Decrease In Thermal Conductivity Research Articles

Grain refinement to improve thermoelectric and mechanical performance in n-type Bi2Te2.7Se0.3 alloys

High-performance thermoelectric (TE) materials are in demand to improve energy conversion efficiency and mitigate the energy crisis for the next generation. In this study, we produced fine-grained n-type Bi2Te2.7Se0.3 materials using high energy ball milling followed by spark plasma sintering techniques. The results demonstrated that milling time strongly influences the thermoelectric properties. The electrical conductivity gradually decreased with increased milling time due to a decrease in carrier mobility by the enhanced carrier scattering at high density grain boundaries. In contrast, the Seebeck coefficient significantly increased and then decreased with prolonged milling time, due to the variation in carrier concentration. A substantial decrease in lattice thermal conductivity (~20% for 60 min) and suppression of bipolar thermal conductivity (~50% for 120 min) resulted from intensified phonon and minority carrier scattering at refined grain boundaries, respectively. A maximum figure of merit (ZT) of 0.88 was achieved at 400 K for the sample ball milled for 60 min, which was about 27% higher than the GA sample. The grain refinement significantly increased the hardness from 53 to 86 Hv and compressive strength from 59.3 to 102.5 MPa, due to grain boundary strengthening. These results provide useful evidence for TE power generation and refrigeration applications.

Thermoelectrical properties of silicon substrates with nanopores synthesized by metal-assisted chemical etching

A silicon substrate consisting of nanoporous silicon film could enhance the thermoelectric performance of bulk silicon due to its low thermal conductivity. Metal-assisted chemical etching (MACE) is a wet method for fabricating diverse nano/micro structures, which uses a noble metal as the catalyst for etching of semiconductor materials. In this study, we report the thermoelectrical properties of silicon substrates with nanopores in different porosities fabricated by MACE employing Ag nanoparticle as a metal catalyst. Different porosities of the nanoporous silicon layer were obtained by adjusting the deposition time of Ag nanoparticles. The lateral nanopores were found on the surface of the vertical nanopores sidewall caused by Ag nanoparticles. With the increase of the porosity, the surface area of the nanopores sidewall became rougher. In comparison with single-crystal silicon, silicon substrates with nanopores can enhance the thermoelectric figure of merit, ZT, due to the relativity high Seebeck coefficient and low thermal conductivity. However, lower electrical conductivity limits the enhancement of the ZT value. The porosity effect on the thermoelectrical properties of silicon substrates with nanopores was evaluated. The Seebeck coefficient has a maximum value at a porosity of 38% and then decreases at a porosity of 49%, and the electrical conductivity and thermal conductivity decrease with the increase of porosity. At a porosity of 38%, the ZT value of silicon substrates with nanopores can reach approximately 0.02, which is 7.3 times larger than that of the original high-doped single-crystalline silicon. Thus the nanoporous silicon film fabricated by MACE can enhance the thermoelectric performance of the bulk silicon.

Specific heat and thermal conductivity of municipal solid waste and its effect on landfill fires

Municipal Solid Waste (MSW) landfills are sources of physical, chemical and microbiological processes and as a result, gases and heat are generated as by-products. The generated heat flows from the higher to lower temperature regions within the landfill. Specific heat and thermal conductivities are two important properties that determine heat flow in MSW landfills. The goal of this study was to determine the thermal conductivity and specific heat capacity of MSW samples of Indian origin and to study its effect on landfill fires. Thermal conductivity and specific heat capacity of waste samples collected from dumpsite at Bhandewadi landfill, Nagpur & Bellahalli landfill, Bangalore (India) and the synthetic MSW (prepared in the lab) were determined using newly designed and fabricated experimental set-up. Results showed that moisture and organic content of MSW are directly proportional to specific heat capacity and indirectly proportional to thermal conductivity. Thermal conductivity of MSW is directly proportional to its density and specific heat is indirectly proportional to the density of MSW. MSW with specific heat and thermal conductivity in the range 0.003 J/g. K − 0.47 J/g. K and 0.35–3.6 J/s. m. K, respectively were found between 30 and 75 °C with 5% to 25% moisture content. As the temperature increases above 75 °C, decrease in thermal conductivity & increase in specific heat was observed and thermal conductivity of 0.07 J/s. m. K was observed at 130–140 °C. As a result of this, heat does not flow and gets concentrated in that region leading to landfill fire.

