Of Co. <sub> 2 </ Sub> Compounds Magnetocaloric Effect Of Gd-tb-co Ternary Phase Diagram And (gd The <sub> 1-x </ Sub> Tb <sub> X </ Sub>)

This paper includes two parts of study work: one is about the isothermal section of the phase diagram of the Gd-Tb-Co ternary system at 500 °C,the other one is about magnetocaloric effects in (Gd_1-xTb_x)Co₂.The isothermal section of the phase diagram of the Gd-Tb-Co ternary system at 500°C was investigated by X-ray powder diffraction, differential thermal analysis and metallographic analysis techniques. In this isothermal section, there are nine single-phase regions, eight two-phase regions and none three-phase region. No ternary compound was found. The compounds Gd₂Co₁₇ and Tb₂Co₁₇, Gd₂Co₇ and Tb₂Co₇, GdCo₃ and TbCo₃, GdCo₂ and TbCo₂, Gd₄Co₃ and Tb₄Co-3, Gd₁₂Co₇ and Tb₁₂Co₇, Gd₃Co and TD₃Co, Gd and Tb form a continuous series of solid solutions. In addition, we experimentally determined the vertical section of pseudobinary system of Gd_1-xTb_xCo₂(x from 0 to 1) series alloys.About magnetocaloric effects in (Gd_1-xTb_x)Co2: The structures and magnetocaloric effects of (Gd_1-xTb_x)Co₂ (x=0, 0.2, 0.4, 0.5, 0.6, 0.7, 0.8, and 1) pseudobinary compounds were investigated by X-ray powder diffraction and magnetic properties measurement. The results show that the Tc of the alloy is near room temperature when X=0.6. The magnetic entropy changes of the compounds increase from 1.7 J/kgK to 3.6 J/kgK with increasing the content of Tb under an applied field up to 2T. All the compounds exhibit second order magnetic change.