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Journal of Advanced Ceramics
Journal Prestige (SJR): 0.365  Citation Impact (citeScore): 1 Number of Followers: 9  Open Access journalISSN (Print) 2226-4108 - ISSN (Online) 2227-8508 Published by SpringerOpen  [229 journals]
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- Oxygen vacancy-mediated WO3 phase junction to steering photogenerated
charge separation for enhanced water splitting
Abstract: Abstract Effective charge separation and transfer is deemed to be the contributing factor to achieve high photoelectrochemical (PEC) water splitting performance on photoelectrodes. Building a phase junction structure with controllable phase transition of WO3 can further improve the photocatalytic performance. In this work, we realized the transition from orthorhombic to monoclinic by regulating the annealing temperatures, and constructed an orthorhombic-monoclinic WO3 (o-WO3/m-WO3) phase junction. The formation of oxygen vacancies causes an imbalance of the charge distribution in the crystal structure, which changes the W-O bond length and bond angle, accelerating the phase transition. As expected, an optimum PEC activity was achieved over the o-WO3/m-WO3 phase junction in WO3-450 photoelectrode, yielding the maximum O2 evolution rate roughly 32 times higher than that of pure WO3-250 without any sacrificial agents under visible light irradiation. The enhancement of catalytic activity is attributed to the atomically smooth interface with a highly matched lattice and robust built-in electric field around the phase junction, which leads to a less-defective and abrupt interface and provides a smooth interfacial charge separation and transfer path, leading to improved charge separation and transfer efficiency and a great enhancement in photocatalytic activity. This work strikes out on new paths in the formation of an oxygen vacancy-induced phase transition and provides new ideas for the design of catalysts.
PubDate: 2022-12-01
- Unique sandwich design of high-efficiency heat-conducting
phosphor-in-glass film for high-quality laser-driven white lighting
Abstract: Abstract Multi-color phosphor-in-glass (PiG) film has been considered as a promising color converter in high-quality laser lighting owing to its outstanding merits of phosphor versatility, tunable luminescence, and simple preparation. However, the opto-thermal properties of PiG film are severely affected by the photon reabsorption and backward scattering of phosphor structure and the heat conduction of substrate. Herein, a unique sandwich design of phosphor structure was introduced in the multi-color PiG film for high-quality laser lighting. By elaborately synthesizing the borosilicate glass with low glass transition temperature (Tg), similar expansion coefficient, and high refractive index (RI), the sandwiched PiGs were prepared by sintering (~600 °C) broadband green and red phosphor glass films on the double sides of sapphire. The green and red PiG films were tightly coated on the sapphire with no delamination and maintained higher luminescence intensity than raw phosphors at high temperatures. By simultaneously coupling photon reabsorption and backward scattering, the sandwiched green PiG film—sapphire—red PiG film (G—S—R PiG) yields a high-quality white light with a high luminous efficacy of 163 lm/W and an excellent color rendering index (CRI) of 85.4 under a laser power of 2.4 W, which are the best comprehensive results yet reported. Benefiting from the ingenious sandwich design with heat-conducting sapphire and thin PiG films, the G—S—R PiG displays low working temperatures (< 200 °C) under high-power laser excitation. This work reveals the role of sandwiched phosphor structure in photon loss and heat dissipation, which provides a new strategy to design PiG films for high-quality laser lighting.
