Hydrothermal Synthesis of Ferroelectric Mixed Potassium Niobate–Lead Titanate Nanoparticles

Potassium niobate–lead titanate solid‐solution nanoparticles have been synthesized using a new hydrothermal method. The key step is an in situ acid–base exothermic reaction with a large excess of KOH, generating an amorphous precipitated gel. This gel, when crystallized in an autoclave for 2 h at 190°C, produces a mixed perovskite solid solution with [KNbO₃]_0.8–[PbTiO₃]_0.2 (KNPT) composition, and parallelepiped particles rang in size from a few tens to a few hundreds of nanometer in length. This study proves that the pure perovskite phase can be obtained in spite of the different solubilities of the reactive cations in an ethanol–water solution. Dielectric measurements show that KNPT ceramic with a grain size of 50 nm is ferroelectric at room temperature. In addition, ceramics sintered at 950°C have an average grain size of 500 nm, and exhibit a maximum permittivity of 2100 at 1 kHz near T_C = 510 K and a remanent polarization P_r = 12 μC/cm²