Even though the PZT ceramic system has been thoroughly studied and modified with different additives, no numerous reports have been published focusing on the PZT double ‘soft’ modification with La3+ and Nb5+ (PLZTN). In this paper, we explore the structural, morphological, dielectric, ferroelectric and piezoelectric properties of the PLZTN system for different doping levels (xLa3+ = xNb5+ = 0.4, 0.6, 0.8, 1.0 and 1.4 at.%) synthesized by conventional powders reaction. The temperature dependence of the piezoelectric response of poled ceramic disks is also analyzed and, according to its overall features, an optimum modification is proposed in order to develop PZT-based sensors for several applications.