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1.
Nonlinearity in regulating the metal to insulator transition of ReNiO3 towards low temperature range
《Ceramics International》2022,48(21):31995-32000
Among the existing material family of the correlated oxides, the rare earth nickelates (ReNiO3) exhibit broadly adjustable metal to insulator transition (MIT) properties that enables correlated electronic applications, such as thermistors, thermochromics, and logical devices. Nevertheless, how to accurately control the critical temperature (TMIT) of ReNiO3 via the co-occupation of the rare-earth elements is yet worthy to be further explored. Herein, we demonstrate the non-linearity in adjusting the TMIT of ReNiO3 towards lower temperatures via introducing Pr co-occupation within ReNiO3 (e.g., PrxNd1-xNiO3 and PrxSm1-xNiO3) as synthesized by KCl molten-salt assisted high oxygen pressure reaction approach. Although the TMIT is effectively reduced via Pr substitution, it does not strictly follow a linear relationship, in particular, when there is large difference in the ionic radius of the co-occupation rare-earth elements. Furthermore, the most significant deviation in TMIT from the expected linear relationship appears at an equal co-occupation ratio of the two different rare-earth elements, while the abruption in the variation of resistivity across TMIT is also reduced. The present work highlights the importance to use adjacent rare-earth elements with co-occupation ratio away from 1:1 for achieving more linear adjustment in designing the metal to insulator transition properties for ReNiO3. 相似文献
2.
Nengbing Long Yanqing Fu Tianxiang Xu Dashuang Ding Shaoqian Zhang Shengzhi Sun Shiliang Kang Tiefeng Xu Shixun Dai Qiuhua Nie Changgui Lin 《Journal of the European Ceramic Society》2021,41(8):4584-4589
The confinement of CsPbX3 (X = Cl, Br, and I) perovskite nanocrystals (NCs) in a stabilized inorganic glass matrix is a new strategy for improving their long-term stability and promoting their applications in the optoelectronic field. Here, in situ nanocrystallization strategy is developed to precipitate CsPbBr3?xIx NCs with arbitrary I/Br ratio among an elaborately designed GeS2–Sb2S3-based chalcogenide glass matrix. Spherical CsPbBr3?xIx NCs are homogeneously distributed in the glass matrix after thermal treatment. The photoluminescence (PL) spectra show that the emission peaks of CsPbBr3?xIx NCs can be tuned from 570 nm to 722 nm with the replacement of Br by I. The fs transient absorption (TA) spectra reveal that there exists some structural defects in the NCs, leading to short PL decay life. This work would shed light on confining CsPbX3 NCs into glassy matrices, facilitating their future applications in photoelectronic fields. 相似文献
3.
4.
Shanquan Chen Sicong Wei Fei Jin Shanming Ke Xierong Zeng Lang Chen Chuanwei Huang 《Ceramics International》2018,44(12):13695-13698
From the perspectives of scientific researches and practical applications, it is desirable to explore high operating temperature ferromagnetic films. The effect of biaxial strain on magnetic properties of (110)-oriented La0.7Sr0.3MnO3 films was studied. High quality La0.7Sr0.3MnO3 films were grown on (110)-oriented perovskite single crystal substrates using pulsed laser deposition, varying substrate-induced misfit strains from ??2.27–0.75%. A remarkable enhancement of Curie temperature has been achieved for (110)-oriented La0.7Sr0.3MnO3 films clamped with small misfit strains (i.e., grown on LAST (110)). The enhanced Curie temperature of (110)-oriented La0.7Sr0.3MnO3 films could be attributed to the misfit strain between the films and the underlying substrates and may have technological implication for applications at high temperature environments. 相似文献
5.
A vacuum-annealed La0.6Ca0.4CoO3−x was consecutively oxygenated in air at temperatures decreasing from 800 to 100 °C, and its electrocatalytic activities for oxygen reduction and evolution were then measured as a function of the oxygenation temperature. The valence of Co cation, changing between +2 and +3, was found susceptible to annealing either in vacuum or air. The catalytic activities initially decrease monotonically as the oxygenation temperature was decreased from 800 to 300 °C, as a result of increasing oxygen content, and then rise abruptly with the oxygen reduction activity reaching a maximum at 200 °C and the oxidation activity at 150 °C. X-ray photoelectron spectroscopy analysis indicated that the enhancements by the low-temperature oxygenation involved increased OH coverage and less charged cations at surface. The results clearly reveal the importance of the post-calcination annealing process for optimizing the performance of La0.6Ca0.4CoO3−x in air electrode applications. 相似文献
6.
