Pub Date : 2023-07-01DOI: 10.1088/2515-7655/ace07c
Z. Haman, M. Kibbou, N. Khossossi, Soukaina Bahti, P. Dey, I. Essaoudi, R. Ahuja, A. Ainane
Through a density functional theory-driven survey, a comprehensive investigation of two-dimensional (2D) Janus aluminum-based monochalcogenides (Al2XY with X/Y = S, Se, and Te) has been performed within this study. To begin with, it is established that the examined phase, in which the Al-atoms are located at the two inner planes while the (S, Se, and Te)-atoms occupy the two outer planes in the unit cell, are energetically, mechanically, dynamically, and thermally stable. To address the electronic and optical properties, the hybrid function HSE06 has been employed. It is at first revealed that all three monolayers display a semiconducting nature with an indirect band gap ranging from 1.82 to 2.79 eV with a refractive index greater than 1.5, which implies that they would be transparent materials. Furthermore, the monolayers feature strong absorption spectra of around 105 cm−1 within the visible and ultraviolet regions, suggesting their potential use in optoelectronic devices. Concerning the photocatalytic performance, the conduction band-edge positions straddle the hydrogen evolution reaction redox level. Also, it is observed that the computed Gibbs free energy is around 1.15 eV, which is lower and comparable to some recently reported 2D-based Janus monolayers. Additionally, the thermoelectric properties are further investigated and found to offer a large thermal power as well as a high figure of merit (ZT) around 1.03. The aforementioned results strongly suggest that the 2D Janus Al-based monochalcogenide exhibits suitable characteristics as a potential material for high-performance optoelectronic and thermoelectric applications.
{"title":"Photocatalytic and thermoelectric performance of asymmetrical two-dimensional Janus aluminum chalcogenides","authors":"Z. Haman, M. Kibbou, N. Khossossi, Soukaina Bahti, P. Dey, I. Essaoudi, R. Ahuja, A. Ainane","doi":"10.1088/2515-7655/ace07c","DOIUrl":"https://doi.org/10.1088/2515-7655/ace07c","url":null,"abstract":"Through a density functional theory-driven survey, a comprehensive investigation of two-dimensional (2D) Janus aluminum-based monochalcogenides (Al2XY with X/Y = S, Se, and Te) has been performed within this study. To begin with, it is established that the examined phase, in which the Al-atoms are located at the two inner planes while the (S, Se, and Te)-atoms occupy the two outer planes in the unit cell, are energetically, mechanically, dynamically, and thermally stable. To address the electronic and optical properties, the hybrid function HSE06 has been employed. It is at first revealed that all three monolayers display a semiconducting nature with an indirect band gap ranging from 1.82 to 2.79 eV with a refractive index greater than 1.5, which implies that they would be transparent materials. Furthermore, the monolayers feature strong absorption spectra of around 105 cm−1 within the visible and ultraviolet regions, suggesting their potential use in optoelectronic devices. Concerning the photocatalytic performance, the conduction band-edge positions straddle the hydrogen evolution reaction redox level. Also, it is observed that the computed Gibbs free energy is around 1.15 eV, which is lower and comparable to some recently reported 2D-based Janus monolayers. Additionally, the thermoelectric properties are further investigated and found to offer a large thermal power as well as a high figure of merit (ZT) around 1.03. The aforementioned results strongly suggest that the 2D Janus Al-based monochalcogenide exhibits suitable characteristics as a potential material for high-performance optoelectronic and thermoelectric applications.","PeriodicalId":48500,"journal":{"name":"Journal of Physics-Energy","volume":" ","pages":""},"PeriodicalIF":6.9,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41523231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-01DOI: 10.1088/2515-7655/ace12c
Bowei Li, Wei Zhang
The power conversion efficiencies of perovskite solar cells (PSCs) have approached 26% for single-junction and 33% for multi-junction cells. Thus, various scalable depositions are studied to improve the manufacturability of PSCs for market entry. Of all types, slot-die coating is a promising technique thanks to its excellent compatibility with versatile systems. However, the complicated ink chemistry and film formation are major obstacles to scaling up devices. In this review, we systematically discuss ink engineering in the fabrication of slot-die-coated PSCs and perovskite minimodules, covering all functional layers that are processed using solution-based means. We then summarize a range of strategies to improve ink compatibility with slot-die coating, focusing on how to optimize the ink formulation to achieve high-quality films. Finally, we highlight the existing challenges and potential avenues for further development of slot-die-coated devices.
