A model for the heat of transport in ionic conductors

Taniguchi, Sachi; Aniya, Masaru

doi:10.1016/j.ssi.2008.09.001

Cited by 14 publications

(8 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The reason is unclear, but might be due to the different thermal transport properties between electron/hole carriers and ion carrier. Taniguchi reported that the ions can jump to a vacant site helped by capturing short wavelength phonons as shown in Figure 4 .…”

Section: Conduction Type and Zt Value For The Cu9s5 Bulk And Other Tymentioning

confidence: 99%

High‐Performance Thermoelectricity in Nanostructured Earth‐Abundant Copper Sulfides Bulk Materials

Liu

Feng

et al. 2016

Advanced Energy Materials

122

View full text Add to dashboard Cite

In-and Cd-doped Cu 9 S 5 and reported that the electrical conductivity was reduced and the thermal power was improved when In and Cd were added to Cu 9 S 5 . However, they did not report the thermal conductivity and ZT value. [ 30 ] In our previous work, we reported that the ZT value of pristine Cu 9 S 5 reached 0.3 at 673 K and the ZT for the optimized sintering temperature sample could be further enhanced to 0.5 because of the existence of a second Cu 1.96 S phase and a considerable number of pores. [ 18 ] Dennler et al. [ 31 ] systematically studied the thermal stability and electrical stability of CuS, Cu 9 S 5, and Cu 2 S. The results showed that the CuS is not stable at temperatures beyond 240 °C either in air or N 2 . Experiments also showed that Cu 2 S is not electrically stable because both cracks and copper whiskers were observed in a Cu 2 S sample after long-time current stress tests (24 A cm −2 /24 h). In contrast, CuS and Cu 9 S 5 samples did not show any degradation in the electrical stability test, even when current densities were increased to as high as 48 A cm −2 . However, the Seebeck coeffi cient, electrical resistivity, crystal structure, and stoichiometry remained constant. [ 31 ] This indicates that only Cu 9 S 5 is both thermally and electrically stable.High-performance TE materials should simultaneously own large Seebeck coeffi cients, high electrical conductivity, and low thermal conductivity, but these three parameters are interrelated with each other. It is diffi cult to improve all the parameters at the same time, for instance, an improvement of electrical conductivity will normally lead to the deterioration in the Secbeck coeffi cient and thermal conductivity. [ 4 ] The main challenges for enhancing TE properties of Cu 9 S 5 -based materials are to improve the Seebeck coeffi cient via carrier concentration optimization. In this work, Na x Cu 9 S 5 ( x = 0, 0.025, 0.05, 0.15, 0.25) nanopowders with an average size of 3 nm were prepared by mechanical alloying (MA). The nanopowders were then sintered to bulk materials by spark plasma sintering (SPS) technology. Metallic Na was doped to Cu 9 S 5 to reduce carrier concentration and improve the Seebeck coeffi cient. Besides, nanopores and nanograins were observed unexpectedly in the Na-doped bulk samples, leading to a signifi cantly reduced thermal conductivity. Overall, a peak ZT value of 1.1 was achieved at 773 K in the composition of Na 0.05 Cu 9 S 5 . Figure 1 a,b shows the transmission electron microscope (TEM) and high-resolution transmission electron microscope (HRTEM) images (inset of Figure 1 b) of Na 0.05 Cu 9 S 5 powders obtained by MA method. Under the low magnifi cation mode, it can be seen that Na 0.05 Cu 9 S 5 powders disperse homogeneously on the microgrid support membrane, show a particle size smaller than 5 nm and an average size of 3 nm. This extremely small particle size obtained directly by MA method is quite astonishing, since the typical particle size of MAed powders is around several hundred nanometer to several micr...

show abstract

Section: Conduction Type and Zt Value For The Cu9s5 Bulk And Other Tymentioning

confidence: 99%

High‐Performance Thermoelectricity in Nanostructured Earth‐Abundant Copper Sulfides Bulk Materials

