Mechanism of PZT crystallisation under hydrothermal conditionsDevelopment of a new synthesis route

On the basis of a 1-stage hydrothermal process, we first investigated the reaction mechanism responsible for the PZT precipitation. In a first sequence, lead diffuses into the amorphous coprecipitate. By increasing the reaction temperature, these particles dissolve, leading to nucleation and growth of PZT well faceted particles. In a second step, we demonstrated that starting from very fine oxide precursors, a homogeneous PZT solid solution could be formed. Under the same conditions but without any lead precursor, a mixture of KTO (a potassium titanium oxide phase) and tetragonal zirconia is formed. A 2-stage process was developed on these assumptions. The first stage consists in producing the KTO–ZrO2(T) mixture. In the second stage, this mixture is hydrothermally treated in presence of lead precursor. Pure and homogeneous PZT and PLZT powders were obtained throughout this new synthesis route.