18 research outputs found
Influence of Synthesis-Related Microstructural Features on the Electrocaloric Effect for 0.9Pb(Mg1/3Nb2/3)O3−0.1PbTiO3 Ceramics
Despite having a very similar electrocaloric (EC) coefficient, i.e., the EC temperature change
divided by the applied electric field, the 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3
(PMN-10PT) ceramic
prepared by mechanochemical synthesis exhibits a much higher EC temperature change than the
columbite-derived version, i.e., 2.37 °C at 107 °C and 115 kV/cm. The difference is due to the almost
two-times-higher breakdown field of the former material, 115 kV/cm, as opposed to 57 kV/cm in
the latter. While both ceramic materials have similarly high relative densities and grain sizes (>96%,
≈5 µm) and an almost correct perovskite stoichiometry, the mechanochemical synthesis contributes
to a lower level of compositional deviation. The peak permittivity and saturated polarization are
slightly higher and the domain structure is finer in the mechanochemically derived ceramic. The
secondary phases that result from each synthesis are identified and related to different interactions
of the individual materials with the electric field: an intergranular lead-silicate-based phase in the
columbite-derived PMN-10PT and MgO inclusions in the mechanochemically derived cerami
Electrocaloric effect and high energy storage efficiency in lead-free BaCaTiSnO ceramic elaborated by sol-gel method
Structural, dielectric, ferroelectric, energy storage properties, and
electrocaloric effect were studied in lead-free ceramic
BaCaTiSnO (BCTSn) elaborated by sol-gel
method. Phase purity structure was confirmed from X-ray data using Rietveld
refinement analysis which revealed the coexistence of tetragonal (P4mm) and
orthorhombic (Amm2) symmetries at room temperature. Phase transitions were
detected by dielectric and differential scanning calorimetry results. Energy
storage properties were determined from P-E hysteresis, and the electrocaloric
properties were calculated indirectly via the Maxwell approach. The large value
of electrocaloric temperature change of T=0.807 K obtained at a
relatively small field of 30 kV cm and high energy storage efficiency
can make BCTSn ceramic a promising candidate for environmentally friendly
refrigeration and energy storage applications
Bulk relaxor ferroelectric ceramics as a working body for an electrocaloric cooling device
The electrocaloric effect (ECE), i.e., the conversion of the electric into the thermal energy has recently become of great importance for development of a new generation of cooling technologies. Here, we explore utilization of [Pb(Mg1/3Nb2/3)O3]0.9[PbTiO3]0.1 (PMN-10PT) relaxor ceramics as active elements of the heat regenerator in an ECE cooling device. We show that the PMN-10PT relaxor ceramic exhibits a relatively large electrocaloric change of temperature TEC >1 K at room temperature. The experimental testing of the cooling device demonstrates the efficient regeneration and establishment of the temperature span between the hot and the cold sides of the regenerator, exceeding several times the TEC within a single PMN-10PT ceramic plate
Influence of Synthesis-Related Microstructural Features on the Electrocaloric Effect for 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 Ceramics
Despite having a very similar electrocaloric (EC) coefficient, i.e., the EC temperature change divided by the applied electric field, the 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 (PMN-10PT) ceramic prepared by mechanochemical synthesis exhibits a much higher EC temperature change than the columbite-derived version, i.e., 2.37 °C at 107 °C and 115 kV/cm. The difference is due to the almost two-times-higher breakdown field of the former material, 115 kV/cm, as opposed to 57 kV/cm in the latter. While both ceramic materials have similarly high relative densities and grain sizes (>96%, ≈5 μm) and an almost correct perovskite stoichiometry, the mechanochemical synthesis contributes to a lower level of compositional deviation. The peak permittivity and saturated polarization are slightly higher and the domain structure is finer in the mechanochemically derived ceramic. The secondary phases that result from each synthesis are identified and related to different interactions of the individual materials with the electric field: an intergranular lead-silicate-based phase in the columbite-derived PMN-10PT and MgO inclusions in the mechanochemically derived ceramic
Enhanced near-ambient temperature energy storage and electrocaloric effect in the lead-free BaTi0.89Sn0.11O3 ceramic synthesized by sol–gel method
International audienceLead-free perovskite materials with high performance have high potential in clean energy storage applications and developments of electrocaloric devices. In this work, we report structural, dielectric, ferroelectric properties, energy storage and electrocaloric effectnear the ambient temperature in barium stannate titanate (BaTi 0.89 Sn 0.11 O 3, BTS 11) ceramic prepared by a sol-gel method. The formation of a single perovskite structure was confirmed using the X-ray diffraction analysis. An average grain size of 18.5µm was found by the mean of the SEM micrograph with a density of 5.91 g/cm 3 .The presence of the multiphase at very near ambient temperature was proved using temperature-dependent micro-Raman measurements and differential scanning calorimetry. The BTS 11 ceramic exhibits a high dielectric constant of 15460and a low dielectric loss (<0.055) with considerable temperature stability. Moreover, a high energy storage density of 122mJ/cm 3 was showed with an efficiency of 79%, and a maximum value of ECE (ΔT) of 0.86 K and finally, an electrocaloric responsivity (ΔT/ΔE) of 0.24 K.mm/kV under the external electricfield of 35 kV/cm near ambient temperature. The enhanced dielectric, ferroelectric and electrocaloric properties in BTS 11 ceramic makes it a great potential candidate for its uses in solid-state cooling technology and high-energy storage applications near ambient temperature
Twist-grain boundary phase induced by Au nanoparticles in a chiral liquid crystal host
International audienceWe report on the stabilisation of the liquid-crystalline, twist-grain boundary A (TGBA) phase in mixtures of a chiral liquid crystal and surface-functionalised spherical Au nanoparticles (NPs) of 10 nm diameter. The results, obtained by calorimetric, optical, small-angle X-ray and plasmon resonance measurements, demonstrate that a TGBA phase, which is metastable for the pure liquid crystal host, can be effectively stabilised for a 3 K range in the presence of NPs. Moreover, the role of NPs size on the TGBA stabilisation is briefly discussed
Caloric effects in liquid crystal-based soft materials
With the increased environmental awareness, the search for environmentally friendlier heat-management techniques has been the topic of many scientific studies. The caloric materials with large caloric effects, such as the electrocaloric (EC) and elastocaloric (eC) effects, have increased interest due to their potential to realize new solid-state refrigeration devices. Recently, caloric properties of soft materials, such as liquid crystals (LCs) and LC elastomers (LCEs), are getting more in the focus of caloric materials investigations, stimulated by large caloric effects observed in these materials. Here, an overview of recent direct measurements of large caloric effects in smectic LC 14CB and main-chain LCEs is given. Specifically, high-resolution thermometric measurements revealed a large EC response in 14CB LC exceeding 8 K. Such a large effect was obtained at a relatively moderate electric field of 30 kV cm−1 compared to solid EC materials. We demonstrate that such a small field can induce the isotropic to smectic A phase transition in 14CB, releasing or absorbing relatively large latent heat that enhances the EC response. Furthermore, it is demonstrated that in main-chain LCEs, the character of the nematic to isotropic transition can be tuned from the supercritical towards the first-order regime by decreasing the crosslinkers' density. Such tuning results in a sharper phase transition and latent heat that enhance the eC response, exceeding 2 K and with the eC responsivity of 24 K MPa−1, about three orders of magnitude larger than the average eC responsivity found in the best shape memory alloys. Significant caloric effects in soft LC-based materials, observed at much smaller fields than in solid caloric materials, demonstrate their ability to play an important role as new cooling elements, thermal diodes, and caloric-active regeneration material in new heat-management devices