Editorial

4 pages, 186 KiB

Open AccessEditorial

High-Performance Dielectric Ceramic for Energy Storage Capacitors

by Jing Wang

Coatings 2022, 12(7), 889; https://doi.org/10.3390/coatings12070889 - 23 Jun 2022

Cited by 3 | Viewed by 1566

In recent years, due to the depletion of fossil fuels, air pollution, carbon emissions, and other issues, it has become urgent to seek the development of renewable, non-polluting, and clean energy [...] Full article

(This article belongs to the Special Issue High-Performance Dielectric Ceramic for Energy Storage Capacitors)

Research

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13 pages, 2634 KiB

Open AccessArticle

First-Principles Investigation of Point Defects on the Thermal Conductivity and Mechanical Properties of Aluminum at Room Temperature

by Touwen Fan, Zixiong Ruan, Baohua Nie, Yikai Liao, Bowen Huang, Zimeng Xu, Yuanzhi Wu, Te Hu and Dongchu Chen

Coatings 2023, 13(8), 1357; https://doi.org/10.3390/coatings13081357 - 02 Aug 2023

Cited by 1 | Viewed by 958

Abstract

The effects of point defects on the mechanical and thermal conductivity of aluminum at room temperature have been investigated based on the first-principles calculations combined with the Boltzmann equation and the Debye model. The calculated results showed the equilibrium lattice constants a₀ [...] Read more.

The effects of point defects on the mechanical and thermal conductivity of aluminum at room temperature have been investigated based on the first-principles calculations combined with the Boltzmann equation and the Debye model. The calculated results showed the equilibrium lattice constants a₀ of all RE_Al are larger than that of Al, and the defective formation energy E_f of all RE_Al is lower than that of V_Al. Both a₀ and E_f increase from Sc to La and then decrease linearly to Lu. The effects of solute atoms on the mechanical properties of the Al matrix were further calculated, and compared with Al, it is found that the RE_Al defects decrease the elastic constant C_ij, Cauchy pressure C₁₂–C₄₄, bulk modulus B, shear modulus G, Young’s modulus E, B/G and Poisson’s ratio ν of Al, except for C₄₄ of RE_Al (RE = La-Nd). With the increase of atomic number, the C₁₁ and E of Al-containing RE_Al decrease from Sc to La and then slowly increase to Lu, whereas C₁₂, C_44, B, and G have little change. Meanwhile, the values of C₁₂–C₄₄ and B/G of Al-containing RE_Al increase from Sc to Ce, and it slightly change after Ce, while ν is nearly unchanged. All defects containing Al present nonuniform and ductility. Finally, the effects of rare earth (RE) atoms on the thermal conductivity (TC) of Al alloys have been investigated based on the first-principles calculations. The reduction of TC of Al alloys by RE solute atoms RE_Al is much greater than that by the L1₂ Al₃RE phase with the same concentration of RE, which is in good agreement with the experiments. With the RE atomic number increasing, the total TC κ of the Al-RE solid solution decreases from Sc to La firstly and then increases linearly to Lu. Moreover, the decrement of TC Δκ of the Al matrix by early RE_Al (RE = La-Sm) is larger than that by V_Al, while the later RE_Al (RE = Gd-Lu) shows the opposite influence. Full article

(This article belongs to the Special Issue High-Performance Dielectric Ceramic for Energy Storage Capacitors)

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12 pages, 2749 KiB

Open AccessArticle

Improvement of Piezoelectricity of (Bi_0.5Na_0.5)_0.94Ba_0.06TiO₃ Ceramics Modified by a Combination of Porosity and Sm³⁺ Doping

by Siyu Xia, Huiling Du, Zhuo Li, Fan Zhao, Qianqian Li, Yuxuan Hu and Le Kang

Coatings 2023, 13(4), 805; https://doi.org/10.3390/coatings13040805 - 21 Apr 2023

Cited by 3 | Viewed by 1534

Abstract

Porous lead-free piezoelectric ceramics are characterized by their environment-friendly, light weight, and large specific surface area. The optimization of porous Na_0.5Bi_0.5TiO₃-based lead-free piezoelectric ceramics can improve piezoelectric properties, enhance force–electric coupling characteristics, and effectively promote energy conversion, [...] Read more.

