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

Dielectric ceramics were synthesised and characterised in the BaO-La2O3-TiO2-Ta2O5 quaternary system for the three typical compositions: Ba3La3Ti5Ta5O30, Ba4La2Ti4Ta6O30 and Ba5LaTi3Ta7O30, which formed the filled tungsten-bronze structures. The ceramics showed high dielectric constant (127.7-148.1) and low dielectric loss tan delta (in the order of 10 exp(-4)-10 exp(-3) at 1 MHz). The temperature coefficient constant varied from -728 to -1347 ppm /C with increasing Ba and Ta and decreasing La and Ti concentration in the temperature range of 20-85 C. The ceramics are promising candidates for high-permittivity and low loss dielectric ceramics, and the suppression of the temperature coefficient of dielectric constant and improvement in the quality factor should be the primary issue in future work. 10 refs.