Electric Properties Of Nanocrystalline BaTiO₃Ceramics

Microstructure and electric properties of the15nm～100nm ceramics were studied in this paper. We measured the electric hysteresis loops, piezoelectric displacement, permittivity-temperature spectrums, C-V curves, J-E and J-T curves by TF Analyzer2000and Impedance Analyzer. Meanwhile, size effect on the electric properties of BaTiO3ceramics were analyzed, and the conduction mechanism of leakage about ultrafine grain BaTiO3ceramics also investigated.Electric field, frequency and temperature effects on80nm、60nm、15nm BaTiO3ceramics have been studied, its ferroelectricity is weaken when the grain size decreasing, thus, ferroelectricity will disappear when the size down to a certain value.100nm is the crucial size between the micron-crystalline and the ultrafine nanocrystalline in BaTiO3ceramics. The result of XRD indicates that tetragonal is the main phase. From the curves of ε-T, there is typical dispersion characteristics in orthorhombic to tetragonal phase transition, and the loss tangent (tan8) is lower than0.02. Temperature dependence on the dielectric and ferroelectric properties of dense BaTiO3ceramic with the nanocrystalline of50nm was investigated. The dispersion parameter was calculated to be1.60at1kHz. The dielectric constant-field (ε-E) loops at different temperatures showed that the permittivity anomalies occurred in a temperature range of110-120℃. The dielectric constant tunability was20.2%at110℃. Moreover, the positive piezoelectric coefficient d33of45pm/V was determined from the slope of the loops.Schottky emission, Poole-Frenkel (PF) conduction and space charge limited current (SCLC) conduction mechanism of leakage is analyzed in ultrafine BaTiO3ceramic. Results and calculations indicate that Poole-Frenkel conduction mechanism is satisfied. Moreover, temperature and field dependence on the leakage is studied, when E=9kV/cm, T=293K, leakage (J) is1.11×10-4A/cm2, T=373K, J is1.17×10-3A/cm2.