{"title":"Ink engineering for slot-die coated perovskite solar cells and minimodules","authors":"Bowei Li, Wei Zhang","doi":"10.1088/2515-7655/ace12c","DOIUrl":"https://doi.org/10.1088/2515-7655/ace12c","url":null,"abstract":"The power conversion efficiencies of perovskite solar cells (PSCs) have approached 26% for single-junction and 33% for multi-junction cells. Thus, various scalable depositions are studied to improve the manufacturability of PSCs for market entry. Of all types, slot-die coating is a promising technique thanks to its excellent compatibility with versatile systems. However, the complicated ink chemistry and film formation are major obstacles to scaling up devices. In this review, we systematically discuss ink engineering in the fabrication of slot-die-coated PSCs and perovskite minimodules, covering all functional layers that are processed using solution-based means. We then summarize a range of strategies to improve ink compatibility with slot-die coating, focusing on how to optimize the ink formulation to achieve high-quality films. Finally, we highlight the existing challenges and potential avenues for further development of slot-die-coated devices.","PeriodicalId":48500,"journal":{"name":"Journal of Physics-Energy","volume":" ","pages":""},"PeriodicalIF":6.9,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43562219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-28DOI: 10.1088/2515-7655/acdd9c
J. Cen, Bonan Zhu, D. Scanlon
The Li-Ni-O phase diagram contains several electrochemically active ternary phases. Many compositions and structures in this phase space can easily be altered by (electro-)chemical processes, yielding many more (meta-)stable structures with interesting properties. In this study, we use ab initio random structure searching (AIRSS) to accelerate materials discovery of the Li-Ni-O phase space. We demonstrate that AIRSS can efficiently explore structures (e.g. LiNiO2) displaying dynamic Jahn-Teller effects. A thermodynamically stable Li2Ni2O3 phase which reduces the thermodynamic stability window of LiNiO2 was discovered. AIRSS also encountered many dynamically stable structures close to the convex hull. Therefore, we confirm the presence of metastable Li-Ni-O phases by revealing their structures and properties. This work will allow Li-Ni-O phases to be more easily identified in future experiments and help to combat the challenges in synthesizing Li-Ni-O phases.
