High permittivity and low loss dielectric ceramics in the BaO-La2O3-TiO2-Ta2O5 system

Dielectric ceramics were synthesized and characterized in the BaO-La2O3-TiO2-Ta2O5 quaternary system for the three typical compositions: Ba3La3Ti5Ta5O3O, Ba4La2Ti4Ta6O30 and Ba5LaTi3Ta7O30, which formed the filled tungsten-bronze structures. The present ceramics indicated high dielectric constant 6 (127.7-148.1) and low dielectric loss tandelta (in the order of 10(-4)-10(-3) at 1 MHz). Meanwhile, the temperature coefficient of dielectric constant tau(epsilon) varied from -728 to -1347 ppm/degreesC with increasing Ba and Ta and decreasing La and Ti concentration in the temperature range of 20-85 degreesC. The present ceramics are promising candidates for high-epsilon and low loss dielectric ceramics, and the suppression of tau(epsilon) should be the primary issue in the future work. (C) 2003 Elsevier Science Ltd. All rights reserved.