this point, volume fraction of rhombohedral phase was almost equal to that of tetragonal phase. In addition, the ceramic exhibited the optimum values of piezoelectric coefficient, bipolar strain, unipolar strain, and inverse piezoelectric coefficient, i.e., 1090 pC/N, 0.135%, 0.165%, and 1493 pm/V, respectively. Moreover, according to in-situ X-ray diffraction, piezoelectric force microscopy, and in-situ strain measurement results, phase structure of 0.5Ta-PNN-PZT revealed relatively stable piezoelectric behavior at 60 °C.     

压电陶瓷驱动器材料

介绍一种压电应变常数ｄ３１大于３００×１０＾－１２ｍ／ｖ，居里温度大于１５０℃，介电常数小于５０００的压电陶瓷驱动器材料。     

无铅压电陶瓷SrBi4Ti4O15的制备工艺与性能研究

研究了SrBi Ti O 无铅压电陶瓷的制备工艺,确定 900℃为合成温度,在 1100℃烧结。对烧结后的 4 4 15样品进行性能测试,SrBi Ti O 无铅压电陶瓷的压电常数为10Pc/N,需要有一些制备方法来提高其在某一方向的 44 1 5压电性能。     

Achieving both large transduction coefficient and high Curie temperature of Bi and Fe co-doped PZT piezoelectric ceramics

Achieving both the large transduction coefficient (the product of piezoelectric charge d₃₃ and voltage coefficients g₃₃) and high Curie temperature is very important to improve the power generation performance and their thermal stability of piezoelectric energy harvesters. It is difficult to improve the transduction coefficient of the commercial PZT based piezoelectric ceramics due to the same variation trend of piezoelectric charge coefficient and dielectric constant with chemical modifications. In this work, Bi₂O₃ and Fe₂O₃ co-modified ((Pb_1-xBi_x)((Zr_0.53Ti_0.47)_1-xFe_x)O₃) ceramics were prepared by conventional solid state reaction method, and their dielectric and piezoelectric properties were studied. The piezoelectric charge coefficient d₃₃ increases by Bi and Fe co-modifications due to the enlarged grain size and reduced lattice distortion, while the dielectric constant ε₃₃ deceases mainly owing to the increased micro-pores in grains, leading to the enhancement transduction coefficient d₃₃×g₃₃. The Curie temperature Tc and maximum transduction coefficient d₃₃×g₃₃ are 346 °C and 17169 × 10^?15 m²/N, respectively, which are both higher than those of commercial PZT and PZN-PZT based piezoelectric ceramics. This work provides a new way to enhance the transduction coefficient of PZT based ceramics for piezoelectric energy harvesters used in wide temperature range.     

Determining the effects of BaTiO3 template alignment on template grain growth of Pb(Mg1/3Nb2/3)O3 –PbTiO3 and effects on piezoelectric properties

Crystallographic texturing of ferroelectric ceramics is an established method of inducing single crystal-like properties in a ceramic material via epitaxial grain growth according to the template used, otherwise known as Templated Grain Growth (TGG). The piezoelectric enhancement is dependent on the degree of TGG throughout the ceramic, which is closely linked to the tape casting parameters and sintering conditions. Pb(Mg1/3Nb2/3)O₃-PbTiO₃ (PMN-PT) perovskite ferroelectrics with morphotropic phase boundary compositions using 3 vol% BaTiO₃ templates were used for analysis. The blade gap and template size have the greatest impact on the overall grain alignment. The varying degrees of template alignment is related to the different enhancements of TGG and the correlating piezoelectric d₃₃ and d*₃₃. The highest piezoelectric property was demonstrated in PMN-31PT with Lotgering factor of 93% where d₃₃ = 1020 pC/N and d*₃₃ = 1420 pm/V were achieved.     

Effect of MnO2 addition on the structure and electric properties of (Ba0.94Ca0.06)(Ti0.9Sn0.1)O3 ceramics

The (Ba_0.94Ca_0.06)(Ti_0.9Sn_0.1)O₃ (BCTS) ceramics with pure perovskite structure were prepared by conventional solid-state reaction route with the addition of 0–0.8?mol% MnO₂. The crystal structure, microstructure, and electric properties were investigated systematically. X-ray diffraction patterns showed that the addition of MnO₂ changed the ratio of the coexistence of orthorhombic and tetragonal phases, which had apparent influences on the piezoelectric properties of ceramics. When the addition amount is 0.2?mol%, the average grain size increases from ~41.88–52.24?µm, and, however, the average grain size decreases with further addition > 0.2?mol%. A good combination of properties and performance could be achieved with the addition of 0.4?mol% MnO₂. The mechanical quality factor Q_m, dielectric loss tanδ, piezoelectric constant d₃₃, and planar electromechanical coefficient k_p measured are 216, 0.011, 578?pC/N, and 0.39, respectively. Therefore, results of this study suggest that the BCTS-Mn ceramics synthesized could exhibit a great potential for piezoelectric component applications.     

Processing and enhanced electrical properties of Sr1-x(K0.5Bi0.5)xBi2Nb2O9 lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics, Sr_1−x(K_0.5Bi_0.5)_xBi₂Nb₂O₉ (SKBN-x, x=0, 0.2, 0.5, 1.0), were synthesized by a conventional solid-state reaction. Structural and electrical properties of SKBN-x ceramics were investigated. X-ray diffraction analysis suggested that the substitution led to the formation of a layered perovskite structure. Plate-like morphologies for the grains were clearly observed in all the samples, which are characteristic for layer-structure Aurivillius compounds. The Curie temperature (T_c) is found to shift to higher temperature from 445 °C to 509 °C with increasing (K, Bi) content. Excellent remanent polarization (2P_r∼15 μC/cm²) were obtained for SKBN-0.2 ceramic. High piezoelectric coefficient of d₃₃∼21  pC/N were obtained for the samples at x=0.5. Additionally, thermal annealing studies indicated that the piezoelectric coefficient (d₃₃) of SKBN-0.5 was unchanged even if annealing temperature increased to be 450 °C, demonstrating the ceramics are the promising candidates for high-temperature applications.     

Evidence of macro–micro domain transition in poled PMN–PZT ceramics

The dielectric properties of unpoled and poled Pb_0.88Ba_0.06Sr_0.06(Mg_1/3Nb_2/3)_0.37Zr_0.375Ti_0.255O₃ (modified PMN–PZT) ceramics were investigated. It was found that the dielectric constant increased while the loss tangent decreased after poling. A frequency independent abrupt transition in the dielectric constant and loss tangent responses was observed for the poled ceramics. This abnormal behavior was believed to be correlated with the macro–micro domain transition and the corresponding pyroelectric measurement exhibited a narrow peak at the normal-relaxor transition temperature T_nr. Furthermore, the presence of double-loop-like hysteresis and two types of current peaks at a temperature slightly higher than T_nr showed another strong evidence of this transition.