ABSTRACT We have investigated the voltage-tunable characteristics of the Na0.5Bi0.5TiO3-NaTaO3 homogeneity region, for which samples were prepared using a conventional solid-state reaction. The highest value of the relative tunability (nr) was obtained for the sample with 5 mol% of NaTaO3, i.e., 47% at 1 MHz and a 70 kV/cm dc bias field. This sample also showed the highest value of the dielectric losses (tanδ) and temperature coefficient of the dielectric constant (τε), i.e., 0.05 and 4478 ppm/K, respectively. As the concentration of NaTaO3 increased up to 90 mol% nr, tanδ, and τε gradually decreased toward 22%, 0.0002 and -899 ppm/K, respectively. The dielectric constant of the samples varied in a similar manner between 662 and 130. At microwave frequencies, the dielectric losses of the samples substantially increased due to their relaxor-type nature. The lowest value was obtained for the samples with 90 mol% of NaTaO3, i.e., 0.002. The tunable characteristics of the samples are related to the ferroelectric and dielectric properties, and it appears that the dielectric tunability of the Na0.5Bi0.5TiO3-NaTaO3 system originates from its relaxor-type behavior.
Digital Object Identifier 10.1109/TUFFC.2007.588
© 2007, by The Institute of Electrical and Electronics Engineers, Inc. All rights reserved.