{"title":"Exploring battery cathode materials in the Li-Ni-O phase diagrams using structure prediction","authors":"J. Cen, Bonan Zhu, D. Scanlon","doi":"10.1088/2515-7655/acdd9c","DOIUrl":"https://doi.org/10.1088/2515-7655/acdd9c","url":null,"abstract":"The Li-Ni-O phase diagram contains several electrochemically active ternary phases. Many compositions and structures in this phase space can easily be altered by (electro-)chemical processes, yielding many more (meta-)stable structures with interesting properties. In this study, we use ab initio random structure searching (AIRSS) to accelerate materials discovery of the Li-Ni-O phase space. We demonstrate that AIRSS can efficiently explore structures (e.g. LiNiO2) displaying dynamic Jahn-Teller effects. A thermodynamically stable Li2Ni2O3 phase which reduces the thermodynamic stability window of LiNiO2 was discovered. AIRSS also encountered many dynamically stable structures close to the convex hull. Therefore, we confirm the presence of metastable Li-Ni-O phases by revealing their structures and properties. This work will allow Li-Ni-O phases to be more easily identified in future experiments and help to combat the challenges in synthesizing Li-Ni-O phases.","PeriodicalId":48500,"journal":{"name":"Journal of Physics-Energy","volume":" ","pages":""},"PeriodicalIF":6.9,"publicationDate":"2023-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43155632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-14DOI: 10.1088/2515-7655/acdbe9
Leo Brody, Mahe Rukh, R. Cai, Azin Saberi Bosari, R. Schomäcker, Fanxing Li
Sorption-enhanced steam reforming (SESR) of toluene (SESRT) using catalytic CO2 sorbents is a promising route to convert the aromatic tar byproducts formed in lignocellulosic biomass gasification into hydrogen (H2) or H2-rich syngas. Commonly used sorbents such as CaO are effective in capturing CO2 initially but are prone to lose their sorption capacity over repeated cycles due to sintering at high temperatures. Herein, we present a demonstration of SESRT using A- and B-site doped Sr1−x A’ x Fe1−y B’ y O3−δ (A’ = Ba, Ca; B’ = Co) perovskites in a chemical looping scheme. We found that surface impregnation of 5–10 mol% Ni on the perovskite was effective in improving toluene conversion. However, upon cycling, the impregnated Ni tends to migrate into the bulk and lose activity. This prompted the adoption of a dual bed configuration using a pre-bed of NiO/γ–Al2O3 catalyst upstream of the sorbent. A comparison is made between isothermal operation and a more traditional temperature-swing mode, where for the latter, an average sorption capacity of ∼38% was witnessed over five SESR cycles with H2-rich product syngas evidenced by a ratio of H2: CO x > 4.0. XRD analysis of fresh and cycled samples of Sr0.25Ba0.75Fe0.375Co0.625O3-δ reveal that this material is an effective phase transition sorbent—capable of cyclically capturing and releasing CO2 without irreversible phase changes occurring.
{"title":"Sorption-enhanced steam reforming of toluene using multifunctional perovskite phase transition sorbents in a chemical looping scheme","authors":"Leo Brody, Mahe Rukh, R. Cai, Azin Saberi Bosari, R. Schomäcker, Fanxing Li","doi":"10.1088/2515-7655/acdbe9","DOIUrl":"https://doi.org/10.1088/2515-7655/acdbe9","url":null,"abstract":"Sorption-enhanced steam reforming (SESR) of toluene (SESRT) using catalytic CO2 sorbents is a promising route to convert the aromatic tar byproducts formed in lignocellulosic biomass gasification into hydrogen (H2) or H2-rich syngas. Commonly used sorbents such as CaO are effective in capturing CO2 initially but are prone to lose their sorption capacity over repeated cycles due to sintering at high temperatures. Herein, we present a demonstration of SESRT using A- and B-site doped Sr1−x A’ x Fe1−y B’ y O3−δ (A’ = Ba, Ca; B’ = Co) perovskites in a chemical looping scheme. We found that surface impregnation of 5–10 mol% Ni on the perovskite was effective in improving toluene conversion. However, upon cycling, the impregnated Ni tends to migrate into the bulk and lose activity. This prompted the adoption of a dual bed configuration using a pre-bed of NiO/γ–Al2O3 catalyst upstream of the sorbent. A comparison is made between isothermal operation and a more traditional temperature-swing mode, where for the latter, an average sorption capacity of ∼38% was witnessed over five SESR cycles with H2-rich product syngas evidenced by a ratio of H2: CO x > 4.0. XRD analysis of fresh and cycled samples of Sr0.25Ba0.75Fe0.375Co0.625O3-δ reveal that this material is an effective phase transition sorbent—capable of cyclically capturing and releasing CO2 without irreversible phase changes occurring.","PeriodicalId":48500,"journal":{"name":"Journal of Physics-Energy","volume":" ","pages":""},"PeriodicalIF":6.9,"publicationDate":"2023-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44496754","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-14DOI: 10.1088/2515-7655/acd8ef
