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=5x=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 xx. A broad permittivity peak is suppressed and shifted to lower temperature with the increase of xx, 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 107–1010Hz, which is of prime importance for tunable microwave application by selecting an appropriate frequency to avoid the relaxation frequency.