Porous lead-free piezoelectric ceramics are characterized by their environment-friendly, light weight, and large specific surface area. The optimization of porous Na_0.5Bi_0.5TiO₃-based lead-free piezoelectric ceramics can improve piezoelectric properties, enhance force–electric coupling characteristics, and effectively promote energy conversion, expanding the application in force-electric coupling devices. This study aimed to prepare [Sm_x(Bi_0.5Na_0.5)_1−3x/2]_0.94Ba_0.06TiO₃ (x = 0, 0.01, 0.02, 0.03, 0.04) lead-free ceramics with porous structures, resulting in the piezoelectric constant d₃₃ = 131 pC/N and the plane electromechanical coupling coefficient k_p = 0.213 at x = 0.01. The presence of pores in lead-free ceramics has a direct impact on the domain structure and can cause the depolarization process to relax. Then, the soft doping of Sm³⁺ makes the A-site ion in porous (Bi_0.5Na_0.5)_0.94Ba_0.06TiO₃ ceramics occupancy inhomogeneous and generates cation vacancies, which induces lattice distortion and makes the domain wall motion easier, resulting in the improvement of piezoelectric properties and electromechanical coupling parameters. Furthermore, the piezoelectric oscillator exhibits greater resistance to resonant coupling in the radial extension vibration mode. These results infer that a combination of porosity and Sm³⁺ doping renders (Bi_0.5Na_0.5)_0.94Ba_0.06TiO₃ ceramics base material for piezoelectric resonators, providing a scientific basis for their application in force–electric coupling devices, such as piezoelectric resonant gas sensors. Full article

(This article belongs to the Special Issue High-Performance Dielectric Ceramic for Energy Storage Capacitors)

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13 pages, 2381 KiB

Open AccessArticle

Enhanced Energy Storage Performance of AgNbO₃:xCeO₂ by Synergistic Strategies of Tolerance Factor and Density Regulations

by Ke An, Gang Li, Tingting Fan, Feng Huang, Wenlin Wang and Jing Wang

Coatings 2023, 13(3), 534; https://doi.org/10.3390/coatings13030534 - 28 Feb 2023

Cited by 2 | Viewed by 1095

Abstract

AgNbO₃-based ceramics have been widely studied as ideal lead-free materials. Herein, AgNbO₃:xCeO₂ (x = 0, 1, 2 mol%) ceramics were successfully prepared by the conventional solid-state reaction method. The optimization of energy storage properties is [...] Read more.

AgNbO₃-based ceramics have been widely studied as ideal lead-free materials. Herein, AgNbO₃:xCeO₂ (x = 0, 1, 2 mol%) ceramics were successfully prepared by the conventional solid-state reaction method. The optimization of energy storage properties is ascribed to the enhanced antiferroelectric (AFE) stability and the increased breakdown strength (E_b). The reduction of the tolerance factor leads to the enhancement of AFE stability. In addition, the enhancement of E_b is due to the increase of actual density, which is achieved through the regulation of CeO₂ amount and grinding procedure in the experimental process. A high recoverable energy density (W_rec) of 5.04 J/cm³ and an energy efficiency (η) of 46.2% were achieved in AgNbO_3:0.01CeO₂ ceramics under an applied electric field up to 390 kV/cm. A higher η of 55.4% was obtained in AgNbO₃:0.02CeO₂ components. This research provides guidance for finding ceramic materials with comprehensive energy storage properties. Full article

(This article belongs to the Special Issue High-Performance Dielectric Ceramic for Energy Storage Capacitors)

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15 pages, 12406 KiB

Open AccessArticle

Metastable Phase Formation, Microstructure, and Dielectric Properties in Plasma-Sprayed Alumina Ceramic Coatings

by Paul Junge, Moritz Greinacher, Delf Kober, Patrick Stargardt and Christian Rupprecht

Coatings 2022, 12(12), 1847; https://doi.org/10.3390/coatings12121847 - 29 Nov 2022

Cited by 6 | Viewed by 1787

Abstract

The need for new solutions for electrical insulation is growing due to the increased electrification in numerous industrial sectors, opening the door for innovation. Plasma spraying is a fast and efficient way to deposit various ceramics as electrical insulators, which are used in [...] Read more.