Yong Li, Xinyue Ye, Lingwei Li, Enke Liu
The emergent evolution of first-order phase transitions from magneto-structural to magneto-elastic and magnetocaloric effect (MCE) have been investigated by X-ray diffraction, differential scanning calorimetry and magnetization measurements. Applying the isostructural alloying principle, the martensitic transition temperature (T M) increases effectively and the Curie temperatures of the two phases increase slightly by substituting the Si content (x). With an appropriate amount of Fe and Si content, an emergent first-order antiferromagnetic–ferromagnetic magnetoelastic transition with thermal hysteresis in the martensitic state occurs for MnCo0.7Fe0.3Ge1–x Si x (x = 0.15–0.40) alloys, which results from the decrease in the nearest-neighbor Mn–Mn distance. Moreover, the values of magnetic entropy change (ΔS M), refrigeration capacity (RC) and temperature-averaged entropy change (TEC, 10 K) with ΔH = 50 kOe reach −12.2 J kg−1 K−1, 112.8 J kg−1 and 11.4 J kg−1 K−1 for MnCo0.7Fe0.3Ge0.8Si0.2 undergoing the ferromagnetic magneto-structural transition in the Curie temperature window. The results facilitate the magnetocaloric/magnetoelastic performance and tunability of multiple phase states in a wider temperature range.
{"title":"Emergent evolution of first-order phase transitions from magneto-structural to magneto-elastic in MnCo1−y Fe y Ge1−x Si x alloys","authors":"Yong Li, Xinyue Ye, Lingwei Li, Enke Liu","doi":"10.1088/2515-7655/acd8ef","DOIUrl":"https://doi.org/10.1088/2515-7655/acd8ef","url":null,"abstract":"The emergent evolution of first-order phase transitions from magneto-structural to magneto-elastic and magnetocaloric effect (MCE) have been investigated by X-ray diffraction, differential scanning calorimetry and magnetization measurements. Applying the isostructural alloying principle, the martensitic transition temperature (T M) increases effectively and the Curie temperatures of the two phases increase slightly by substituting the Si content (x). With an appropriate amount of Fe and Si content, an emergent first-order antiferromagnetic–ferromagnetic magnetoelastic transition with thermal hysteresis in the martensitic state occurs for MnCo0.7Fe0.3Ge1–x Si x (x = 0.15–0.40) alloys, which results from the decrease in the nearest-neighbor Mn–Mn distance. Moreover, the values of magnetic entropy change (ΔS M), refrigeration capacity (RC) and temperature-averaged entropy change (TEC, 10 K) with ΔH = 50 kOe reach −12.2 J kg−1 K−1, 112.8 J kg−1 and 11.4 J kg−1 K−1 for MnCo0.7Fe0.3Ge0.8Si0.2 undergoing the ferromagnetic magneto-structural transition in the Curie temperature window. The results facilitate the magnetocaloric/magnetoelastic performance and tunability of multiple phase states in a wider temperature range.","PeriodicalId":48500,"journal":{"name":"Journal of Physics-Energy","volume":" ","pages":""},"PeriodicalIF":6.9,"publicationDate":"2023-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45806358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-07DOI: 10.1088/2515-7655/acdc53
S. Hirose, T. Usui, T. Hiroto, B. Nair, X. Moya, N. Mathur
Bulk PbMg0.5W0.5O3 (PMW) is an antiferroelectric in which an electric field of 12 V μm−1 is sufficient to initiate a nominally reversible transition to a dipole-aligned (ferroelectric) phase if operating just below the Néel temperature T N, near room temperature (Li et al 2021 Adv. Funct. Mater. 31 2101176). Here we describe multilayer capacitors (MLCs) of PMW that permit 27 V µm−1 to be applied without breakdown. Below T N, nominally reversible driving of the partial (full) antiferroelectric–ferroelectric (AF–FE) transition over a wide (narrow) range of temperatures yields large inverse electrocaloric (EC) effects that peak at ΔTj ∼ –2.6 K when applying 25 V μm−1 at 293 K (ΔTj denotes directly measured temperature jumps). Above T N, nominally reversible driving of the partial (full) paraelectric–ferroelectric (PE–FE) transition yields large conventional EC effects that peak at ΔTj ∼ +5.2 K when applying 25 V μm−1 at 302 K. This good EC performance near room temperature implies that MLCs of PMW could be exploited in prototype EC coolers.
