Structural, electrical, and dielectric study of the influence of 3.4% lanthanide (Ln3+ = Sm3+ and La3+) insertion in the A-site of perovskite Ba0.95Ln0.034Ti0.99Zr0.01O3

Abstract

This paper presents a systematic study of the substitution effect by lanthanides (Ln³⁺ = Sm³⁺ and La³⁺) in the A-site of perovskite Ba_(1−x)Ln_2x/3(Ti_0.99Zr_0.01)O₃ with a substitution rate equal to 3.4%. All samples were synthesized by the classical solid-state reaction route and characterized by X-ray diffraction and a complex impedance spectroscopy technique. The synthesized compounds exhibit single-phase perovskite structures without detectable secondary phases. The P4mm space group was verified by the Rietveld method from the X-ray diffraction data, with the tetragonal distortion decreasing with the increasing ionic radius of the lanthanides. SEM micrographs of all ceramics revealed high densification, low porosity and homogeneous distribution of grains of different sizes over the entire surface. The dielectric properties of non-doped and Sm³⁺ and La³⁺ doped Ba_(1−x)Ln_2x/3(Ti_0.99Zr_0.01)O₃ compound are studied in the temperature range of 40–250 °C. The dielectric permittivity ε′ increases and the ferroelectric–paraelectric phase transition temperature decreases when the lanthanides are inserted into the A-site of Ba_(1−x)Ln_2x/3(Ti_0.99Zr_0.01)O₃ perovskite. The Nyquist plots indicate a non-Debye type relaxation process. Conductivity and electrical modulus plots as a function of frequency (10 to 10⁶ Hz) include two electrical responses corresponding to grain and grain boundary effects for all ceramics studied.