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Highly-oriented (104) polycrystalline α-Al2O3 transparent ceramics prepared by a templated grain growth method
摘要： Highly-oriented (104) polycrystalline α-Al2O3 transparent ceramics were prepared by a templated grain growth (TGG) method using A-plane single-crystal sapphire as the template. This is the first report, to best of our knowledge, on polycrystalline α-Al2O3 ceramics oriented to non-optical axes. XRD and SEM results indicate that samples with high oriented grains and high-density structure are prepared. Compared to random samples, the oriented samples exhibited an increase in the real in-line transmittance (at 650 nm) from ~23% to ~62%. Moreover, the transmission remains a high level as the wavelength shifts toward the UV range (< 300 nm). This method can be extended to other uniaxial materials without optical axes in order to produce polycrystalline ceramics with excellent optical transparency.
关键词： polycrystalline α-Al2O3,oriented,transparent ceramics,grain growth
更新于2025-09-10 09:29:36
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An inverse approach to the characterisation of material parameters of piezoelectric discs with triple-ring-electrodes
摘要： For its usage in simulation-based design processes a precise knowledge of the employed material properties is inevitable. In the case of piezoelectric ceramics, the provided material parameters often suffer from large uncertainties and even inconsistencies since the standardised measurement procedure needs several specimens to determine a single set of material parameters. In contrast, the presented measurement set-up allows to calculate material parameters using one unique disc-shaped specimen with an optimised electrode topology. Using an inverse problem approach, fitting material parameters can be found using an optimisation procedure.
关键词： piezoelectric ceramics,Parameter identification,optimisation,inverse problem
更新于2025-09-10 09:29:36
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AIP Conference Proceedings [AIP Publishing LLC 41ST ANNUAL REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION: Volume 34 - Boise, Idaho (20–25 July 2014)] - Feasibility of PZT ceramics for impact damage detection in composite structures
摘要： Fiber reinforced plastic composites are becoming widely used in vehicles and airframe structures due to their high strength to weight ratio. However unlike metals, the multilayered composite structures are more susceptible to damage mechanisms such as disbonds and delaminations due to impacts. It is often dif?cult to visually detect the damage. Lead-Zirconate-Titanate (PZT) thin ?lms are becoming popular for in-situ structural health monitoring due to their small size, high piezoelectric coupling coef?cient, and ease of surface-mounting and/or embedding in composite structures. A network of such transducers could be utilized for damage detection using guided wave techniques, impedance techniques, or passive impact detection techniques. However, the PZT ?lms are subject to the same impact probabilities that the structure encounters. If the transducers fail due to the subjected impacts, they can result in false readings and ultimately failing to correctly detect damage in the structure. This paper presents a feasibility study using the guided wave S0 mode for detecting impact damage. The health of the structure is quanti?ed using guided wave measurements, and the PZT health is monitored using impedance methods.
关键词： impact damage detection,impedance techniques,PZT ceramics,composite structures,guided wave techniques
更新于2025-09-10 09:29:36
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Influence of additives on structure and ferroelectric properties of NBT-BT-BMT ceramics
摘要： Influence of various over stoichiometric additives on phase formation, unit cell parameters, microstructure, dielectric and ferroelectric properties of solid solutions 0.8[0.8(Na0.5Bi0.5)TiO3-0.2BaTiO3]-0.2Bi(Mg0.5Ti0.5)O3 system has been studied. The unit cell volume slightly decreased in case of the V2O5 additives but did not change in case of Bi2O3, LiF, and KCl additives. Increase in dielectric parameters ert and tandrt values at the room temperature was revealed for compositions doped by KCl additives, while these parameters decreased in compositions doped by the V2O5 additives. Linear correlation between piezoelectric coefficient d33 measured for separate grains using the Piezoresponse Force Microscopy method and dielectric permittivity ert values at the room temperature was confirmed.
