Studium strukturních a magnetických vlastností materiálů na bázi (NdxPr1-x)2Fe14B pro nízkoteplotní aplikace

Abstract

The work deals with the preparation and complex study of magnetic and structural properties of hard magnetic materials on the base of Pr-Nd-Fe-B for low temperature applications. Sintered permanent magnets on the base of Pr-Nd-Fe-B with the nominal chemical composition: Nd - 23; Pr - 10; Ti - 0.9; Al - 0.3; B - 1.3; Cu - 0.9; Co - 0.5; Fe 64.5 (samples N1 to N3) and Nd - 20; Pr - 10; Ti - 0.9; Al - 0.3; B - 1.3; Cu - 0.9; Co - 0.5; Fe 64.5 (sample N4) were prepared by traditional technology of powdered metallurgy and subjected to various conditions of heat treatment. It was found that the stoichiometric composition of grains of the main intermetallic phase corresponds with (Pr0,3Nd0,7)2Fe14B (samples N1-N3) and (Pr0,4Nd0,6)2Fe14B (sample N4). The best magnetic characteristics were achieved for N2 and N4 samples that have been thermally processed at 500 °C for 2 hours, which is probably related to the formation of a nearly continuous layer of Nd(Pr)-rich phase at the grain boundaries and lower oxygen content. Performed thermo-magnetic analysis of samples with the proposed composition and optimal heat treatment showed a spin reorientation transition at 95 K (sample N2) and 75 K (sample N4). These materials may be recommended for low temperature applications, e.g. in undulators.