Tailoring the structure and thermoelectric properties of BaTiO3 via Eu2+ substitution
authors Xiao, XX; Widenmeyer, M; Xie, WJ; Zou, TH; Yoon, S; Scavini, M; Checchia, S; Zhong, ZC; Hansmann, P; Kilper, S; Kovalevsky, A; Weidenkaff, A
nationality International
journal PHYSICAL CHEMISTRY CHEMICAL PHYSICS
keywords BARIUM-TITANATE; PIEZOELECTRIC PROPERTIES; ELECTRONIC-STRUCTURE; TRANSPORT-PROPERTIES; OPTICAL-PROPERTIES; THIN-FILMS; SRTIO3; FERROELECTRICITY; CE1-XGDXO2-X/2; PERFORMANCE
abstract A series of Ba1-xEuxTiO3-delta (0.1 <= x <= 0.9) phases with similar to 40 nm particle size were synthesized via a Pechini method followed by annealing and sintering under a reducing atmosphere. The effects of Eu2+ substitution on the BaTiO3 crystal structure and the thermoelectric transport properties were systematically investigated. According to synchrotron X-ray diffraction data only cubic perovskite structures were observed. On the local scale below about 20 angstrom (equal to similar to 5 unit cells) deviations from the cubic structure model (Pm% (3) over barm) were detected by evaluation of the pair distribution function (PDF). These deviations cannot be explained by a simple symmetry breaking model like in EuTiO3-delta. The best fit was achieved in the space group Amm2 allowing for a movement of Ti and Ba/Eu along < 110 > of the parent unit cell as observed for BaTiO3. Density functional calculations delivered an insight into the electronic structure of Ba1-xEuxTiO3-delta. From the obtained density of states a significant reduction of the band gap by the presence of filled Eu2+ 4f states at the top of the valence band was observed. The physical property measurements revealed that barium-europium titanates exhibit n-type semiconducting behavior and at high temperature the electrical conductivity strongly depended on the Eu2+ content. Activation energies calculated from the electrical conductivity and Seebeck coefficient data indicate that at high temperatures (800 K < T < 1123 K) the conduction mechanism of Ba1-xEuxTiO3-delta (0.1 <= x <= 0.9) is a polaron hopping when 0 <= x <= 0.6 and is a thermally activated process when 0.6 < x < 1. Besides, the thermal conductivity increases with increasing Eu2+ concentration. Due to a remarkable improvement of the power factor, Ba0.1Eu0.9TiO3-delta showed a ZT value of 0.24 at 1123 K.
publisher ROYAL SOC CHEMISTRY
issn 1463-9076
year published 2017
volume 19
issue 21
beginning page 13469
ending page 13480
digital object identifier (doi) 10.1039/c7cp00020k
web of science category Chemistry, Physical; Physics, Atomic, Molecular & Chemical
subject category Chemistry; Physics
unique article identifier WOS:000402488300009
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journal analysis (jcr 2017):
journal impact factor 3.906
5 year journal impact factor 4.224
category normalized journal impact factor percentile 73.037
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