Dielectric and ferroelectric properties of bismuth-layer high Curie point Na0.5Bi4.5Ti4O15 ceramics with Mg-doping

Abstract

Abstract As a new kind family of lead-free Na 0.5 Bi 0.5 TiO 3 (NBT) ceramics, bismuth layer-structured ferroelectrics (BLSFs), Na 0.5 Bi 4.5 Ti 4 Mg x O 15+ x and Na 0.5 Bi 4.5 Ti 4- x Mg x O 15- x ceramics (with x = 0.04, 0.08) were artificially compounded by a conventional mixed oxide route. Under different sintering temperatures, we changed the Ti content of ceramics or Mg-doping on Ti-site in order to explore the ferroelectric and dielectric properties. XRD standard patterns of Na 0.5 Bi 4.5 Ti 4 Mg x O 15+ x and Na 0.5 Bi 4.5 Ti 4- x Mg x O 15- x (with x = 0.04, 0.08) proved that the materials were a single phase of BLSFs. By analysing the data of impedance spectra, we found that the Na 0.5 Bi 4.5 Ti 4 Mg 0.04 O 15.04 ceramics sintered at 1100 °C showed prominent dielectric properties with a dielectric constant of 1915.65 at 100 kHz and a dielectric loss of 0.0020 at 1 MHz, which were enhanced much compared with other samples. Meanwhile, the Curie temperature ( T c ) of all samples were about 660 °C. Moreover, the ferroelectric hysteresis loops of all the samples revealed that they were ferroelectric materials, which possessed a remanent polarization (2 P r ) from 5.16 to 8.78 µC/cm 2 and a coercive field from 101 to 127.78 kV/cm. The cross-section SEM showed that all samples had no c-axis orientation, whose grain distribution was more and more uniform and regular when activation energy ( E a ) increased. The E a can be calculated in the range of 1.10–1.47 eV, which indicated they were dielectric ceramics. Consequently, the ceramics have the prospect of application in high-temperature capacitors and phase shifter field because of their high dielectric constant, low dielectric loss and wide operating temperature range.