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21.
Sanju Gupta 《Journal of the American Ceramic Society》2023,106(4):2209-2224
Lead scandium tantalate (PbSc0.5Ta0.5O3, PST), an order/disorder ferroelectric, is a potential candidate for electrocaloric cooling and pyroelectric infrared (IR) detector. In this work, we report the phase transformation kinetics from two series of samples containing pure amorphous and mixture of amorphous and pyrochlore to desired perovskite phase using postdeposition rapid thermal processing (RTP) as well as growth mechanism of RF sputtered PST thin films using excess lead target on platinized silicon (Pt/Ti/SiO2/Si) substrates. We find that small changes in the temperature ramp have a large effect on the degree of perovskite conversion (ferroelectric phase), orientation (crystallographic texture), and long-range order parameter (< S111 >). Through isothermal annealing, we obtained optimal perovskite phase at ≥700°C temperature. The phase transformation is characterized by spontaneous formation of center-type in-plane radial rosette-like structures revealed by scanning electron microscopy. The PST perovskite crystallites were found to coexist with pyrochlore in RTP annealed films. The volume fractions for perovskite and pyrochlore phase were obtained from the analysis of “rosettes” and respective X-ray diffraction intensities which helped to determine various parameters associated with phase kinetics (n, k, and activation energy, Ea) and accompanying growth. The effective activation energies of perovskite transition and growth were found to be 332 ± 11 kJ/mol (345 ± 11 kJ/mol) and 114 ± 10 kJ/mol (122 ± 10 kJ/mol), respectively, for pure amorphous only (and mixed amorphous and pyrochlore) phase following nucleation-growth controlled Avrami's equation. A linear growth rate (n∼1) for the perovskite phase indicates predominant interface-controlled process and diffusion-limited phenomena thus inhibiting rosette size owing to reactant depletion and soft impingement at the grain boundary. However, the growth behavior is isotropic in two-dimension parallel to the plane of the substrates for both sample series. Lead loss was severe for in-situ growth and RTP combined with conventional furnace annealing than those of RTP only films, which were closer to stoichiometric albeit with excess lead and marginal oxygen vacancies (Vo). 相似文献
22.
采用固相法制备了(Ba0.3Sr0.7)0.35(Bi0.5Na0.5)0.65TiO3-xwt%CaCu3Ti4O12(BSBNT-xwt%CCTO,其中x=5,10,15,20)陶瓷,研究了CCTO含量对BSBNT陶瓷的相结构、显微结构和电学性能影响。当x≤15时,陶瓷存在BSBNT和CCTO两相;而当x=20时,检测出少量的CuxOy氧化物相。CCTO的引入使得陶瓷晶粒尺寸明显降低,且保持良好的致密度。同时,陶瓷的介电峰逐渐展宽,温度稳定性TCC150℃获得提高,介电常数与损耗也呈现良好的频率稳定性。随着CCTO含量增加,BSBNT-xwt%CCTO陶瓷的电滞回线逐渐向“细长”型转变。在E=80 kV/cm电场强度下,BSBNT-10wt%CCTO陶瓷具有优化的能量密度Wrec... 相似文献
23.
《Ceramics International》2023,49(8):12214-12223
In recent years, “high-entropy” materials have attracted great attention in various fields due to their unique design concepts and crystal structures. The definition of high-entropy is also more diverse, gradually expanding from a single phase with an equal molar ratio to a multi-phase with a non-equimolar ratio. This study selected (Na0.2Bi0.2Ba0.2Sr0.2Ca0.2)TiO3 high entropy ceramics with excellent relaxation behavior. The A-site elements are divided into (x = Na, Bi, Ba) and ((1-3x)/2 = Sr, Ca) according to their inherent properties. A novel ABO3 structural energy storage ceramics (NaBaBi)x(SrCa)(1-3x)/2TiO3 (x = 0.19, 0.195, 0.2, 0.205 and 0.21) was successfully fabricated using the high entropy design concept. The ferroelectric and dielectric properties of non-equimolar ratio high-entropy ceramics were studied in detail. It was found that the dielectric constant of ∼4920 and the recoverable energy storage density of 3.86 J/cm3 (at 335 kV/cm) can be achieved simultaneously at x = 0.205. The results indicate that the design concept of high-entropy materials with a non-equal molar ratio is an effective means to achieve distinguished energy storage performance in lead-free ceramics. 相似文献
24.
