Effect of BaTi₄O₉ fibers on dielectric properties of 0.64 BaTi₄O₉ + 0.36 BaEu₂Ti₄O₁₂ composites

BaTi₄O₉ (f)/(0.64 BaTi₄O₉-0.36 BaEu₂Ti₄O₁₂) (BET) composites were prepared for a new kind of microwave dielectric ceramic with modifiable dielectric constant and low dielectric loss. Microstructure, dielectric properties, and the chemical state of Ti element on the sample surface were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), LCR meter method and X-ray photoelectron spectroscopy (XPS). The results show that this system is composed of two phases, i.e. BaTi₄O₉ and BaEu₂Ti₄O₁₂. Eu ions are distributed in the BaTi₄O₉ grains and when the content of Eu element in the BaTi₄O₉ phase is more than 1 at.%, there are small BaEu₂Ti₄O₁₂ grains formed at triple junctions of BaTi₄O₉ phases. XPS results show that the content of Ti³⁺ and Ti²⁺ decreases in the BET composites due to the addition of BaTi₄O₉ fibers, which improve the dielectric properties of this system. BET10 sample, which has 10% BaTi₄O₉ fibers, has the best dielectric properties in this system with σ_r = 55 and tgδ = 3 × 10^-4 (at 1 MHz), respectively.