Measurement Techniques for Thermal Conductivity and Interfacial Thermal Conductance of Bulk and Thin Film Materials

Zhao, Dongliang; Qian, Xin; Gu, Xiaokun; Jajja, Saad A.; Yang, Ronggui

doi:10.1115/1.4034605

Cited by 401 publications

(249 citation statements)

References 127 publications

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“…Therefore, evaluation of thermal conductivity is very fundamental and important, but the measurement could sometimes be a great challenge. [17] It is well known that the heat capacity (C P ) can be significantly increased during phase transition because the extra energy is required to transit a low temperature structure to a high temperature structure in materials (see Figure 1a). [16] The energy exchange during phase transitions gives rise to a few fundamental questions on thermal conductivity measurement.…”

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Thermal Conductivity during Phase Transitions

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high thermal conductivity are widely used in heat dissipating applications, [3][4][5][6] while the materials with low thermal conductivity [7][8][9][10] are used as thermal insulation. In particular, thermal conductivity is one of the key parameters in thermoelectric materials and also plays an important role in other energy materials such as solar cells and battery materials. Therefore, evaluation of thermal conductivity is very fundamental and important, but the measurement could sometimes be a great challenge. The understanding and measurement of thermal conductivity are especially questionable for materials with phase transitions while these materials exist extensively and have been exploited for different fields including thermoelectrics, [11][12][13][14] solid state memory, [15] and switches. [16] The energy exchange during phase transitions gives rise to a few fundamental questions on thermal conductivity measurement. Transient measurement methods such as laser flash method (LFA) are commonly used to measure thermal diffusivity λ and the thermal conductivity κ is calculated using the equation of κ = C P × d × λ (d is the density and C P is the heat capacity), due to the significant advantages of transient methods over the steady-state measurements. [17] It is well known that the heat capacity (C P ) can be significantly increased during phase transition because the extra energy is required to transit a low temperature structure to a high temperature structure in materials (see Figure 1a). Recent study also shows that the thermal diffusivity (λ) can be lowered in some phase transition materials such as Cu 2 Se, Cu 2 S, and Ag 2 S, but is almost unaffected by phase transition in Ag 2 Se (see Figure 1b). The understanding on thermal conductivity during phase transitions is not established yet. This leads to the thermal conductivity calculated with different heat capacity values highly deviated, although the measured heat capacity and thermal diffusivity are quite close or similar. For example, a dramatic decrease in κ in Cu 2 Se second-order phase transition is reported by Liu et al. [11] when using the Dulong-Petit value for heat capacity, while an increased κ is reported by Brown et al. [18] after adding the contribution of phase transition to heat capacity (Figure 1c). Such different κ values change the thermoelectric figure of merit (zT) from a moderate value of 0.6 to an extremely high value of 2.3 (which can be considered as a breakthrough in thermoelectrics) in Cu 2 Se during its second-order phase transition. More confusingly, the heat capacity ( Figure 1a) and electrical transport measurements ( Figure S6, Supporting Information) clearly show that Cu 2 S and Ag 2 S have first-order phase transitions with Thermal conductivity is a very basic property that determines how fast a material conducts heat, which plays an important and sometimes a dominant role in many fields. However, because materials with phase transitions have been widely used recently, understanding and measuring temperature-dependent t...

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Thermal Conductivity during Phase Transitions

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“…The sample tested needs to be relatively large (in the cm scale) and needs to be prepared in a standard circular or rectangular shape. Also, the testing time is usually long, in the range of a few hours [32].…”

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Characterisation of Ground Thermal and Thermo-Mechanical Behaviour for Shallow Geothermal Energy Applications

et al. 2017

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Increasing use of the ground as a thermal reservoir is expected in the near future. Shallow geothermal energy (SGE) systems have proved to be sustainable alternative solutions for buildings and infrastructure conditioning in many areas across the globe in the past decades. Recently novel solutions, including energy geostructures, where SGE systems are coupled with foundation heat exchangers, have also been developed. The performance of these systems is dependent on a series of factors, among which the thermal properties of the soil play a major role. The purpose of this paper is to present, in an integrated manner, the main methods and procedures to assess ground thermal properties for SGE systems and to carry out a critical review of the methods. In particular, laboratory testing through either steady-state or transient methods are discussed and a new synthesis comparing results for different techniques is presented. In situ testing including all variations of the thermal response test is presented in detail, including a first comparison between new and traditional approaches. The issue of different scales between laboratory and in situ measurements is then analysed in detail. Finally, the thermo-hydro-mechanical behaviour of soil is introduced and discussed. These coupled processes are important for confirming the structural integrity of energy geostructures, but routine methods for parameter determination are still lacking.

