Dielectric properties of some low-lead or lead-free perovskite-derived materials: Na_(0.5)Bi_(0.5)TiO_3-PbZrO_3, Na_(0.5)Bi_(0.5)TiO-3-BiScO_3 and ceramics

摘要

Na_(0.5)Bi_(0.5)TiO_3 (NBT) and its modifications are known to be new lead-free ferroelectric materials and are promising for environment friendly devices. The systems under investigation were (i) NBT (trigonal ferroelectric)-PbZrO_3 (orthorhombic antiferroelectric); (ii) NBT (trigonal ferroelectric)-BiScO_3 (trigonal paraelectric); and (iii) NBT (trigonal ferroelectric)-BiFeO_3 (trigonal antiferromagnetic). The lattice parameters change as expected from the respective ionic radii values. For NBT-PZ, the dielectric permittivity shows a large frequency and temperature dispersion suggesting a relaxor-like behaviour dependent on the thermal annealing of the samples. For NBT-BS, the Curie temperature increases with BS content as well as the diffuseness of the phase transition, connected with the introduced disorder. For NBT-BF, the overall behaviour of the permittivity of NBT is maintained up to 50 percent BF but anomalies of the permittivity appeared close to 600 deg C, which might be connected with the onset of magnetic influence for high BF content.