Relaxor behavior and dielectric properties of (1−x)Ba0.6Sr0.4TiO3–xMg0.7Zn0.3TiO3 composite ceramics for tunable microwave applications

(1−x)Ba0.6Sr0.4TiO3(BST)-xMg0.7Zn0.3TiO3 (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 107– 10 10 Hz , which is of prime importance for tunable microwave application by selecting an appropriate frequency to avoid the relaxation frequency.