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Electronic Properties of Perovskite Oxides
Published in Gibin George, Sivasankara Rao Ede, Zhiping Luo, Fundamentals of Perovskite Oxides, 2020
Gibin George, Sivasankara Rao Ede, Zhiping Luo
The electrocaloric effect is opposite to the pyroelectric effect and is applicable in refrigeration. In the electrocaloric effect, the applied electric field along the polar axis induces changes in temperature of the crystal structure of perovskites. LiTaO3 with Tc ~ 618°C, PbTiO3 with Tc ~ 490°C, and the relaxor ferroelectrics such as Pb(Sc0.5Ti0.5)O3, Pb(Mg0.33Nb0.67)O3, and Pb(Sc0.5Sb0.5)O3 are good examples of electrocaloric and pyroelectric materials. However, the theoretical study of these two phenomena is still under debate, but few researchers have suggested the relationship between fundamental properties and the estimated change in temperature in electrocaloric perovskite as follows (Pirc et al. 2011): ΔTs=(TlnΩ)Ps2/(3ε0θC)
Foundations of Piezoelectrics
Published in Kenji Uchino, High-Power Piezoelectrics and Loss Mechanisms, 2020
For capacitor dielectrics, the peak dielectric constant around the transition (Curie) temperature is utilized, while for memory applications, the material must be ferroelectric at room temperature (refer to Figure 2.22). A large temperature dependence of the spontaneous polarization below TC is sought for pyroelectric sensors. The converse pyroelectric effect is the electrocaloric effect (electric field generates the temperature decrease), which is becoming a hot research topic in this energy-saving age.
Pyroelectric Devices
Published in Kenji Uchino, Ferroelectric Devices, 2018
The converse effect of pyroelectricity is “electrocaloric effect.” By applying the electric field on a pyrocrystal, we can expect a temperature rise/fall according to the polarity. The cooling function is of particular interest, aiming at the refrigeration application.
Measurement of the dynamic temperature response of electrocaloric effect in solid ferroelectric materials via thermoreflectance
Published in Phase Transitions, 2023
Layla Farhat, Mathieu Bardoux, Stephane Longuemart, Benoit Duponchel, Ziad Herro, Abdelhak Hadj Sahraoui
Electrocaloric (EC) effect is defined as the adiabatic temperature or isothermal entropy changes, induced by an electric field, of a dielectric material [3]. Despite being a promising alternative to VC refrigeration, this phenomenon has been largely disregarded in term of application because only humble EC responses (ΔTad= 2.6K) have been detected in bulk ceramics materials such as Pb0.99Nb0.02(Zr0.75Sn0.20Ti0.05)0.98O3 [4]. However, the discovery of a ‘giant electrocaloric effect’ in thin films by Mischenko et al. in 2006 [5] (up to ΔTad= 12 K with E = 480 KV.cm−1) renewed interest in electrocaloric materials and related cooling technologies and applications. Instead of using bulk materials, the development of thin structures is needed to obtain higher dielectric rigidity and significant electrocaloric responses.
The electrocaloric effect in BaTiO3:Eu ceramics determined by an indirect method
Published in Phase Transitions, 2021
Przemysław Gwizd, Dorota Sitko, Irena Jankowska-Sumara, Magdalena Krupska-Klimczak
The electrocaloric effect (EC) is a coupling of electrical and thermal properties which results in an adiabatic temperature change ΔT in response to an externally applied electric field ΔE [1]. The EC effect is relatively new and a challenging research topic in the field of ferroelectric materials. The EC refrigeration by ferroelectric materials is gaining recently much interest in the field of solid-state cooling applications. In recent years, the attention on EC effect has grown rapidly, due to the discovery of giant EC effects in some ferroelectric thin film materials what is promising to meet the needs in microelectronic and microelectromechanical devices for energy-efficient and environmental friendly solid-state refrigeration [2]. Thus potential expectations of EC effect in cooling micro-devices are enlivened by searching for new more efficient materials.
Electrocaloric Refrigeration using Multi-Layers of Electrocaloric Material Films and Thermal Switches
Published in Heat Transfer Engineering, 2018
Shigeki Hirasawa, Tsuyoshi Kawanami, Katsuaki Shirai
The electrocaloric effect in thin films of electrocaloric material has the potential to be used for efficient refrigerators and cooling systems for high power electronic devices. When an electrocaloric material is not exposed to an electric field, the electric (dipole) moments in the material are randomly orientated. However, when an electric field is applied, the electric moments become orientated in the direction of the applied electric field. This phenomenon leads to a rearrangement of the inner structure of the electrocaloric material. It results in a decreasing of the material's entropy and an increasing of the material's temperature [1]. This process is reversible. This phenomenon seems that the application of the electric field to the electrocaloric material generates heat energy, and decreasing the field generates cold energy. Here, cold energy means negative heat energy. Figure 1 shows a basic model of the electrocaloric refrigeration system. Thin electrocaloric material is coupled with two thermal switches. The electrocaloric material generated heat energy and cold energy alternately according to the change of the electric field. The heat energy was transferred to the hot side of the system, and the cold energy was transferred to the cold side separately. The thin electrocaloric material coupled with thermal switches works as an efficient refrigerator. It is easy to enhance the cooling