Effect of sintering temperature on properties of Prsub(0.75)Smsub(0.25)Cosub(5) permanent magnets

To explain the character of the dependence of the coercive force sub(1)Hsub(c) of magnets from compounds PrCo5 and SmCo5 on the temperature of sintering Tsub(st), a study was made of the effect of Tsub(st) upon the properties and the structure of magnets from the compound Prsub(0.75)Smsub(0.25)Cosub(5). It was found that the increase of Tsub(st) from 1117 to 1140 deg C involves a sharp rise in the coercive force sub(1)Hsub(c) of magnets. In subsequent rise of Tsub(st), the coercive force falls off negligibly, although the size of grains of the sintered magnet increases substantially. The observed variations of the properties are related to the appearance, at the high sintering temperature, of a liquid phase which forms a boundary layer during solidification and so prevent the ''cooperative'' magnetization of grains