Process for transforming pure Y2 BaCuO5 into a superconducting matrix of YBa2 Cu3 O7-x with fine and homogeneously dispersed Y2 BaCuO5 inclusions

Abstract

A new process for more easily making a superconducting matrix of YBa 2 Cu 3 O 7-x with fine and homogeneously dispersed Y 2 BaCuO 5 inclusions smaller than one micron compacts powders of YBa 2 Cu 3 O 7-x and Y 2 BaCuO 5 into samples which are first sintered for improved mechanical stability and then placed into contact with each other. The samples are placed into a furnace above the peritectic temperature of the YBa 2 Cu 3 O 7-x and held at that temperature for less than about fifteen minutes so that the YBa 2 Cu 3 O 7-x begins to melt and be absorbed by capillary action into the Y 2 BaCuO 5 sample. The combined sample is cooled to a temperature below the peritectic temperature by a variety of alternative cooling cycles where it is transformed by a reaction into a superconducting matrix of YBa 2 Cu 3 O 7-x with fine and homogeneously dispersed Y 2 BaCuO 5 . BaCuO 2 +CuO may be substituted for the YBa 2 Cu 3 O 7-x and Y 2 O.sub. 3 substituted for the Y 2 BaCuO 5 as starting components.

We claim: 
     
       1. A method for making a ceramic superconductor, comprising the steps of: (a) providing a supply of Y 2  BaCuO 5  ;   (b) providing a supply of YBa 2  Cu 3  O 7-x  ;   (c) placing the two supplies in contact with each other;   (d) next placing the two supplies into a furnace at a temperature above the peritectic temperature of YBa 2  Cu 3  O 7-x  for a period of less than about fifteen minutes so that the supply of YBa 2  Cu 3  O 7-x  begins to melt and so that the resulting melt begins to be absorbed by capillary action into the supply of Y 2  BaCuO 5  ; and,   (e) next cooling the resulting material to a temperature lower than the peritectic temperature of YBa 2  Cu 3  O 7-x  and holding that temperature for a period of time to promote growth of YBa 2  Cu 3  O 7-x .   
     
     
       2. The method for making a ceramic superconductor according to claim 1, wherein the temperature above the peritectic temperature in step (d) is about 1100° C. 
     
     
       3. The method for making a ceramic superconductor according to claim 1, wherein step (e) is characterized as next quickly cooling the resulting material to the peritectic temperature of Y 2  BaCuO 7-x , then slowly cooling the resulting material to 960° C. and then holding that temperature for a period of about twenty-four hours. 
     
     
       4. The method for making ceramic superconductor according to claim 1, wherein step (e) comprises quickly cooling the resulting material to about 960° C. and then holding that temperature for a period of about twenty-four hours. 
     
     
       5. The method for making a ceramic superconductor according to claim 1, wherein the starting density of the supply of Y 2  BaCuO 5  is in the range of 35-43% of its theoretical maximum density. 
     
     
       6. A method for making a ceramic superconductor, comprising the steps of: (a) providing a supply of Y 2  BaCuO 5  ;   (b) mixing into the supply of Y 2  BaCuO 5  an amount by weight of the combined supplies of 5 to 30 percent of YBa 2  Cu 3  O 7-x  ;   (c) next placing the combined supplies of Y 2  BaCuO 5  and YBa 2  Cu 3  O 7-x  into a furnace at a temperature above the peritectic temperature of YBa 2  Cu 3  O 7-x  for a period of less than about fifteen minutes so that the supply of YBa 2  Cu 3  O 7-x  begins to melt and so that the resulting melt begins to be absorbed by capillary action throughout the Y 2  BaCuO 5  ; and,   (e) next cooling the resulting material to a temperature lower than the peritectic temperature of YBa 2  Cu 3  O 7-x  and holding that temperature for a period of time to promote growth of YBa 2  Cu 3  O 7-x .   
     
     
       7. A method for making a ceramic superconductor, comprising the steps of: (a) providing a supply of RE 2  BaCuO 5 , wherein RE is defined as at least one member selected from the group consisting of Y, La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu;   (b) providing a supply of REBa 2  Cu 3  O 7-x  ;   (c) placing the two supplies in contact with each other;   (d) next placing the two supplies into a furnace at a temperature above the peritectic temperature of REBa 2  Cu 3  O 7-x  for a period of less than about fifteen minutes so that the supply of REBa 2  Cu 3  O 7-x  begins to melt and so that the resulting melt begins to be absorbed by capillary action into the supply of RE 2  BaCuO 5  ; and,   (e) next cooling the resulting material to a temperature lower than the peritectic temperature of the REBa 2  Cu 3  O 7-x  and holding that temperature for a period of time to promote growth of REBa 2  Cu 3  O 7-x .   
     
     
       8. The method for making a ceramic superconductor according to claim 7, wherein step (e) comprises next quickly cooling the resulting material to the peritectic temperature of REBa 2  Cu 3  O 7-x , then slowly cooling the resulting material to 960° C. and then holding that temperature for a period of about twenty-four hours. 
     
     
       9. The method for making a ceramic superconductor according to claim 7, wherein step (e) comprises quickly cooling the resulting material to about 960° C. and then holding that temperature for a period of about twenty-four hours.