Enhanced electrical properties of new lead-free 0.995Bi<inf>0.5</inf>(Na<inf>0.80</inf>K<inf>0.20</inf>)<inf>0.5</inf>TiO<inf>3</inf>-0.005LiNbO<inf>3</inf> ceramics by (Ba<inf>0.98</inf>Nd<inf>0.02</inf>)TiO<inf>3</inf> doping

Abstract

It is well known that the Bi0.5(Na0.80K0.20)0.5TiO3 or BNKT ceramic possesses quite high piezoelectric coefficient (i.e., d33 ~ 151 pC/N). This research attempted to prepare (1-y)[0.995Bi0.5(Na0.80K0.20)0.5TiO3-0.005LiNbO3]-y(Ba0.98Nd0.02)TiO3 or (1-y)[0.995BNKT-0.005LN]-yBNdT (where y = 0–0.05 mol fraction) lead- free ceramics by conventional sintering method. The optimum sintering condition was found to be 1100°C with a 2 h dwell time with a heating/cooling rate of 5°C/min. The XRD patterns of all samples showed pure perovskite phase. The optimized electrical properties were found in the sample having the composition of y = 0.03 mol fraction. Its dielectric constant was ~1980 with the dielectric loss of 0.0508 at room temperature and ~5987 with dielectric loss of 0.0540 at 268°C. The maximum S max value of 0.25% with d*33 = 491 pm/V, and the piezoelectric coefficient of 258 pC/N were also obtained. The polarization-electric field hysteresis loops of pure and lightly-doped samples indicated a normal ferroelectric behavior. The transition to anti-ferroelectric behavior was observed for the samples with high BNdT content. This showed that the electrical properties of BNKT-LN ceramics could be tuned by small addition of BNdT with the optimum FoM values of 3.80 pm2/N. These lead-free compounds may be suitable for energy harvesting applications.