Liu

Feng

et al. 2016

Advanced Energy Materials

122

View full text Add to dashboard Cite

show abstract

“…Among these, we can mention the temperature [14,15] and pressure dependences [17] of the effective charge, estimation of the effective number of valence electrons [38], origin of the correlated motion between diffusing ions [3] or caterpillar mechanism [39], photoinduced ionic motion in chalcogenide glasses [16,40,41], and heat of transport due to collective motion of ions [42]. The bond fluctuation model was originally proposed to explain the properties of crystalline ionic conductors.…”

Section: Recent Applications Of the Bond Fluctuation Modelmentioning

confidence: 99%

Bond Fluctuation Model of Superionic Conductors: Concepts and Applications

Aniya

2010

Integrated Ferroelectrics

Self Cite

View full text Add to dashboard Cite

The bond fluctuation model of superionic conductors provides a framework to understand the characteristic properties of superionic materials. According to the model, the superionic behavior is related to a change of bonding that occurs locally and fluctuates in time. In the present report, after presenting the concept of the model and summarizing the main results obtained till now, some recent applications of the model is reviewed. Topics such as new interpretation of the power law exponent of ac conductivity observed in superionic glasses, model for the anomalous electronic properties observed in liquid silver chalcogenides, and prediction of nonlinear optical constants of ionic conducting glasses are covered.

show abstract

“…Interactions of charge carriers and phonons play a major role in the correlation between these two material's properties – activation energy for chemical diffusion and the heat of transport of a mobile component. Taniguchi et al concluded that rather flat phonon dispersion curves (large number of optical phonons) with many modes having similar energies support collective ion dynamics and, therefore, lead to almost equal activation energies and heats of transport . This close similarity is experimentally proven for superionic conducting materials .…”

Section: Thermodiffusion Experimentsmentioning

confidence: 93%

Thermomigration and Soret effect in Na_xCoO₂ as thermoelectric material: Preparation and characterization of sodium cobaltate thin films

Schneider

Schichtel

Mogwitz

et al. 2015

Physica Status Solidi (a)

View full text Add to dashboard Cite

Sodium cobaltate (NaxCoO2, NCO) is a model type thermoelectric material for high temperature applications, which is representative for the class of non‐stoichiometric and mixed ion‐electron conducting thermoelectrics (e.g., Cu2 – xSe). The present study deals with the kinetic instability of the originally homogeneous chemical composition when a temperature gradient is applied – a common situation in thermoelectric materials with a mobile component (element), but rarely considered in thermoelectric materials research so far. In order to investigate a well reproducible system, highly epitaxial thin films of NaxCoO2 with an atmosphere protective capping layer of alumina are prepared via pulsed laser deposition on sapphire (001) and lanthanum aluminate (111). A self‐designed non‐isothermal set‐up allows the precise determination of the heat of transport for mobile sodium as 8.3 kJ mol−1 and, therefore, the quantification of thermodiffusion (i.e., the Ludwig‐Soret effect in the stationary state). The experiments also allow to estimate the chemical diffusion coefficient of sodium at 422 K as about D˜Na = 5 × 10−4 cm2 s−1.

show abstract

A model for the heat of transport in ionic conductors

Cited by 14 publications

References 29 publications

High‐Performance Thermoelectricity in Nanostructured Earth‐Abundant Copper Sulfides Bulk Materials

High‐Performance Thermoelectricity in Nanostructured Earth‐Abundant Copper Sulfides Bulk Materials

Bond Fluctuation Model of Superionic Conductors: Concepts and Applications

Thermomigration and Soret effect in Na_xCoO₂ as thermoelectric material: Preparation and characterization of sodium cobaltate thin films

Contact Info

Product

Resources

About

A model for the heat of transport in ionic conductors

Cited by 14 publications

References 29 publications

High‐Performance Thermoelectricity in Nanostructured Earth‐Abundant Copper Sulfides Bulk Materials

High‐Performance Thermoelectricity in Nanostructured Earth‐Abundant Copper Sulfides Bulk Materials

Bond Fluctuation Model of Superionic Conductors: Concepts and Applications

Thermomigration and Soret effect in NaxCoO2 as thermoelectric material: Preparation and characterization of sodium cobaltate thin films

Contact Info

Product

Resources

About

Thermomigration and Soret effect in Na_xCoO₂ as thermoelectric material: Preparation and characterization of sodium cobaltate thin films