Relaxor behavior and dielectric properties of (1-x)Ba0.6Sr0.4TiO3-xMg(0.7)Zn(0.3)TiO(3) composite ceramics for tunable microwave applications

摘要

(1 - x)Ba0.6Sr0.4TiO3(BST)-xMg(0.7)Zn(0.3)TiO(3) (MZT) composite ceramics, where x = 5, 10, 20, 30 wt, were fabricated by the conventional solid-state reaction and their relaxor behavior and microwave properties were studied. The new phases BaMg6Ti6O19 and Ba2ZnTi5O13 are formed in BST composite ceramics with increasing x. A broad permittivity peak is suppressed and shifted to lower temperature with the increase of x, accompanying strong frequency dispersion due to the ionic substitution, which follows well the Vogel-Fulcher relationship. The obtained tunability is above 23 under 30 kV/cm biasing at room temperature. The dielectric relaxation is observed in the range 10(7)-10(10) Hz, which is of prime importance for tunable microwave application by selecting an appropriate frequency to avoid the relaxation frequency.