Showing papers in "Journal of the American Ceramic Society in 2022"

Dielectric temperature stability and energy storage performance of NBT‐based ceramics by introducing high‐entropy oxide

Abstract: In this study, a high-entropy perovskite oxide Sr(Zr0.2Sn0.2Hf0.2Ti0.2Nb0.2)O3 (SZSHTN) was first introduced to Na0.5Bi0.5TiO3 (NBT) lead-free ferroelectric ceramics to boost both the high-temperature dielectric stability and energy storage performance. Excellent comprehensive performance was simultaneously obtained in the 0.8NBT–0.2SZSHTN ceramic with high ε′ value (> 2000), wide ε′-temperature stable range (TCC < 5%, 52.4–362°C), low tanδ value in a wide range (<0.01, 90–341°C) and high energy storage performance (Wrec = 3.52 J/cm3, Wrec and η varies ±6.08% and ±7.4% from 20 to 150°C), which endows it the promising potential to be used in high-temperature environments.

Optical transition properties, internal quantum efficiencies, and temperature sensing of Er ³⁺ doped BaGd ₂ O ₄ phosphor with low maximum phonon energy

Abstract: The hosts with low maximum phonon energy (MPE) are preferred since the nonradiative consumption of the luminescence centers in them are low. Among the low MPE hosts, the oxide ones are more favored owing to their excellent stability and easy synthesis. In this work, the optical and spectroscopic properties of BaGd2O4:Er3+ phosphor were studied. The MPE of BaGd2O4 host was observed from Eu3+ phonon sideband (PSB) spectrum and Raman spectrum to be 477 cm−1 which does not second to the fluoride hosts. The refractive index, which is indispensable for Judd–Ofelt calculation, was confirmed from the both approaches of the Eu3+-probe and the band gap energy, and the similar refractive indices were confirmed, therefore the average refractive index 2.01 was used in the Judd–Ofelt calculation. The Judd–Ofelt parameters of Er3+ in BaGd2O4 host was confirmed to be = 7.91 × 10−21 cm2, = 2.36 × 10−21 cm2, and = 9.00 × 10−22 cm2. Furthermore, the internal quantum efficiencies for 4F9/2 and 4IJ (J = 9/2, 11/2, and 13/2) levels were determined. Finally, the optical temperature sensing properties were studied in detail, and the temperature calibration curve was experimentally derived, meanwhile the maximum absolute sensitivity was confirmed to be 0.0028 K−1.

Understanding electrocaloric cooling of ferroelectrics guided by phase‐field modeling

Abstract: With the urgent need to explore low-cost, high-efficiency solid-state refrigeration technology, the electrocaloric effects of ferroelectric materials have attracted much attention in the past decades. With the development of modern computing technology, the phase-field method is widely used to simulate the evolution of microstructure at mesoscale and predict the properties of different types of ferroelectric materials. In this article, we review the recent progress of electrocaloric effects from phenomenological Landau thermodynamics theory to phase-field simulation by discussing the microcosmic composition, mesoscopic domain structures, macroscopic size/shape, and external stimulus of strain/stress. More importantly, in searching for new ferroelectric electrocaloric cooling materials, it is possible to find materials whose free energy barrier height changes rapidly with temperature, such materials have a faster change rate with polarization temperature in terms of ferroelectric macroscopic properties, from them could get superior electrocaloric effects. We compile a relatively comprehensive computational design on the high performance of electrocaloric effects in different types of ferroelectrics and offer a perspective on the computational design of electrocaloric refrigeration materials at the mesoscale microstructure level.

