Structural, dielectric, electromechanical, piezoelectric, elastic and ferroelectric properties of lanthanum and sodium co-substituted barium titanate ceramics

In this paper, the polycrystalline ceramics Ba(1-x) (La, Na)xTiO30≤x≤0.08 were synthesized by microwave assisted heating of the starting materials. Room temperature X-ray diffraction along with Rietveld refinement analysis confirmed the formation of single-phase polycrystalline compound with the tetragonal crystal structure. A dense microstructure with several grains having different size distribution throughout the sintered pellet has been observed. The incorporation of La3+ and Na+ ions in BaTiO3 enhanced the room temperature relative permittivity. The studies of the temperature dependence of dielectric permittivity indicate ferroelectric-paraelectric phase transition with a clear shift in the Curie temperature (Tc) of BaTiO3 towards lower temperature side on co-substitution. The co-substituted sample with x = 0.08 exhibited superior dielectric constant (ɛ' = 4226) with low dielectric loss (tanδ = 0.0113) which is highly essential for the fabrication of ceramic capacitors. Resonance and antiresonance characteristics of impedance and phase for poled Ba(1-x)(La,Na)xTiO3 samples have been investigated in the frequency range of 300 kHz-1 MHz. Based on IRE standards for piezoelectric ceramics the piezoelectric response has been discussed. The room temperature P-E loop is investigated at an applied electric field of 80 kV/cm at 33 Hz frequency using Precision Premier II. •Ba1-x(La,Na)xTiO3 (0 ≤ x ≤ 0.08) ceramic was prepared by solid state reaction method.•The permittivity increases with increasing x.•The dielectric losses and Curie temperature decrease with increasing x.•They are class II multilayer ceramic capacitor dielectrics suitable for MLCC.