Enhanced electrical properties near the morphotropic phase boundary in lead-free Bi0.5Na0.34K0.11Li0.05Ti1-xNixO3-δ ceramics.

Bi 0.5 Na 0.34 K 0.11 Li 0.05 Ti 1-x Ni x O 3-δ (BNKLT-xNi with x = 0, 0.005, 0.010, 0.015 and 0.020) lead-free piezoelectric ceramics have been synthesized by the solid-state combustion technique. The effect of x on the phase formation, microstructure, electrical and magnetic properties were investigated. A pure perovskite phase was obtained from all samples. Coexisting tetragonal and rhombohedral phases were found in all samples and the rhombohedral phase increased with increasing x, which was detected by XRD, Raman spectroscopy and XAS with the EXAFS technique. Moreover, the EXAFS technique provided the quantity of the rhombohedral phase, that increased from 38.8% to 57.0% when increasing x from 0 to 0.020. The morphotropic phase boundary (MPB) was identified at an x content of 0.010, with the ratio of the tetragonal to rhombohedral phases being 49.5:50.5%. This composition exhibited a high dielectric constant, at T m of 5428, a maximum strain of 0.170%, with a piezoelectric coefficient factor (d 33 ∗) of 340 p.m./V and large ferroelectric properties (P r of 26.1 μC/cm2 and E c of 17.9 kV/cm). Furthermore, the saturation magnetization (M s) at room temperature was increased by increasing x content. • BNKLT-0.010Ni showed MPB region with rhombohedral:tetragonal phase of 50.5:49.5%. • EXAFS revealed that the tetragonal phase continuously decreased from 61.2 to 43.0%. • Oxygen vacancy content was increased with increasing Ni substitution. • At the MPB composition, high S max (0.17%) and d 33 ∗ (340 p.m./V) were obtained. [ABSTRACT FROM AUTHOR]