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13 pages, 4284 KiB

Open AccessArticle

Bonding State and Thermal Expansion Coefficient of Mn-Doped Ba_0.5Sr_0.5FeO_3−δ Perovskite Oxides for IT-SOFCs

by Taeheun Lim, Sung-sin Yun, Kanghee Jo and Heesoo Lee

Nanomaterials 2024, 14(1), 82; https://doi.org/10.3390/nano14010082 - 27 Dec 2023

Cited by 2 | Viewed by 1564

The oxygen vacancy formation behavior and electrochemical and thermal properties of Ba_0.5Sr_0.5Fe_1−xMn_xO_3−δ (BSFMnx, x = 0–0.15) cathode materials were investigated. For thermogravimetric analysis, the weight decreased from 1.98% (x = 0) to 1.81% (x = 0.15) in the 400–950 °C range, which was due to oxygen loss from the lattice. The average oxidation state of the B-site increased, the O_ads/O_lat ratio decreased, and the binding energy of the O_lat peak increased with Mn doping. These results indicate that Mn doping increases the strength of the metal–oxygen bond and decreases the amount of oxygen vacancies in the lattice. The electrical conductivity of BSFMnx increased with the temperature due to the thermally activated small-polaron hopping mechanism showing a maximum value of 10.4 S cm⁻¹ (x = 0.15) at 450 °C. The area-specific resistance of BSFMn0.15 was 0.14 Ω cm² at 700 °C and the thermal expansion coefficient (TEC) gradually decreased to 12.7 × 10⁻⁶ K⁻¹, which is similar to that of Ce_0.8Sm_0.2O₂ (SDC) (12.2 × 10⁻⁶ K⁻¹). Mn doping increased the metal–oxygen bonding energy, which reduced the oxygen reduction reaction activity but improved the electrical conductivity and thermal stability with SDC. Full article

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13 pages, 2374 KiB

Open AccessArticle

Characterization and Differentiation of Wild and Cultivated Berries Based on Isotopic and Elemental Profiles

by Gabriela Cristea, Adriana Dehelean, Romulus Puscas, Florina-Dorina Covaciu, Ariana Raluca Hategan, Csilla Müller Molnár and Dana Alina Magdas

Appl. Sci. 2023, 13(5), 2980; https://doi.org/10.3390/app13052980 - 25 Feb 2023

Cited by 1 | Viewed by 2257

Abstract

The isotopic content (δ¹³C, δ²H, δ¹⁸O) and concentrations of 30 elements (Li, Na, Mg, P, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Rb, Sr, Ag, Cd, Ba, Pb, La, Ce, Pr, Nd, [...] Read more.

The isotopic content (δ¹³C, δ²H, δ¹⁸O) and concentrations of 30 elements (Li, Na, Mg, P, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Rb, Sr, Ag, Cd, Ba, Pb, La, Ce, Pr, Nd, Sm, Eu, Gd, and Tb) were determined in different wild and cultivated berries (raspberry, seaberry, blackberry, cranberry, and blueberry). Partial least squares discriminant analysis (PLS-DA) was applied in order to develop models for differentiating berries according to their botanical origin and growing system. δ¹³C, δ²H, δ¹⁸O, Li, Na, Mg, P, Ca, V, Mn, Co, Ni, Zn, As, Rb, Sr, Ba, and Eu were identified as significant elements for the differentiation of berry species, based on which an 85% PLS-DA model accuracy was obtained. Similarly, the PLS-DA model developed for the growing system differentiation correctly classified 94.4% of the cultivated berries and 77.2% of the wild ones, based on the main predictors: δ¹³C, δ¹⁸O, Li, Na, Ca, Cr, Mn, Ni, Rb, and Ba. The developed PLS-DA model for the discrimination of wild blueberries from cultivated ones showed excellent levels of sensitivity (100%), specificity (100%), and accuracy (100%). Full article

(This article belongs to the Special Issue Emerging Technologies in Food and Beverages Authentication)

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16 pages, 6763 KiB

Open AccessArticle

Synthesis and Properties of the Gallium-Containing Ruddlesden-Popper Oxides with High-Entropy B-Site Arrangement

by Juliusz Dąbrowa, Jan Adamczyk, Anna Stępień, Marek Zajusz, Karolina Bar, Katarzyna Berent and Konrad Świerczek

