Effect of Co²⁺ substitution in B-sites of the perovskite system on the phase formation, microstructure, electrical and magnetic properties of Bi_0.5(Na_0.68K_0.22Li_0.10)_0.5TiO₃ ceramics

Abstract

Bi_0.5(Na_0.68K_0.22Li_0.10)_0.5Ti_1−xCo _xO₃ lead-free perovskite ceramics (BNKLT−xCo, x = 0, 0.005, 0.010, 0.015 and 0.020) were fabricated via the solid-state combustion technique. A small-amount of Co²⁺ ion substitution into Ti-sites led to modification of the phase formation, microstructure, electrical and magnetic properties of BNKLT ceramics. Coexisting rhombohedral and tetragonal phases were observed in all samples using the X-ray diffraction (XRD) technique. The Rietveld refinement revealed that the rhombohedral phase increased from 39% to 88% when x increased from 0 to 0.020. The average grain size increased when x increased. With increasing x, more oxygen vacancies were generated, leading to asymmetry in the bipolar strain (S−E) hysteresis loops. For the composition of x = 0.010, a high dielectric constant (ε _m) of 5384 and a large strain (S _max) of 0.23% with the normalized strain (d*₃₃) of 460 pm·V⁻¹ were achieved. The BNKLT−0Co ceramic showed diamagnetic behavior but all of the BNKLT−xCo ceramics exhibited paramagnetic behavior, measured at 50 K.

Keywords

BNKLT−xCo / dielectric / ferroelectric / strain / magnetic

References

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