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“…Two common techniques are 3ω method and thermoreflectance. 64 Thermoreflectance is used in this thesis and utilize the change in reflectance with temperature. A measurement setup is shown in figure 6.3, where a pumping laser heats up a spot on the specimen and a probing laser measures how the refractive index changes as the specimen cools down.…”

Section: Thermal Conductivity Measurementmentioning

confidence: 99%

Growth and thermoelectric properties of CaMnO3-based thin films

Ekström¹

2018

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The field of thermoelectrics started in early 19 th century. Since the discovery of the Seebeck effect and the Peltier effect, thermoelectric modules have found their way into, mostly, niche applications such as radioisotope thermoelectric generators on space missions. Thermoelectric modules can also be used for cooling, utilizing the Peltier effect.Thermoelectrics are promising materials due to the operation nature of the modules. That is, they have no moving parts, no exhaust, long lifetime without maintenance, features that make them attractive for many applications. Despite these promising properties, thermoelectric modules are mostly used in niche applications. The main reason for this is conventional modules with the highest efficiency are commonly made of expensive and/or rare elements which prevents mass production.To tackle this problem, new materials are investigated to find a module that can be made widely available. Oxides are one possibility, where an added benefit is that they are chemically stable even at elevated temperature. The perovskite CaMnO3 is one of the more promising oxides, with elements that are abundant on earth and cheap. The material does suffer from low electrical conductivity which results in a low electrical conductivity and efficiency. A substantial effort has been put in to increase the efficiency of CaMnO3, but it still needs improvement.In my thesis, I have investigated the CaMnO3 system. CaMnO3 was synthesized using co-reactive RF-magnetron sputtering and post annealing. The synthesis method is already known but has not been used for deposition of perovskites. I have also demonstrated that this synthesis method can be used to dope CaMnO3 with niobium at appropriate levels for enhancing the efficiency. During the course of research underlying this thesis, I was enrolled in Agora Materiae, a multidisciplinary doctoral program at Linköping University, Sweden. VI VII Populärvetenskaplig SammanfattningMed dagens utveckling av teknologi ökar behovet av elektricitet. Många teknologier är små saker som behöver egna energikällor t.ex. sensorer. Dessa kan sitta på människokroppen, i datorer, i olika industrier och andra miljöer. Det de har gemensamt är att alla behöver en tillförlitlig kraftkälla som i många fall behöver fungera utan något underhåll samt ta lite plats.Ett annat problem i samhället är det stora slöseriet med energi i form av spillvärme, det vill säga en oönskad restprodukt, från i stort sett alla processer. Denna värme är i många fall helt outnyttjad och om man kunde ta till vara på denna värme skulle effektiviteten av många processer kunna ökas.Jag har undersökt material som skulle kunna lösa dessa problem, nämligen termoelektriska material. Sådana material har förmågan att omvandla värme till elektricitet och det som driver denna förmåga är Seebeck-effekten, uppkallad efter Thomas Seebeck som upptäckte den i början av 1820-talet. De fungerar genom att materialet har en varm och en kall sida. På den varma sidan rör sig elektronerna snabbare än på den kalla sid...

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Measurement Techniques for Thermal Conductivity and Interfacial Thermal Conductance of Bulk and Thin Film Materials

Cited by 401 publications

References 127 publications

Thermal Conductivity during Phase Transitions

Thermal Conductivity during Phase Transitions

Characterisation of Ground Thermal and Thermo-Mechanical Behaviour for Shallow Geothermal Energy Applications

Growth and thermoelectric properties of CaMnO3-based thin films

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