La ( Fe , Co , Si ) 13 bulk alloys and ribbons with high temperature magnetocaloric effect

Abstract

La ( Fe 1 − x − y Co x Si y ) 13 ingots with x=0.112, 0.154, and 0.170 and y=0.021, 0.042, 0.063, and 0.085 were processed by Ar arc melting and annealing at 1050 °C for different periods of time up to 12 days. For y=0.085, the Curie temperature of the specimens, optimally annealed to develop the cubic NaZn13-type phase, increases from 88 to 149, and 169 °C for x=0.112, 0.154, and 0.170, respectively. By adding La excess, it becomes more facile to eliminate the secondary bcc (Fe,Co) phase by annealing at 1050 °C, while the structure contains more La(Fe,Co)Si nonmagnetic precipitates. With the decrease in the Si content, it becomes harder to form the La(Fe,Co,Si)13 phase and the morphology of secondary phases are more complex with La(Fe,Co)Si precipitates in form of stripes within La3Co inclusions. Selected La(Fe0.745Co0.17Si0.085)13 ribbons prepared by melt spinning and annealed for a shorter time than ingots maintain residual bcc (Fe,Co) phase. The largest peak in magnetic entropy change occurred at 161 °C with 3.5 J/kg K for La(Fe0.767Co0.170Si0.063)13 specimens with the optimal 1:13 structure, under a field variation of 17 kOe. The peak of magnetic entropy change in annealed ribbons was smaller and broader than in the annealed ingot counterparts.

Corrosion behavior of magnetic refrigeration material La–Fe–Co–Si in distilled water

“…During the corrosion process, ␣-Fe phase works as cathode, while matrix phase works as anode to be corroded. Corrosion occurs 11.7 Si 1.3 compound were analyzed by X-ray photoelectron spectroscopy (XPS) analysis. Fig.…”

“…Recent investigations reveal that partial substitution of Fe by Co in La(Fe x Si 1−x ) 13 compounds leads to increase in Curie temperature and the weakening of the first-order magnetic transition. Although the substitution of Co produces a decrease in magnetic entropy change, a small hysteresis loss and a large RCP can be realized [5][6][7][8][9][10][11]. Besides the reduction of hysteresis loss, preparation time for La(Fe,Co,Si) 13 compounds is shortened through new methods [12,13].…”

High-temperature phase transition and magnetic property of LaFe11.6Si1.4 compound

“…The result shows that these alkaline solutions is necessary to ensure that a protection film can be formed on the surface of metal and have a good inhibition effect on the LaFe 13−x Si x compounds in a certain. Although the La(Fe 1−x Co x ) 11.9 Si 1.1 compounds with 0.055 < x < 0.122 produced by powder metallurgy, La(Fe0 .745 Co 0.17 Si 0.085 ) 13 ribbons prepared by melt spinning and annealed for a shorter time, and the LaFe 13-x Si x (x = 1.4, 1.6, 1.8, 2.0) series synthesized by high energy ball-milling have been investigated [20][21][22], most of LaFe 13−x Si x compounds with NaZn13-type structure (hereinafter 1:13 phase) are prepared by long time annealing for several weeks at between 1173 K and 1373 K, and then quenching rapidly in medium. In the LaFe 13−x Si x compounds, 1:13 phase is hard to be obtained directly from common solidification process due to the intrinsic incompleteness of a peritectic reaction: ␥-Fe + L → La(Fe,Si)13( 1a ), which often results in the mixed microstructure of ␣-Fe + La(Fe,Si)13( 1a ) + LaFeSi( 4 ) [23].…”

Windows open for highly tunable magnetostructural phase transitions

“…4 Tunable magnetocaloric effects (MCEs) over a wide temperature range may provide expended chance for different applications. Especially, high-temperature MCEs, which may be used at elevated temperatures especially above water boiling point (373 K) for magnetic heat pumps, 5 electric power generation, 6,7 or magnetic cooling 8,9 are seldom reported. In recent years, hexagonal MM ′ X (M, M ′ = transition metals, X = carbon or boron group elements) compounds have been extensively investigated due to the tunable MSTs and associated giant MCEs.…”