Interpreting the optical properties of oxide glasses with machine learning and shapely additive explanations

Abstract: Due to their excellent optical properties, glasses are used for various applications ranging from smartphone screens to telescopes. Developing compositions with tailored Abbe number (Vd) and refractive index at 587.6 nm (nd), two crucial optical properties, is a major challenge. To this extent, machine learning (ML) approaches have been successfully used to develop composition–property models. However, these models are essentially black boxes in nature and suffer from the lack of interpretability. In this paper, we demonstrate the use of ML models to predict the composition-dependent variations of Vd and nd. Further, using Shapely additive explanations (SHAP), we interpret the ML models to identify the contribution of each of the input components toward target prediction. We observe that glass formers such as SiO2, B2O3, and P2O5 and intermediates such as TiO2, PbO, and Bi2O3 play a significant role in controlling the optical properties. Interestingly, components contributing toward increasing the nd are found to decrease the Vd and vice versa. Finally, we develop the Abbe diagram, using the ML models, allowing accelerated discovery of new glasses for optical properties beyond the experimental pareto front. Overall, employing explainable ML, we predict and interpret the compositional control on the optical properties of oxide glasses.

Reactive flash sintering and electrical transport properties of high‐entropy (MgCoNiCuZn) 1‐ x Li x O oxides

Abstract: In this paper, high-entropy (MgCoNiCuZn)1-xLixO oxides (x = 0, 0.1, 0.15, 0.2, and 0.3) were synthesized via reactive flash sintering (RFS), and the effect of RFS process on the microstructure and electrical property of the materials were studied. The Li-doped materials exhibited a mixed ionic–electronic transport behavior. The oxidation of Co2+ into Co3+ upon Li incorporation into the materials synthesized via the conventional solid-state reaction route was not evidenced in the flash sintered materials. Instead, the charge unbalance in the Li-doped materials synthesized via RFS was compensated by oxygen vacancies and holes in the valence band of the oxides, which were accounted for the ionic conduction and electronic conduction, respectively. The ionic conductivity increased upon increasing the Li concentration as more oxygen vacancies were formed. The attraction between defects with different charges (LiM/ and VO••), which formed defect complexes, led to a decrease in the mobility of the defects, thus resulting in a less pronounced increase in the ionic conductivity at high Li concentrations. The change in the charge compensation mechanism of the materials indicates that the microstructure of such kind of oxides could be altered through RFS, and thus the property may be manipulated.

Excellent thermal stability and energy storage properties of lead‐free Bi 0.5 Na 0.5 TiO 3 ‐based ceramic

Abstract: The ceramic capacitors with excellent energy storage properties and wide operating temperature are the main challenges in power system applications. Here, the lead-free (1-x)Bi0.5Na0.5TiO3-xCaTiO3 (BNT-xCT) ceramics were synthesized through solid-state reaction method. The introduction of CT reduced the temperature of permittivity peak of BNT ceramic, guaranteeing excellent thermal stability over a wide temperature range of -100 ∼ 136°C. Meanwhile, the long-range order structure of BNT was destructed by structural distortion and the relaxor behavior was enhanced after doping CT. Moreover, the direct current breakdown strength was improved from 203 to 455 kV/cm, and the high recoverable energy density (Wrec ∼ 2.74 J/cm3) with high efficiency (η ∼ 91%) was achieved for BNT-0.25CT ceramic, along with a fast discharge speed (t0.9 ∼ 110 ns) superior cycle stability, and thermal stability. Those properties enabled a promising practical prospect of BNT-CT ceramics. This article is protected by copyright. All rights reserved

Barium hexaferrites with narrow ferrimagnetic resonance linewidth tailored by site‐controlled Cu doping

Abstract: Barium hexagonal ferrites exhibiting unique self-biasing characteristics have great potential for application in planar microwave devices, such as self-biased circulators. Cu doping is an effective method to tailor their anisotropy field and ferrimagnetic resonance (FMR) linewidth to meet the requirements for low-frequency low-loss microwave devices. However, the regulation mechanism of Cu doping is still obscure, and its regulation effect is not optimized. Here, the magnetic and microwave properties of two groups of barium hexaferrites with site-controlled Cu doping are reported. The diffusion dynamics of Cu2+ ions are comprehensively investigated, revealing significant differences in the concentration distribution and polycrystalline morphology, when comparing CuO as a reactant and sintering additive. The accumulation of Cu2+ ions at grain boundaries contributes to the increase in coercivity, whereas the dispersion of Cu2+ ions in crystallites leads to the decrease in the anisotropy field. Moreover, by introducing Cu2+ ions into the interstitial positions of the lattice, barium hexaferrites with a narrow FMR linewidth of 303 Oe and a high remanence ratio of 0.82 are achieved. These results represent the lowest FMR linewidth reported in polycrystalline hexagonal ferrites and prove the great technological value and commercial potential of Cu-doped barium hexaferrites for next-generation planar microwave devices.