Materials 2022, 15(18), 6500; https://doi.org/10.3390/ma15186500 - 19 Sep 2022

Cited by 8 | Viewed by 2729

Abstract

For the first time, the possibility of obtaining B-site disordered, Ruddlesden–Popper type, high-entropy oxides has been proven, using as an example the LnSr(Co,Fe,Ga,Mn,Ni)O₄ series (Ln = La, Pr, Nd, Sm, or Gd). The materials were synthesized using the Pechini method, followed by sintering at a temperature of 1200 °C. The XRD analysis indicated the single-phase, I4/mmm structure of the Pr-, Nd-, and Sm-based materials, with a minor content of secondary phase precipitates in La- and Gd-based materials. The SEM + EDX analysis confirms the homogeneity of the studied samples. Based on the oxygen non-stoichiometry measurements, the general formula of LnSr(Co,Fe,Ga,Mn,Ni)O_4+δ, is established, with the content of oxygen interstitials being surprisingly similar across the series. The temperature dependence of the total conductivity is similar for all materials, with the highest conductivity value of 4.28 S/cm being reported for the Sm-based composition. The thermal expansion coefficient is, again, almost identical across the series, with the values varying between 14.6 and 15.2 × 10⁻⁶ K⁻¹. The temperature stability of the selected materials is verified using the in situ high-temperature XRD. The results indicate a smaller impact of the lanthanide cation type on the properties than has typically been reported for conventional Ruddlesden–Popper type oxides, which may result from the high-entropy arrangement of the B-site cations. Full article

(This article belongs to the Special Issue Feature Papers in the Section Advanced and Functional Ceramics and Glasses)

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11 pages, 3695 KiB

Open AccessArticle

Negative Thermal Expansion Properties of Sm_0.85Sr_0.15MnO_3-δ

by Yucheng Li, Yang Zhang, Yongtian Li and Yifeng Wu

J. Compos. Sci. 2022, 6(6), 156; https://doi.org/10.3390/jcs6060156 - 25 May 2022

Cited by 3 | Viewed by 2554

Abstract

A novel negative thermal expansion (NTE) material composed of Sm_0.85Sr_0.15MnO_3-δ was synthesized using the solid-state method. By allowing Sr²⁺ to partially replace Sm³⁺ in SmMnO₃, the ceramic material Sm_0.85Sr_0.15MnO_3-δ exhibits NTE properties between 360K and 873K, and its average negative thermal expansion coefficient was −10.08 × 10⁻⁶/K. The structure of Sm_0.85Sr_0.15MnO_3-δ is orthogonal, the space group is pbnm, the morphology is regular, and the grain size is uniform. The results of X-ray diffraction and XPS (X-ray photoelectron spectroscopy) suggest that the NTE phenomenon is related to the electron transfer of Mn ions. With the increase in temperature, Mn⁴⁺ is rapidly transformed into Mn³⁺, accompanied by Mn⁴⁺O₆ octahedron distortion and oxygen defects. It was found that the sample volume continually decreased at the same time. Full article

(This article belongs to the Special Issue Metal Composites)

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14 pages, 3978 KiB

Open AccessArticle

Improvement of La_0.8Sr_0.2MnO_3−δ Cathode Material for Solid Oxide Fuel Cells by Addition of YFe_0.5Co_0.5O₃

by Michał Mosiałek, Małgorzata Zimowska, Dzmitry Kharytonau, Anna Komenda, Miłosz Górski and Marcel Krzan

Materials 2022, 15(2), 642; https://doi.org/10.3390/ma15020642 - 15 Jan 2022

Cited by 8 | Viewed by 3016

Abstract

The high efficiency of solid oxide fuel cells with La_0.8Sr_0.2MnO_3−δ (LSM) cathodes working in the range of 800–1000 °C, rapidly decreases below 800 °C. The goal of this study is to improve the properties of LSM cathodes working in the range of 500–800 °C by the addition of YFe_0.5Co_0.5O₃ (YFC). Monophasic YFC is synthesized and sintered at 950 °C. Composite cathodes are prepared on Ce_0.8Sm_0.2O_1.9 electrolyte disks using pastes containing YFC and LSM powders mixed in 0:1, 1:19, and 1:1 weight ratios denoted LSM, LSM1, and LSM1, respectively. X-ray diffraction patterns of tested composites reveal the presence of pure perovskite phases in samples sintered at 950 °C and the presence of Sr₄Fe₄O₁₁, YMnO₃, and La_0.775Sr_0.225MnO_3.047 phases in samples sintered at 1100 °C. Electrochemical impedance spectroscopy reveals that polarization resistance increases from LSM1, by LSM, to LSM2. Differences in polarization resistance increase with decreasing operating temperatures because activation energy rises in the same order and equals to 1.33, 1.34, and 1.58 eV for LSM1, LSM, and LSM2, respectively. The lower polarization resistance of LSM1 electrodes is caused by the lower resistance associated with the charge transfer process. Full article