The need for new solutions for electrical insulation is growing due to the increased electrification in numerous industrial sectors, opening the door for innovation. Plasma spraying is a fast and efficient way to deposit various ceramics as electrical insulators, which are used in conditions where polymers are not suitable. Alumina (Al

_{2}

O

_{3}

) is among the most employed ceramics in the coating industry since it exhibits good dielectric properties, high hardness, and high melting point, while still being cost-effective. Various parameters (e.g., feedstock type, spray distance, plasma power) significantly influence the resulting coating in terms of microstructure, porosity, and metastable phase formation. Consequently, these parameters need to be investigated to estimate the impact on the dielectric properties of plasma-sprayed alumina coatings. In this work, alumina coatings with different spray distances have been prepared via atmospheric plasma spray (APS) on copper substrates. The microstructure, porosity, and corresponding phase formation have been analyzed with optical microscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Moreover, we present an in-depth analysis of the fundamental dielectric properties e.g., direct current (DC) resistance, breakdown strength, dielectric loss tangent, and permittivity. Our results show that decreasing spray distance reduces the resistivity from 6.31 ×

10^{9}

Ω

m (130 mm) to 6.33 ×

10^{8}

Ω

m (70 mm), while at the same time enhances the formation of the metastable

δ

-Al

_{2}

O

_{3}

phase. Furthermore, space charge polarization is determined as the main polarization mechanism at low frequencies. Full article

(This article belongs to the Special Issue High-Performance Dielectric Ceramic for Energy Storage Capacitors)

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9 pages, 1761 KiB

Open AccessArticle

Dielectric and Antiferroelectric Properties of AgNbO₃ Films Deposited on Different Electrodes

by Qingzhu Ma, Xiang Li, Yanle Zhang, Zhijin Duo, Suwei Zhang and Lei Zhao

Coatings 2022, 12(12), 1826; https://doi.org/10.3390/coatings12121826 - 25 Nov 2022

Cited by 1 | Viewed by 1336

Abstract

AgNbO₃ antiferroelectric materials have become a hot topic due to their typical double polarization–electric field loops. AgNbO₃ films usually exhibit superior properties to bulks. In this work, AgNbO₃ films were fabricated via the pulsed laser deposition on (001) SrTiO₃ [...] Read more.

AgNbO₃ antiferroelectric materials have become a hot topic due to their typical double polarization–electric field loops. AgNbO₃ films usually exhibit superior properties to bulks. In this work, AgNbO₃ films were fabricated via the pulsed laser deposition on (001) SrTiO₃ substrate with (La_0.5Sr_0.5)CoO₃, LaNiO₃ and SrRuO₃ bottom electrodes, in which the (La_0.5Sr_0.5)CoO₃, LaNiO₃ and SrRuO₃ bottom electrodes were used to regulate the in-plane compressive stress of AgNbO₃ films. It is found that AgNbO₃ films deposited on (La_0.5Sr_0.5)CoO₃, LaNiO₃ and SrRuO₃ bottom electrodes are epitaxial with dense microstructure. In changing the bottom electrodes from (La_0.5Sr_0.5)CoO₃, LaNiO₃ to SrRuO₃, the in-plane compressive stress of AgNbO₃ thin films becomes weaker, which leads to increased relative dielectric permittivity and reduced antiferroelectric–ferroelectric phase transition electric field E_F from 272 kV/cm to 190 kV/cm. The reduced E_F implies weakened antiferroelectric stability in AgNbO₃ films. It can be seen that the antiferroelectric stability of AgNbO₃ films could be regulated by changing the bottom electrodes. Full article