Thermoelectric Properties and Low-Energy Carrier Filtering by Mo Microparticle Dispersion in an n-Type (CuI)0.003Bi2(Te,Se)3 Bulk Matrix.

We investigate the thermoelectric properties of (CuI)0.003Bi2Te2.7Se0.3/Mo (Mo: 0.0, 0.9, 1.3, 1.8, 3.1, and 4.3 vol %) composites, which were synthesized by extrinsic phase mixing with hot press sintering. From X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX) measurements, we confirm that micro-sized Mo particles are dispersed homogeneously in the (CuI)0.003Bi2Te2.7Se0.3 matrix without doping. While the electrical resistivity of Mo-dispersed (CuI)0.003Bi2Te2.7Se0.3 composites is not changed significantly, the Seebeck coefficient is significantly increased. Because the work function (5.3 eV) of the (CuI)0.003Bi2Te2.7Se0.3 compounds, measured by ultraviolet photoelectron spectroscopy (UPS), is larger than that of Mo particles (4.95 eV), we expect the potential barrier near the interfaces between the BTS matrix and Mo particles. The band bending effect and potential barrier can give rise to the low-energy carrier filtering. For a low concentration dispersion of Mo particles (<2 vol %), a decrease of Hall carrier concentration, an increase of Hall mobility, a decrease of effective mass, and an increase of Seebeck coefficient also support the formation of low-energy carrier filtering. The Mo dispersion does not affect the decrease in the lattice thermal conductivity but enhances the power factor significantly, leading to the high ZT value above 1.0 at room temperature, which is a high level in n-type thermoelectric room-temperature applications.

Thermal and mechanical properties of thermal energy storage lightweight aggregate mortar incorporated with phase change material

The aim of the work is to design lightweight thermal insulation mortar with function of improved thermal characteristics using glazed hollow beads and micro-encapsulated phase change materials (PCM). Various experimental methods are carried out to investigate the effect on physical, mechanical, thermal characteristics and air void distribution of different compositions and mix. The results show that the mortar composition has a significant effect on its physical, mechanical and thermal characteristics. Thermal conductivity and thermal effusivity decrease with increasing PCM content. Thermal characteristic tests using room device indicated that the room device prepared with PCM board can reduce both the maximum indoor center temperature and temperature fluctuations, and this effect becomes more significant as the PCM content increases. Meanwhile, high PCM content will increase the average air void size, which will increase the air void content of the mortar specimen significantly.

Thermal and mechanical performances of cement-based mortars reinforced with vegetable synthetic sponge wastes and silica fume

Appropriate sand for construction is getting scarce in many countries leading to a growing interest in the use of wastes from several origins in mortar and concrete production. This paper investigates the performances of mortar containing the industrial wastes of vegetable synthetic sponges (VSS) as natural sand replacement. After preparation, different amounts of VSS particles (up to 20 wt% of sand replacement) were incorporated in the cementitious matrix containing 20% of silica fume by weight of cement. The use of silica fume improved the cement-aggregate interface leading to reduce the porosity and to increase consequently the mechanical strength. The replacement of the natural sand with VSS improved the thermal performance of the studied composites by causing a decrease of thermal conductivity up to 63% for 20 wt% of sand replacement by VSS. The thermal diffusivity of composites decreased and the specific heat capacity increased. The combination of VSS and silica fume in cementitious materials can largely improve the post-cracking extension and fracture energy, even if the compression strength is reduced. The study showed that the use of vegetable synthetic sponge wastes provides good potential to answer a major challenge: reducing environmental impact of this material while providing a new use with optimum technical properties, as found with 8 wt% of VSS.

Effective phonon scattering and enhancement of thermoelectric performance in Ga-excess Bi0.4Sb1.6Te3 compounds

We investigate the thermoelectric properties on Ga-excess p-type GaxBi0.4Sb1.6Te3 compounds. Even though the random distribution of Ga-doping increases electrical resistivity giving rise to the decrease of power factor, the significant decrease of lattice thermal conductivity by the excess Ga-doping induces significant enhancement of ZT value (1.13 at 350 K) for the Ga x = 0.03 doped compound. From the X-ray diffraction and elemental mapping by energy dispersive X-ray spectroscopy, we observed Sb and Ga phase separation leading to the phonon scattering. The Sb precipitation implies atomic defect in the matrix which can induce short wavelength phonon scattering. The synergetic phonon scatterings from various scattering sources such as point defect, alloy scattering, and grain boundary phonon scattering have an important role in the enhancement of thermoelectric performance.

