[en] The microstructure and the flux pinning capability of SiO₂-added YBa₂Cu₃O_y thick films on Ag substrates were investigated. A series of YBa₂Cu₃O_y thick films with small amounts (0–0.5 wt%) of nano-sized SiO₂ particles (12 nm) was prepared. The thicknesses of the prepared thick films was approximately 100 µm. Phase analysis by X-ray diffraction and microstructure examination by scanning electron microscopy were performed and the critical current density dependence on the applied magnetic field J_c(H) and electrical resistivity ρ(T) were investigated. The magnetic field and temperature dependence of the critical current density (J_c) was calculated from magnetization measurements using Bean’s critical state model. The results showed that the addition of a small amount (≤0.02 wt%) of SiO₂ was effective in enhancing the critical current densities in the applied magnetic field. The sample with 0.01 wt% of added SiO₂ exhibited a superconducting characteristics under an applied magnetic field for a temperature ranging from 10 to 77 K. (author)