Effect of ferroelectric polarization on piezo/photocatalysis in Ag nanoparticles loaded 0.5(Ba _0.7 Ca _0.3 )TiO ₃ –0.5Ba(Zr _0.1 Ti _0.9 )O ₃ composites towards the degradation of organic pollutants

Abstract: A 0.5(Ba0.7Ca0.3)TiO3–0.5Ba(Zr0.1Ti0.9)O3 (BCT-BZT) ceramic was studied for photocatalysis and piezocatalysis effects using dye degradation (methylene blue, rhodamine B, and methyl orange) and bacterial (Escherichia coli) disinfection from aqueous solution. To examine the effect of ferroelectric polarization, BCT-BZT powder was poled using the corona poling technique. Same time, BCT-BZT was converted into Ag/BCT-BZT composites as Ag induced surface plasmon resonance effect during photocatalysis. Piezocatalysis performance was assessed for dyes mineralization under ultrasonication. There was a significant impact of silver nanoparticles on the photo/piezocatalysis performance of BCT-BZT. Similarly, electric poling has also played a positive role in improving the photo/piezocatalysis in view of various dye degradation. These samples also showed effective antibacterial performance.

Porous ceramics with near‐zero‐shrinkage and low thermal conductivity from hazardous secondary aluminum dross

Abstract: Herein, a simple, versatile, and low-cost approach has been proposed to realize the green utilization of secondary aluminum dross, the hazardous solid waste, namely directly sintering dry-pressed green bodies from secondary aluminum dross to fabricate porous ceramics according to high-temperature foaming process spontaneously without adding spare foaming agents. Aluminum nitride (AlN) in secondary aluminum dross was employed to realize high-temperature foaming due to its oxidation, which makes traditional AlN and salts removal process needless. Moreover, near-zero shrinkage or even expansion during sintering of porous ceramics have occurred because in-situ foaming process together with the oxidation of Al particles well offset the sintering shrinkage. After sintering at 1400°C for 2 h, porous ceramics composed of α-Al2O3 and spinel phases with open porosity of 37.91%, sintering expansion rate of 1.13%, flexural strength of 45.67 MPa, and thermal conductivity of 0.97 W/(m·K) have been prepared. Cenospheres as pore-forming agents have been added to further improve the porosity, and alumina-based porous ceramics with open porosity of 28.39%–43.20% and flexural strength of 15.80–52.48 MPa have been obtained. This effective solution for recycling secondary aluminum dross could supply high-performance porous ceramics, which is expected to be applied in the fields of light-weight structural components and thermal insulations.

Oxygen vacancy‐rich ZnO nanorods‐based MEMS sensors for swift trace ethanol recognition

Abstract: Ethanol vapor plays a significant role in the aspects of human health and industrial production, thus necessitating a swift, sensitive, and low-power ethanol detection in the field of future gas sensors. In this work, we prepared micro–electro–mechanical system ethanol sensors based on ZnO nanorods (NRs) and nanoparticles (NPs) for trace ethanol detection. Both ZnO samples were synthesized by a facile hydrothermal method. The comparison results exhibited that ZnO NRs based sensors prevailed over NPs-based counterparts in terms of sensitivity, optimal operation temperature, and reaction speeds. Briefly, that ZnO NRs-based sensors presented a large response (11.5 toward 5 ppm), fast response/recovery times (5 s/5 s), ultralow detection limit (400 ppb), and tiny power consumption (30 mW) at 245°C, surpassing most of recently reported ethanol sensors and commercial products based metal oxides. The abundant oxygen vacancies, large specific surface area, and porous structure were primarily responsible for the excellent sensor performance. This work also offers a facile and competitive approach to realize a sensitive and swift trace ethanol recognition with minimal power consumption, catering for the demanding requirements of future gas sensors in the fields of wearable devices and Internet of Things.

