E. N. Kablov

Role of interphase boron diffusion in the formation of the magnetic properties of sintered (Pr, Dy)-(Fe, Co)-B materials

Sintered (Pr, Dy)-(Fe1 − yCoy)-B materials (y = 0.15–0.5 at %) have been studied. It is found that, with increasing cobalt content, the coercive force of the sintered materials decreases down to zero at y ∼ 0.5. The volume contents of all phases present in the compositions with y = 0.2–0.9 are determined. The interphase boron diffusion is shown to play a key role in the formation of the magnetic properties during sintering and annealing.

Effect of copper on the properties of Pr-Dy-Fe-Co-B sintered magnets

The effect of copper on the properties of magnets (Pr0.52Dy0.48)13(Fe65Co0.35)80.3 − xCuxB6.7 (x = 0–10) has been studied. Alloying with copper is shown to decrease the sintering temperature and to increase the content of the principal (Pr,Dy)2(Fe,Co)14B magnetic phase. For compositions with x = 1.3–3.3, copper is found to affect the value and sign of the temperature induction coefficient (TIC). It is shown that the effect of copper on the TIC is determined by the substitution of copper ions for iron ions in lattice sites, which are coupled via an antiferromagnetic exchange interaction.

Role of boron in the formation of the magnetic properties of sintered Nd-Dy-Fe-Co-B materials with a high cobalt content

Sintered materials having the compositions (Nd1 − xDyx)S(Fe1 − yCoy)balB6–8 (atomic fractions x = 0.09–0.71, y = 0.19–0.34, S = 13.3–15 at %) have been studied. It is shown that, as the content of the boron-containing (Nd, Dy)(Fe, Co)4B phase increases, the coercive force decreases abruptly. This effect is explained by the transition of boron atoms from the principal magnetic boron-containing (Nd, Dy)2(Fe, Co)14B phase to the (Nd, Dy)(Fe, Co)4B phase during sintering.

Effect of copper on the temperature dependence of the magnetization of sintered (Pr, Dy)-(Fe, Co)-B materials

The effect of copper on the temperature dependence of the magnetization of sintered (Pr0.52Dy0.48)13(Fe0.65Co0.35)balCuxB7 materials with x = 0–6.3 at % has been studied in the temperature range from −60 to +80°C. Copper is made a part of composition at the stage of powder processing. It was found that the temperature dependences of magnetization for compositions with x = 0, 1.3, 2.1, and 6.3 at % are characterized by a maximum. The maximum deviation of the maximum magnetization from the magnetization at −60°C does not exceed 5.5%.

Pr-Dy-Fe-Co-B materials for navigation instruments

The temperature dependence of the magnetization of (Pr1 − xDyx)13–14(Fe1 − yCoy)balB7 (x = 0.48–0.73, y = 0.24–0.35) sintered materials has been studied in a temperature range of 20–100°C. A theoretical model is proposed to describe the temperature dependence of the magnetization of materials. The results of testing the materials with a pendulous accelerometer are reported and compared with the results of testing the existing device materials.

Effect of samarium on the temperature induction coefficient of Nd-Dy-Fe-Co-B materials

Sintered (Nd1 − x − zDyxSm2)-(Fe1 − yCoy)-B (atomic fractions x = 0.27, 0.32, 0.39; y = 0.17, 0.23, 0.28; and z = 0.04–0.18) materials have been studied. It is shown that the magnetic moments of samarium ions and the iron-cobalt sublattice are ordered antiferromagnetically and, as the samarium content increases, the content of dysprosium and samarium in the basic A magnetic phase decreases and increases, respectively. As the samarium content (z) in sintered magnets (Nd0.61 − zDy0.39Smz)17.5(Fe0.72Co0.28)76.3B6.2 increases, the thermal induction coefficient is found to decrease monotonically from 0.021 to 0.006%/°C, i.e., by 3.5 times. In this case, residual inductance Br is unchanged (0.8 T).

Effect of cerium on the temperature stability of Nd-Dy-Fe-Co-B magnets

Sintered (Nd0.6 − xCexDy0.4)14.4(Fe0.72Co0.28)balB6.4 (at %) materials (with x = 0.03–0.23) have been studied. A correlation between the compositions of the base magnetic phase and sintered material has been found. It is shown that alloying with cerium can decrease the absolute value of the temperature coefficient of induction. The decrease in the absolute value of the temperature coefficient of induction is explained by the redistribution of neodymium and dysprosium atoms over certain crystal lattice sites of the base magnetic phase.

Effect of Annealing of a Pr–Dy–Fe–Co–B Alloy on Its Phase Composition and the Properties of Related Sintered Magnets

The effect of annealing of a (Pr0.41Ce0.12Dy0.47)13.46(Fe0.64Co0.36)80.3B6.24 alloy at 1000°C on its microstructure and the properties of sintered magnets made of it has been studied. In the annealed state, the composition of the main magnetic phase (Pr,Dy)2(Fe,Co)14B changes sharply (dysprosium content changes), the residual induction of the sintered magnets made of the annealed alloy increases by 6%, and the coercive force determined from magnetization increases by 8.5%. The volume content of the main magnetic phase R2(Fe,Co)14B in sintered magnets (Nb,Dy)–(Fe,Co)–B and (Pr,Dy)–(Fe,Co)–B is found. The content of this phase in neodymium-based magnets is approximately half as much.

Effect of gadolinium on the properties of Pr–Dy–Fe–Co–B materials

Sintered (Pr1–x–yDyxGdy)13–14(Fe1–zCoz)balB6–7 materials (x = 0.18–0.58, y = 0.05–0.33, z = 0.2–0.36) have been studied. The magnetic moments of gadolinium ions and those of the sublattice formed by Fe and Co ions are shown to be ordered antiferromagnetically. It is noted that an increase in the content of gadolinium, which substitutes for dysprosium, leads to an increase in residual induction Br, a decrease in coercive force HcJ, and an increase in the absolute value of the temperature coefficient of induction. The opposite effect takes place in the case of substitution of gadolinium for praseodymium in materials with a fixed dysprosium content.

Sintering of Pr-Dy-Fe-Co-B materials

The properties of sintered magnets (Pr1 − xDyx)-(Fe1 − yCoy)-B (x ≳ 0.6 at %, y ≳ 0.2 at %) as functions of the milling time and the sintering conditions are studied. Minima in the coercive force and the density as functions of the sintering temperature are detected. The dependence of the minimum depth on the milling time is detected. In the case of long-term sintering or additional sintering, the values of these parameters are restored. The minimum in the (Pr1 − xDyx)-(Fe1 − yCoy)-B (x ≳ 0.6 at %, y ≳ 0.2 at %) materials is assumed to be related to the deceleration of diffusion processes in them as compared to the (Nd1 − xDyx)-(Fe1 − yCoy)-B (x = 0.71 at %, y = 0.34 at %) system, in which this minimum is insignificant.