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[Lecture Notes in Mechanical Engineering] Advances in Thin Films, Nanostructured Materials, and Coatings (Selected Papers from the 2018 International Conference on “Nanomaterials: Applications & Properties”) || Stain Effect on the Properties of Polar Dielectric Thin Films
摘要： Low cost scalable processing and substrates are critical for optimized polar dielectric performance of functional oxide thin ?lms if they are to achieve commercialization. Here, we present a comprehensive investigation of the role low-cost MgO, Al2O3, SrTiO3 and Si substrates on the structural and electrical properties of sol-gel derived SrTiO3 (ST) and K0.5Na0.5NbO3 (KNN) thin ?lms. The substrate is found to have a strong effect on the stress/stain state and, consequently, on the dielectric and ferroelectric response of the ?lms. A tensile stress induced in-plane by the thermal expansion mismatch between the substrates and the ?lms observed for ST and KNN ?lms deposited on platinized Al2O3 and Si substrates, respectively, lowers the relative permittivity and remanent polarization values in the parallel plate capacitor geometry. In contrast, a compressive stress/strain observed for ST ?lms deposited on MgO/Pt and KNN ?lms on SrTiO3/Pt substrates result in superior polarization and dielectric permittivity, corresponding to enhanced out-of-plane displacement of Ti4+ ions in ST ?lms and Nb5+ ions in KNN ?lms. It is thus demonstrated that for polycrystalline polar dielectric thin ?lms the relative permittivity and polarization may be optimized through an induced compressive stress state.
关键词： Dielectric properties,Sol-gel,Thin ?lms,Stress/strain,Thermal expansion,Ferroelectric hysteresis
更新于2025-11-14 17:28:48
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AIP Conference Proceedings [Author(s) 4TH ELECTRONIC AND GREEN MATERIALS INTERNATIONAL CONFERENCE 2018 (EGM 2018) - Bandung, Indonesia (27–28 July 2018)] - Design and analysis of fiber Bragg grating tunable filter utilizing thermal technique
摘要： In this paper a tunable filter based on fiber Bragg grating (FBG) utilizing thermal technique is theoretically investigated and experimentally validated. According to the results, a tuning range is achieved about 1.5 nm in C-band region. While, for L-band region the wavelength shift is slightly greater than in the C-band region about 1.6 nm. This shifting is due to changing in thermo-optic and thermal expansion of fiber, which causes changing in refractive index and then Bragg wavelength. The experimental validation is done at wavelength 1552.7 nm, the tunability is about 1.2428 nm when the temperature is varied from 21°C to 61°C.
关键词： thermal expansion,fiber Bragg grating,thermo-optic effect,thermal technique,tunable filter
更新于2025-09-23 15:23:52
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Evaluation of thermal-deformation reduction method through prototyping space antenna's shape control mechanisms; 宇宙アンテナ形状制御機構の熱変形低減法の試作による評価;
摘要： This study aims to develop an actively deformable space antenna system for radio astronomy around 100GHz. In order to reduce the thermal deformation in active control mechanisms composed of multiple materials, a method to cancel the mismatch of the coefficients of thermal expansion (CTE) is proposed and tested. The CTE mismatch between piezoelements and Super Invar structures is cancelled by adding another metallic part. For effective CTE cancellation, this study clarifies the cause of thermal deformation induced by the preloading mechanisms for a piezoelectric stack actuator. In addition, it shows the effect of the dimension tolerance of the piezoelements is significant, but still manageable by the proposed CTE cancellation method. The effectiveness of proposed method is validated by the use of finite-element analysis, prototyping models, and thermal deformation measurement experiments.
关键词： Adaptive structures,Smart structures,Space antenna,Coefficients of thermal expansion mismatch cancellation,Space structures,Thermal deformation
更新于2025-09-23 15:22:29
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Pyroelectric Property of Binary Nitrides (AlN, GaN and InN)
摘要： The pyroelectric (PY) property of binary nitrides (AlN, GaN and InN) has been explored theoretically. The spontaneous and piezoelectric (PZ) polarization modifies the thermal conductivity of these nitrides. The thermal conductivities as a function of temperature including and excluding the polarization mechanism (kp and k) predict a transition temperature (T p) between primary and secondary PY effects. Below T p, thermal conductivity kp is lower than k. This is due to negative thermal expansion in binary nitrides. Above T p, kp is greater than k. kp is significantly contributed by PZ polarization due to thermal expansion which is the reason of secondary PY effect. The transition temperature T p for AlN, GaN and InN has been predicted as 100 K, 70 K and 60 K, respectively. This study suggests that thermal conductivity study can reveal PY property in semiconductors.
关键词： Thermal expansion,Thermal property,Pyroelectric coefficient,III–V Binary nitride,Built-in polarization
更新于2025-09-23 15:22:29
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[IEEE 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Shanghai (2018.8.8-2018.8.11)] 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Study of the fabrication and organization properties of copper-based Ba<inf>1?x</inf>Sr<inf>x</inf>TiO<inf>3</inf> composites
摘要： Barium strontium titanate ceramic particles which have negative thermal expansion properties when it reaches reinforcement and copper which have high thermal conductivity are choosen as matrix of composites. Different content of strontium in barium strontium titanate ceramic particles reinforced copper matrix composites are prepared by Spark Plasma Sintering for electronic packaging applications. The methods of microstructure analysis are employed to observe the morphology of reinforcement and matrix in composites, and interfacial characteristics. Thermal expansion instrument and thermal conductivity equipment are used to test and analyze the thermal expansion and thermal conductive ability of the composites. And the conductivity of the composites is tested by intelligent resistance tester.
