Ceramics

18 pages, 2148 KiB

Open AccessArticle

Structural and Dielectric Impedance Studies of Mixed Ionic–Electronic Conduction in SrLaFe_1−xMn_xTiO₆ (x = 0, 0.33, 0.67, and 1.0) Double Perovskites

by Abdelrahman A. Elbadawi, Elsammani A. Shokralla, Mohamed A. Siddig, Obaidallah A. Algethami, Abdullah Ahmed Alghamdi and Hassan H. E. Idris

Ceramics 2025, 8(3), 87; https://doi.org/10.3390/ceramics8030087 - 7 Jul 2025

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Abstract

The structural and electrical properties of double perovskite compounds SrLaFe_1−xMn_xTiO_6−δ (x = 0, 0.33, 0.67, and 1.0) were studied using X-ray diffraction (XRD) and dielectric impedance measurements. The reparation of perovskite compounds was successfully achieved through the precursor [...] Read more.

The structural and electrical properties of double perovskite compounds SrLaFe_1−xMn_xTiO_6−δ (x = 0, 0.33, 0.67, and 1.0) were studied using X-ray diffraction (XRD) and dielectric impedance measurements. The reparation of perovskite compounds was successfully achieved through the precursor solid-state reaction in air at 1250 °C. The purity phase and crystal structures of perovskite compounds were determined by means of the standard Rietveld refinement method using the FullProf suite. The best fitting results showed that SrLaFeTiO_6−δ was orthorhombic with space group Pnma, and both SrLaFe_0.67Mn_0.33TiO_6−δ and SrLaFe_0.33Mn_0.67TiO_6−δ were cubic structures with space group Fm3m, while SrLaMnTiO_6−δ was tetragonal with a I/4m space group. The charge density maps obtained for these structures indicated that the compounds show an ionic and mixed ionic–electronic conduction. The dielectric impedance measurements were carried out in the range of 20 Hz to 1 MHz, and the analysis showed that there is more than one relaxation mechanism of Debye type. Doping with Mn was found to reduce the dielectric impedance of the samples, and the major contribution to the dielectric impedance was established to change from a capacitive for SrLaFeTiO_6−δ to a resistive for SrLaMnTiO_6−δ. The fall in values of electrical resistance may be related to the possible occurrence of the double exchange (DEX) mechanism among the Mn ions, provided there is oxygen deficiency in the samples. DC-resistivity measurements revealed that SrLaFeTiO_6−δ was an insulator while SrLaMnTiO_6−δ was showing a semiconductor–metallic transition at ~250 K, which is in support of the DEX interaction. The dielectric impedance of SrLaFe_0.67Mn_0.33TiO_6−δ was found to be similar to that of (La,Sr)(Co,Fe)O_3-δ, the mixed ionic–electronic conductor (MIEC) model. The occurrence of a mixed ionic–electronic state in these compounds may qualify them to be used in free lead solar cells and energy storage technology. Full article

(This article belongs to the Special Issue Advances in Electronic Ceramics, 2nd Edition)

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17 pages, 15703 KiB

Open AccessArticle

Improving of Thermoelectric Efficiency of Layered Sodium Cobaltite Through Its Doping by Different Metal Oxides

by Natalie S. Krasutskaya, Ekaterina A. Chizhova, Julia A. Zizika, Alexey V. Buka, Hongchao Wang and Andrei I. Klyndyuk

Ceramics 2025, 8(3), 86; https://doi.org/10.3390/ceramics8030086 - 5 Jul 2025

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Abstract

Na₀.₈₉Co_0.90Me_0.10O₂ (Me = Cr, Ni, Mo, W, Pb, and Bi) ceramic samples were prepared using a solid-state reaction method, and their crystal structure, microstructure, and electrical, thermal, and thermoelectric properties were investigated. The effect [...] Read more.

Na₀.₈₉Co_0.90Me_0.10O₂ (Me = Cr, Ni, Mo, W, Pb, and Bi) ceramic samples were prepared using a solid-state reaction method, and their crystal structure, microstructure, and electrical, thermal, and thermoelectric properties were investigated. The effect of the nature of the doping metal (Me = Cr, Ni, Mo, W, and Bi) on the structure and properties of layered sodium cobaltite Na_0.89CoO₂ was analyzed. The largest Seebeck coefficient (616 μV/K at 1073 K) and figure-of-merit (1.74 at 1073 K) values among the samples studied were demonstrated by the Na_0.89Co_0.9Bi_0.1O₂ solid solution, which was also characterized by the lowest value of the dimensionless relative self-compatibility factor of about 8% within the 673–873 K temperature range. The obtained results demonstrate that doping of layered sodium cobaltite by transition and heavy metal oxides improves its microstructure and thermoelectric properties, which shows the prospectiveness of the used doping strategy for the development of new thermoelectric oxides with enhanced thermoelectric characteristics. It was also shown that samples with a higher sodium content (Na:Co = 0.89:1) possessed higher chemical and thermal stability than those with a lower sodium content (Na:Co = 0.55:1), which makes them more suitable for practical applications. Full article

