Specific heat and thermal conductivity of BaTiO3 polycrystalline thin films

Davitadze, S. T.; Kravchun, S. N.; Strukov, B. A.; Goltzman, B. M.; Lemanov, V. V.; Shulman, S. G.

doi:10.1063/1.1454212

Cited by 32 publications

(25 citation statements)

References 9 publications

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“…[12][13][14] We show a consistent trend in the thermal conductivity of the BaTiO 3 films as a function of grain size, similar to what we have previously observed in nanograined SrTiO 3 films; we note that this consistency in the effects of nano-structuring on the thermal conductivity of BaTiO 3 does not appear among previous works. 15,16 Our data agree well with predictions for the grain boundary scattering effects on the thermal conductivity of BaTiO 3 using a simplified semi-classical model. The temperature trends suggest that phonon-boundary scattering events, both at grains and the film/substrate boundary, are the dominant source of thermal resistance.…”

supporting

confidence: 76%

“…The current literature values regarding the effects of nano-structuring on BaTiO 3 range from studies with 150 nm grains exhibiting near-bulk thermal conductivities of 5.1 W m À1 K À1 (Ref. 16) to studies with grain sizes of 100 nm exhibiting thermal conductivities of 10.22 W m À1 K À1 , which is over twice that reported for the bulk thermal conductivity of BaTiO 3 . 18 See supplementary material for further discussion of these current discrepancies in the literature.…”

mentioning

confidence: 96%

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Spectral phonon scattering effects on the thermal conductivity of nano-grained barium titanate

Donovan

Foley

Ihlefeld

et al. 2014

Applied Physics Letters

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We study the effect of grain size on thermal conductivity of thin film barium titanate over temperatures ranging from 200 to 500 K. We show that the thermal conductivity of Barium Titanate (BaTiO3) decreases with decreasing grain size as a result of increased phonon scattering from grain boundaries. We analyze our results with a model for thermal conductivity that incorporates a spectrum of mean free paths in BaTiO3. In contrast to the common gray mean free path assumption, our findings suggest that the thermal conductivity of complex oxide perovskites is driven by a spectrum of phonons with varying mean free paths.

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supporting

confidence: 76%

mentioning

confidence: 96%

Spectral phonon scattering effects on the thermal conductivity of nano-grained barium titanate

Donovan

Foley

Ihlefeld

et al. 2014

Applied Physics Letters

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“…I show a consistent trend in the thermal conductivity of the BaTiO 3 films as a function of grain size, similar to what Foley et al [94] has previously observed in nanograined SrTiO 3 films; this consistency in the effects of nano-structuring on the thermal conductivity of BaTiO 3 does not appear among previous works [268,269]. My data agree well with predictions for the grain boundary scattering effects on the thermal conductivity of Therefore, this work demonstrates the spectral nature of the thermal mean free paths of phonons in BaTiO 3 with typical length scales well beyond that predicted by a gray approximation using kinetic theory [270].…”

Section: Phonon Interactions With Grain Boundaries In Batiosupporting

confidence: 73%

“…Current literature values [269] regarding the effects of nano-structuring Jezowski et al [268] also found that for the ceramics with 30 nm grains the thermal conductivity was around 1.7 Wm −1 K −1 , which is lower than bulk and to be expected with nano-structuring.…”

Section: Literature Thermal Conductivity Of Batiomentioning

confidence: 99%

Understanding Phonon Interactions with Defects in Functional Oxide Materials

Donovan¹

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Understanding of nano-scale thermal transport has enabled significant advances in a wide variety of fields including microelectronics, alternative energy, optics, and many more [1][2][3][4]. Utilized in many of these applications are a class of materials known as functional oxides. These materials are oxygen compounds with specific functional properties of interest (e.g., dielectrics [5][6][7][8], piezoelectrics [9][10][11], photovoltaics [12][13][14], thermoelectrics [15][16][17][18][19]). Often it is the defects in these materials that enable functionality and, depending on the processing and operating conditions, the concentration and types of defects that are present in these materials can vary widely [20]. In this dissertation, I aim to identify the role that defects play in functional oxide materials with respect to thermal transport.The major thermal carriers in most functional oxide crystals are collective lattice vibrations, or phonons [21]. Phonon-dominated thermal conductivity is dictated by the scattering of these thermal carriers with a variety of other components or the material system, including defects in the crystal [22,23]. I concentrate on three types of defects that are common in functional oxides: boundaries, extrinsic point defects, and intrinsic point defects.Boundaries such as film boundaries and grain boundaries with nano-scale dimensions can be detrimental to the thermal conductivity of a material. As the length of the uninterrupted crystal reduces to the phonon mean free paths in the crystal, phonons will scatter readily off of nano-scale boundaries and will not be able to propagate as they would in a bulk environment. This becomes particularly relevant in technologies such as the microelectronics industry, where device size scales are well below common phonon mean free paths in the constituent materials. To study this, I turn to one of the more common functional oxides used in the microelectronics industry, BaTiO 3 .I study the effects of nano-scale grains on thin films of BaTiO 3 grown via chemical solution deposition. The films studied are 150 nm and range in grain size from 36 nm -63 nm. I show that the thermal conductivity of these nano-grained films scales with the grain size and film thickness and demonstrate agreement of this trend with analytical models. This result demonstrates that despite a complex crystal structure, there is a mean free path spectrum of phonons in BaTiO 3 that significantly exceeds the dimensions of the grains and film (contrary to the common "gray" mean 2 free path assumption seen in literature).To address the role of extrinsic point defects, or dopants, on the thermal conductivity of functional oxides, I study the effects of dysprosium doping in thin films of cadmium oxide deposited by molecular beam epitaxy. In this experiment, the addition of Dy dopants in CdO actually increases the thermal conductivity initially, owing to a reduction in the equilibrium concentration of oxygen vacancies (a type of defect that is intrinsic to all oxides). The de...

