Impact of Li-substitution on dielectric, structural and sintering behavior of Li (Sr0.5Ba0.5)1−/2Nb2O6 ceramics

Li x (Sr 0.5 Ba 0.5 ) 1− x /2 Nb 2 O 6 ceramics were prepared by a solid state synthesis and sintered at 1300 °C. XRD investigations reveal single phase samples up to a substitution limit of x = 0.275. For higher lithium contents, the appearance of LiNbO 3 as secondary phase was observed. The density of the ceramics increases with lithium content. The microstructures show globular grains which turns to pillar-like grains with rising lithium substitution. Dielectric investigations confirm relaxor ferroelectric behavior and the diffuse phase transition is shifted towards higher temperatures with increasing lithium content from 129 °C ( x = 0) to 221 °C ( x = 0.275). The diffuseness coefficient increases with the lithium content. From high-temperature XRD measurements the length of the tetragonal cell parameter c decreases with increasing temperature, reaches a minimum at about 150−230 °C (depending on x ) and afterward increases with increasing temperature. Additionally, a significant shift of the Nb(2) position with temperature can be observed. • Substitution of earth alkaline metals by lithium in Sr0.5Ba0.5Nb2O6 samples • Influence of Li-content on e.g. density, grain growth, resistivity, dielectric constant, and lattice parameters. • Considerable increase of the diffuse ferroelectric/paraelectric phase transition temperature. • Investigations of the lattice parameters and niobium positions during the phase transition