PubDate: 2022-12-01
- In-situ growth of carbon nanotubes on ZnO to enhance thermoelectric and
mechanical properties
Abstract: Abstract As a high-temperature thermoelectric (TE) material, ZnO offers advantages of non-toxicity, chemical stability, and oxidation resistance, and shows considerable promise as a true ready-to-use module under air conditions. However, poor electrical conductivity and high thermal conductivity severely hinder its application. Carbon nanotubes (CNTs) are often used as a reinforcing phase in composites, but it is difficult to achieve uniform dispersion of CNTs due to van der Waals forces. Herein, we developed an effective in-situ growth strategy of homogeneous CNTs on ZnO nanoparticles by exploiting the chemical vapor deposition (CVD) technology, in order to improve their electrical conductivity and mechanical properties, as well as reducing the thermal conductivity. Meanwhile, magnetic nickel (Ni) nanoparticles are introduced as catalysts for promoting the formation of CNTs, which can also enhance the electrical and thermal transportation of ZnO matrices. Notably, the electrical conductivity of ZnO is significantly boosted from 26 to 79 S·cm−1 due to the formation of dense and uniform conductive CNT networks. The lattice thermal conductivity (κL) is obviously declined by the intensification of phonon scattering, resulting from the abundant grain boundaries and interfaces in ZnO-CNT composites. Importantly, the maximum dimensionless figure of merit (zT) of 0.04 at 800 K is obtained in 2.0% Ni-CNTs/ZnO, which is three times larger than that of CNTs/ZnO prepared by traditional ultrasonic method. In addition, the mechanical properties of composites including Vickers hardness (HV) and fracture toughness (KIC) are also reinforced. This work provides a valuable reference for dispersing nano-phases in TE materials to enhance both TE and mechanical properties.
PubDate: 2022-12-01
- Corrosion behavior and failure mechanism of SiC whisker and c-AlPO4
particle-modified novel tri-layer Yb2Si2O7/mullite/SiC coating in burner
rig tests
Abstract: Abstract The corrosion behavior of environmental barrier coatings (EBCs) directly affects the service life and stability of ceramic matrix composite (CMC) structural parts in the aero-engines. The silicon carbide (SiC) whisker toughening phase and c-AlPO4 bonding phase are firstly used to improve the service life of novel tri-layer Yb2Si2O7/mullite/SiC EBCs in the burner rig test. The formation of penetrating cracks in Yb2Si2O7/mullite/SiC coating caused the failure of coating at 1673 K. The SiC whiskers in mullite middle coating significantly inhibited the formation of penetrating cracks in Yb2Si2O7/mullite/SiC coating, and efficiently prevented the oxidation of carbon fiber reinforced silicon carbide (Cf/SiC) samples for 360-min thermal cycles (24 times) with a weight loss of 6.19×10−3 g·cm−2. Although c-AlPO4 particles further improved the service life of SiCw-mullite (SM) coating, the overflow of POx gas aggravated the formation and expansion of cracks in the Yb2Si2O7 outer coating, and caused the service life of overall Yb2Si2O7/c-AlPO4-SiCw-mullite (ASM)/SiC coating to be slightly lower than that of Yb2Si2O7/SM/SiC coating. This study guides the design of modified tri-layer EBCs with long service life in high-temperature and high-speed gas environment.
PubDate: 2022-12-01
- Layer-structured Cr/CrxN coating via electroplating-based nitridation
achieving high deuterium resistance as the hydrogen permeation barrier
Abstract: Abstract Hydrogen isotope permeation through structural materials is a key issue for developing nuclear fusion energy, which will cause fuel loss and radioactive pollution. Developing ceramic coatings with high thermal shock and hydrogen resistance is an effective strategy to solve this issue. In this work, a layer-structured Cr/CrxN coating was successfully fabricated by a facile electroplating-based nitridation technique, which is easy, facile, and applicable to coating complex-shaped substrates. The Cr/CrxN coating, composed of a bottom Fe/Cr interdiffusion zone, a middle Cr layer, and a top CrxN layer, exhibits high bonding strength, high anti-thermal-shock ability, and high deuterium permeation resistance. Its bonding strength achieves 43.6 MPa. The Cr/CrxN coating remains intact even after suffering 300 thermal shock cycles under a 600 °C-water condition. Through optimizing the nitridation temperature, the Cr/CrxN coating achieves a deuterium permeation reduction factor (PRF) as high as 3599 at 500 °C. Considering its scalable fabrication technique and considerable properties, the developed Cr/CrxN coating may serve as a novel high-performance hydrogen permeation barrier in various fields.
