Synthesis and properties of barium titanate stannate thin films by chemical solution deposition

Abstract

Barium titanate stannate (BaTi1−xSnxO3, 0 ≤ x ≤ 0.25) thin films were deposited directly on copper foil substrates via a chelate chemical solution process. The films were subsequently crystallized in a reducing atmosphere such that substrate oxidation was avoided and that the 2-valent state of tin could be stabilized. Despite the stabilization of the low-melting temperature SnO oxidation state at high temperatures, the final grain size was smaller with increased tin incorporation similar to other B-site substituted BaTiO3 films. Temperature and field-dependent dielectric measurements revealed a reduction in dielectric constant and dielectric tuning with increasing tin concentration. The reduction in permittivity with reduced grain size is consistent with the well-known trends for ceramic barium titanate and in combination with a defect-dipole model involving Sn acceptors, can be used to explain the experimental trends. Phase transition frequency dependence was studied and for compositions containing up to 25 mole percent tin. No phase transition dispersion was observed and thus no strong evidence of relaxor-like character. The phase transition became increasingly diffuse with deviation from Curie–Weiss behavior, but the observed transition temperatures agreed well with bulk reference data.