Sub-coercive field non-linearities in 0.5 (Ba 0.7 Ca 0.3 TiO 3)-0.5 (BaZr 0.2 Ti 0.8 O 3) (BCTZ 50/50) thin film elaborated using pulsed laser deposition are studied using permittivity and phase angle of the third harmonic measurements as function of the AC measuring field E AC and temperature. The global phase transition temperature T max for which the permittivity is maximum, decreases from 330 K to 260 K when E AC increases. Rayleigh analysis of the AC field dependence of the relative permittivity shows a regular decrease of the domain wall motion contributions as temperature increases up to T max and an even more pronounced decrease above T max. This measurement reveals that the ferroelectric behavior subsists 70 K above the global phase transition. The phase angle of the third harmonic at temperatures below 275 K, is characteristic of a conventional ferroelectric and from 275 K to T max = 330 K of a relaxor. Above T max , the thin film exhibits a peculiar phase angle of the third harmonic, which consists of-180 • →-225 • → +45 • → 0 • instead of the-180 • →-90 • → 0 • found for relaxor. This peculiar behavior is observed only on heating, and is tentatively attributed to changes in the correlations between polar nanoregions.