An 85 nm-thick morphotropic PbZr0.52Ti0.48O3 (PZT) film grown epitaxially and [001]-oriented onto a SrTiO3-buffered Si-wafer is investigated using temperature dependent X-ray diffraction. Two phase transitions, at Trt 500K and Tc 685 K, are evidenced and are attributed to structural phase transitions from monoclinic-like to tetragonal-like phase and from tetragonal to paraelectric phase, respectively. The stronger upper shift of Trt value with respect to the bulk one and the weakly affected Tc (Tc bulk 665 K) are explained assuming misfit strain changes when crossing Trt. This finding opens new perspectives for piezoelectric PZT films in harsh applications.