Abstract
The lanthanum deficiency manganites La0.8-x□xCa0.2MnO3 (x = 0, 0.1 and 0.2), where □ is a lanthanum vacancy, were prepared using the classic ceramic methods with different thermal treatments (1373 K and 973 K). The structural, magnetic, and magnetocaloric properties of these compounds were studied as a function of annealing temperature. It was noted that the annealing temperature did not affect the crystal structure of our samples (orthorhombic structure with Pnma space group). Nevertheless, a change in the variation of the unit cell volume V, the average bond length dMn–O, and the average bond angles θMn–O–Mn were observed. Magnetization versus temperature study has shown that all samples exhibited a magnetic transition from ferromagnetic (FM) to paramagnetic (PM) phase with increasing temperature. However, it can be clearly seen that the annealing at 973 K induced an increase of the magnetization. In addition, the magnetocaloric effect (MCE) as well as the relative cooling power (RCP) were estimated. As an important result, the values of MCE and RCP in our Lanthanum-deficiency manganites are reported to be near to those found in gadolinium, considered as magnetocaloric reference material.
Highlights
Magnetic refrigeration technique is one of the most promising techniques in cooling technology due to the efficient and environmentally safe cooling applications, which have encouraged the experimental and the theoretical studies in this direction
That is why the parameter necessary for selecting magnetic refrigerants is based on the cooling power per unit volume and the relative cooling power (RCP)
La0.8−x xCa0.2MnO3 (x = 0; 0.1 and x = 0.2) compounds annealed at 973 K are
Summary
Magnetic refrigeration technique is one of the most promising techniques in cooling technology due to the efficient and environmentally safe cooling applications, which have encouraged the experimental and the theoretical studies in this direction. This parameter is a measure of the amount of heat transfer between the cold and hot sinks in a refrigeration cycle, estimating the range of operating temperature To ameliorate this parameter, wide-ranging research has been conducted, the development of many synthetic methods of producing these materials, such as solid state reaction, sol–gel, coprecipitation, high-energy ball-milling, polyol process, spark plasma sintering, etc. All these research works have confirmed that this parameter, wide-ranging research has been conducted, the development of many synthetic methods of producing these materials, such asby solid reaction, the electronic, magnetic, and transport properties are significantly affected thestate grain size. Temperature magnetic magnetocaloric properties of La0.8−x x Ca0.2 MnO3 It is in this context that the present research work lies to study the effect of the sintering.
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