Study of the structural, ferroelectric, dielectric, and pyroelectric properties of the K0.5Na0.5NbO3 system doped with Li+, La3+, and Ti4

Pure K 0.5 Na 0.5 NbO 3 (KNN) and KNN doped with Li + (6% mole), La 3+ (1.66%, 5%, 6% mole), and Ti 4+ (10% mole) were prepared by mixture of oxides using high-energy milling and conventional solid-state reaction. The effects of the dopant on the physical properties of pure KNN have been evaluated based on the structural, ferroelectric, pyroelectric, and dielectric measurements. The XRD measurements show that KNN pure sample contains a mixture of monoclinic and orthorhombic crystalline phases, with a slightly higher concentration of monoclinic phase. In contrast, all doped samples show a higher concentration of the orthorhombic phase, as well as the presence of a secondary phase (K 6 Nb 10.8 O 30 ), also detected by Raman measurements. The samples with a higher concentration of this secondary phase, also present greater dielectric losses and lower values of remnant polarization. The dielectric measurements allowed us to detect temperatures of structural transitions (orthorhombic-tetragonal, O-T) previous to the ferroelectric-paraelectric transition (tetragonal-cubic, T-C), and also in this set of samples, a direct correlation was found between the values of remnant polarization and the corresponding pyroelectric signal response.