PHASE STRUCTURE AND MAGNETOCALORIC EFFECT OF SHORT HIGH TEMPERATURE ANNEALED LaFe_(13-x)Si_x SYSTEM COMPOUNDS

摘要

The magnetocaloric properties of LaFe_(13-x)Si_x compounds were widely investigated and proved to be a very attractive candidate for magnetic refrigerants. However, the preparation of homogenous single cubic NaZn_(13)-type structure samples by common solidification process is rather difficult due to the intrinsic incompleteness of a peritectic reaction. In the present study, phase formation with NaZn_(13)-type structure of LaFe_(13-x)Si_x system compounds (x=1.1, 1.2, 1.3, 1.4, 1.5) by high-temperature annealing at 1573K for 1 hour have been systematically investigated. The magnetocaloric property of LaFe_(13-x)Si_x (x=1.4) was selected to study. Results of phase structure analysis by X-ray diffraction (XRD) and scanning electron microscopy (SEM) demonstrate that the NaZn_(13)-type structure was formed in these compounds after short high temperature annealing. Both temperature and magnetic field dependence of magnetization was measured by a superconducting quantum interference device (SQUID) magnetometer for LaFe_(13-x)Si_x (x=1.4). For LaFe_(11.6)Si_(1.4) magnetic entropy changes of 17.56 J/kgK and 13.2 J/kgK were obtained at T_c=190K under the magnetic field changes of 0～5T and 0～2T, respectively.