{"title":"Large conventional and inverse electrocaloric effects in PbMg0.5W0.5O3 multilayer capacitors above and below the Néel temperature","authors":"S. Hirose, T. Usui, T. Hiroto, B. Nair, X. Moya, N. Mathur","doi":"10.1088/2515-7655/acdc53","DOIUrl":"https://doi.org/10.1088/2515-7655/acdc53","url":null,"abstract":"Bulk PbMg0.5W0.5O3 (PMW) is an antiferroelectric in which an electric field of 12 V μm−1 is sufficient to initiate a nominally reversible transition to a dipole-aligned (ferroelectric) phase if operating just below the Néel temperature T N, near room temperature (Li et al 2021 Adv. Funct. Mater. 31 2101176). Here we describe multilayer capacitors (MLCs) of PMW that permit 27 V µm−1 to be applied without breakdown. Below T N, nominally reversible driving of the partial (full) antiferroelectric–ferroelectric (AF–FE) transition over a wide (narrow) range of temperatures yields large inverse electrocaloric (EC) effects that peak at ΔTj ∼ –2.6 K when applying 25 V μm−1 at 293 K (ΔTj denotes directly measured temperature jumps). Above T N, nominally reversible driving of the partial (full) paraelectric–ferroelectric (PE–FE) transition yields large conventional EC effects that peak at ΔTj ∼ +5.2 K when applying 25 V μm−1 at 302 K. This good EC performance near room temperature implies that MLCs of PMW could be exploited in prototype EC coolers.","PeriodicalId":48500,"journal":{"name":"Journal of Physics-Energy","volume":" ","pages":""},"PeriodicalIF":6.9,"publicationDate":"2023-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43311412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-26DOI: 10.1088/2515-7655/acd95b
E. Ghorbani, M. Schiller, Hans H. Falk, Leonard A. Wägele, S. Eckner, F. d’Acapito, R. Scheer, K. Albe, C. Schnohr
Vanadium doped indium sulphide, In2S3:V, is studied as a potential absorber material for intermediate band (IB) solar cells. Based on electronic considerations, it is usually assumed that V occupies octahedrally coordinated In sites, although geometrical considerations would favour tetrahedral In sites. In this study, we therefore combined experimental x-ray diffraction and x-ray absorption spectroscopy with ab initio theoretical calculations of both α and β phase to elucidate the incorporation of V in In2S3:V thin films grown with different V content and different growth temperatures. Comparing shape and position of the measured and calculated x-ray absorption edge of V, comparing experimentally determined and calculated V–S bond lengths, and evaluating the calculated heat of solution of V on different lattice sites all indicate that V is incorporated on octahedral rather than tetrahedral sites in the In2S3 matrix. For this material system, the electronic benefit of octahedral coordination thus outweighs the mechanical stress of the associated lattice relaxation. Finally, we studied the electronic structure of V-substituted α - In2S3 using hybrid density functional calculations and find that for a concentration of 1.9 at %, V on octahedrally coordinated In sites forms an empty IB isolated from valence band and conduction band (CB). By increasing the V content to 3.8 at %, however, the gap between IB and CB closes, which results in a reduction of the band gap. This differs from the electronic structure calculated for β - In2S3 :V and clearly demonstrates that both crystal structure and V incorporation site affect the resulting electronic material properties.