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“…Such a small efficiency stems from the fact that the energy required to increase the temperature of the lattice is nearly always much larger than the energy required to destroy part of the polarization, thus releasing electric charges 2 . In our case of study the pyroelectric-engine efficiency is evaluated as where 19 . The temperature span is taken large enough so that the pumped transition heat as to have a constant temperature in isothermal processes, is neglegible 2,6,8 .…”

mentioning

confidence: 99%

Efficient thermal energy harvesting using nanoscale magnetoelectric heterostructures

Etesami

Berakdar

2016

Applied Physics Letters

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Thermomechanical cycles with a ferroelectric working substance convert heat to electrical energy. As shown here, magnetoelectrically coupled ferroelectric/ferromangtic composites (also called multiferroics) add new functionalities and allow for an efficient thermal energy harvesting at room temperature by exploiting the pyroelectric effect. By virtue of the magnetoelectric coupling, external electric and magnetic fields can steer the operation of these heat engines. Our theoretical predictions are based on a combination of LandauKhalatnikov-Tani approach (with a Ginzburg-Landau-Devonshire potential) to simulate the ferroelectric dynamics coupled to the magnetic dynamics. The latter is treated via the electric-polarization-dependent Landau-Lifshitz-Gilbert equation. Performing an adapted Olsen cycle we show that a multiferroic working substance is potentially much more superior to sole ferroelectrics, as far as thermal energy harvesting using pyroelectric effect is concerned. Our proposal holds promise not only for low-energy consuming devices but also for cooling technology.It's been known for more than half a century that the temperature-dependency of hysteresis loops in ferroelectrics(FE) can be exploited to convert heat into electrical energy, known as pyroelectric effect 1-9 . The converse pyroelectric effect is also an established fact called the electrocaloric effect [10][11][12][13] , which as expected is used in cooling technology. In the quest for environmentally friendly pyroelectric devices that have low energy consumption, multiple functionalities, and being amenable to integration in nano circuits, we explore in this work the potential of engineered nanoscale multiferroic structures for harvesting waste heat. In particular, we focus on two-phase multiferroic layered structures consisting of a thin layer of the prototypical ferroelectric BaTiO 3 (BTO) deposited on Co. At room temperatures a strong magnetoelectric (ME) coupling between BTO and Co 14 was observed. This means that the ferromagnetic Co or BTO respond to an electric (E) or magnetic field (H), respectively opening thus new opportunities for controlling and the possibility for enhancing the device operation. Particularly important are room temperature devices in which case BTO is in the tetragonal phase 15-17 (see also the supplementary material 18 , Fig. S2). To exploit the pyroelectric effect to generate electricity, different thermal-electrical cycles were proposed. We perform the Olsen cycle 6,8 : The core idea of the pyroelectric engine is the temperature-dependency of the hysteresis loop (or in other words polarization P ) since it provides us with the opportunity to create clockwise cycles in E − P space (see the supplementary material 18 , Fig. S1). The area enclosed by the clockwise cycles determines the amount of harvested thermal energy asViewing the ferroelectric (FE) to be consisting of building blocks (cells or domains) each with a volume a 3 (see Fig. 1) then the FE volume is V F E = n a 3 .V F E P = n a 3 P n is the total ch...

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Specific heat and thermal conductivity of BaTiO3 polycrystalline thin films

Cited by 32 publications

References 9 publications

Spectral phonon scattering effects on the thermal conductivity of nano-grained barium titanate

Spectral phonon scattering effects on the thermal conductivity of nano-grained barium titanate

Understanding Phonon Interactions with Defects in Functional Oxide Materials

Efficient thermal energy harvesting using nanoscale magnetoelectric heterostructures

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