Thin films of PbZr$_{(1-x)}$TixO3 have been elaborated using the sol-gel process. We have characterised the thermal behaviour of the sol and of the film of PZT. The different orientations were observed according to the temperature of pyrolysis: [111] at 500 °C, [100] at 450 °C. Finally, an advanced method of electrical characterisation of ferroelectrics is used by separating the reversible and irreversible contributions of polarisation. An experimental Preisach density is then measured and modeled and allows to extract ferroelectric properties. These parameters are independent from electric field strength applied through the sample, leading to a powerful tool to characterise the electrical behaviour.