TEMPERATURE-INDEPENDENT DIELECTRIC PROPERTIES OF 0.82[0.94Bi_(0.5)Na_(0.5)TiO_3-0.06BaTiO_3]-0.18K_(0.5)Na_(0.5)NbO_3 CERAMICS

摘要

In order to explore the high temperature stability of ceramic capacitor, we present temperature-independent dielectric properties of 0.82[0.94Bi_(0.5)Na_(0.5)TiO_3-0.06BaTiO_3]-0.18K_(0.5)Na_(0.5)NbO_3 (BNT-BT- 18KNN) ceramics. For different sintered temperature and annealing treatment, the pseudoternary system showed a ε_r of 2265 at 1 kHz at 35℃ with a normalized permittivity ε/ε-35℃ varying less than ±15% from 11℃ to 382℃. This pure perovskitc phase with slimmer and heat proof P-E loops possessed energy density of 0-616 J/cm~3 with a tolerance of about ±3% in a temperature interval ranging from 20℃ to 120℃, which is higher and more temperature stable than most ceramic capacitors, such as PLZST and 0.89BNT-0.06BT-0.05KNN. This relaxor ferroelectric (at room temperature) with parabolic bipolar strain-electric (S(E)) curve showed a quite low temperature dependence of positive strain with less than ±6.5% tolerance from the average value of 0.091% between 20℃ and 120℃, which is also more temperature stable than the same composition Zhang et al. reported. These merits demonstrate that the newly produced BNT-BT-18KNN ceramics should be a promising candidate for the development of high-temperature capacitor and actuator materials.