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11 pages, 2553 KiB

Open AccessArticle

Effect of Ni²⁺ Doping on the Crystal Structure and Properties of LiAl₅O₈ Low-Permittivity Microwave Dielectric Ceramics

by Xuekai Lan, Huatao Tang, Bairui Chen and Bin Tian

Ceramics 2025, 8(3), 85; https://doi.org/10.3390/ceramics8030085 - 4 Jul 2025

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Abstract

Low-permittivity microwave dielectric ceramics are essential for high-frequency communication and radar systems, as they minimize signal delay and interference, thereby enabling compact and high-performance devices. In this study, LiAl_5−xNi_xO_8−0.5x (x = 0.1–0.5) ceramics were synthesized [...] Read more.

Low-permittivity microwave dielectric ceramics are essential for high-frequency communication and radar systems, as they minimize signal delay and interference, thereby enabling compact and high-performance devices. In this study, LiAl_5−xNi_xO_8−0.5x (x = 0.1–0.5) ceramics were synthesized via a solid-state reaction method to investigate the effects of Ni²⁺ substitution on crystal structure, microstructure, and dielectric properties. X-ray diffraction and Rietveld refinement reveal a phase transition from the P4₃32 to the Fd

\bar{3}

m spinel structure at x ≈ 0.3, accompanied by a systematic increase in the lattice parameter (7.909–7.975 Å), attributed to the larger ionic radius of Ni²⁺ compared to Al³⁺. SEM analysis confirms dense microstructures with relative densities exceeding 95% and grain size increases from less than 1 μm at x = 0.1 to approximately 2 μm at x = 0.5. Dielectric measurements show a decrease in permittivity (ε_r) from 8.24 to 7.77 and in quality factor (Q × f) from 34,605 GHz to 20,529 GHz with increasing Ni content, while the temperature coefficient of the resonant frequency (τ_f) shifts negatively from −44.8 to −69.1 ppm/°C. Impedance spectroscopy indicates increased conduction losses and reduced activation energy with higher Ni²⁺ concentrations. Full article

(This article belongs to the Special Issue Advances in Electronic Ceramics, 2nd Edition)

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11 pages, 998 KiB

Open AccessArticle

Study on the Absorbing Properties of V-Doped MoS₂

by Jiang Zou and Quan Xie

Ceramics 2025, 8(3), 84; https://doi.org/10.3390/ceramics8030084 - 2 Jul 2025

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Abstract

This study employed a hydrothermal method to prepare V-doped MoS₂. The influence of varying filler ratios (30 wt%, 40 wt%, 50 wt%) on its absorption properties was analyzed. For annealing studies, a precursor powder with a 40 wt% filler ratio was [...] Read more.

This study employed a hydrothermal method to prepare V-doped MoS₂. The influence of varying filler ratios (30 wt%, 40 wt%, 50 wt%) on its absorption properties was analyzed. For annealing studies, a precursor powder with a 40 wt% filler ratio was heat-treated at 600 °C for 2 h. The results obtained through characterization and testing indicate that the unannealed 40 wt% filler sample demonstrates superior absorption performance, with minimum reflection loss (RL_min) of −32.24 dB, an effective absorption bandwidth (EAB) of 4.40 GHz, and 99.9% electromagnetic (EM) wave attenuation. However, upon subjecting the sample with a 40 wt% filling ratio to annealing treatment, a notable decrease in impedance matching degree was observed, and regions with impedance matching values close to 1 were no longer present. Consequently, it can be concluded that at a filling ratio of 40 wt%, the sample’s excellent attenuation coefficient in conjunction with its good impedance matching collectively contribute to its superior comprehensive absorption performance. Full article

(This article belongs to the Special Issue Advances in Electronic Ceramics, 2nd Edition)

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21 pages, 3185 KiB

Open AccessArticle

Sustainable Use of Gypsum Waste for Applications in Soil–Cement Bricks: Mechanical, Environmental, and Durability Performance

by Elvia Soraya Santos Nascimento, Herbet Alves de Oliveira, Cochiran Pereira dos Santos, Maria de Andrade Gomes, Mário Ernesto Giroldo Valerio and Zélia Soares Macedo

Ceramics 2025, 8(3), 83; https://doi.org/10.3390/ceramics8030083 - 1 Jul 2025

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Abstract

This study investigates the use of gypsum waste from civil construction as a partial substitute for cement in soil–cement formulations, aiming to produce eco-friendly bricks aligned with circular economy principles. Formulations were prepared using a 1:8 cement–soil ratio, with gypsum replacing cement in [...] Read more.

