Neutron diffraction texture analysis and thermoelectric properties of BiCaCoO misfit compounds

Guilmeau, Emmanuel; Pollet, M.; Grebille, D.; Chateigner, D.; Vertruyen, Bénédicte; Cloots, Rudi; Funahashi, Ryoji; Ouladiaff, B.

doi:10.1016/j.materresbull.2007.02.043

Cited by 18 publications

(19 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As it can be easily seen, the ρ(T) curve exhibits a semiconducting behavior from high (400 K) to low temperature (5 K) independently of the growth rate. This semiconducting behavior is in agreement with earlier reports on this cobaltite system (8,14). The resistivity values decrease when lower growth speeds are used, as a consequence of the better grain alignment and the larger grain sizes.…”

Section: Resultssupporting

confidence: 92%

See 1 more Smart Citation

Cerámicas termoeléctricas Bi2Ca2Co1.7Ox texturadas mediante fusión zonal flotante inducida por láser

Sotelo¹,

Guilmeau²,

Madre³

et al. 2008

Bol. Soc. Esp. Ceram. Vidr.

Self Cite

View full text Add to dashboard Cite

Thermoelectric performance on cobaltite ceramics can be increased raising the electrical conductivity. This can be performed by increasing grain size and aligning them along a preferential direction by the Laser Floating Zone (LFZ) method. In this work, Bi 2 Ca 2 Co 1.7 O x ceramics have been directionally grown at three different speeds, 15, 30 and 50 mm/h. It has been found a small influence of the growth conditions on the thermoelectric properties. In all the cases, the microstructure shows alternated cobaltite layers with small CoO inclusions. In despite, the thermopower is higher than usual in misfit cobaltites obtained by conventional solid state routes. This preliminary result originates probably from oxygen vacancies. Keywords: Electrical properties, cobaltites, thermoelectric power.Cerámicas termoeléctricas Bi 2 Ca 2 Co 1.7 O x texturadas mediante fusión zonal flotante inducida por láser Las prestaciones termoeléctricas de las cerámicas basadas en óxidos de cobalto pueden ser aumentadas por la disminución de la resistividad eléctrica. Esto puede realizarse aumentando el tamaño de grano y alineándolo en una dirección preferencial, utilizando el método de zona flotante inducida por láser (LFZ). En este trabajo, se han crecido cerámicas termoeléctricas de composición Bi 2 Ca 2 Co 1.7 O x a tres velocidades diferentes, 15, 30 y 50 mm/h. Se ha encontrado que las condiciones de crecimiento tienen poca influencia en las propiedades termoeléctricas. En todos los casos, la microestructura está formada por capas alternadas de cobaltitas, con pequeñas inclusiones de CoO. A pesar de ello, el poder termoeléctrico medido es mayor de lo habitual para este tipo de materiales preparados por métodos convencionales en estado sólido. Este resultado preliminar está originado, probablemente, por la formación de vacantes de oxígeno.Palabras clave: Propiedades eléctricas, cobaltitas, poder termoeléctrico.

show abstract

Section: Resultssupporting

confidence: 92%

“…It can be clearly seen that all the obtained RXD diagrams show the same pattern. Major peaks correspond to the misfit cobaltite Bi 2 Ca 2 Co 1.7 O x (14). Figure 2 shows the polished transversal surface of the textured bars.…”

Section: Resultsmentioning

confidence: 99%

Cerámicas termoeléctricas Bi2Ca2Co1.7Ox texturadas mediante fusión zonal flotante inducida por láser

Sotelo¹,

Guilmeau²,

Madre³

et al. 2008

Bol. Soc. Esp. Ceram. Vidr.

Self Cite

View full text Add to dashboard Cite

show abstract

“…1 together with their Rietveld pattern matching performed with FullProf [32] using the Bi 2 Ca 2 Co 1.7 O x (C2/m space group #12) and Ag (Fm3 m space group #225) cells. As it can be observed in the figure, all the samples show very similar patterns and the most intense peaks correspond to the misfit cobaltite Bi 2 Ca 2 Co 1.7 O x phase, in agreement with previously reported data [33]. From these patterns, it can be deduced that the performed thermal treatment has been effective to produce nearly single cobaltite phase, independently of Ag content.…”

Section: Resultssupporting

confidence: 90%

Role of Ag in textured-annealed Bi2Ca2Co1.7Ox thermoelectric ceramic

et al. 2016

View full text Add to dashboard Cite

Bi 2 Ca 2 Co 1.7 O x thermoelectric ceramics with small Ag additions (0, 1, 2, 3, 4, and 5 wt.%) have been successfully grown from the melt, using the laser floating zone method and subsequently annealed at 800 ºC for 24 h. The microstructure has shown a reduction of the amount of secondary phases for Ag contents up to 4 wt.%.This microstructural evolution leads to a decrease of the electrical resistivity values until an Ag content of 4 wt.%, whereas Seebeck coefficient has been maintained unchanged. This is in agreement with the presence of metallic Ag in all samples, confirmed not only by Energy Dispersive Spectrometry but also by X-ray photoelectron and Auger spectroscopy. These electrical properties lead to maximum power factor values of about 0.30 mW/K 2 .m at 650 ºC for the 4 wt.% Ag containing samples, which is among the best results obtained for this type of materials.

