Effect of porosity on thermal and electrical properties of polycrystalline bulk ZrN prepared by spark plasma sintering

Adachi, Jun; Kurosaki, Ken; Uno, Masayoshi; Yamanaka, Shinşuke

doi:10.1016/j.jallcom.2006.05.115

Cited by 77 publications

(78 citation statements)

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“…Where the effect of porosity on ZT is usually small if not negligible [19], individual transport parameters must be corrected for porosity in order to judge the effect of nanostructuring alone. To do so, we follow Adachi et al by using a Maxwell-Eucken expression [21]:…”

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ZT Enhancement in Solution-Grown Sb_(2−x)Bi_xTe₃ Nanoplatelets

et al. 2010

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We report a solution-processed, ligand supported synthesis of 15-20 nm thick Sb (2−x) BixTe3 nanoplatelets. After complete ligand removal by a facile NH3-based etching procedure, the platelets are spark plasma sintered to a p-type nanostructured bulk material with preserved crystal grain sizes. Due to this nanostructure, the total thermal conductivity is reduced by 60 % in combination with a reduction in electric conductivity of as low as 20 % as compared to the bulk material demonstrating the feasibility of the phonon-glass electron-crystal concept. An enhancement in the dimensionless thermoelectric figure of merit of up to 15 % over state-of-the-art bulk materials is achieved meanwhile shifting the maximum to significantly higher temperatures.Recently, Bi 2 Te 3 based nanostructured materials have received great attention due to their outstanding thermoelectric properties. From the first reports in the 1950s until today, the dimensionless thermoelectric figure of merit (ZT) of such materials at room temperature has been improved threefold. ZT is estimated to require a value of 3 to be competitive with conventional cooling devices and to open up novel pathways for efficient and greener power generation.The record high efficiency of 2.4 was reported for molecular beam epitaxy engineered thin films of Bi 2 Te 3 /Sb 2 Te 3 layers, which may be difficult to use in large-scale applications but convincingly demonstrated the potential for further improvements to come from nanostructured Bi 2 Te 3 based materials [5].In order to fabricate such materials on a macroscopic scale, one conventionally applies high pressure and suitable temperatures to sinter a Bi 2 Te 3 based nanopowder to a dense nanocomposite with preserved crystal grain boundaries. Such nanocomposites have been studied by the means of transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) [6] and scanning electron microscopy (SEM) [7]. It is believed that the unique structural details in these materials such as laminated structure, coherent interfaces, nanoprecipitates with defect concentrations and broad size distribution of crystalline domains effect all three parameters of ZT, namely the thermopower, electric and * Electronic address: scheele@chemie.uni-hamburg.de thermal conductivity and can lead to an overall improvement of thermoelectric efficiency.Synthetic strategies to Bi 2 Te 3 based nanopowders can be divided into two approaches: (a) ligandless or (b) ligand supported nanograin growth. Advantages of the former are the absence of organic impurities and the good alloying possibilities by standard semiconductor manipulations. As a matter of this, the ligandless approach was more successful recently and all of the mile stone achievements in enhancing zT as cited above were due this strategy. An instructive summary has been provided recently by Ren and coworkers [8]. However, it is found almost impossible to achieve a good size control and narrow size distribution of nanoparticles by this strategy. This is the major advan...

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confidence: 99%

ZT Enhancement in Solution-Grown Sb_(2−x)Bi_xTe₃ Nanoplatelets

et al. 2010

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“…2) The thermal conductivities of ZrN corrected to 100%TD, together with the reported values, 2,3,13,14) are shown in Fig. 5.…”

Section: Discussionmentioning

confidence: 95%

“…It was found that the thermal conductivity values of ZrN obtained in this study were located in the range of 62 to 66 Wm À1 K À1 and had smaller temperature dependence than reported in the literature. Adachi et al 14) suggested that the phonon contribution of thermal conductivity for ZrN was approximately equal to the electron contribution. Thus, it can be surmised that the small temperature dependence of thermal conductivity resulted from the fact that the temperature dependence of the thermal conductivity of phonon and electron contributions canceled each other out.…”

Section: Discussionmentioning

confidence: 99%

“…Thus, it can be surmised that the small temperature dependence of thermal conductivity resulted from the fact that the temperature dependence of the thermal conductivity of phonon and electron contributions canceled each other out. The large scattering of the thermal conductivity of ZrN seen in the literature 2,3,13,14) was thought to be derived from the difference in characteristics of the samples subjected to measurement. For example, the ZrN sample prepared by Basini et al The thermal conductivities of the Zr-based TRU nitride solid solutions corrected to 100%TD were fitted to a polynomial temperature equation, i.e., a þ b T þ c T 2 , using the least-squares method.…”

