Author
Jesús Prado-Gonjal
Other affiliations: University of Reading, Centre national de la recherche scientifique, Complutense University of Madrid
Bio: Jesús Prado-Gonjal is an academic researcher from Spanish National Research Council. The author has contributed to research in topics: Perovskite (structure) & Thermoelectric effect. The author has an hindex of 14, co-authored 46 publications receiving 897 citations. Previous affiliations of Jesús Prado-Gonjal include University of Reading & Centre national de la recherche scientifique.
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TL;DR: In this paper, the formation of the internal barrier layer capacitor (IBLC) structure in CaCu3Ti4O12 (CCTO) ceramics was found to be facilitated by the ceramic heat treatment.
Abstract: The formation of the internal barrier layer capacitor (IBLC) structure in CaCu3Ti4O12 (CCTO) ceramics was found to be facilitated by the ceramic heat treatment. Electrically insulating grain boundary (GB) and semi-conducting grain interior areas were characterized by impedance spectroscopy to monitor the evolution of the IBLC structure with increasing sintering temperature TS (975–1100 °C). The intrinsic bulk and GB permittivity increased by factors of ≈2 and 300, respectively and the bulk resistivity decreased by a factor of ≈103. These trends were accompanied by increased Cu segregation from the CCTO ceramics as detected by scanning electron microscopy and quantitative energy dispersive analysis of X-rays. The chemical changes due to possible Cu-loss in CCTO ceramics with increasing TS are small and beyond the detection limits of X-ray absorption spectroscopy near Cu and Ti K-edges and Raman Spectroscopy.
263 citations
TL;DR: X-ray diffraction, Raman spectroscopy, and temperature-dependent dielectric permittivity data do not indicate potential noncentrosymmetry in the crystal or concomitant ferroelectricity, and strong correlations between the magnetic and dielectrics properties were not encountered, and microwave-synthesized (RE)CrO(3) may not be classified as magnetoelectric or multiferroic materials.
Abstract: The full rare-earth (RE) chromites series (RE)CrO3 with an orthorhombic distorted (Pnma) perovskite structure and the isostructural compound YCrO3 can be synthesized through a simple microwave-assisted technique, yielding high-quality materials. Magnetization measurements evidence that the Neel temperature for antiferromagnetic Cr3+–Cr3+ ordering strongly depends on the RE3+ ionic radius (IOR), and a rich variety of different magnetic spin interactions exists. Dielectric spectroscopy on sintered pellets indicates electronic inhomogeneity in all samples as manifested by the presence of at least two dielectric relaxation processes associated with grain boundary and grain interior bulk contributions. X-ray diffraction, Raman spectroscopy, and temperature-dependent dielectric permittivity data do not indicate potential noncentrosymmetry in the crystal or concomitant ferroelectricity. Strong correlations between the magnetic and dielectric properties were not encountered, and microwave-synthesized (RE)CrO3 may...
96 citations
TL;DR: In this article, three different methods for preparing BiFeO3 polycrystals are compared: hydrothermal synthesis, microwave heating in the solid state and the combination of both, that is a Hydrothermal method using microwave heating.
94 citations
TL;DR: In this paper, the authors used the Brunauer-Emmett-Teller method to confirm large powder surface area and X-ray diffraction was used to confirm high density and low surface porosity of the sintered ceramics.
60 citations
TL;DR: A series of lanthanum perovskites, LaMO 3 (M = Al, Cr, Mn, Fe, Co), having important technological applications, have been successfully prepared by a very fast, inexpensive, reproducible, environment-friendly method: the microwave irradiation of the corresponding mixtures of nitrates as mentioned in this paper.
55 citations
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TL;DR: The electronic structure of the perovskite LaCoO3 for different spin states of Co ions was calculated in the local-density approximation LDA+U approach and shows that Co 3d states of t(2g) symmetry form narrow bands which could easily localize, while e(g) orbitals, due to their strong hybridization with the oxygen 2p states, form a broad sigma* band.
Abstract: The electronic structure of the perovskite LaCoO$_3$ for different spin states of Co ions was calculated in the LDA+U approach. The ground state was found to be a nonmagnetic insulator with Co ions in a low-spin state. Somewhat higher in energy we found two intermediate-spin states followed by a high-spin state at significantly higher energy. The calculation results show that Co 3$d$ states of $t_{2g}$ symmetry form narrow bands which could easily localize whilst $e_g$ orbitals, due to their strong hybridization with the oxygen 2$p$ states, form a broad $\sigma^*$ band. With the increase of temperature which is simulated by the corresponding increase of the lattice parameter, the transition from the low- to intermediate-spin states occurs. This intermediate-spin (occupation $t_{2g}^5e_g^1$) can develop an orbital ordering which can account for the nonmetallic nature of LaCoO$_3$ at 90 K$<$T$<$500 K. Possible explanations of the magnetic behavior and gradual insulating-metal transition are suggested.
531 citations
TL;DR: In-depth analysis of TEGs is presented, starting by an extensive description of their working principle, types, used materials, figure of merit, improvement techniques including different thermoelectric materials arrangement (conventional, segmented and cascaded), and used technologies and substrates types (silicon, ceramics and polymers).
352 citations
TL;DR: Chemistry: From Fundamentals to Manufacturing Helen J. Kitchen, Simon R. Vallance, Nuria Tapia-Ruiz,† Lucia Carassiti,† Andrew Harrison, A. Gavin Whittaker, Timothy D. Kingman,‡ and Duncan H. Gregory are authors of this book.
Abstract: Chemistry: From Fundamentals to Manufacturing Helen J. Kitchen,† Simon R. Vallance,†,‡ Jennifer L. Kennedy,†,§ Nuria Tapia-Ruiz,† Lucia Carassiti,† Andrew Harrison, A. Gavin Whittaker, Timothy D. Drysdale, Samuel W. Kingman,‡ and Duncan H. Gregory*,† †WestCHEM, School of Chemistry, University of Glasgow, Joseph Black Building, Glasgow G12 8QQ, United Kingdom ‡Department of Chemical and Environmental Engineering, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom School of Engineering, University of Glasgow, James Watt South Building, Glasgow G12 8QQ, United Kingdom Institut Laue-Langevin, 6 rue Jules Horowitz, BP 156, F 38042, Grenoble, Cedex 9, France Tan Delta Microwaves Limited, 7 Nettlingflat, Heriot EH38 5YF, United Kingdom
342 citations