Thermoelectric properties in Ca3Co4-xMnxOy ceramics

Ca3Co4-xMnxOy polycrystalline thermoelectric ceramics with small amounts of Mn have been prepared by the classical solid state method. X-ray diffraction data have shown that Ca3Co4O9 is the major phase, with small amounts of the Ca3Co2O6 one. Moreover, they show that the Mn has been incorporated into these two phases. Electrical resistivity decreases, compared with the values for undoped samples, with Mn content until a minimum for the 0·03 doped ones, increasing for higher Mn substitution. Seebeck coefficient does not change in all the measured temperature range, independently of Mn content. The improvement in electrical resistivity leads ∼30% higher power factor values for the 0·03 Mn doped samples than that obtained in the undoped ones. The maximum power factor at 800°C, ∼0·28 mW K-2 m-1, is close to that obtained in much higher density samples, clearly indicating the good thermoelectric properties of these samples.The authors wish to thank the Gobierno de Aragón (Research Groups T12 and T87) and the MINECO-FEDER (MAT2013-46505-C3-1-R) for financial support. Authors would also like to acknowledge the use of Servicio General de Apoyo a la Investigación-SAI, Universidad de Zaragoza. The technical contributions of C. Estepa and C. Gallego are also acknowledged. Sh. Rasekh acknowledges a JAE-PreDoc 2010 grant from CSIC.Peer Reviewe

Thermoelectric properties of directionally grown Bi2Ba2Co2Oδ/Ag composites: effect of annealing

Bi2Ba2Co2Oδ thermoelectric ceramics with Ag additions (0, 1, 3, and 5 wt%) have been successfully textured using the laser floating zone method. Microstructure has shown that samples are composed by thermoelectric grains, together with a high amount of secondary phases, and that 3 wt% Ag addition leads to the best grain orientation. These microstructural benefits have been reflected in the highest thermoelectric performances determined in these samples. It has also been found that annealing procedure leads to a drastic decrease of secondary phases amount and raises the oxygen content in the thermoelectric phase. These modifications are reflected in an important decrease of electrical resistivity, ρ (compared to the as-grown samples) without drastic modification of Seebeck coefficient, S. As a consequence, the highest thermoelectric performances, determined through the power factor, have been reached in the 3 wt% Ag textured and annealed samples in the whole measured temperature range. The maximum PF (=S/ρ) values at 650 °C determined in these samples are very close to the highest reported in single crystals or very low rate LFZ grown Bi2Ba2Co2Oδ compounds, making them very attractive for practical applications.This research has been supported by the Spanish MINECO-FEDER (MAT2013-46505-C3-1-R). The authors wish to thank the Gobierno de Aragón and Fondo Social Europeo (Consolidated Research Groups T87 and T12) for financial support.Peer Reviewe

Thermoelectric doping effect in Ca3Co4-xNixO9 ceramics

Ca3Co4-xNixO9 (x=0.01, 0.03, and 0.05) polycrystalline thermoelectric ceramics have been prepared by the classical solid state method. As a result of the Ni addition an increase in porosity has been detected. Moreover, the presence of Ni has been related with the increase of Ca2Co3O6 secondary phase and the appearance of a new NiO-CoO solid solution. However, for the 0.01-Ni doped samples an improvement in the thermoelectric performances has been measured. This effect has been related with a decrease in the resistivity values and an increase in the Seebeck coefficient. The raise in the power factor for the 0.01-Ni doped samples, compared with the undoped ones, is between 10 and 25% at 50 and 800 °C respectively. Moreover, the maximum power at 800 °C, around 0.25 mW/K2.m, is significantly higher than the best results obtained in Ni doped samples reported previously in the literature

Challenges for the representation of morphology in ontology lexicons

Recent years have experienced a growing trend in the publication of language resources as Linguistic Linked Data (LLD) to enhance their discovery, reuse and the interoperability of tools that consume language data. To this aim, the OntoLex-lemon model has emerged as a de facto standard to represent lexical data on the Web. However, traditional dictionaries contain a considerable amount of morphological information which is not straightforwardly representable as LLD within the current model. In order to fill this gap a new Morphology Module of OntoLex-lemon is currently being developed. This paper presents the results of this model as on-going work as well as the underlying challenges that emerged during the module development. Based on the MMoOn Core ontology, it aims to account for a wide range of morphological information, ranging from endings to derive whole paradigms to the decomposition and generation of lexical entries which is in compliance to other OntoLex-lemon modules and facilitates the encoding of complex morphological data in ontology lexicons

Enhanced electrical and thermoelectric properties from textured Bi1.6Pb0.4Ba2Co2Oy/Ag composites

Bi1.6Pb0.4Ba2Co2Oy/3 wt% Ag composites have been textured using the laser floating zone technique. Microstructural observations have shown the formation of relatively high amounts of secondary phases and cracks along the plate-like grains in the as-grown materials. In spite of these microstructural features, electrical properties have not been drastically decreased. Annealing of these as-grown rods has enhanced the grains connectivity, decreased the contents of the secondary phases, and healed the cracks, thereby increasing their electrical performances. It has been deduced that oxygen content in the thermoelectric phase has not been significantly modified through annealing, as demonstrated by the very similar Seebeck values at room temperature in the as-grown and annealed samples. As a consequence of the low electrical resistivity values in the annealed materials, they reached higher power factor values than the as-grown ones. The highest power factor at room temperature is in the range of those reported for single crystals, while at 650 °C, it is the highest reported in Bi–Ba–Co–O polycrystalline family so far