PubDate: 2022-12-01
- Development and prospects of garnet ceramic scintillators: A review
Abstract: Abstract Garnet ceramic scintillators are a class of inorganic scintillation materials with excellent overall performance. The flexibility of cation substitution in different lattice positions leads to tunable and versatile properties and a wide range of applications. This paper starts with an overview of the development history of the inorganic scintillation materials, followed by a description of major preparation methods and characterization of garnet scintillation ceramics. Great progress obtained in recent years consisting in applying the band-gap and defect engineering strategies to the garnet scintillation ceramics is reviewed. Finally, the respective problems in the preparation and performance of multicomponent garnet single crystals and ceramics and the effective solutions are discussed. The garnet scintillation ceramics with the highest application potential are summarized, and the future development directions are proposed.
PubDate: 2022-11-18
- Mechanical properties of additively-manufactured cellular ceramic
structures: A comprehensive study
Abstract: Abstract Cellular ceramic structures (CCSs) are promising candidates for structural components in aerospace and modern industry because of their extraordinary physical and chemical properties. Herein, the CCSs with different structural parameters, i.e., relative density, layer, size of unit cells, and structural configuration, were designed and prepared by digital light processing (DLP)-based additive manufacturing (AM) technology to investigate their responses under compressive loading systematically. It was demonstrated that as the relative density increased and the size of the unit cells decreased, the mechanical properties of one-layer CCSs increased. The mechanical properties of three-layer CCSs were more outstanding than those of the CCSs with one and two layers. In addition, structural configurations also played a vital role in the mechanical properties of the CCSs. Overall, the mechanical properties of the CCSs from superior to inferior were that with the structural configurations of modified body-centered cubic (MBCC), Octet, SchwarzP, IWP, and body-centered cubic (BCC). Furthermore, structural parameters also had significant impacts on the failure mode of the CCSs under compressive loading. As the relative density increased, the failure mode of the one-layer CCSs changed from parallel—vertical—inclined mode to parallel—vertical mode. It was worth noting that the size of the unit cells did not alter the failure mode. Inclined fracture took a greater proportion in the failure mode of the multi-layer CCSs. But it could be suppressed by the increased relative density. Similarly, the proportions of the parallel—vertical mode and the fracture along a specific plane always changed with the variation of the structural configurations. This study will serve as the base for investigating the mechanical properties of the CCSs.
PubDate: 2022-11-17
- Interfacial energy barrier tuning of hierarchical Bi2O3/WO3
heterojunctions for advanced triethylamine sensor
Abstract: Abstract Traditional triethylamine (TEA) sensors suffer from the drawback of serious cross-sensitivity due to the low charge-transfer ability of gas-sensing materials. Herein, an advanced anti-interference TEA sensor is designed by utilizing interfacial energy barriers of hierarchical Bi2O3/WO3 composite. Benefiting from abundant slit-like pores, desirable defect features, and amplification effect of heterojunctions, the sensor based on Bi2O3/WO3 composite with 40% Bi2O3 (0.4-Bi2O3/WO3) demonstrates remarkable performance in terms of faster response/recovery time (1.7-fold/1.2-fold), higher response (2.1-fold), and lower power consumption (30 °C-decrement) as compared with the pristine WO3 sensor. Furthermore, the composite sensor exhibits long-term stability, reproducibility, and negligible response towards interfering molecules, indicating the promising potential of Bi2O3/WO3 heterojunctions in anti-interference detection of low-concentration TEA in real applications. This work not only offers a rational solution to design advanced gas sensors by tuning the interfacial energy barriers of heterojunctions, but also provides a fundamental understanding of hierarchical Bi2O3 structures in the gas-sensing field.
