Characteristics of NaNbO3 templates and improvement of electrical properties of textured KNLNS-BNKT ceramics

Abstract

In this study, plate-like perovskite NaNbO₃ (NN) templates were formed from Bi_2.5Na_3.5Nb₅O₁₈ (BiNN5) precursors via a molten salt method. The structure and microstructure of BiNN5 precursors and NN templates were studied. As a result, the platelike BiNN5 precursor particles have a bismuth layer perovskite structure, which is the basis for forming the synthesized plate-like NN particles that have a high aspect ratio with a width of 2-7 μm, a length of 5-12 μm and a thickness of 0.5-1 μm. From NN templates, we fabricated textured lead-free 0.98(K_0.48Na_0.48Li_0.04)(Nb_0.95Sb_0.05)O₃ − 0.02Bi_0.5(Na_0.4K_0.1)TiO₃ (KNLNS- BNKT) ceramic by the grain orientation technique. Experimental results show that the KNLNS-BNKT ceramics have a single-phase orthorhombic structure in which textured KNLNS-BNKT ceramics with 67% grain orientation. The electrical properties of the oriented ceramic are significantly improved compared to the non-oriented ceramic fabricated by the traditional method. Specifically, the electrical properties of the resulting KNLNS-BNKT oriented ceramics have a high dielectric constant (ε = 1323, an increase of 17%); large remnant polarization (P_r = 13.5 mC/cm², an increase of 11.9%); high piezoelectric coefficient (d₃₃ = 205 pC/N, an increase of 32%) and high electromechanical coupling coefficient (k_p = 0.4, an increase of 11%).