Improved thermoelectric performances in textured Bi1.6Pb0.4Ba2Co2Oy/Ag composites

Bi1.6Pb0.4Ba2Co2Oy thermoelectric ceramics with small Ag additions (0, 1, 3, and 5 wt%) have been textured using the laser floating zone method. Microstructure has shown a slight decrease on the secondary phases content and a better grain alignment in Ag added samples. These microstructural features are reflected in the thermoelectric properties, which have shown a significant decrease of electrical resistivity, when the Ag content is raised. In spite of a corresponding decrease of Seebeck coefficient, all the Ag-containing samples possess higher Power Factor values than the Bi1.6Pb0.4Ba2Co2Oy ones. Moreover, the maximum Power Factor values (about 0.36 mW/K2.m at 650 °C) have been measured in Bi1.6Pb0.4Ba2Co2Oy+3 wt% Ag samples, which are the best results reported in this family of materials

Effect of Na doping on the Ca3Co4O9 thermoelectric performance

Ca3-xNaxCo4O9 polycrystalline thermoelectric ceramics with small amounts of Na (x=0, 0.01, 0.03, 0.05, 0.07, and 0.10) have been prepared using the classical solid state method. Microstructural characterization has shown that Na has been incorporated into the Ca3Co4O9 phase and that no Na-based secondary phases have been produced. It has also been found that Na addition promotes grain growth and favours sintering due to the formation of a small amount of liquid phase. Electrical resistivity decreases when Na content increases until 0.07Na addition while Seebeck coefficient is maintained practically unchanged. The improvement in electrical resistivity leads to higher power factor values than the usually obtained in samples prepared by more complex and expensive techniques.This research has been supported by the Spanish MINECO-FEDER (MAT2013-46505-C3-1-R). The authors wish to thank the Gobierno de Aragón-Fondo Social Europeo (Consolidate research group T12 and consolidated research group T87) for financial support.Peer Reviewe

Efecto del dopaje en la propiedades termoeléctricas de cerámicas Ca3Co4-xNixO9

[EN]: Ca3Co4-xNixO9 (x=0.01, 0.03, and 0.05) polycrystalline thermoelectric ceramics have been prepared by the classical solid state method. As a result of the Ni addition an increase in porosity has been detected. Moreover, the presence of Ni has been related with the increase of Ca2Co3O6 secondary phase and the appearance of a new NiO-CoO solid solution. However, for the 0.01-Ni doped samples an improvement in the thermoelectric performances has been measured. This effect has been related with a decrease in the resistivity values and an increase in the Seebeck coefficient. The raise in the power factor for the 0.01-Ni doped samples, compared with the undoped ones, is between 10 and 25% at 50 and 800 ºC respectively. Moreover, the maximum power at 800 ºC, around 0.25 mW/K2.m, is significantly higher than the best results obtained in Ni doped samples reported previously in the literature.[ES]: Se han preparado muestras policristalinas de Ca3Co4-xNixO9 (x = 0,01, 0,03 y 0,05) mediante reacción en estado sólido. Se ha detectado un incremento de la porosidad en las muestras dopadas con Ni. La adición de Ni también ha provocado el aumento de la fase secundaria Ca2Co3O6, así como la aparición de una nueva fase consistente en una solución sólida de NiO-CoO. A pesar de ello se ha detectado una mejora de las prestaciones termoeléctricas en las muestras con un 0,01 de Ni. Esta mejora ha sido provocada por una disminución de la resistividad eléctrica y un aumento del coeficiente Seebeck.The authors wish to thank the Gobierno de Aragón and the Fondo Social Europeo (Research Groups T12 and T87) and MINECO-FEDER (Project MAT2013-46505-C3-1-R) for financial support.Peer Reviewe

Enhancement of mechanical and thermoelectric properties of Ca3Co4O9 by Ag addition

Ca3Co4O9 + x wt.% Ag (x = 0, 1, 3, 5, and 10) polycrystalline thermoelectric ceramics have been prepared by a sol–gel route via nitrates followed by high temperature treatment before sintering. Out-of-plane XRD data have shown that major phase is the Ca3Co4O9 one, accompanied by metallic Ag. SEM observations have agreed with the XRD data. Apparent density measurements have revealed that all samples possess densities ranging between 80% and 90% when Ag content is raised. Mechanical properties have shown a drastic increase of bending stress when Ag is added to the samples. Electrical resistivity decreases with the Ag content, compared with the pure ones, while Seebeck coefficient slightly decreases. Maximum power factor values around 0.43 mW/K2 m at 800 °C have been achieved for the 10 wt.% Ag samples which is much higher than the measured in the pure Ca3Co4O9 samples.This research has been supported by MINECO-FEDER (MAT2013-46505-C3-1-R). The authors wish to thank the Gobierno de Aragón-Fondo Social Europeo (Consolidated Research Groups T12 and T87) for financial support.Peer Reviewe