PubDate: 2022-11-17
- K-doped BaCo0.4Fe0.4Zr0.2O3−δ as a promising cathode material for
protonic ceramic fuel cells
Abstract: Abstract Slow oxygen reduction reaction (ORR) involving proton transport remains the limiting factor for electrochemical performance of proton-conducting cathodes. To further reduce the operating temperature of protonic ceramic fuel cells (PCFCs), developing triple-conducting cathodes with excellent electrochemical performance is required. In this study, K-doped BaCo0.4Fe0.4Zr0.2O3−δ (BCFZ442) series were developed and used as the cathodes of the PCFCs, and their crystal structure, conductivity, hydration capability, and electrochemical performance were characterized in detail. Among them, Ba0.9K0.1Co0.4Fe0.4Zr0.2O3−δ (K10) cathode has the best electrochemical performance, which can be attributed to its high electron (e−)/oxygen ion (O2−)/H+ conductivity and proton uptake capacity. At 750 °C, the polarization resistance of the K10 cathode is only 0.009 Ω·cm2, the peak power density (PPD) of the single cell with the K10 cathode is close to 1 Wcm−2, and there is no significant degradation within 150 h. Excellent electrochemical performance and durability make K10 a promising cathode material for the PCFCs. This work can provide a guidance for further improving the proton transport capability of the triple-conducting oxides, which is of great significance for developing the PCFC cathodes with excellent electrochemical performance.
PubDate: 2022-11-17
- An effective strategy for preparing transparent ceramics using nanorod
powders based on pressure-assisted particle fracture and rearrangement
Abstract: Abstract Achieving full densification of some ceramic materials, such as Y2O3, without sintering aids by spark plasma sintering (SPS) is a great challenge when plastic deformation contributes limitedly to the densification as the yield stress of the material at an elevated temperature is higher than the applied sintering pressure. Herein, we demonstrate that particle fracture and rearrangement is an effective strategy to promote the densification during the pressure-assisted sintering process. Specifically, Y2O3 nanocrystalline powders composed of nanorod and near-spherical particles were synthesized and sintered at various temperatures by the SPS. The results show that the relative density of the ceramics prepared by the nanorod powders is higher than the density of the ceramics from the near-spherical powders after 600 °C due to the fracture and rearrangement of the nanorods at low temperatures, which leads to the decrease of particle size and the increase of density and homogeneity. Based on this novel densification mechanism, ultrafine-grained Y2O3 transparent ceramics with good optical and mechanical properties were fabricated successfully from the nanorod powders.
PubDate: 2022-11-12
- Taking advantage of Li-evaporation in LiCoO2 as cathode for
proton-conducting solid oxide fuel cells
Abstract: Abstract LiCoO2, a widely used electrode material for Li-ion batteries, was found to be suitable as a cathode material for proton-conducting solid oxide fuel cells (H-SOFCs). Although the evaporation of Li in LiCoO2 was detrimental to the Li-ion battery performance, the Li-evaporation was found to be beneficial for the H-SOFCs. The partial evaporation of Li in the LiCoO2 material preparation procedure led to the in-situ formation of the LiCoO2+Co3O4 composite. Compared to the cell using the pure phase LiCoO2 cathode that only generated moderate fuel cell performance, the H-SOFCs using the LiCoO2+Co3O4 cathode showed a high fuel cell performance of 1160 mW·cm−2 at 700 °C, suggesting that the formation of Co3O4 was critical for enhancing the performance of the LiCoO2 cathode. The first-principles calculation gave insights into the performance improvements, indicating that the in-situ formation of Co3O4 due to the Li-evaporation in LiCoO2 could dramatically decrease the formation energy of oxygen vacancies that is essential for the high cathode performance. The evaporation of Li in LiCoO2, which is regarded as a drawback for the Li-ion batteries, is demonstrated to be advantageous for the H-SOFCs, offering new selections of cathode candidates for the H-SOFCs.
