2007 年 71 巻 10 号 p. 850-852
After the development of Nd-Fe-B magnets, rare earth magnets are now essential components in many fields of technology. In the industry of Nd-Fe-B sintered magnets in Japan, the total amount of production has increased about 20% from year to year. Especially, the use for the motors in hybrid cars is considered as one of the most attractive applications in Japan. Because of usage environment of hybrid cars, in which temperature increases up to 200°C, high coerecivity and high heat resistance are required to Nd-Fe-B sintered magnets. It is well known that Dy addition is effective for increase in coerecivity. However, the natural abundance of Dy is quite smaller than that of Nd and the resource locality is limited in the world, which leads to the escalating price of Dy. Therefore, the decrease of Dy content in Nd-Fe-B magnets is strongly demanded. This article reviews the status and trend in the research for saving Dy in Nd-Fe-B sintered magnets.