{"title":"Elucidating the local structure of V substitutes in In2S3 as potential intermediate band material by x-ray absorption spectroscopy and first principles calculations","authors":"E. Ghorbani, M. Schiller, Hans H. Falk, Leonard A. Wägele, S. Eckner, F. d’Acapito, R. Scheer, K. Albe, C. Schnohr","doi":"10.1088/2515-7655/acd95b","DOIUrl":"https://doi.org/10.1088/2515-7655/acd95b","url":null,"abstract":"Vanadium doped indium sulphide, In2S3:V, is studied as a potential absorber material for intermediate band (IB) solar cells. Based on electronic considerations, it is usually assumed that V occupies octahedrally coordinated In sites, although geometrical considerations would favour tetrahedral In sites. In this study, we therefore combined experimental x-ray diffraction and x-ray absorption spectroscopy with ab initio theoretical calculations of both α and β phase to elucidate the incorporation of V in In2S3:V thin films grown with different V content and different growth temperatures. Comparing shape and position of the measured and calculated x-ray absorption edge of V, comparing experimentally determined and calculated V–S bond lengths, and evaluating the calculated heat of solution of V on different lattice sites all indicate that V is incorporated on octahedral rather than tetrahedral sites in the In2S3 matrix. For this material system, the electronic benefit of octahedral coordination thus outweighs the mechanical stress of the associated lattice relaxation. Finally, we studied the electronic structure of V-substituted α - In2S3 using hybrid density functional calculations and find that for a concentration of 1.9 at %, V on octahedrally coordinated In sites forms an empty IB isolated from valence band and conduction band (CB). By increasing the V content to 3.8 at %, however, the gap between IB and CB closes, which results in a reduction of the band gap. This differs from the electronic structure calculated for β - In2S3 :V and clearly demonstrates that both crystal structure and V incorporation site affect the resulting electronic material properties.","PeriodicalId":48500,"journal":{"name":"Journal of Physics-Energy","volume":" ","pages":""},"PeriodicalIF":6.9,"publicationDate":"2023-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48698166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-24DOI: 10.1088/2515-7655/acd86f
A. Grünebohm, Sheng-Han Teng, M. Marathe
The electrocaloric (EC) effect is the adiabatic temperature change of a material in a varying external electric field, which is promising for novel cooling devices. While the fundamental understanding of the caloric response of defect-free materials is well developed, there are important gaps in the knowledge about the reversibility and time-stability of the response. In particular, it is not settled how the time-dependent elements of microstructure that are always present in real materials act on the field-induced temperature changes. Ab initio based molecular dynamics simulations allow us to isolate and understand the effects arising from domain walls (DWs) and defect dipoles and to study their interplay. We show that DWs in cycling fields do not improve the response in either the ferroelectric (FE) phase or at the FE phase transition, but may result in irreversible heat losses. The presence of defect dipoles may be beneficial for the EC response for proper field protocols, and interestingly this benefit is not too sensitive to the defect configuration.
