This paper focuses on the deformation origin of PbZr0.52Ti0.48O3 (PZT) fiber mats obtained by electrospinning. The main cause of deformation of the green mats during heating was found to be a nonuniform relaxation of the stretched PVP polymer, due to nonuniform thermal decomposition of the Pb-hexanoate in the fibers. This relaxation starts under 100 degrees C, well below the polymer decomposition temperature. The shrinkage was found to accelerate above the polymer glass transition point, giving rise to an overall linear change of almost 50%. The green PZT mats were easily separated from the collector by first depositing a pure PVP sublayer on the collector. An optimal fabrication and slow multistep thermal treatment process that provides fiber mats with desired PZT phase and overcomes the nonuniform deformation is described.