关键词： Thermal expansion ability,Barium strontium titanate,Copper matrix composites
更新于2025-09-23 15:22:29
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Structural Stability of Hafnia-Based Materials at Ultra-High Temperature
摘要： This study assesses the structural stability at ultra-high temperature of the following selected compositions: 6.5 and 14 mol. % of RE2O3 (RE = Dy, Y, Er, Yb, and Lu) doped HfO2. Under thermal cycling and thermal shock, the structural stability was evaluated at 2400°C with water vapor flux using a specific test bench with a 3 kW CO2 laser. The cubic phase stability, which is theoretically important in the broad temperature range from 25 to 2800°C, was determined by a quantitative analysis of the X-ray diffractograms. Fully and partially stabilized HfO2, obtained respectively with 14 mol. % and 6.5 mol. % of dopants, showed different behaviors to thermal damage. Thermal expansion was measured up to 1650°C to anticipate dimensional changes of these stabilized samples and to be able to design an optimized material solution fitting with future combustion chamber requirements. All of these results were then considered in order to exhibit a trend on the thermal stability at 2400°C of the ionic radius of the dopants and their optimal doping rates.
关键词： Phase stability,UHTC,Thermal expansion,Spacecraft propulsion,HfO2
更新于2025-09-23 15:22:29
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Fabry–Perot Cavity Sensing Probe with High Thermal Stability for an Acoustic Sensor by Structure Compensation
摘要： Fiber Fabry–Perot cavity sensing probes with high thermal stability for dynamic signal detection which are based on a new method of structure compensation by a proposed thermal expansion model, are presented here. The model reveals that the change of static cavity length with temperature only depends on the thermal expansion coefficient of the materials and the structure parameters. So, fiber Fabry–Perot cavity sensing probes with inherent temperature insensitivity can be obtained by structure compensation. To verify the method, detailed experiments were carried out. The experimental results reveal that the static cavity length of the fiber Fabry–Perot cavity sensing probe with structure compensation hardly changes in the temperature range of ?20 to 60 °C and that the method is highly reproducible. Such a method provides a simple approach that allows the as-fabricated fiber Fabry–Perot cavity acoustic sensor to be used for practical applications, exhibiting the great advantages of its simple architecture and high reliability.
关键词： high thermal stability,thermal expansion model,structure compensation,Fabry–Perot cavity,acoustic sensor
更新于2025-09-23 15:21:21
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Anisotropy of acoustic and thermal expansion properties of TlInSe <sub/>2</sub> crystals
摘要： Based on experimental studies of acoustic wave velocities in TlInSe2 crystals, all components of their elastic stiffness and compliance tensors are determined. TlInSe2 has three acoustic axes parallel to the principal crystallographic directions. The lowest velocities of acoustic eigenwaves are used to estimate the acousto-optic figure of merit. We analyse deviations from purely longitudinal and transverse polarization states, as well as the obliquity of acoustic energy flow. Temperature dependences of strains along the three principal crystallographic directions and of acoustic wave velocities v11, v22 and v33 are measured. Anomalous behaviour of these parameters occur at T1≈245 K and T2≈145 K. It is shown that the symmetry of TlInSe2 becomes lower than tetragonal below the temperature point T1.
关键词： TlInSe2 crystals,Ferroics,elastic properties,thermal expansion,anisotropy,acoustic wave velocity
更新于2025-09-23 15:21:21
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Electrical Properties and Thermal Expansion Characteristics of (1- <i>x</i> )Ba <sub/>0.948</sub> Ca <sub/>0.05</sub> Er <sub/>0.002</sub> Ti <sub/>0.94</sub> Zr <sub/>0.06</sub> O <sub/>3</sub> -( <i>x</i> )Pr Lead-Free Piezoelectric Ceramics Sintered at a Low-Temperature
摘要： (1 (cid:1) x)Ba0.948Ca0.05Er0.002Ti0.94Zr0.06O3–(x)Pr (x ? 0–0.75 mol%) ceramics are sintered at 1240 (cid:3)C by conventional solid-state reaction method using the as-synthesized nanoparticles, which are prepared by a modified Pechini method. The structural, morphological, electrical, and thermal expansion properties as a function of varying x are systematically investigated. All samples feature rhombohedral phase, and their lattice parameters are accurately calculated by Rietveld refinement software. Volume of oxygen vacancies initially decreases and then increases with increasing x, leading to diversified electrical properties. Deteriorated electrical properties of the ceramics with excessive x are attributed to the increment of defect complexes with a large volume of oxygen vacancies. The coefficient of thermal expansion values of the ceramics that is influenced by phase evolution and structure defects under different temperature ranges are studied. The respective optimal electrical properties, that is, d33 ? 186 pC N mol%. This research is believed to be insightful to practical application of the lead-free multifunctional electron components.
关键词： thermal expansion coefficient,defect complexes,praseodymium-doping,BCEZT ceramics,piezoelectricity
更新于2025-09-23 15:21:21
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[IEEE 2019 14th Symposium on Piezoelectrcity, Acoustic Waves and Device Applications (SPAWDA) - Shijiazhuang, China (2019.11.1-2019.11.4)] 2019 14th Symposium on Piezoelectrcity, Acoustic Waves and Device Applications (SPAWDA) - A Simplified Model for Thermal Stress Analyses of Bi-Layers With Extreme Dissimilar Thermal Properties in Solar Cell
摘要： This paper aims at developing a simplified analytical model, as verified by the Hilbert-Riemann theoretical solution of interfacial cracks, to study the thermal stress distributions in solar cell laminated structures under thermal loadings. The interface thermal failure problem is analyzed in terms of the packaging materials and solar cell materials of simulated models, maximum interfacial normal stress, and stress critical point. It provides some guidance for the design and optimization of solar modules.
关键词： Solar cell,Thermal expansion,Critical point,Simplified model
更新于2025-09-23 15:21:01