{"title":"Influence of domain walls and defects on the electrocaloric effect","authors":"A. Grünebohm, Sheng-Han Teng, M. Marathe","doi":"10.1088/2515-7655/acd86f","DOIUrl":"https://doi.org/10.1088/2515-7655/acd86f","url":null,"abstract":"The electrocaloric (EC) effect is the adiabatic temperature change of a material in a varying external electric field, which is promising for novel cooling devices. While the fundamental understanding of the caloric response of defect-free materials is well developed, there are important gaps in the knowledge about the reversibility and time-stability of the response. In particular, it is not settled how the time-dependent elements of microstructure that are always present in real materials act on the field-induced temperature changes. Ab initio based molecular dynamics simulations allow us to isolate and understand the effects arising from domain walls (DWs) and defect dipoles and to study their interplay. We show that DWs in cycling fields do not improve the response in either the ferroelectric (FE) phase or at the FE phase transition, but may result in irreversible heat losses. The presence of defect dipoles may be beneficial for the EC response for proper field protocols, and interestingly this benefit is not too sensitive to the defect configuration.","PeriodicalId":48500,"journal":{"name":"Journal of Physics-Energy","volume":" ","pages":""},"PeriodicalIF":6.9,"publicationDate":"2023-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45393715","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-22DOI: 10.1088/2515-7655/acd7a2
G. Ouyang, Chaochao Pan, Benjamin Hilliard, Agata Czernuszewicz, J. Slaughter, Jun Cui
Cu-Al-Mn alloys display martensitic transformation over a wide range of temperatures. In addition to low cost, this alloy is known for its low transformation stress with reasonable latent heat favoring elastocaloric applications. However, the ductility of Cu-Al-Mn can be limited owing to ordering and intergranular fracture. Through rapid solidification by melt spinning, we show that Cu-Al-Mn ribbon can be made highly ductile (greater than 8% tensile strain in the as-spun state and 10% tensile strain after heat treatment). The ductility of the melt-spun ribbon is related to the suppression of L21 ordering that is characterized through magnetic property measurement. Heat treatment of the ribbon promotes bamboo grain formation, and the latent heat is increased to 6.4 J g−1. Under tensile conditions, we show that the ribbon exhibited about 4 °C temperature change (4.4 °C on heating and 4.2 °C on cooling from 6.3% strain).
{"title":"Rapid solidified ductile Cu-Al-Mn ribbon and its elastocaloric potential","authors":"G. Ouyang, Chaochao Pan, Benjamin Hilliard, Agata Czernuszewicz, J. Slaughter, Jun Cui","doi":"10.1088/2515-7655/acd7a2","DOIUrl":"https://doi.org/10.1088/2515-7655/acd7a2","url":null,"abstract":"Cu-Al-Mn alloys display martensitic transformation over a wide range of temperatures. In addition to low cost, this alloy is known for its low transformation stress with reasonable latent heat favoring elastocaloric applications. However, the ductility of Cu-Al-Mn can be limited owing to ordering and intergranular fracture. Through rapid solidification by melt spinning, we show that Cu-Al-Mn ribbon can be made highly ductile (greater than 8% tensile strain in the as-spun state and 10% tensile strain after heat treatment). The ductility of the melt-spun ribbon is related to the suppression of L21 ordering that is characterized through magnetic property measurement. Heat treatment of the ribbon promotes bamboo grain formation, and the latent heat is increased to 6.4 J g−1. Under tensile conditions, we show that the ribbon exhibited about 4 °C temperature change (4.4 °C on heating and 4.2 °C on cooling from 6.3% strain).","PeriodicalId":48500,"journal":{"name":"Journal of Physics-Energy","volume":" ","pages":""},"PeriodicalIF":6.9,"publicationDate":"2023-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42397706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-17DOI: 10.1088/2515-7655/acd661
Lingmei Ni, E. Davydova, Ramesh K. Singh, Lubov Kolik-Shmuel, Dario R. Dekel, U. Kramm
Nickel-based catalysts reach a high activity for the hydrogen oxidation reaction (HOR) in anion exchange membrane fuel cells. While incorporation of iron significantly decreases the HOR overpotential on NiFe-based catalysts, the reason for the enhanced activity remains only partially understood. For the first time, in situ 57Fe Mössbauer spectroscopy is used to gain insights into the iron-related composition at different potentials. The aim is to evaluate which changes occur on iron at potentials relevant for the HOR on the active Ni sites. It is found that different pre-conditionings at low potentials stabilize the iron at a low oxidation state as compared to the as-prepared catalyst powder. It is likely that the lower average oxidation state enables a higher exchange current density and a more efficient OH adsorption, which make the Volmer step much faster in the HOR. Insights from in situ Mössbauer spectroscopy enlighten the role of iron in the nickel-iron catalyst, paving the way for developing improved Ni-based catalysts for HOR catalysis.
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