High-temperature dielectric properties of Bi0.5Na0.5TiO3–NaNbO3–Sr0.8Na0.4Nb2O6 ceramics

Abstract

Dielectric materials 0.99((1-x)Bi0.5Na0.5TiO3-xNaNbO3)-0.01Sr0.8Na0.4Nb2O6 (BNT-xNN-SNN) with x = 0.15, 0.20, 0.25 and 0.30 have been developed for high-temperature capacitors. Temperature-dependent dielectric permittivity ε′ and loss tanδ, DC resistivity and ferroelectric properties are reported. The ε′ and tanδ of the BNT-0.25NN-SNN ceramic are very stable over a wide temperature range (<-55 °C ∼ >350 °C), in which the variable rates of ε′ (∣ε′- ε′25 °C∣/ε′25 °C), and tanδ are no more than 15% and 0.02, respectively. In addition, ε′ at a reference temperature 25 °C is 1250. The resistivity is also high on the order of magnitude of 1011 Ω m at 100 °C and 108 Ω m at 300 °C. The RC constant is approximately 2.8 s at 300 °C. The results show that the BNT-0.25NN-SNN ceramic is a good candidate material for high-temperature capacitors.