FUNCTIONAL-GRADIENT RARE-EARTH PERMANENT MAGNET Russian patent published in 2010 - IPC H01F1/53 

FIELD: metallurgy.

SUBSTANCE: functional-gradient magnet has a composition R¹ _aR² _bT_cA_dF_eO_fM_g, where R¹ is one of rare earth elements, including Sc and Y and excluding Tb and Dy, R² - Tb and/or Dy, T is iron and/or cobalt, A is boron and/or carbon, F is fluorine, O is oxygen, and M is at least one of Al, Cu, Zn, In, Si, P, S, Ti, V, Cr, Mn, Ni, Ga, Ge, Zr, Nb, Mo, Pd, Ag, Cd, Sn, Sb, Hf, Ta and W. Indices a-g indicate atomic percent contents and have the following values: 10 ≤ a+b ≤ 15, 3 ≤ d ≤ 15, 0.01 ≤ e ≤ 4, 0.04 ≤ f ≤ 4, 0.01 ≤ g ≤ 11, c - the rest. Concentration R²/(R¹+R²) contained on borders of grains surrounding grains of a primary phase (R¹+R²)₂T₁₄A of tetragonal system inside sintered body of magnet is higher, than concentration R²/(R¹+R²) contained in grains of the primary phase. R² is distributed so, that its concentration in average increases from the centre to surface of magnet body. Oxy-fluoride (R¹, R²) is present on borders of grains in region spreading from surface of magnet body to depth of 20 mcm; also magnet body has surface layer of higher coercive force, than in internal part.

EFFECT: permanent magnet possesses improved thermo-resistance.

5 cl, 4 dwg, 2 tbl, 3 ex