Structural, electrical properties and stability in microwave dielectric properties of (1−x) MgTiO3-x SrTiO3 composite ceramics

Abstract

Development of (1−x) MgTiO3 (MTO)-x SrTiO3 (STO) (for x = 0.04, 0.1–0.5) composite ceramics and tuning of temperature coefficient of resonant frequency (τf) near to zero through solid state reaction method have been reported. The MTO and STO crystals physically diffused together to form a single crystal structure without any trace of chemical interaction. A gradual improvement in dielectric constant (18.74–85.55) with an increase in STO content is obtained for the composite ceramics. Further, the dielectric constant remained almost invariant for a broad frequency range (100 Hz–100 MHz). However, temperature-dependent dielectric constant exhibited significant dispersion. The perusal of Mott’s variable range hopping 3-d model revealed the dominance of short-range hopping (<3 nm) in the composite ceramics. The activation energies for conduction are found to be decreasing (172–83 meV) with STO content which might be attributed to the increase in density of states from 1.65 × 1019 eV−1 cm−3 to 3.413 × 1020 eV−1 cm−3. The (1-x) MgTiO3-x SrTiO3 (for x = 0.04) composite ceramics exhibited best microwave dielectric properties with moderate quality factor (Q × f0) ~26,154 GHz at 8.08 GHz and better thermal stability (τf ~1.76 ppm/K). All the physical parameters followed cubic relation with STO content. The obtained microwave dielectric properties of 0.96MTO-0.04STO composite ceramics are suitable for microwave communication applications as microwave filters, resonators.