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The development of low-dimensional multifunctional devices has become increasingly important as the size of field-effect transistors decreases.

The lead-free ceramics 0.92Na0.5Bi0.5TiO3-0.06BaTiO3-0.02K0.5Na0.5NbO3 and 0.92Na0.5Bi0.5TiO3-0.06BaTiO3-0.02K0.5Na0.5NbO3 with the addition of 0.2 wt% Co2O3 were prepared by using a solid state reaction method. The ceramics were sintered in O2 and N2 atmospheres, respectively. The rhombohedral-tetragonal morphotropic phase boundary exists in all samples, with the relative amount of tetragonal phase varying with the sintering atmospheres which does not affect grain size of the ceramics. In the dielectric constant-temperature curves for all samples, two dielectric anomalies appear. The phase transition temperatures and maximum values of dielectric constant are closely related to the sintering atmospheres. The mechanism was also discussed.

(1 − x )(0.93Na 0.5 Bi 0.5 TiO 3 –0.07BaTiO 3 )– x BiAlO 3 (BNBT- x BA, x = 0, 0.01, 0.02, 0.06) lead-free ceramics were synthesized via a conventional solid state reaction method. Crystallite structure, microstructure, dielectric and ferroelectric properties of the BNBT– x BA ceramics were studied in detail. X-ray diffraction results show that all ceramics exhibit typical diffraction peaks of ABO 3 perovskite structure. Scanning electron microscope images show that all samples have fine microstructures. Both Curie temperature and maximum dielectric constant vary with the change in the BiAlO 3 amounts. The values of hysteresis loop squareness were calculated to be 1.26, 0.81, 0.51 and 0.36 for the ceramics with x = 0, 0.01, 0.02 and 0.06, respectively, indicating a decreased switching behavior of polarization. The changes in dielectric and ferroelectric properties of the ceramics are also discussed.

Lead-free ceramics, 0.97[(Na 0.5 Bi 0.5 ) 1−1.5 x La x ]TiO 3 –0.03BaTiO 3 (NBTB-xLa, x = 0, 0.01, 0.02, 0.03, 0.05 and 0.08), were prepared by using a conventional solid state reaction method. The ceramics with x ⩽ 0.05 have pure perovskite, while a secondary phase appears in the sample with x = 0.08. The doping of La 3+ decreases grain size of the ceramics. For both the unpoled and poled NBTB-xLa ceramics, there exist two dielectric anomalies. For the poled ceramics with x = 0, 0.01, 0.02 and 0.03, a new dielectric anomaly appears at depolarization temperature ( T d ). The T d peak is not observed in the e r –T curves for the ceramics with x = 0.05 and 0.08. The phase transition temperature ( T m ) increases with increasing amount of La 3+ , but the values of T d and maximum dielectric constant ( e m ) decrease gradually . Piezoelectric constants ( d 33 ) of the ceramics with x = 0, 0.01, 0.02, 0.03, 0.05 and 0.08 are 91, 87, 77, 56, 7 and 2 pC/N, respectively. The change in ferroelectric properties of the samples with increasing content of La 3+ is also discussed.

(Na0.47Bi0.46Ba0.06K0.01)(Nb0.02Ti0.98-xZrx)O3 lead-free ceramics (BNBKT-xZr, x = 0, 0.01, 0.02, 0.04) were synthesized via conventional solid state reaction method. Crystallite structure of the ceramics was studied using X-ray diffraction. The rhombohedral phase and tetragonal phase coexist in the BNBKT-xZr ceramics. The doping of Zr4+ into BNBKT lattice increases the percentage of the tetragonal phase. The size and shape of grains in the ceramics were affected by the doping of Zr4+ ions. For all the unpoled ceramics, two dielectric anomalies are observed in the dielectric constant-temperature curves. The maximum values of dielectric constant and corresponding temperatures change with the variation of Zr4+ amount. The doping of Zr4+ ions causes a decrease in the ferroelectric properties.