show abstract

“…This behavior is in agreement with the electrical resistivity evolution discussed previously. Anyway, all the samples show higher thermopower values at room temperature (∼250 and 175µV/K for samples grown without current and with 300mA, respectively) than the reported for Bi 2 Ca 2 Co 2 O x single crystals (150µV/K at the same temperature) [19]. The large thermopower values measured in these samples are due to the large amount of oxygen vacancies in the thermoelectric Bi 2 Ca 2 Co 1.7 O x phase produced by the laser floating zone technique [20].…”

mentioning

confidence: 55%

“…The effect of this improvement of the grain alignment is reinforced by the slight decrease on the secondary phases content and the presence of the Ca 3 Co 4 O 9 phase which is known to possess lower electrical resistivity than the Bi 2 Ca 2 Co 1.7 O x one. In any case, it is important to highlight that the lowest resistivity value obtained for the samples grown with 300 mA at room temperature, ∼20mΩ.cm, is only slightly higher than the one obtained on Bi 2 Ca 2 Co 2 O x single crystals at the same temperature, around 11mΩ.cm [19].…”

mentioning

confidence: 68%

Development of a new thermoelectric Bi2Ca2Co1.7Ox+Ca3Co4O9 composite

Rasekh¹,

Ferreira²,

Costa³

et al. 2014

Scripta Materialia

View full text Add to dashboard Cite

Thermoelectric (TE) power generation is a promising technology to harvest wasted heat from different energy transformation systems. As a consequence, it can be very useful in order to reduce CO 2 emissions, helping to reach a global warming solution. For these applications, TE materials with high efficiency are required to be used in commercial devices. The performances of these materials are usually quantified by the dimensionless figure of merit, ZT, defined as TS 2 /ρκ (where S is the Seebeck coefficient, T the absolute temperature, ρ the electrical resistivity and κ the thermal conductivity; S 2 /ρ is the power factor, PF The cobaltites crystal structure is formed by two different layers, which can be described as an alternate stacking of a common conductive CdI 2 -type CoO 2 layer with a twodimensional triangular lattice, and a block layer, composed of insulating rock-salt-type (RS) layers. These two sublattices possess common a-and c-axis lattice parameters and β angles while having different b-axis length, causing a misfit along the b-direction [7][8][9]. As a consequence, layered cobaltites possess a very high crystallographical anisotropy which, in turn, produces a high electrical one. otherwise it would decompose in the molten zone, producing CO 2 bubbles inside the melt in the LFZ process, leading to the solidification front destabilization. The thermally treated powders were then milled, introduced into a latex tube (inner diameter ~3mm), and isostatically cold pressed at 200MPa for one minute to obtain green ceramic cylinders (~100mm long). The resulting cylinders were subsequently used as feed in a EALFZ device equipped with a continuous power CO 2 laser (λ=10.6µm, Spectron SLC)with an external DC power supply (ISO TECH IPS 603) which is described elsewhere [17].All the EALFZ grown samples were processed, with 0 and 300mA applied current, at 30mm/h under air, with a seed rotation of 3rpm anticlockwise while the feed was rotated at 15rpm, in the opposite direction, in order to assure the molten zone compositional homogeneity. After the texturing process, long (∼100mm) and geometrically homogeneous (∼2mm diameter) textured cylindrical rods have been produced. Finally, the textured bars were cut into pieces with the adequate dimensions for their TE characterization (~15mm long pieces).The grain orientation in textured samples has been determined on transversal sections of the samples by pole figures performed on the (020) The electrical resistivity of all the samples as a function of temperature is shown in Fig. 2. In the graph, it can be seen that the sample grown without current exhibit semiconductor-like behavior (δρ/δT<0) in all the measured temperature range, which is the typical one for this kind of materials [18]. When the external current is applied during the growth process, the electrical resistivity values decrease significantly (∼80%) when compared with samples grown without current. Moreover, the samples behavior changes from the semiconducting-like one to a nearly temperature independe...

show abstract

Neutron diffraction texture analysis and thermoelectric properties of BiCaCoO misfit compounds

Cited by 18 publications

References 9 publications

Cerámicas termoeléctricas Bi<sub>2</sub>Ca<sub>2</sub>Co<sub>1.7</sub>O<sub>x</sub> texturadas mediante fusión zonal flotante inducida por láser

Cerámicas termoeléctricas Bi<sub>2</sub>Ca<sub>2</sub>Co<sub>1.7</sub>O<sub>x</sub> texturadas mediante fusión zonal flotante inducida por láser

Role of Ag in textured-annealed Bi2Ca2Co1.7Ox thermoelectric ceramic

Development of a new thermoelectric Bi2Ca2Co1.7Ox+Ca3Co4O9 composite

Contact Info

Product

Resources

About