This study investigates the use of gypsum waste from civil construction as a partial substitute for cement in soil–cement formulations, aiming to produce eco-friendly bricks aligned with circular economy principles. Formulations were prepared using a 1:8 cement–soil ratio, with gypsum replacing cement in proportions ranging from 5% to 40%. The raw materials were characterized in terms of chemical composition, crystalline phases, plasticity, and thermal behavior. Specimens, molded by uniaxial pressing into cylindrical bodies and cured for either 7 or 28 days, were evaluated for compressive strength, water absorption, durability, and microstructure. Water absorption remained below 20% in all samples, with an average value of 16.20%. Compressive strength after 7 days exhibited a slight reduction with increasing gypsum content, ranging from 16.36 MPa (standard formulation) to 13.74 MPa (40% gypsum), all meeting the quality standards. After 28 days of curing, the formulation containing 10% gypsum achieved the highest compressive strength (26.7 MPa), surpassing the reference sample (25.2 MPa). Mass loss during wetting–drying cycles remained within acceptable limits for formulations incorporating up to 20% gypsum. Notably, samples with 5% and 10% gypsum demonstrated superior mechanical performance, while the 20% formulation showed performance comparable to the standard formulation. These findings indicate that replacing up to 20% of cement with gypsum waste is a technically and environmentally viable approach, supporting sustainable development, circular economy, and reduction of construction-related environmental impacts. Full article

(This article belongs to the Special Issue Ceramics in the Circular Economy for a Sustainable World)

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19 pages, 9642 KiB

Open AccessArticle

Niobium Nitride Cavitation Erosion Resistance: An Approach on the Gas Mixture Influence in Plasma Nitrided Niobium Surfaces

by Ricardo Kertscher, Jair Carlos Dutra, Regis Henrique Gonçalves e Silva and Silvio Francisco Brunatto

Ceramics 2025, 8(3), 82; https://doi.org/10.3390/ceramics8030082 - 1 Jul 2025

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Abstract

This work shows an approach on the role of the gas mixture used in the pulsed DC plasma nitriding aiming to enhance the niobium cavitation erosion resistance through the formation of niobium nitride on the treated surfaces. For this purpose, nitriding was carried [...] Read more.

This work shows an approach on the role of the gas mixture used in the pulsed DC plasma nitriding aiming to enhance the niobium cavitation erosion resistance through the formation of niobium nitride on the treated surfaces. For this purpose, nitriding was carried out at 1353 K (1080 °C) for 2 h, under a pressure of 1.2 kPa (9 Torr), and a 5 × 10⁻⁶ Nm³s⁻¹ (300 sccm) flow rate for three distinct gas mixtures, namely 30% N₂ + 50% H₂ + 20% Ar, 50% N₂ + 30% H₂ + 20% Ar, and 70% N₂ + 10% H₂ + 20% Ar. Surfaces were comparatively characterized before and after nitriding through scanning electron microscopy (SEM), X-ray diffractometry, 3D roughness, and nanoindentation hardness measurements. The cavitation erosion test was carried out in accordance with ASTM G32-09, obtaining the cumulative mass loss (CML) curve and the average (AER) and maximum (MER) erosion rate of the tested surfaces. Surfaces showed multiphase layers mainly constituted of ε-NbN and β-Nb₂N nitride phases, for the three distinct gas mixture conditions investigated. A CML of 25.0, 20.2, and 34.6 mg, and an AER of 1.56, 1.27, and 2.16 mg h⁻¹ was determined to the 960 min (16 h) cavitation erosion testing time, for NbN surfaces obtained at the 30% N₂, 50% N₂, and 70% N₂ gas mixture, respectively. In this case, the nominal incubation period (NIP) was 600, 650, 550 min, and the maximum erosion rate (MER) was 4.2, 3.4, and 5.1 mg h⁻¹, respectively. Finally, the enhancement of the cavitation erosion resistance, based on the NIP of the NbN surfaces, regarding the Nb substrates (with NIP of ≈100 min), was up ≈6 times, on average, thus significantly improving the cavitation erosion resistance of the niobium. Full article

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9 pages, 2249 KiB

Open AccessArticle

ZrB₂ Gear Fabrication by Spark Plasma Sintering Coupled to Interface 3D Printing

by Charles Manière and Claude Estournès

Ceramics 2025, 8(3), 81; https://doi.org/10.3390/ceramics8030081 - 28 Jun 2025

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Abstract

The production of ultra-high-temperature ceramic parts, like ZrB₂, is very challenging, as they cannot be conventionally sintered without using significant amounts of additives, which reduce their high-temperature properties. However, it is possible to sinter these ceramics using spark plasma sintering (SPS) [...] Read more.

