Stable dielectric properties of Na1+xBiTi6O14+0.5x (x = −0.02, − 0.01, 0.01, 0.02) ceramics with low loss and high operating temperature

New lead-free dielectric ceramics, Na1+xBiTi6O14+0.5x (x = −0.02, − 0.01, 0.01, 0.02), were prepared by the conventional solid-state method. Micro-structural and electrical properties of Na1+xBiTi6O14+0.5x were studied. XRD showed all the samples exhibited a single structured phase. Grains decreased at the beginning, then grew with the increasing x content in SEM. Impedance spectra (IS) analysis evidenced the phenomena that the dielectric permittivity increased firstly, then decreased, while the loss had the opposite trend. Z* plots showed that Na1+xBiTi6O14+0.5x ceramics were a kind of dielectrics. The activation energy (Ea) could be calculated in the range of 1.53-1.65 eV, which indicated they were dielectric ceramics. Na1+xBiTi6O14+0.5x ceramics (x = 0.01) sintered at 1040 °C showed prominent dielectric properties with a dielectric constant of 25.76, loss of 0.07%, Ea of 1.65 eV, density of 3.463 g/cm3, impedance of 0.532 MΩ cm, -Z′′max of 0.1958 MΩ cm, capacitance of 5.56 pF/cm (600 ℃), which were enhanced much compared with other samples. The existence of dielectric properties with high dielectric constant, low dielectric loss and wide operating temperature range makes it possible to develop the ceramics into high-temperature capacitors.