Impact of biochar addition on soil thermal properties: Modelling approach

Little information is available on the effect of biochar on both measured and model-predicted soil thermal properties although they play a crucial role in the accumulation and transfer of heat and water through the soil. This study aimed at evaluation of the impact of biochar addition on soil thermal properties in field experiments conducted in China and Poland. The experimental data included biochar doses, soil texture, quartz and other minerals, bulk density, particle density, water content, air-filled porosity, and organic matter content. The data were then used to validate three models (analytic of de Vries, analytic of Zhao et al., and statistical-physical) and improve the predictability of the soil thermal properties. The biochar doses in the field experiments were from 4.5 to 40 Mg ha−1 and those in the modelling study ranged from 52 to 267 Mg ha−1. Pure biochar was used as well. The biochar additions caused a significant decrease in thermal conductivity and thermal diffusivity and exerted a less pronounced effect on the heat capacity. As shown by classic statistics and Bland-Altman plots, the agreement between the predicted and measured heat capacity of the Chinese soil was good and similar to the Zhao et al. and de Vries models. The best agreement between the statistical-physical model predicted and measured the thermal conductivity and diffusivity was obtained using the geometric mean of the native soil organic matter and biochar and after reduction of the quartz content in the sand fraction (2–0.05 mm) from 100 to 72%. The thermal diffusivity decreased with increasing biochar dose at comparable water contents and its characteristic maximum shifted towards higher water contents with increasing biochar dose. As thermal diffusivity enhances the smoothing of the temperature wave, these results imply that application of different biochar rates may help in regulation of soil temperature, which is an essential determinant of plant growth and soil processes and functions.

A new anisotropic thermal conductivity equation for h-BN/polymer composites using finite element analysis

A new anisotropic thermal conductivity equation of h-BN/polymer composites was successfully derived from a series of numerical calculation and mathematical analysis. A simple finite element model of polymer composite filled with oriented hexagonal boron nitride (h-BN) was firstly established to simulate its thermal transportation. This numerical model was validated by other thermal conductive models and experimental data. Then the influence of many factors on the anisotropic thermal conductivity of h-BN/polymer composites was mathematically investigated, including matrix thermal conductivity, h-BN thermal conductivity, size, aspect ratio and oriented angles, interfacial thermal resistance, and non-uniform factors. It is found that thermal conductivity of polymer composites increases with filler content as a power function; decreases with interfacial thermal resistance in a negative power function form; increases almost proportionally with thermal conductivity of polymer matrix; does not change with h-BN thermal conductivity when the in-plane thermal conductivity of h-BN is higher than 100 W·m−1·K−1 and out-of-plane thermal conductivity of h-BN is higher than 2 W·m−1·K−1; and does not change with h-BN size under the same aspect ratio. With the increasing h-BN aspect ratio, in-plane thermal conductivity of composites increases, while out-of-plane thermal conductivity decreases. The change ranges of position and tilt angle correction factors were also obtained.

Thermal transport in phase-stabilized lithium zirconate phosphates

The thermal properties of yttrium-stabilized lithium zirconate phosphate [LZP: Li1+x+yYxZr2−x(PO4)3 with x = 0.15, −0.2 ≤ y ≤ 0.4 and with x = 0.0, y = 0.0] are presented over a wide temperature range from 30 to 973 K, elucidating the interplay between structural phase transformations and thermal properties in a solid state superionic conducting material. At room temperature, the thermal conductivity decreases by more than 75% as the stoichiometry is changed from lithium deficient to excess and increases with increasing temperature, indicative of defect-mediated transport in the spark plasma sintered materials. The phase transformations and their stabilities are examined by x-ray diffraction and differential scanning calorimetry and indicate that the Y3+ substitution of Zr4+ is effective in stabilizing the ionically conductive rhombohedral phase over the entire temperature range measured, the mechanism of which is found through ab initio theoretical calculations. These insights into thermal transport of LZP superionic conductors are valuable as they may be generally applicable for predicting material stability and thermal management in the ceramic electrolyte of future all-solid-state-battery devices.

