Effects of Ag2O nanoparticles addition on electrical conductivity and microhardness properties of polycrystalline YBa2Cu3O7−δ

Polycrystalline YBa2Cu3O7−δ is a highly promising material for bulk superconductivity. It can be doped with a suitable element to enhance its superconducting properties. In this study, polycrystalline YBa2Cu3O7−δ was added with Ag2O nanoparticles and the effects on electrical conductivity and microhardness properties were investigated. The amount of Ag2O nanoparticles (< 100 nm) was varied at 1.0 to 9.0 wt. % and mixed with YBa2Cu3O7−δ powder (∼50 nm) using solid state reaction. The mixture was pelletized and sintered at 950 °C for 1 h The resultant FTIR curves indicated the existence of Ag2O as the strongest peak representing YBa2Cu3O7−δ at around 1468 cm−1 was shifted to 1451 cm−1, the vibration modes of Ag-O. For the composition with more than 3.0 wt. % Ag2O, the XRD analysis revealed that the incorporation of Ag into YBa2Cu3O7−δ structure altered the orthorhombicity of the samples. The presence of Ag in YBa2Cu3O7-δ in each sample was further confirmed by EDX analysis. From the SEM images, the Ag2O nanoparticles were observed to be distributed in the YBa2Cu3O7−δ grain-boundaries in samples with 3.0 wt. % Ag2O and less. The agglomeration of Ag2O nanoparticles was observed for the samples with more than 3.0 wt. % Ag2O. The electrical conductivity as measured using Van Der Pauw method at room temperature, improved as the Ag2O amount was increased above 1.0 wt. %. In term of the superconducting properties, TC of samples with ≤ 3.0 wt. % Ag2O slightly exceeds the TC of pure YBa2Cu3O7−δ. The TC is significantly reduced by ∼10 K as the Ag2O amount is increased beyond 3.0 wt. % to 9.0 wt. %. The hardness of Ag2O added YBa2Cu3O7−δ increases with the addition of Ag2O but decreases as the amount exceeds 3.0 wt. % due to the agglomeration of Ag2O nanoparticles.