SOL-GEL PREPARATION AND CHARACTERIZATION OF FLUORINE-SUBSTITUTED BI(PB)SCCO-2223 HTSC

Bi2-xPbxSr2Ca2Cu3OyF0.7 was prepared by sol-gel using citric acid and ethylene glycol. Thermodynamic calculations showed that a considerable loss of fluorine is to be expected. The samples were characterized by structural, thermal and physical methods. AAS showed that no apprecia ble amount of lead was lost during sintering. For x=0.35 the highest T c was observed, viz. 116K(onset). Using a selective fluorine electrode it was found that only up to 10% of the initial fluorine remained. Th e EPMA results showed that up to 90% of the sample contained (BiPb)SCC O-2223 the rest being (SrCa)(2)Cu3Oy. Fluorine could not be detected b y this method. Fluorine lead to significant enhancement of the phase f ormation.