General correlation for frost thermal conductivity on parallel surface channels

Growth of frost layer on cold fins of tube-fin heat exchangers leads to an increase in the pressure drop and a decrease in the frost thermal conductivity and thereby the heat transfer rate. There is a lack of a general model in the literature for estimating the frost thermal conductivity on parallel plate channels, including almost all parameters affecting this factor. In this study, for the first time, the general explicit semi-empirical correlations consist of dimensionless parameters are developed, which apply to parallel surface channels. The dimensionless input parameters include the wall temperature, air temperature, air velocity, frost porosity, relative humidity, specific heat of moist air, latent heat of sublimation, and operating time. The comparative results indicate that the best correlation predicts data points with an coefficient of determination, average absolute relative error, and relative root mean square error equal 0.9921, 2.755%, and 3.713%, respectively. Other available published correlations present higher deviations using the same dataset. Furthermore, to provide a good insight into this study, a sensitivity analysis is carried out employing the validated model. It is shown that the effective thermal conductivity of the frost layer is not only a function of frost density but also depends on a group of dimensionless parameters. It is observed that the thermal conductivity of the frost layer increases with the increase in the Reynolds number, Fourier number, air humidity, and it decreases with the increase in the dimensionless temperature, modified Jakob number, and porosity.

Influence and sensitivity analysis of thermal parameters on temperature field distribution of active thermal insulated roadway in high temperature mine

To study active heat insulation roadway in high temperature mines, the typical high temperature roadway of − 965 m in Zhujidong Coal Mine of Anhui, China, is selected as prototype. The ANSYS numerical simulation method is used for sensitivity analysis of heat insulation layer with different thermal conductivity and thickness, as well as surrounding rock with different thermal conductivity and temperature on a heat-adjusting zone radius, surrounding rock temperature field and wall temperature. The results show that the heat-adjusting zone radius will entirely be in the right power index relationship to the ventilation time. Decrease in thermal conductivity and increase in thickness of insulation layer can effectively reduce the disturbance of airflow on the surrounding rock temperature, hence, beneficial for decreasing wall temperature. This favourable trend significantly decreases with ventilation time, increase in thermal conductivity and temperature of surrounding rock, heat-adjusting zone radius, surrounding rock temperature field, and wall temperature. Sensitivity analysis shows that the thermal physical properties of surrounding rock determine the temperature distribution of the roadway, hence, temperature of surrounding rock is considered as the most sensitive factor of all influencing factors. For the spray layer, thermal conductivity is more sensitive, compared to thickness. It is concluded that increase in the spray layer thickness is not as beneficial as using low thermal conductivity insulation material. Therefore, roadway preferential consideration should be given to the rocks with low temperature and thermal conductivity. The application of the insulation layer has positive significance for the thermal environment control in mine roadway, however, increase in the layer thickness without restriction has a limited effect on the thermal insulation.

Effects of isovalent doping on the thermoelectric properties of environmentally-friendly phosphide Ag6Ge10P12

The electrical and thermal transport properties of the isovalent Cu- or Sn-doped ternary phosphide Ag6Ge10P12 have been investigated. Polycrystalline ingots of Cu- and Sn-doped Ag6Ge10P12 were grown by the melting method. In Ag6−xCuxGe10P12 (x ≤ 0.3) and Ag6Ge10−ySnyP12 (y ≤ 0.25), the lattice thermal conductivity accounted for ∼95% of the total thermal conductivity. The lattice thermal conductivity of Cu- and Sn-doped Ag6Ge10P12 decreased with increasing doping concentration. Because of the decrease of the lattice thermal conductivity, the figure of merit ZT value of Ag5.85Cu0.15Ge10P12 reached ∼0.26, which was ∼60% higher than that of non-doped Ag6Ge10P12. Although the lattice thermal conductivity of Sn-doped Ag6Ge10P12 decreased, the electrical resistivity of Sn-doped Ag6Ge10P12 increased, resulting in the ZT value of Sn-doped Ag6Ge10P12 monotonically decreasing. Therefore, Cu doping of Ag6Ge10P12 is the effective way to enhance the thermoelectric performance.

