The effect of gadolinium substitution on the structural, ferroelectric and magnetic properties of bismuth ferrite ceramics

Abstract

Bi1-xGdxFeO3 (x = 0.01; 0.05; 0.075; 0.09; 0.10; 0.20; 0.30) powders were synthesized by hydro-evaporation method. The optimization of sintering conditions indicated that temperature of 870 °C and time of 6 hours (after pressing at 9 t/cm2) provided the densest ceramics samples (up to 88 % of theoretical density) and the lowest amount of secondary phases ( 5.5 wt%). The increase of gadolinium content resulted in polar-to-nonpolar (R3c  Pnma) structural phase transition at about x = 0.10, which was reflected on deterioration of ferroelectric property. Structural analysis indicated decrease of unit cell volume with the increase of x, but the (Bi,Gd)–Fe distance did not exhibit regularity in change. The bismuth ferrite ceramics samples doped with x = 0.075 and x = 0.09 of gadolinium showed the greatest lattice distortion along the [111] axis. These samples also exhibited larger values of remnant electric polarization and less leakage processes than the pure bismuth ferrite ceramics samples. Magnetic behavior of Bi1-xGdxFeO3 samples revealed that the weak ferromagnetic moment strengthened with increase of the gadolinium content.