R. Wongmaneerung W. Chaisan O. Khamman R. Yimnirun S. Ananta 《Ceramics International》2008,34(4):813-817
The potential of the vibro-milling technique as a simple method to obtain usable quantities of single-phase electroceramic powders with nanosized particles was examined. A detailed study considering the role of both milling time and firing condition on phase formation and particle size of the final product was performed. The calcination temperature for the formation of the desired phase was lower when longer milling times have been applied. More importantly, by employing an appropriate choice of the milling time and calcination condition, high purity electroceramic nanopowders have been successfully prepared with a simple solid-state reaction method. 相似文献
7.
The search for dielectric materials with a high dielectric constant and ′r = ƒ(T) curves with a flat profile fitting the X7R specification is still ongoing. Promising results were obtained by mixing compounds with closely related structures, such as the tetragonal tungsten bronze (TTB) niobate K2Sr4Nb10O30 and the perovskite Pb(Mg1/3Nb2/3)O3 (PMN). The present study, based on three methods of synthesis, explores the origin of the spreading out of the dielectric curves ′r = ƒ(T). For the composition 10x K0.2Sr0.4NbO3 (KSN) + (1 − x)Pb(Mg1/3Nb2/3)O3 (PMN) with x = 0.3–0.6, the three synthesis methods provided similar characteristics and for the highest perovskite ratio (x = 0.3), the ′r = ƒ(T) curve exhibits a flat profile. When lithium is used as a sintering agent, ′r = ƒ(T) curves present a linear dependency with the temperature. These materials are also characterized by a structural and a microstructural inhomogeneity. Two phases TTB and perovskite type, different from KSN and PMN, are present after calcination and sintering, but not evenly distributed. The PbO loss during sintering also contributes to the evolution of the properties of the material. 相似文献
8.
Nanosized lead zirconate titanate (PZT) powder with Zr:Ti ratio in the morphotropic phase boundary region was synthesized by homogeneous precipitation of metal ions. The powder precipitated at 90°C and at pH 6.7 resulted single-phase perovskite lead zirconate titanate powder when calcined at 550°C and above for 4 hours in air. The solution pH and the precipitation temperature strongly affect the composition of the calcined powder. The results obtained by structural characterization of homogeneously precipitated powder were compared with that obtained from the conventional precipitation method using ammonia in terms of crystallization, homogeneity, and microstructure. The homogeneously precipitated powder showed smaller particle size, minimum agglomeration and uniform shape on calcination and annealing. Powdered samples that precipitated by homogeneous precipitation crystallized directly to perovskite PZT, without any intermediate pyrochlore phase formation. In contrast, the NH3 precipitated powder converted to perovskite PZT via metastable pyrochlore and it showed phase segregation upon annealing at higher temperatures. The reaction kinetics has been studied by X-ray diffraction, differential thermal analysis, and differential scanning calorimetry. 相似文献
9.
Francesco Donsì Stefano Cimino Almerinda Di Benedetto Raffaele Pirone Gennaro Russo 《Catalysis Today》2005,105(3-4):551-559
The oxidative dehydrogenation of ethane is carried out in short contact time reactors over Pt and LaMnO3 based catalysts supported on a large number of different ceramic substrates (45, 60 and 80 ppi foam monoliths and 200, 400, 600, 900 and 1200 cpsi honeycomb monoliths). Experimental results, obtained under the same conditions at varying the C2H6/O2 ratio, showed that the highest performance in terms of ethylene selectivity and yield is always attained on LaMnO3 catalysts. Furthermore, the results are significantly influenced by the morphology and cell density of the support, with 45 and 60 ppi foams and 400 and 600 cpsi honeycombs giving the best performance. The experimental results are explained by means of geometrical and fluid dynamic considerations on the support, and by means of a 2D mathematical model, which clearly indicates an optimal intermediate cell density for maximising ethylene selectivity and yield. 相似文献
10.
Jesús Canales-Vázquez Juan Carlos Ruiz-Morales David Marrero-López Juan Peña-Martínez Pedro Núñez Pedro Gómez-Romero 《Journal of power sources》2007
In the work presented herein, the potential use of La4Sr8Ti12−xFexO38−δ (LSTF) materials as electrodes for a new concept of solid oxide fuel cells, symmetrical fuel cells (SFCs), is considered. Such fuel cells use simultaneously the same material as anode and cathode, which notably simplifies the assembly and further maintenance of the cells. Therefore, we search for materials showing high conductivity in a wide range of oxygen partial pressures in addition to certain degree of catalytic activity for the oxidation of the fuel and reduction of the oxidant, respectively. The preliminary electrochemical experiments performed reveal that the overall conductivity increases notably upon Fe substitution, being the main contribution electronic n-type. The fuel cell tests indicate that LSTF composites with YSZ and CeO2 perform reasonably well under H2 conditions, although the performance in methane is rather modest and require further optimisation. 相似文献