《Journal of the European Ceramic Society》2022,42(11):4528-4538
Ideal relaxor antiferroelectrics (RAFEs) have high field-induced polarization, low remnant polarization and very slim hysteresis, which can generate high recoverable energy storage Wrec and high energy storage efficiency η, thus attracting much attention for energy storage applications. True RAFEs, on the other hand, are extremely rare, and the majority of them contain environmentally hazardous lead. In this work, we use a viscous polymer rolling process to synthesize a novel and eco-friendly 0.65Bi0.5Na0.4K0.1TiO3-0.35[2/3SrTiO3-1/3Bi(Mg2/3Nb1/3)O3] (BNKT-ST-BMN) dielectric material, which possesses a very typical RAFE-like characteristic. As a result, this material has a high Wrec of 4.43 J/cm3 and a η of 86% at an electric felid of 290 kV/cm, as well as a high thermal stability of Wrec (>3 J/cm3) over a wide range of 30–140 °C at 250 kV/cm. Our findings suggest that the BNKT-ST-BMN material could be a potential candidate for use in energy storage pulse capacitors. 相似文献
25.
Qiumei Wei Lovro Fulanovic Kodumudi Venkataraman Lalitha Mupeng Zheng Yudong Hou Mankang Zhu Linjing Liu Yunfei Chang Rui Xue 《Journal of the American Ceramic Society》2022,105(5):3312-3321
Innovative cooling technologies are recognized by many industries as a crucial part of their system design. A large electrocaloric effect (ECE) and extended working temperature are the key issues hindering the realization of electrocaloric refrigeration technology. In this work, large ECE (ΔT = 0.8–0.9°C @ 4 kV/mm) with an ultrawide temperature span from 30 to 120°C is noted for lead-free (Na1/2Bi1/2)0.80Sr0.20(Zn1/3Nb2/3)xTi1-xO3 ceramics. The excellent ECE performance can be ascribed to the evolution of polar nanoregions. Our work suggests that this material is promising for applications in solid-state refrigeration systems with a broad range of operating temperatures. 相似文献
26.
Juan-Nan Chen Qian Wang Xian Zhao Chun-Ming Wang 《Journal of the American Ceramic Society》2022,105(7):4815-4826
Bismuth layer–structured ferroelectric calcium bismuth niobate (CaBi2Nb2O9, CBN) is considered to be one of the most potential high-temperature piezoelectric materials due to its high Curie temperature Tc of ∼940°C, but the drawbacks of low electrical resistivity at elevated temperature and low piezoelectric performance limit its applications as key electronic components at high temperature (HT). Herein, we report significantly enhanced dc electrical resistivity and piezoelectric properties of CBN ceramics through rare-earth element Tb ions compositional adjustment. The nominal compositions of Ca1−xTbxBi2Nb2O9 (abbreviated as CBN-100xTb) have been fabricated by conventional solid-state reaction method. The composition of CBN-3Tb exhibits a significantly enhanced dc electrical resistivity of 1.97 × 106 Ω cm at 600°C, which is larger by two orders of magnitude compared with unmodified CBN. The donor substitutions of Tb3+ ions for Ca2+ ions reduce the oxygen vacancy concentrations and increase the band-gap energy, which is responsible for the enhancement of dc electric resistivity. The temperature-dependent dc conduction properties reveal that the conduction is dominated by the thermally activated oxygen vacancies in the low-temperature region (200–350°C) and by the intrinsic conduction in the HT region (350–650°C). The CBN-3Tb also exhibits enhanced piezoelectric properties with a high piezoelectric coefficient d33 of ∼13.2 pC/N and a high Tc of ∼966°C. Moreover, the CBN-3Tb exhibits good thermal stabilities of piezoelectric properties, remaining 97% of its room temperature value after annealing at 900°C. These properties demonstrate the great potentials of Tb-modified CBN for high-temperature piezoelectric applications. 相似文献
27.
28.
在不同热解温度下,采用溶胶-凝胶法在Pt/Ti/SiO2/Si衬底上制备镧、锰共掺杂铁酸铋铁电薄膜Bi0.9La0.1Fe0.95Mn0.05O3(BLFMO)。利用热失重仪(TGA)分析BLFMO原粉的质量损失,用 X 射线衍射仪(XRD)和原子力显微镜(AFM)分析 BLFMO 薄膜的晶体结构和表面形貌。在热解温度为420℃时,得到BLMFO薄膜的剩余极化值为21.2μC/cm2,矫顽场为99 kV/cm,漏电流密度为7.1×10-3 A/cm2,说明薄膜在此热解温度下具有较好的铁电性能。 相似文献
29.
(Na,K)NbO_3基无铅压电陶瓷的研究进展 总被引:2,自引:1,他引:2
本文主要综述近几年来国内外有关(Na,K)NbO3基无铅压电陶瓷体系的加压固相烧结技术、液相助烧致密化技术、掺杂改性、相结构调控以及相关机理研究方面的研究进展和动向,并展望该陶瓷体系在医疗超声换能器技术方面的应用前景。 相似文献
30.