Influence of post-annealing, defect chemistry and high pressure on the magnetocaloric effect of non-stoichiometric La0.8-xK0.2Mn1+xO3 compounds. Issue 17 (1st September 2021)

• Record Type: Journal Article
• Authors: Wei, Ziyu; Liedienov, N.A.; Li, Quanjun; Pashchenko, A.V.; Xu, Wei; Turchenko, V.A.; Yuan, Mengyun; Fesych, I.V.; Levchenko, G.G.
• Is Part Of: Ceramics international. Volume 47:Issue 17(2021)
• Page Start: 24553
• Page End: 24563
• Publication Date: 2021-09-01
• Subjects: Manganite -- Post-annealing -- Defect chemistry -- Curie temperature -- Magnetocaloric effect -- High pressure; Ceramics -- Periodicals; Céramique industrielle -- Périodiques; Ceramics; Periodicals; Electronic journals; 666
• DOI: 10.1016/j.ceramint.2021.05.174
• Languages: English
• ISSNs: 0272-8842

Abstract

Abstract: In view of the need to limit harmful emissions of chlorofluorocarbons into the atmosphere and sharp increase in life support areas that require cooling, the search for new magnetocaloric materials is very urgent at the present time. In this work, we suggest the ways for improving the magnetocaloric properties of the promising La0.8- x K0.2 Mn1+ x O3 (0 ≤ x ≤ 0.2) perovskites and compare the functional properties of nanocrystalline samples of about 40 nm with polycrystalline samples of about 1 μ m. The structure, morphology, magnetic properties and magnetocaloric effect of these compounds were studied as a function of manganese doping level. The main crystalline phase of all samples is a rhombohedral R 3 ‾ c perovskite structure. The maximum doping level of excess manganese for preserving single-phase structure of the nanocrystalline La0.8- x K0.2 Mn1+ x O3 compounds is x = 0.10. As x increases the Curie temperature T C is increased slightly. The best composition with the highest entropy change Δ S M max = −3.629 J/(kg⋅K) under 3 T at T C = 332 K is the La0.8- x K0.2 Mn1+ x O3 with x = 0.05. On the other hand, the La0.8- x K0.2 Mn1+ x O3 polycrystalline manganite with x = 0.10 exhibits the highest Δ S M max = −4.176 J/(kg⋅K) under 3 T at T C = 274 K. Additionally, the effect of hydrostatic pressure P up to 1.4 GPa has been investigated for the La0.7 K0.2 Mn1.1 O3 polycrystalline sample that leads to increasing T C to 287 K and reducing Δ S M max to −3.145 J/(kg⋅K) under 3 T. The obtained results demonstrate the ways for controlling magnetocaloric properties of the La0.8- x K0.2 Mn1+ x O3 compounds under internal and external conditions.