关键词： ferroelectric phase transitions,additives,dielectric properties,perovskite structure,Ceramics (Na0.5Bi0.5)TiO3 - BaTiO3 - Bi(Mg0.5Ti0.5)O3
更新于2025-09-10 09:29:36
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Recent Advances in Porous Ceramics || Physical Properties of Porous Pure and Zr/Sn-Doped Nanocrystalline BaTiO3 Ceramics
摘要： Polycrystalline BaTiO3 and Ba(Ti0.96SnxZr0.04-x)O3 ceramics (x=0.02-0.04) were prepared by a combination of solid-state and mechanochemical process and characterized at room temperature by X-ray diffraction for phase composition. Their crystal structures were found to be of the cubic and tetragonal symmetries, respectively. The grain size and porosity which were determined using Field Emission Scanning Electron Microscope (FESEM) and densitometer, respectively showed decrease and increase of relative density respectively, with increase in doping concentration. The variations of dielectric constant and loss with frequency and temperature show a maximum dielectric constant of 1660 at room temperature for Ba(Ti0.96Sn0.03Zr0.01)O3. The remnant polarization (Pr) and coercive field (Ec) of BT were found to be 581.73 V/cm and 0.27 μC/cm2. Increase in Sn content led to an increase in Pr of 0.58, 3.07, 3.73 C/cm2, and Ec of 1766.8, 2855.7, 2661.1 V/cm, respectively and are expected to lead to a significant reduction in the thickness of the multilayer ceramic capacitors. Impedance spectroscopy of polycrystalline Ba(Ti0.96Sn0.02Zr0.02)O3 in a wide frequency and temperature range showed Nyquist plots with presence of grain and grain boundary at 400°C and a negative temperature coefficient of resistance (NTCR) for Ba(Ti0.96Sn0.02Zr0.02)O3. The dielectric relaxation showed a non-Debye character.
关键词： porous ceramics,barium titanate,doping,MLCC,ferroelectrics
更新于2025-09-10 09:29:36
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Structure and property of lead-free (K,Na)NbO3–(Bi1/2Na1/2)ZrO3–CaTiO3 piezoelectric ceramics
摘要： Simultaneous improvement of piezoelectricity and temperature stability is vital for developing high-performance KNN-based lead-free materials. Here, effects of CaTiO3 on phase structure, piezoelectricity and temperature stability of (1 – x)[0.95(K0.5Na0.5)NbO3–0.05(Bi0.5Na0.5)ZrO3]–xCaTiO3–0.2%MnO2 ceramics were studied. It was found that the orthorhombic-tetragonal phase transition temperature can be gradually decreased by increasing CaTiO3 content. Particularly, the improved strain temperature stability (strain varied < 15% when measurement temperature reaches 110 °C) and enhanced electrical properties (d33 ~ 296 pC/N and strain ~ 0.14%) can be observed in the ceramics with x = 0.02. Therefore, shifting the TO?T below room temperature is an effective way to promote temperature stability and electrical properties of KNN-based piezoelectric materials.
关键词： Lead-free piezoelectric ceramics,Temperature stability,CaTiO3,Piezoelectricity,KNN-based
更新于2025-09-10 09:29:36
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Functional properties of LaxCe1?xO2?δ nanocrystals and their bulk ceramics
摘要： Structure–property correlations were investigated for LaxCe1?xO2?δ (x = 0.05, 0.15) system (for both nanoparticles and ceramic). The nanoparticles were synthesized by the co-precipitation route and characterized for their structural, catalytic and visible light driven photocatalytic properties. Synthesised LaxCe1?xO2?δ nanopowders depicted phase purity with excellent compositional control as confirmed by various structural characterisation tools. The 15% La3+-doped ceria nanoparticles portrayed superior photocatalytic properties; complete degradation (99%) of the methylene blue dye was observed within 60 min of visible light irradiation under an alkaline medium. High density (> 96%) of the ceramics (sintered at 1580 °C for 2 h) confirmed promising sinterability of the synthesised powders. The ionic conductivities of the LaxCe1?xO2?δ ceramics increased with temperature and frequency owing to enhanced oxygen vacancies in the ceria matrix as a result of doping (of La3+-ions); a maximum conductivity of ~ 8.4 × 10?2 S cm?1 was obtained at 900 °C for the 15% La3+-doped ceria ceramics at 1 MHz frequency.