Energy storage performance of BiFeO 3 ‐SrTiO 3 ‐BaTiO 3 relaxor ferroelectric ceramics

Abstract: Dielectric capacitors reveal great potential in the application of high power and/or pulsed power electronic devices owing to their ultrafast charge–discharge rate and ultrahigh power density. Among various dielectric capacitors, the environment-friendly lead-free dielectric ceramics have drawn extensive investigations in recent years. Nevertheless, the relatively small recoverable energy storage density (Wrec) is still an obstacle for their application. Herein, the (0.55−x)BiFeO3–0.45SrTiO3–xBaTiO3 ternary ceramics with 0.1 wt% MnO2 were prepared by the solid-state reaction, and achieved enhanced relaxor behavior as well as breakdown strength Eb. As a result, the x = 0.12 ceramic exhibited superior comprehensive energy storage performance of large Eb (50.4 kV/mm), ultrahigh Wrec (7.3 J/cm3), high efficiency η (86.3%), relatively fast charge–discharge speed (t0.9 = 6.1 μs) and outstanding reliability under different frequency, fatigue, and temperature, indicating that the BiFeO3-based relaxor ferroelectric ceramics are prospective alternatives for electrostatic energy storage.

Role of tellurium addition on the linear and non‐linear optical, structural, morphological properties of Ag _60‐ <i> _x </i> Se ₄₀ Te <i> _x </i> thin films for nonlinear applications

Abstract: The tellurium (Te)-doped Ag60-xSe40Tex (x = 0%, 5%, 10%, 15%) thin films of thickness ∼800 nm were prepared from the bulk sample by thermal evaporation method on a glass substrate. The X-ray diffraction study revealed the amorphous nature of the films whereas the change in vibrational modes was noticed from the Raman spectroscopy. The composition of the films was verified by energy dispersive X-ray analysis and the surface morphology pictures were taken by field emission scanning electron microscopy and atomic force microscope. The changes in optical properties (linear and non-linear) with Te addition were studied from UV-Visible spectroscopy data and related empirical formulas. The addition of Te reduced the bandgap values significantly and the reduction in transmission resulted in the increase of the linear refractive index. The decrease in optical bandgap is due to an increase in disorder while the width of the tail in the gap increased with Te%. The optical density, dispersion energy, extinction coefficient, carrier concentration, dielectric constant, oscillator wavelength increased while the oscillator energy, oscillator strength, optical electronegativity decreased with Te content. The electrical susceptibility increased with Te content. The non-linear susceptibilities and the non-linear refractive index increased which is good for the nonlinear photonic devices.

Morphology‐controlled preparation and tunable electromagnetic wave absorption performance of manganese dioxide nanostructures

Abstract: The development of electromagnetic wave (EMW) absorption materials with lightweight, wide absorption bandwidth, thin thickness, and strong EMW absorption performance has become a hotspot. Herein, the morphology-controlled preparation of α-manganese dioxide (α-MnO2) was successfully obtained via a facile hydrothermal method, and the EMW absorption performance of α-MnO2 was investigated in detail. The results indicated the as-obtained Mn-1.0-120 possessed the best EMW absorption performance with minimum reflection loss of −53.43 dB at about 5.2 GHz with a thickness of 4.1 mm originated from the synergistic effects of multiply scattering, dielectric loss, and magnetic loss. This contribution demonstrates that the MnO2 has promising candidates with a tunable EMW absorption performance for applications in the electromagnetic field in the future.

