Nanodiamond influence on the nucleation and growth of YBCO superconducting film deposited by metal-organic decomposition

It was recently shownthat the introduction of nanodiamond(ND)into a superconducting metal-organic deposited YBa2Cu3O7-& delta; (YBCO) film produces anincrease in critical current density in self-field conditions (B = 0 T). Such improvement appears to be due to the formationof denser and smoother films than the samples deposited without ND.This paper presents the work done to understand the role of ND duringYBCO nucleation and growth. A detailed study on YBCO+ND films quenchedat different temperatures of the crystallization process was carriedout. Results showed that the reaction responsible for YBCO productionappeared effectively affected by ND. In particular, ND stabilizesone of the YBCO precursors, BaF2(1-x)O x , whose conversion into YBCO requiresa prolonged time. Therefore, the YBCO nucleation is slowed down byND and begins when the experimental conditions favor both thermodynamicallyand kinetically the formation of YBCO along the c-axis. This effect has important implications because the growthof a highly epitaxial c-axis YBCO film enables excellentsuperconducting performance.Thenucleation and growth of a YBCO epitaxial film can bedelayed by the presence of nanodiamond (ND). Since YBCO nucleationoccurs at a higher temperature, the c-axis grainformation is favored from both a thermodynamic and kinetic point ofview. This effect can explain the improvement of superconducting propertiesobserved in a YBCO+ND film.