| 简介 |
PCT No. PCT/FR97/01369 Sec. 371 Date Apr. 27, 1999 Sec. 102(e) Date Apr. 27, 1999 PCT Filed Jul. 23, 1997 PCT Pub. No. WO98/04655 PCT Pub. Date Feb. 5, 1998Compositions including at least three metals (M1, M2, M3) are disclosed. The first metal (M1) is at least one metal selected from the iron group or the manganese group, and is preferably selected from iron, manganese, cobalt and nickel. The second metal (M2) is at least one metal selected from the rare earth group and is preferably selected from cerium, lanthanum, neodymium and praseodymiium. The third metal (M3) is selected from the group of alkaline or alkaline-earth metals, and is preferably selected from barium, strontium, calcium and lithium. The weight ratio (R) of metal (M3) to metal (M2) is greater than 0.15, and preferably greater than 1.5. |
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