Section: Discussionmentioning

confidence: 99%

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Thermal Conductivities of Zr-based Transuranium Nitride Solid Solutions

Nishi¹,

Takano²,

Ichise³

et al. 2011

J. Nucl. Sci. Technol.

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In this study, the authors prepared sintered samples of (Zr 0:58 Pu 0:21 Am 0:21 )N, (Zr 0:80 Pu 0:10 Am 0:10 )N, and (Zr 0:70 Np 0:06 Pu 0:15 Am 0:075 Cm 0:015 )N solid solutions. The thermal diffusivities and heat capacities of these Zr-based transuranium nitride solid solutions were measured using a laser flash method and drop calorimetry, respectively. Thermal conductivities from 473 to 1,473 K were determined from the measured thermal diffusivity, heat capacity, and bulk density. The thermal conductivities of Zr-based transuranium nitride solid solutions were found to be higher than that of (Pu 0:5 Am 0:5 )N due to the high thermal conductivity of ZrN as the principal component, although they were lower than that of ZrN due to the impurifying effect of the transuranium elements. At 873 K, the thermal conductivities of ZrN, 9, 15.8, 25.5, 20.6, and 8.9 Wm À1 K À1 , respectively. In these results, the thermal conductivities of the Zr-based transuranium nitride solid solutions increased with increasing ZrN concentration.

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“…Due to this increased interest recent work has focused on assessing thermophysical properties of ZrN and mixed phases of actinide nitrides dispersed in ZrN. However difficulty in determining purity and stoichiometry of these materials has lead to much scatter in these properties with the bulk of experimental data being presented for commercially available powders [9][10][11][12][13]. Our work has shown that thermal conductivity of ZrC x N y ceramics increases with increasing nitrogen content [14].…”

Section: Introductionmentioning

confidence: 97%

On the fabrication of ZrC x N y from ZrO 2 via two-step carbothermic reduction–nitridation

Harrison

Rapaud

Pradeilles

et al. 2015

Journal of the European Ceramic Society

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This study examined the processing parameters of a two-step carbothermal reduction-nitridation of ZrO 2 as a UO 2 /PuO 2 simulant to fabricate ZrN. Variables studied were the reaction time, reaction temperature and the starting powder composition Higher temperatures, longer reaction times and higher initial amounts of carbon in the starting material lead to increased nitridation similar to previous work with uranium oxide but that reaction rate decreases with time. SEM and TEM of the reacted powders reveal regions of ZrC with ledges indicative of crystal defects with small particles of ZrN growing on the ZrC bulk material suggesting a reaction that occurs via Zr transport to the reaction site either through mass diffusion or evaporation-condensation of Zr (g) and with N 2(g) forming the nitride. Annealing experiments on these mixed phases shows formation of a solid solution is rapid compared to the nitridation, where there is no formation of a mixed phase.

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Effect of porosity on thermal and electrical properties of polycrystalline bulk ZrN prepared by spark plasma sintering

Cited by 77 publications

References 11 publications

ZT Enhancement in Solution-Grown Sb_(2−x)Bi_xTe₃ Nanoplatelets

ZT Enhancement in Solution-Grown Sb_(2−x)Bi_xTe₃ Nanoplatelets

Thermal Conductivities of Zr-based Transuranium Nitride Solid Solutions

On the fabrication of ZrC x N y from ZrO 2 via two-step carbothermic reduction–nitridation

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Effect of porosity on thermal and electrical properties of polycrystalline bulk ZrN prepared by spark plasma sintering

Cited by 77 publications

References 11 publications

ZT Enhancement in Solution-Grown Sb(2−x)BixTe3 Nanoplatelets

ZT Enhancement in Solution-Grown Sb(2−x)BixTe3 Nanoplatelets

Thermal Conductivities of Zr-based Transuranium Nitride Solid Solutions

On the fabrication of ZrC x N y from ZrO 2 via two-step carbothermic reduction–nitridation

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ZT Enhancement in Solution-Grown Sb_(2−x)Bi_xTe₃ Nanoplatelets

ZT Enhancement in Solution-Grown Sb_(2−x)Bi_xTe₃ Nanoplatelets