The production of ultra-high-temperature ceramic parts, like ZrB₂, is very challenging, as they cannot be conventionally sintered without using significant amounts of additives, which reduce their high-temperature properties. However, it is possible to sinter these ceramics using spark plasma sintering (SPS) without additives or with minimal amounts. The challenge, then, lies in obtaining complex shapes. In this work, we report a solution for the fabrication of ZrB₂ gears through the use of PLA-printed interfaces and graphite powder. This process is relatively simple and utilizes a fused deposition modeling (FDM) printer. The pros and cons of this approach are discussed with the aim of identifying what shapes can be produced using this method. Full article

(This article belongs to the Special Issue Ceramic Materials for Industrial Decarbonization)

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24 pages, 2387 KiB

Open AccessReview

Application of Ceramic Membranes Derived from Waste and Natural Materials for the Removal of Organic Dyes from Wastewater: A Review

by Keotshepile A. Malebadi, Lawrence Sawunyama, Naledi H. Seheri and Damian C. Onwudiwe

Ceramics 2025, 8(3), 80; https://doi.org/10.3390/ceramics8030080 - 25 Jun 2025

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Abstract

The growing demand for organic dyes across industries increases their environmental impact since wastewater containing organic dyes poses serious risks to aquatic life, human beings, and the environment. The removal of organic dye residues is a challenge for traditional wastewater treatment facilities, highlighting [...] Read more.

The growing demand for organic dyes across industries increases their environmental impact since wastewater containing organic dyes poses serious risks to aquatic life, human beings, and the environment. The removal of organic dye residues is a challenge for traditional wastewater treatment facilities, highlighting the need for advanced treatment techniques that balance cost-effectiveness and sustainability in the face of today’s strict environmental regulations. The use of low-cost starting materials in ceramic membrane technology has recently become more popular as a feasible option because of its affordability and effectiveness, leveraging the synergy of adsorption and filtration to improve dye removal. Recent developments in ceramic membranes derived from waste and natural materials are examined in this review paper, along with their types, mechanisms, and applications in eliminating organic dyes from wastewater. The various forms of ceramic membranes derived from waste and natural materials are classified as follows: those composed solely of inexpensive starting materials, composites of inexpensive materials, hybrids of inexpensive and commercial materials, and inexpensive materials functionalized with cutting-edge materials such as carbon nanotubes and nanoparticles. These membranes have shown promising results in lab-scale research, but their large-scale use is still limited. The factors that negate the commercialization of these membranes are also critically discussed. Finally, key challenges and future research opportunities in the development of sustainable ceramic membranes for highly efficient dye removal are highlighted. Full article

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15 pages, 2699 KiB

Open AccessArticle

Sunflower Shells Biomass Fly Ash as Alternative Alkali Activator for One-Part Cement Based on Ladle Slag

by Aleksandar Nikolov, Vladislav Kostov, Nadia Petrova, Liliya Tsvetanova, Stanislav V. Vassilev and Rositsa Titorenkova

Ceramics 2025, 8(3), 79; https://doi.org/10.3390/ceramics8030079 - 20 Jun 2025

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Abstract

This study explores the synergistic potential of ladle slag (LS) and sunflower shell fly ash (SSFA) in alkali-activated binder systems, focusing on their chemical and mineralogical characteristics and the influence of SSFA addition on the mechanical performance of LS-based pastes. X-ray fluorescence and [...] Read more.

This study explores the synergistic potential of ladle slag (LS) and sunflower shell fly ash (SSFA) in alkali-activated binder systems, focusing on their chemical and mineralogical characteristics and the influence of SSFA addition on the mechanical performance of LS-based pastes. X-ray fluorescence and XRD analysis revealed that LS is rich in CaO and latent hydraulic phases such as γ-belite and mayenite, while SSFA is dominated by K₂O, SO₃, and KCl/K₂SO₄ phases, reflecting its biomass origin. Infrared spectroscopy and thermal analysis confirmed the presence of carbonate, hydroxide, and hydrate phases, with SSFA exhibiting more complex thermal behavior due to volatile-rich composition. When used alone, LS produced weak binders; however, a 10 wt% SSFA addition tripled compressive strength to nearly 30 MPa, indicating a significant activation effect. Further increases in SSFA content led to strength reduction, likely due to increased porosity and excess salts. Microstructural analysis showed that SSFA promotes the formation of AFm phases such as Friedel’s salt and hydrocalumite, altering hydration pathways and enhancing early strength through chemical activation and carbonation processes. The findings highlight the potential of combining LS and SSFA as a sustainable binder system, offering a waste-derived alternative for low-carbon construction materials. Full article

(This article belongs to the Special Issue Ceramics in the Circular Economy for a Sustainable World)

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Ceramics, Volume 8, Issue 3 (September 2025) – 9 articles

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