In this work we report the study of chemical solution deposited (CSD) YBa2Cu3O7-δ (YBCO) nanocomposite thin films, with diluted Ba2YTaO6 (BYTO) nanoparticles. We studied the influence of thermal treatment on the properties of nanocomposites, with different content of secondary phases (6%, 10% and 20%). We measured the film microstructure, nanostrain and the superconducting properties: critical temperature (Tc) and critical current density (Jc). The films were characterized using X-rays diffraction and SQUID inductive measurements. The use of two steps in the thermal treatment allowed to increase the nanostrain up to 0.30% for high nanoparticle loads (20%BYTO), decrease the nanoparticle size down to 15 nm and lead a smoother Jc(H) dependence, compared with the standard (single-step) thermal process and the pristine YBCO films.