Method of producing solid solutions of magnetic oxides

Claim 1

A METHOD FOR THE PREPARATION OF SOLID SOLUTIONS OF IRON AND COBALT OF THE TYPE (Y - FE2O3)1-Y (COFE2O4)Y WITH 0<Y <0.876 BY HOMOGENEOUS AND CONTROLLED SUBSTITUTION OF DIVALENT COBALT IONS FOR FE3+ IONS IN Y - FE2O3, COMPRISING THE FOLLOWING STEPS: A. PREPARING BY CO-PRECIPITATION A WATER INSOLUBLE MIXED OXALATE CONTAINING FE2+ IONS AND DIVALENT COBALT IONS, SAID MIXED OXALATE CORRESPONDING TO THE OFRMULA: FE1-XCOX(C2O4)2H2O WHEREIN THE VALUE OF X IS SUCH THAT THE RATIO OF OF COBALT TO IRON IN SAID OXALATE IS THE SAME AS THE RATIO OF COBALT TO IRON IN SAID SOLID SOLUTION; B. HEATING UNIFORMLY SAID MIXED OXALATE IN AIR AT A PROGRESSIVELY INCREASING TEMPERATURE IN THE RANGE OF 210*C TO 300*C UNTIL IT IS DECOMPOSED AND MOST OF THE RESULTANT CARBON IS ELIMATED, SAID HEATING STEP BEING STOPPED BEFORE ANY FORMATION OF RHOMBOEDRIC OXIDE A - FE2O3 AND OF SPINEL OXIDE COFE2O4; C. HEATING THE PRODUCT OF STEP B) IN A WET HYDROGEN ATMOOSPHERE CONTAINING ABOUT 7 PERCENT BY VOLUME OF STEAM AT SUCH A TEMPERATURE AS TO PRODUCE A SUBSTITUTED MAGNETITE FORMED OF CRYSTALLITES AND SUBSTANTIALLY FREE FROM RESIDUAL CARBON; D. AND HEATING IN AIR SAID SUBSTITUTED MAGNETITE TO A TEMPERATURE SUCH AS TO OXIDIZE SAME, SAID TMEPRATURE BEING BETWEEN ABOUT 210*C AND 380*C AND INCREASING IN DIRECT PROPORTION TO THE VALUE OF Y.

Claim 2

A METHOD FOR THE PREPARATION OF SOLID SOLUTIONS OF IRON AND COBALT OF THE TYPE (Y - FE2O3)1-Y (COFE2O4)Y WITH 0<Y <0.876 BY HOMOGENEOUS AND CONTROLLED SUBSTITUTION OF DIVALENT COBALT IONS FOR FE3+ IONS IN Y - FE2O3, COMPRISING THE FOLLOWING STEPS: A. PREPARING BY CO-PRECIPITATION A WATER INSOLUBLE MIXED OXALATE CONTAINING FE2+ IONS AND DIVALENT COBALT IONS, SAID MIXED OXALATE CORRESPONDING TO THE OFRMULA: FE1-XCOX(C2O4)2H2O WHEREIN THE VALUE OF X IS SUCH THAT THE RATIO OF OF COBALT TO IRON IN SAID OXALATE IS THE SAME AS THE RATIO OF COBALT TO IRON IN SAID SOLID SOLUTION; B. HEATING UNIFORMLY SAID MIXED OXALATE IN AIR AT A PROGRESSIVELY INCREASING TEMPERATURE IN THE RANGE OF 210*C TO 300*C UNTIL IT IS DECOMPOSED AND MOST OF THE RESULTANT CARBON IS ELIMATED, SAID HEATING STEP BEING STOPPED BEFORE ANY FORMATION OF RHOMBOEDRIC OXIDE A - FE2O3 AND OF SPINEL OXIDE COFE2O4; C. HEATING THE PRODUCT OF STEP B) IN A WET HYDROGEN ATMOOSPHERE CONTAINING ABOUT 7 PERCENT BY VOLUME OF STEAM AT SUCH A TEMPERATURE AS TO PRODUCE A SUBSTITUTED MAGNETITE FORMED OF CRYSTALLITES AND SUBSTANTIALLY FREE FROM RESIDUAL CARBON; D. AND HEATING IN AIR SAID SUBSTITUTED MAGNETITE TO A TEMPERATURE SUCH AS TO OXIDIZE SAME, SAID TMEPRATURE BEING BETWEEN ABOUT 210*C AND 380*C AND INCREASING IN DIRECT PROPORTION TO THE VALUE OF Y.