(This article belongs to the Special Issue High-Performance Dielectric Ceramic for Energy Storage Capacitors)

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11 pages, 3489 KiB

Open AccessArticle

Facile Hydrothermal Synthesis of Binder-Free Hexagonal MnO₂ Nanoparticles for a High-Performance Supercapacitor’s Electrode Material

by Qasim Abbas, Lianghua Wen, Abdul Mateen, Najam Ul Hassan, Asim Idrees, Zia Ur Rehman, Majed A. Bajaber and Muhammad Sufyan Javed

Coatings 2022, 12(8), 1101; https://doi.org/10.3390/coatings12081101 - 03 Aug 2022

Cited by 1 | Viewed by 1879

Abstract

Manganese dioxide (MnO₂)-based nanostructures are promising electrode materials for supercapacitors (SCs) due to their low cost, eco-friendly nature, and high theoretical capacitance. However, the conductivity of MnO₂ is poor, which is a big problem when trying to achieve the desired [...] Read more.

Manganese dioxide (MnO₂)-based nanostructures are promising electrode materials for supercapacitors (SCs) due to their low cost, eco-friendly nature, and high theoretical capacitance. However, the conductivity of MnO₂ is poor, which is a big problem when trying to achieve the desired capacitance value. Herein, hexagonal-phase MnO₂ nanoparticles (NPs) are directly grown on a 3D conductive carbon cloth (CC) (denoted as MnO₂-NPs@CC) as a binder-free electrode through a simple and scalable hydrothermal strategy. The results show that MnO₂-NPs@CC with a large specific surface area and high porosity could be employed as a positive electrode material for high-performance SCs. Owing to these attractive properties, the MnO₂-NPs@CC electrode delivers a high specific capacitance of 660 F/g at a current density of 2 A/g in 6 M KOH aqueous electrolytes. Moreover, the MnO₂-NPs@CC electrode demonstrates excellent cycling stability with high capacitance retention of 92.8% over 10,000 cycles. Such remarkable findings suggest that MnO₂-NPs@CC with enhanced electrochemical performance is a favorable electrode material for next-generation high-performance SCs. Full article

(This article belongs to the Special Issue High-Performance Dielectric Ceramic for Energy Storage Capacitors)

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17 pages, 5525 KiB

Open AccessArticle

Dielectric Properties of Plasma-Sprayed Fully Natural Garnets

by Pavel Ctibor, Josef Sedláček and Libor Straka

Coatings 2022, 12(7), 1017; https://doi.org/10.3390/coatings12071017 - 18 Jul 2022

Cited by 1 | Viewed by 1249

Abstract

Various kinds of natural garnets belonging to the almandine type (3FeO·Al₂O₃·3SiO₂) were sprayed by plasma spray technique to build coatings on metallic substrates. The experimental garnet powders came from different mines in the Czech Republic and Mongolia. [...] Read more.

Various kinds of natural garnets belonging to the almandine type (3FeO·Al₂O₃·3SiO₂) were sprayed by plasma spray technique to build coatings on metallic substrates. The experimental garnet powders came from different mines in the Czech Republic and Mongolia. After coating and cooling the substrates were removed. In this way, self-supporting plates were obtained and further studied with microscopy, X-ray diffraction, and dielectric spectroscopy. Mechanical properties were in our focus as well. Microhardness was measured on cross sections dedicated to microstructure observation. Wear resistance in wet conditions was tested in a slurry. Reflectance was measured applying visible and infrared (VIS-NIR) radiation. Dielectric properties of coatings were studied at low voltage capacitance, loss tangent and also under direct current (DC) resistance. The results show that garnet minerals are interesting candidates for various optical and electronic applications; they have similar dielectric behavior as, for example, aluminum oxide or similar high-purity synthetic oxides, and, simultaneously, they have extraordinarily low reflectance in VIS-NIR radiation. The differences between natural powders and resulting coatings are discussed in connection with their chemical and phase compositions. Full article

(This article belongs to the Special Issue High-Performance Dielectric Ceramic for Energy Storage Capacitors)

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