Combined effects of cooling rate and salt on physical properties of yellow sandstone collected from Eastern China

Yellow sandstone is a widely used natural building stone that undergoes a number of changes when subjected to high heat sources. Therefore, this study considers the effect of high temperatures on some properties of yellow sandstone. For this purpose, yellow sandstone samples were exposed to temperatures of 25, 300, 400, 500, 550, 600, 700, and 800 °C and then rapidly cooled in water with various saline concentrations at 0 °C. The major findings are as follows: as temperature increased, the brightness L* and b* of color decreased, and the value of a* increased. Additionally, with increasing temperature, the surface roughness of sandstone increased approximately linearly, while the thermal conductivity decreased gradually with temperature and then decreased rapidly at 500 °C due to thermal damage. Moreover, thermal cracks appeared on the sandstone surface due to thermal damage. The thermal cracks in the sandstone first increased at temperatures of 400–600 °C and then decreased above 600 °C. At 600 °C, the cracks connected and formed a trap network. In addition, from analyzing the surface mesoscopic changes of the sandstone, it was found that the crystallization of salt solution on the sandstone surface also diminished the increase in roughness and the decrease in thermal conductivity to a certain extent.

Fabrication and characterization of novel excellent thermal-protection Gd2Zr2O7/ZrO2 composite ceramic fibers with different proportions of Gd2Zr2O7

Three kinds of Gd2Zr2O7/ZrO2 (GZC) composite fibers with different proportions of Gd2Zr2O7 were prepared by electrospinning method through changing the amount of Gd3+ in precursor solutions. The thermal decomposition, crystallization process, high temperature stability and heat-conducting properties of GZC fibers were fully characterized. The results showed that there were three crystalline phases, tetragonal phase ZrO2, cubic phase ZrO2 and defect fluorite phase Gd2Zr2O7 in all the GZC fibers. The content of Gd2Zr2O7 increased gradually with the increase of Gd3+ in precursor solutions which led to the gradual slowing down of grain growth rate, the decrease of thermal conductivity and the increase of high temperature stability of the obtained composite fibers. The thermal conductivities of all the GZC fiber sheets were lower than that of 7YSZ fiber sheet. The sheets of all the GZC fibers could keep the high temperature stability up to 1300 °C.

Thermal properties study of silicon nanostructures by photoacoustic techniques

The photoacoustic method with piezoelectric detection for the simultaneous evaluation of the thermophysical properties is proposed. The approach is based on the settling of an additional heat sink for redistribution of heat fluxes deposited on the sample surface. First, the approach was tested on the porous silicon with well-defined morphology and well-studied properties. Then, heat capacity and thermal conductivity of silicon nanowire arrays were investigated by recovering the experimental data through numerical simulations. The decrease in heat capacity and effective thermal conductivity of the samples upon increasing thickness and porosity of the sample was observed. Such a behavior could be caused by the increase of the structure heterogeneity. In particular, this can be related to a larger disorder (increased density of broken nanowires and larger porosity) that appears during the etching process of the thick layers.

Spark Plasma Sintering Effect on Thermoelectric Properties of Nanostructured Bismuth Telluride Synthesized by High Energy Ball Milling.

Thermoelectric properties of high energy ball milled nano structured bismuth telluride (Bi₂Te₃) have been reported. By high energy ball milling, alloyed bulk crystalline ingots crush into nanopowder and followed by spark plasma sintering (SPS), we have demonstrate high figure of merit (ZT) in bismuth telluride pellet samples. In this work systematic study carried out on three pellet samples of Bi₂Te₃, synthesized by high ball milling for the time period of 4 hours, 8 hours and 12 hours and followed by SPS at the same processing parameters. A peak value of dimensionless figure of merit of about 1.22 at the temperature of 473 K has been achieved for 8 hours ball milled pellet sample. This enhancement in ZT value is mostly due to decrease in thermal conductivity. Results of this study demonstrate that ball milling and SPS has a major effect in controlling the density of grain boundaries of Bi₂Te₃ nano particles, while the pressure exerted on the powder samples during SPS introduce stress at the boundaries of the crystallites. These disordered crystallite boundary regions exert scattering of thermal energy carriers which reduced the thermal conductivity of the materials.