关键词： LaxCe1?xO2?δ,nanocrystals,photocatalytic properties,co-precipitation,ionic conductivity,bulk ceramics
更新于2025-09-10 09:29:36
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The doping effects of ZnNb <sub/>2</sub> O <sub/>6</sub> on the phase, microstructure and energy storage properties of (Sr <sub/>0.98</sub> Ca <sub/>0.02</sub> )TiO <sub/>3</sub> paraelectric ceramics
摘要： Zn(NbO3)2 doped Sr0.98Ca0.02TiO3 (SCT-xZN) paraelectric ceramics have been obtained by the traditional electroceramic processing. Phase structures and doping effects were investigated by using XRD and Raman. Surface morphology was observed by SEM to evaluate grain growth. The P-E curves were measured and employed to calculate the energy storage density and efficiency. The doping effects on dielectric properties such as permittivity, dielectric loss and breakdown strength were also measured and discussed.
关键词： phases and microstructures,ZnNb2O6 doped,Paraelectric ceramics,energy storage
更新于2025-09-10 09:29:36
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Crystal structure, microwave dielectric properties and low temperature sintering of (Al0.5Nb0.5)4+ co-substitution for Ti4+ of LiNb0.6Ti0.5O3 ceramics
摘要： The phase composition, microstructure, microwave dielectric properties of (Al0.5Nb0.5)4+ co-substitution for Ti site in LiNb0.6Ti0.5O3 ceramics and the low temperature sintering behaviors of Li2O-B2O3-SiO2 (LBS) glass were systematically discussed. XRD patterns and EDS analysis result confirmed that single phase of Li1.075Nb0.625Ti0.45O3 solid solution was formed in all component. The increase of dielectric constant (εr) is ascribed to the improvement of bulk density. The restricted growth of grain has a negative influence on quality factor (Q×f) value. The τf value could be continuously shifted to near zero as the doping content increases. Great microwave dielectric properties were obtained in LiNb0.6Ti(0.5-x)(Al0.5Nb0.5)xO3 ceramics (x = 0.10) when sintered at 1100℃ for 2 h: εr = 70.34, Q×f = 5144 GHz, τf = 4.8ppm/℃. The sintering aid, LBS glass, can effectively reduce the temperature and remain satisfied microwave performance. Excellent microwave dielectric properties for x = 0.10 were obtained with 1.0 wt. % glass: εr = 70.16, Q×f = 4153 GHz (at 4 GHz), τf = -0.65ppm/℃ when sintered at 925℃ for 2 h.
关键词： LiNb0.6Ti0.5O3 ceramics,low temperature sintering,Li2O-B2O3-SiO2 (LBS) glass,microwave dielectric properties
更新于2025-09-10 09:29:36
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Pressureless joining of SiC ceramics at low temperature
摘要： Pressureless joining of SiC ceramics at low temperature was developed using Ti powder interlayer. Phase assemblage and microstructure of SiC joint revealed that the products after diffusion bonding mainly consisted of Ti5Si3 and TiC owing to the comparatively low joining temperature. Additionally, Si and C elements were found to be with higher penetration depth in the Ti interlayer. Benefitting from the lower proportion of the brittle Ti5Si3 phase and porosity, shear strength reached a relatively higher value of 41 MPa after joining at 1200oC for 30 min.
关键词： SiC ceramics,Shear strength,Ti powder,Diffusion bonding,Pressureless joining
更新于2025-09-10 09:29:36