Solar/visible light photocatalytic dye degradation using BaTi 1‐x Fe x O 3 ceramics

Abstract: BaTi1−xFexO3 compositions (for x = 0, 0.1, and 0.2) were prepared via a solid-state reaction route. The presence of iron (Fe) in barium titanate (BaTiO3) eventually decreased the energy bandgap; thus, its utilization for water cleaning application through photocatalysis process was explored (using methylene blue [MB] dye as an indicative pollutant in water). Characterization of the synthesized powder was performed through scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. The bandgap of the synthesized powder was calculated as 3.2, 2.12, and 1.67 eV for BaTi1−xFexO3 compositions (for x = 0, 0.1, and 0.2), respectively. BaTi0.8Fe0.2O3 powder showed excellent results, and ∼71% of the MB dye (∼5 mg/L concentrated) was degraded using the photocatalysis process under visible light. To check the potentiality of BaTi1−xFexO3 compositions (for x = 0, 0.1, and 0.2), the photocatalysis process was carried out by changing the concentration of MB dye (2.5–10 mg/L with a step of 2.5 mg/L) and the amount of BaTi0.8Fe0.2O3 powder (0.05–0.2 g with a step of 0.05 g) for ∼5-mg/L concentrated MB dye. The treated water was further used as a growth parameter and phytotoxicity analysis through germination index on the wheat seeds. Lastly, the BaTi1−xFexO3 compositions (for x = 0, 0.1, and 0.2) were explored for water cleaning applications under real-time solar irradiation.

Bi 3+ /Mn 4+ co‐doped dual emission phosphors for potential plant lighting

Abstract: Developing environment-friendly dual-emission phosphors of both blue–cyan and deep-red lights is desirable for the utilized indoor plant lighting research. Notably, the naked 6s and 6p Bi3+ ions are sensitive to the lattice sites, which emit from Ultraviolet (UV) to red lights in various crystal compounds. Meanwhile, the 2E → 4A2g transition of Mn4+ ions promises its deep-red light emissions, which satisfies the demand for specific wavelength lights for plants growth. Hence, a Bi3+/Mn4+ co-doped Sr2LaGaO5: Bi3+, Mn4+ (SLGO:Bi3+:Mn4+) phosphor was finally synthesized. The phase, micromorphology and luminescent properties were systematically evaluated. Upon excitation at 350 nm light, dual emissions of both blue–cyan (470 nm) and deep-red (718 nm) lights were observed. Besides, due to the pronounced photoluminescence (PL) spectral overlap between Bi3+ and Mn4+ ions, a potential energy transfer process from Bi3+ to Mn4+ ions was confirmed. The relative PL intensities between Bi3+ and Mn4+ ions can be tuned just by adjusting the Mn4+ ion concentration. Besides, Li+ co-doping has been evidenced to improve the deep-red emissions (718 nm) of SLGO:0.005Mn4+ due to charge compensation and rationally designed lattice distortion, together with the improved thermal stability. Finally, the emissions of SLGO:Bi3+, Mn4+, Li+ phosphor suit properly with the absorption of the four fundamental pigments for plant growth, indicating that the prepared phosphorescent materials may have a prospect in plant light-emitting diodes lighting.

The Magnetic, thermal transport properties, magnetothermal effect and critical behavior of Co 3 Sn 2 S 2 single crystal

Abstract: Through the magnetic/thermal transport measurements combined with the analyses of magnetocaloric effect and critical behavior of Co3Sn2S2 single crystal, the main results we obtained are as follows: in the case of the magnetic field H//c axis, Co3Sn2S2 exhibits the phase separation state below Tc in the low field region (H < 500 Oe). Tc increases slightly from 174 K to 177 K with increasing H from 100 Oe to 10 kOe. The second-order magnetic phase transition near Tc and the itinerant ferromagnetism below Tc are identified. The magnetization below Tc matches well with the three-dimensional (3D) Ising model, instead of the mean field model. In the case of H//ab, Tc changes between 175 K and 178 K with varying H. Noticeably, M above Tc exhibits a small positive value, instead of the null M as commonly expected in the paramagnetic region. An extra phase transition below 166 K is observed. The magnetic transition near Tc seems not to be the second-order phase transition. All results show a significant characteristic of anisotropic magnetic phase transition for the Co3Sn2S2 single crystal; They support mutually those in previous reports, moreover, some new phenomena are also observed; They provides the experimental evidences for the deep insight into the magnetic phase transition behavior of Co3Sn2S2. This article is protected by copyright. All rights reserved

