Abstract:Caloric effects of solids can provide us with innovative refrigeration systems more efficient and environment-friendly than the widely-used conventional vapor-compression cooling systems. Exploring novel caloric materials is challenging but critically important in developing future technologies. Here we discovered that the quadruple perovskite structure ferrimagnet BiCu3Cr4O12 shows large multiple caloric effects at the first-order charge transition occurring around 190 K. Large latent heat and the correspondi… Show more
“…3a), which is synthesized by a solid–state reaction under high-pressure (9 GPa) and high-temperature (1000 °C) conditions, contains the unusually high-valence Cr 3.75+ ions at the B site. 31,49 In contrast to the intersite charge transfer transition in NdCu 3 Fe 4 O 12 , the compound shows charge disproportionation transition of Cr 3.75+ to Cr 3+ and Cr 4+ (4Cr 3.75+ → Cu 3+ + 3Cr 4+ ) at 190 K to relieve its electronic instability. The high-temperature Bi 3+ Cu 3 2+ Cr 4 3.75+ O 12 phase thus changes to the low-temperature Bi 3+ Cu 3 2+ Cr 3+ Cr 3 4+ O 12 phase, and the first-order-type transitions in electronic transport, magnetic, and lattice properties are observed, as respectively shown in Fig.…”
Section: Giant Barocaloric and Magnetocaloric Effects In Bicu3cr4o12mentioning
confidence: 98%
“…Interesting examples were recently found in oxide materials containing unusually high-valencestate transition-metal ions. 30,31 A phase transition was primarily induced by relieving the electronic instability of the unusually high valence state of the constituent transition-metal ion, and drastic changes in electronic, magnetic, and structural properties ocurred concomitantly. Significant latent heat associated with phase transition was observed, and more importantly, the observed large latent heat was accessed by applying external fields.…”
Caloric effects of solids can provide us with highly efficient and environmentally friendly energy systems. Exploring novel caloric materials is challenging but critically important in developing future technologies. Typical solid...
“…3a), which is synthesized by a solid–state reaction under high-pressure (9 GPa) and high-temperature (1000 °C) conditions, contains the unusually high-valence Cr 3.75+ ions at the B site. 31,49 In contrast to the intersite charge transfer transition in NdCu 3 Fe 4 O 12 , the compound shows charge disproportionation transition of Cr 3.75+ to Cr 3+ and Cr 4+ (4Cr 3.75+ → Cu 3+ + 3Cr 4+ ) at 190 K to relieve its electronic instability. The high-temperature Bi 3+ Cu 3 2+ Cr 4 3.75+ O 12 phase thus changes to the low-temperature Bi 3+ Cu 3 2+ Cr 3+ Cr 3 4+ O 12 phase, and the first-order-type transitions in electronic transport, magnetic, and lattice properties are observed, as respectively shown in Fig.…”
Section: Giant Barocaloric and Magnetocaloric Effects In Bicu3cr4o12mentioning
confidence: 98%
“…Interesting examples were recently found in oxide materials containing unusually high-valencestate transition-metal ions. 30,31 A phase transition was primarily induced by relieving the electronic instability of the unusually high valence state of the constituent transition-metal ion, and drastic changes in electronic, magnetic, and structural properties ocurred concomitantly. Significant latent heat associated with phase transition was observed, and more importantly, the observed large latent heat was accessed by applying external fields.…”
Caloric effects of solids can provide us with highly efficient and environmentally friendly energy systems. Exploring novel caloric materials is challenging but critically important in developing future technologies. Typical solid...
“…The behavior is completely different from those observed in normal second-order magnetic transitions induced by usual magnetic interactions between the constituent spins. 33),50), 51) The projected magnetic transition temperature extrapolated from the fitting with a Brillouin function to the temperature dependent refined magnetic moment is 643 K, which is much higher than the actual magnetic transition temperature induced by the intermetallic-chargetransfer-transition occurring near room temperature. Given a simple orderdisorder magnetic transition model of the S = 5/2 (Fe 3+ ) spins, the magnetic entropy change is expected to be RIn(2S + 1) = 79 J K ¹1 kg ¹1 .…”
Oxides containing unusually high-valence transition-metal ions often exhibit charge transitions to relieve the electronic instabilities. A-site-ordered quadruple perovskites LnCu 3 Fe 4 O 12 with the unusually high-valence Fe 3.75+ , which are synthesized under high-pressure conditions, show intermetallic-charge-transfer transitions. In this review article, novel thermo-related functional properties induced by the charge transitions in LnCu 3 Fe 4 O 12 are highlighted. A large negative-thermal-expansion behavior was observed at the intermetallic-charge-transfer transition temperature. The negative-thermal-expansion property is primarily caused by the size effect of constituent ions by the charge changes. The property is useful for developing materials to compensate the normal positive thermal expansion. Significant latent heat was also found to be provided by the intermetallic-charge-transfer transition in LnCu 3 Fe 4 O 12 . The large latent heat is considered to be related with unusual first-order magnetic entropy change induced by the charge transition. The large entropy change can be utilized for thermal control through a caloric effect, which can make effective energy systems for thermal energy storage and refrigeration.
“…A similar large entropy change induced by the charge-disproportionation transition was also found in BiCu 3 Cr 4 O 12 , where a latent heat of 5.23 kJ kg −1 can be utilized by applying both magnetic elds and pressure. 15 In the caloric effects of NdCu 3 Fe 4 O 12 and BiCu 3 Cr 4 -O 12 , the charge transitions induced unusual rst-order magnetic transitions, and large changes in the magnetic entropies were abruptly yielded at the charge-transition temperatures. 16 These results aroused interest in exploring novel transitionmetal oxides showing charge-transfer transitions for solid caloric materials.…”
Thermal properties and phase transition behaviors of possible caloric materials Bi0.95Ln0.05NiO3 (Ln = La, Nd, Sm, Eu, Gd, Dy), which show intersite charge transfer between Bi and Ni ions, were investigated. Although...
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