PubDate: 2022-11-08
- Elucidating the role of preferential oxidation during ablation: Insights
on the design and optimization of multicomponent ultra-high temperature
ceramics
Abstract: Abstract Multicomponent ultra-high temperature ceramics (UHTCs) are promising candidates for thermal protection materials (TPMs) used in aerospace field. However, finding out desirable compositions from an enormous number of possible compositions remains challenging. Here, through elucidating the role of preferential oxidation in ablation behavior of multicomponent UHTCs via the thermodynamic analysis and experimental verification, the correlation between the composition and ablation performance of multicomponent UHTCs was revealed from the aspect of thermodynamics. We found that the metal components in UHTCs can be thermodynamically divided into preferentially oxidized component (denoted as MP), which builds up a skeleton in oxide layer, and laggingly oxidized component (denoted as ML), which fills the oxide skeleton. Meanwhile, a thermodynamically driven gradient in the concentration of MP and ML forms in the oxide layer. Based on these findings, a strategy for pre-evaluating the ablation performance of multicomponent UHTCs was developed, which provides a preliminary basis for the composition design of multicomponent UHTCs.
PubDate: 2022-11-03
- Photo-assisted charging of carbon fiber paper-supported CeO2/MnO2
heterojunction and its long-lasting capacitance enhancement in dark
Abstract: Abstract It is important to develop green and sustainable approaches to enhance electrochemical charge storage efficiencies. Herein, a two-step in-situ growth process was developed to fabricate carbon fiber paper-supported CeO2/MnO2 composite (CeO2/MnO2—CFP) as a binder-free photo-electrode for the photo-assisted electrochemical charge storage. The formation of CeO2/MnO2 type II heterojunction largely enhanced the separation efficiency of photo-generated charge carriers, resulting in a substantially enhanced photo-assisted charging capability of ∼20%. Furthermore, it retained a large part of its photo-enhanced capacitance (∼56%) in dark even after the illumination was off for 12 h, which could be attributed to its slow release of stored photo-generated electrons from its specific band structure to avoid their reaction with O2 in dark. This study proposed the design principles for supercapacitors with both the photo-assisted charging capability and its long-lasting retainment in dark, which may be readily applied to other pseudocapacitive materials to better utilize solar energy.
PubDate: 2022-11-01
- Field-driven merging of polarizations and enhanced electrocaloric effect
in BaTiO3-based lead-free ceramics
Abstract: Abstract Solid-state cooling technology based on electrocaloric effect (ECE) has been advanced as an alternative to replace the vapour-compression approach to overcome the releasing of the global warming gases. However, the development in high ECE materials is still a challenge. In this work, polarization merging strategy was proposed to achieve a large ECE in xBa(Sn0.07Ti0.93)O3-(1−x)Ba(Hf0.1Ti0.9)O3 ferroelectric ceramics, where x = 0, 0.2, 0.4, 0.6, 0.8, and 1. Ba(Sn0.07Ti0.93)O3 with an orthorhombic phase and Ba(Hf0.1Ti0.9)O3 with a rhombohedral phase at room temperature were prepared beforehand as precursors, and phase-coexisted xBSnT-(1−x)BHfT ceramics were formed via a solid-state reaction approach. Phase coexisting structures were confirmed using the X-ray diffraction. The merged polarization was confirmed by the dielectric and ferroelectric properties. Optimal ECEs were obtained for 0.2BSnT-0.8BHfT ceramics, i.e., adiabatic temperature change ΔT = 2.16±0.08 K at 80 °C and 5 MV/m, and ΔT = 3.35±0.09 K at 80 °C and 7 MV/m.