Defect engineering in rare‐earth‐doped BaTiO ₃ ceramics: Route to high‐temperature stability of colossal permittivity

Abstract: High-performance colossal-permittivity (CP) materials have huge potential applications in the miniaturization of electronic components and high-energy storage applications. Here, we report CP behavior in rare-earth Ln-doped BaTiO3 (Ln = La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, and Er) ceramics. CP (>1 × 105) and low loss (<5% at 1 kHz) were achieved. Additionally, all ceramic samples with excellent temperature stability over a wide temperature range (25–250°C). X-ray photoelectron spectroscopy verified the existence of point defects (Ti3+ and V O • • $V_{\rm{O}}^{{\rm{ \bullet \bullet }}}$ ) in Ln-doped BaTiO3 ceramic samples annealed in an N2 atmosphere. Electron paramagnetic resonance further demonstrated the existence of Ti3+. The coupling of point defects forms an electron-pinned defect-dipoles (EPDD) effect and induces strong hopping polarization. In addition, an internal barrier layer capacitance (IBLC) effect and a surface barrier layer capacitor (SBLC) effect are identified by impedance spectroscopy and DC bias voltage. The CP is attributed to the combined effect of EPDD, IBLC, and SBLC. Furthermore, the high-temperature stability of CP is related to the strong coupling of defect-dipole complexes.

Amelioration on energy storage performance of KNN–based transparent ceramics by optimizing the polarization and breakdown strength

Abstract: Transparent ceramic capacitors have broad application prospects in electronic devices due to their excellent optical transparency and energy storage properties. However, the low polarizability and high remnant polarization of the existing transparent dielectric ceramics limit the promotion of energy storage performance. Here, Bi(Li0.5Nb0.5)O3 (BLN) was chosen to modify the (K0.5Na0.5)NbO3 (KNN)-based ceramics to optimize the optical transmittance and energy storage characteristics simultaneously. On the one hand, the grain growth is inhibited, contributing to the improved breakdown strength and transmittance. On the other hand, the doping BLN could reduce the polar nanoregions size, which makes them respond more quickly to the external electric field and, thus, improves the energy storage efficiency. As a consequence, 0.95KNN–0.05BLN ceramic possesses the excellent Wrec of 4.39 J/cm3, η of 81.4%, and transparency of 77.9% with an average grain size of ∼109 nm. This work opens up a paradigm to develop a transparent pulse capacitor.

Synthesis and flash sintering of zirconium nitride powder

Abstract: Zirconium nitride (ZrN) is a transition metal nitride of great interest due to its excellent physical and chemical properties. This study aims to synthesize ZrN fine powders by a facile and low-cost urea route that avoids the use of any solvent. ZrCl4 and urea mixtures were heat-treated at up to 1600˚C in nitrogen gas. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and thermogravimetric analysis. The effects of different processing parameters such as metal to urea molar ratio, heat treatment temperature, and dwelling time on the product phase and stoichiometry were studied to understand the synthesis method. In addition, synthesized ZrN powder was consolidated into near fully dense single-phase bulk ceramic with a homemade flash sintering setup. A constant DC electrical field of ∼80 V/cm and pressure of ∼14 MPa at room temperature triggered flash sintering without pre-heating, and the entire process finished in 200 s. The composition, microstructure, density, hardness, and oxidation properties of the sintered pellet were also characterized.