Characterization of hydrofluoric acid treated Y-Ba-Cu-O oxides

Effects of hydrofluoric acid (HF) treatment on the properties of Y-Ba-Cu-O oxides were investigated. No obvious etching of bulk Y-Ba-Cu-O and no degradation of zero resistance temperature were observed even though the oxides were placed into 49% HF solution for up to 20 h. Surface passivation of Y-Ba-Cu-O due to HF immersion was verified by subsequent immersion of Y-Ba-Cu-O in water. A thin layer of amorphous fluoride formed on the surface of the Y-Ba-Cu-O during HF treatment, which limited further reaction between Y-Ba-Cu-O and HF, and later reaction with water. Thin film Y-Ba-Cu-O was passivated by HF vapors and showed no degradation in T_c-zero after 30 min immersion in water. The properties of the surface layer of Y-Ba-Cu-O oxide after HF treatment are reported from Auger electron spectroscopy, x-ray diffraction, and scanning electron microscopy studies.