PubDate: 2022-11-01
- Formation mechanism and roles of oxygen vacancies in melt-grown
Al2O3/GdAlO3/ZrO2 eutectic ceramic by laser 3D printing
Abstract: Abstract Laser three-dimensional (3D) printing has become a significant technique to fabricate high-performance Al2O3-based eutectic ceramics based on melt growth. However, oxygen vacancies are inevitable crystal defects during this process, and their formation mechanism and roles in the as-deposited ceramics are still unclear. In this paper, Al2O3/GdAlO3/ZrO2 ternary eutectic ceramics were prepared by laser 3D printing, and the formation mechanism of the oxygen vacancies was revealed by conducting a well-designed annealing experiment. In addition, the effects of the oxygen vacancies on the structure and mechanical property of the as-solidified eutectic ceramic were investigated. The formation of oxygen vacancies is revealed to be a result of the transfer of oxygen atoms from the oxide ceramic to the oxygen-deficient atmosphere by means of vacancy migration mechanism. Besides, the presence of oxygen vacancies has no obvious effects on crystalline structure and microstructure of the additively manufactured eutectic ceramic. However, the chemical bond property changes to some extent due to the formation of these crystal defects, which may affect the mechanical property of the as-deposited eutectic ceramic. It is found that the hardness decreases by 3.9%, and the fracture toughness increases by 13.3% after removing the oxygen vacancies. The results may provide a potential strategy to regulate the mechanical property of the oxide ceramic materials.
PubDate: 2022-11-01
- Self-assembled Ag4V2O7/Ag3VO4 Z-scheme heterojunction by pH adjustment
with efficient photocatalytic performance
Abstract: Abstract Semiconductor heterojunction plays a pivotal role in photocatalysis. However, the construction of a heterojunction with a fine microstructure usually requires complex synthetic procedures. Herein, a pH-adjusted one-step method was employed to controllably synthesize Ag4V2O7/Ag3VO4 heterojunction with a well-tuned 0D/1D hierarchical structure for the first time. It is noteworthy that the ordered stacking of vanadium oxide tetrahedron \((\rm{VO}_3^-)\) guided by the pH value wisely realizes the in-situ growth of Ag4V2O7 nanoparticles on the surface of Ag3VO4 nanorods. Furthermore, comprehensive characterization and calculation decipher the electronic structures of Ag4V2O7 and Ag3VO4 and the formation of Z-scheme heterojunction, benefiting the visible light harvesting and carrier utilization. Such a new Ag4V2O7/Ag3VO4 heterojunction exhibits remarkable photocatalytic activity and excellent stability. Complete degradation of Rhodamine B (RhB) can be achieved in 10 min by the Ag4V2O7/Ag3VO4 heterojunction under visible light irradiation, demonstrating an outstanding reaction rate of 0.35 min−1 that is up to 84-fold higher than those of other silver vanadates. More importantly, this integration of synthesis technology and heterojunction design, based on the intrinsic crystal and electronic structures, could be inspiring for developing novel heterostructured materials with advanced performance.
PubDate: 2022-11-01
- Ti4+-incorporated fluorite-structured high-entropy oxide
(Ce,Hf,Y,Pr,Gd)O2−δ: Optimizing preparation and CMAS corrosion behavior
Abstract: Abstract Environmental barrier coatings (EBCs) with excellent chemical resistance and good high-temperature stability are of great significance for their applications in next-generation turbine engines. In this work, a new type of high-entropy fluorite-structured oxide (Ce0.2Hf0.2Y0.2Pr0.2Gd0.2)O2−δ (HEFO-1) with different Ti4+ contents were successfully synthesized. Minor addition of Ti4+ could be dissolved into a high-entropy lattice to maintain the structure stable, effectively reducing the phase formation temperature and promoting the shrinkage of bulk samples. Heat treatment experiments showed that all the samples remained a single phase after annealing at 1200–1600 °C for 6 h. In addition, high-entropy (Ce0.2Hf0.2Y0.2Pr0.2Gd0.2Ti0.2x)O2−δ demonstrated great resistance to calcium—magnesium—alumina—silicate (CMAS) thermochemical corrosion. When the content of Ti was increased to x = 0.5, the average thickness of the reaction layer was about 10.5 after being corroded at 1300 °C for 10 h. This study reveals that high-entropy (Ce0.2Hf0.2Y0.2Pr0.2Gd0.2Ti0.2x)O2−δ is expected to be a candidate for the next-generation EBC materials with graceful resistance to CMAS corrosion.
