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

Dielectric materials 0.99((1-x)Bi0.5Na0.5TiO3-NaNbO3)-0.01Sr(0.8)Na(0.4)Nb(2)O(6) (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 epsilon' and loss tan delta, DC resistivity and ferroelectric properties are reported. The epsilon' and tan delta of the BNT-0.25NN-SNN ceramic are very stable over a wide temperature range (<-55 degrees C similar to >350 degrees C), in which the variable rates of epsilon' (vertical bar epsilon' - epsilon'(25) degrees(C)vertical bar/epsilon'(25) degrees(C)), and tan delta are no more than 15% and 0.02, respectively. In addition, epsilon' at a reference temperature 25 degrees C is 1250. The resistivity is also high on the order of magnitude of 10(11) Omega m at 100 degrees C and 10(8)Omega m at 300 degrees C. The RC constant is approximately 2.8 s at 300 degrees C. The results show that the BNT-0.25NN-SNN ceramic is a good candidate material for high-temperature capacitors.