Thermal conductivity of polycaprolactone/three-dimensional hexagonal boron nitride composites and multi-orientation model investigation

Three-dimensional boron nitride (3D-BN) scaffolds were fabricated by the ice-templating method, and polycaprolactone/3D-BN (PCL/3D-BN) composites were prepared by vacuum impregnation of caprolactone monomers into 3D-BN scaffolds and then polymerization via the microwave-assisted technique. The results reveal that hexagonal boron nitrides (hBNs) in the PCL/3D-BN composites present three orientation patterns, that is, parallel (z-direction) and vertical (x-direction) alignment in the direction of ice-crystal and random orientation. Moreover, the orientation of hBNs plays an essential role in improving the thermal conductivity of the composite. The maximum thermal conductivities of the PCL/3D-BN composite are 1.42 and 1.01 W m−1 K−1 in the z-direction and x-direction, which are 7.10 and 5.05 times higher than that of the pure PCL, respectively. However, the existing models cannot be used to analyze the orientation of hBNs in the composites quantitatively. In this work, based on two-phase models, a multi-orientation model was developed to explore the volume fractions of hBNs oriented in each pattern. The results indicate that the hBN ratio of random orientation (fr/f) enhances with the increase of hBN content in the PCL/3D-BN composites, and especially while increasing the hBN content from 13.41 vol% to 15.48 vol%, the value of fr/f has soared from 33.0% to 63.7%, leading to the decrease of thermal conductivities. The predictions from the multi-orientation model are in good agreement with the experimental data for the other composites, implying that the model could be used to analyze the orientation of fillers quantitatively and guide the design of thermally conductive scaffolds.

Experimental investigation of the effect of temperature on thermal conductivity of organic-rich shales

Experimental data on thermal conductivity of hydrocarbon reservoirs and surrounding formations at elevated temperatures are important for a variety of purposes: determining heat flow density; designing and optimizing thermal methods of enhanced oil recovery (EOR); basin and petroleum system modeling; exploitation of geothermal reservoirs; and design of radioactive waste disposal. However, there is an acute shortage of such data at present, particularly for unconventional reservoir rocks. We helped to fill this data gap by using a new, sophisticated technique to carry out thermal conductivity measurements on 28 oil shale samples from various unconventional formations in a temperature range of 30–300°С. The formations studied were Bazhenov and Abalak (West Siberia, Russia), Mendym, Domanic, Sargaev and Timan (Volga-Ural, Russia). Divided-bar and optical scanning methods were combined in the thermal conductivity measurements in order to account for thermal anisotropy and heterogeneity of the rocks and improve quality of the experimental data. Application of the optical scanning technique enabled us to select representative full-diameter or split-core samples from the continuous thermal core logging data and to choose an optimal location for drilling of core plugs from the core samples for measurement of thermal conductivity at elevated temperatures, with due account for anisotropy and heterogeneity inherent to oil shales. This approach enabled us to reveal and overcome systematic errors in previous measurements of oil shale samples using the divided-bar method and to develop an approach for the correction of measurement results. The measurements of thermal conductivity of our samples at elevated temperatures found a 5–27% decrease of rock thermal conductivity with temperature increase from 30 to 300°С. New methodology of the rock thermal conductivity determining at elevated temperatures is reported that includes a combination of two instruments: Thermal Conductivity and Thermal Diffusivity Scanner and DTC-300. It allowed to account for the contact resistance, non-ideal form of rock samples prepared for study (nonparallelism of rock samples surfaces), and changes in rock samples structure after heating.

Thermoelectric composite with enhanced figure of merit via interfacial doping

In order to improve the thermoelectric conversion efficiency and figure of merit, ZT, composite materials of organic or inorganic constituents often are considered. The limitation of this approach is set by the effective medium theory, which states that the ZT in a composite material cannot exceed the greatest value of any single constituent, if the constituents do not interact. Here, we describe a method that circumvents this limit, based on the introduction of interfacial doping. An electrically and thermally insulating medium is distributed into a conventional thermoelectric host material but is coated with an aliovalent acceptor that is allowed to diffuse locally into the host matrix, thereby doping it locally. The thermal conductivity decreases when the insulating material is added, but the more electrically conducting region around the insulator prevents an equally large increase in electrical resistivity. Employing this method in p-type (Bi1-xSbx)2Te3 compounds results in a maximum figure of merit zT = 1.3, an over 10% improvement compared to the host material alone. We report synthesis and measurement techniques in addition to thermoelectric transport properties. While we report on one material system, the concept is not specific to that system and may be used to provide functionality in other thermoelectric composites.