(This article belongs to the Special Issue Solid Oxide Fuel Cells (SOFCs): From Design to Applications)

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16 pages, 9818 KiB

Open AccessArticle

Formation of Solid Solutions and Physicochemical Properties of the High-Entropy Ln_1−xSr_x(Co,Cr,Fe,Mn,Ni)O_3−δ (Ln = La, Pr, Nd, Sm or Gd) Perovskites

by Juliusz Dąbrowa, Klaudia Zielińska, Anna Stępień, Marek Zajusz, Margarita Nowakowska, Maciej Moździerz, Katarzyna Berent, Maria Szymczak and Konrad Świerczek

Materials 2021, 14(18), 5264; https://doi.org/10.3390/ma14185264 - 13 Sep 2021

Cited by 15 | Viewed by 3632

Abstract

Phase composition, crystal structure, and selected physicochemical properties of the high entropy Ln(Co,Cr,Fe,Mn,Ni)O_3−δ (Ln = La, Pr, Gd, Nd, Sm) perovskites, as well as the possibility of Sr doping in Ln_1−xSr_x(Co,Cr,Fe,Mn,Ni)O_3−δ series, are reported is this work. With the use of the Pechini method, all undoped compositions are successfully synthesized. The samples exhibit distorted, orthorhombic or rhombohedral crystal structure, and a linear correlation is observed between the ionic radius of Ln and the value of the quasi-cubic perovskite lattice constant. The oxides show moderate thermal expansion, with a lack of visible contribution from the chemical expansion effect. Temperature-dependent values of the total electrical conductivity are reported, and the observed behavior appears distinctive from that of non-high entropy transition metal-based perovskites, beyond the expectations based on the rule-of-mixtures. In terms of formation of solid solutions in Sr-doped Ln_1−xSr_x(Co,Cr,Fe,Mn,Ni)O_3−δ materials, the results indicate a strong influence of the Ln radius, and while for La-based series the Sr solubility limit is at the level of x_max = 0.3, for the smaller Pr it is equal to just 0.1. In the case of Nd-, Sm- and Gd-based materials, even for the x_Sr = 0.1, the formation of secondary phases is observed on the SEM + EDS images. Full article

(This article belongs to the Section Advanced and Functional Ceramics and Glasses)

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9 pages, 4535 KiB

Open AccessArticle

Semiconductor-Ionic Nanocomposite La_0.1Sr_0.9MnO_3−δ-Ce_0.8Sm_0.2O_2−δ Functional Layer for High Performance Low Temperature SOFC

by Zhaoqing Wang, Xunying Wang, Zhaoyun Xu, Hui Deng, Wenjing Dong, Baoyuan Wang, Chu Feng, Xueqi Liu and Hao Wang

Materials 2018, 11(9), 1549; https://doi.org/10.3390/ma11091549 - 28 Aug 2018

Cited by 12 | Viewed by 3682

Abstract

A novel composite was synthesized by mixing La_0.1Sr_0.9MnO_3−δ (LSM) with Ce_0.8Sm_0.2O_2−δ (SDC) for the functional layer of low temperature solid oxide fuel cell (LT-SOFC). Though LSM, a highly electronic conducting semiconductor, was used in the functional layer, the fuel cell device could reach OCVs higher than 1.0 V without short-circuit problem. A typical diode or rectification effect was observed when an external electric force was supplied on the device under fuel cell atmosphere, which indicated the existence of a junction that prevented the device from short-circuit problem. The optimum ratio of LSM:SDC = 1:2 was found for the LT-SOFC to reach the highest power density of 742 mW·cm⁻² under 550 °C The electrochemical impedance spectroscopy data highlighted that introducing LSM into SDC electrolyte layer not only decreased charge-transfer resistances from 0.66 Ω·cm² for SDC to 0.47–0.49 Ω·cm² for LSM-SDC composite, but also decreased the activation energy of ionic conduction from 0.55 to 0.20 eV. Full article

(This article belongs to the Section Energy Materials)

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