PubDate: 2022-10-26
- Sintering and mechanical properties of carbon bulks from ordered
mesoporous carbon and nano diamond
Abstract: Abstract Powder metallurgy is important in material preparation. Due to the inertness of carbon materials, however, sintering powdered carbon into physically coherent bulks has been a great challenge even at a high temperature (2000 °C). Improving the sintering activity of carbon powders is the key to the success of the consolidation of the carbon powders. Here ordered mesoporous carbon (OMC) is used as the starting material to produce highly homogeneous novel carbon bulks. During sintering at 1800 °C, the huge specific surface area of the OMC greatly promotes the migration of carbon atoms and thus the sintering of the OMC by surface diffusion mechanism. When nanodiamond (ND) is added, the volume expansion associated with the phase transformation of diamond to graphite facilitates the densification of the powder compacts. The strong connection between the OMC and the graphite onions derived from the ND bestows the as-prepared carbon bulks with excellent mechanical properties. The current research pioneers a novel way to prepare high-strength carbon materials at relatively low temperatures.
PubDate: 2022-10-26
- Solid-phase sintering and vapor-liquid-solid growth of BP@MgO quantum dot
crystals with a high piezoelectric response
Abstract: Abstract Low-dimensional piezoelectric and quantum piezotronics are two important branches of low-dimensional materials, playing a significant role in the advancement of low-dimensional devices, circuits, and systems. Here, we firstly propose a solid-phase sintering and vapor-liquid-solid growth (SS-VLS-like) method of preparing a quantum-sized oxide material, i.e., black phosphorus (BP)@MgO quantum dot (QD) crystal with a strong piezoelectric response. Quantum-sized MgO was obtained by Mg slowly released from MgB2 within the confinement of a nanoflake BP matrix. Since the slow release of Mg only grows nanometer-sized MgO to hinder the further growth of MgO, we added a heterostructure matrix constraint: nanoflake BP. With the BP as the matrix confinement, MgO QDs embedded in the BP@MgO QD crystals were formed. These crystals have a layered two-dimensional (2D) structure with a thickness of 11 nm and are stable in the air. In addition, piezoresponse force microscopy (PFM) images show that they have extremely strong polarity. The strong polarity can also be proved by polarization reversal and a simple pressure sensor.
PubDate: 2022-10-19
- Low thermal conductivity and anisotropic thermal expansion of ferroelastic
(Gd1−xYx)TaO4 ceramics
Abstract: Abstract In this paper, (Gd1−xYx)TaO4 ceramics had been fabricated by solid-phase synthesis reaction. Each sample was found to crystallize in a monoclinic phase by X-ray diffraction (XRD). The properties of (Gd1−xYx)TaO4 were optimized by adjusting the ratio of Gd/Y. (Gd1−xYx)TaO4 had a low high-temperature thermal conductivity (1.37–2.05 W·m−1·K−1), which was regulated by lattice imperfections. The phase transition temperature of the (Gd1−xYx)TaO4 ceramics was higher than 1500 °C. Moreover, the linear thermal expansion coefficients (TECs) were 10.5×10−6 K−1 (1200 °C), which was not inferior to yttria-stabilized zirconia (YSZ) (11×10−6 K−1, 1200 °C). (Gd1−xYx)TaO4 had anisotropic thermal expansion. Therefore, controlling preferred orientation could minimize the TEC mismatch when (Gd1−xYx)TaO4 coatings were deposited on different substrates as thermal barrier coatings (TBCs). Based on their excellent properties, it is believed that the (Gd1−xYx)TaO4 ceramics will become the next generation of high-temperature thermal protective coatings.
PubDate: 2022-09-07
