Microwave dielectric properties of BaTi₄O₉-BaSm ₂Ti₄O₁₂ composite ceramics

BaTi₄O₉ and BaSm₂Ti₄O ₁₂ possess large dielectric performances and low dielectric loss, but their temperature-dependent properties could not meet with the practical use. In this paper, a composite ceramic system BaTi₄O₉/ BaSm₂Ti₄O₁₂ (BaTi₄O₉ + xSm₂O₃, x = 20, 40, 60, 80 mol%) was prepared and their dielectric properties was presented. The composite ceramic precursor were modeled by a cool iso-static press (CIP) and calcined at 1300°C for 6 h. The measured densities of ceramic samples increased, but the relative densities decreased with the increase of x. XRD patterns showed there existed two phases of BaTi₄O₉ and BaSm₂Ti₄O ₁₂ in the composite. The dielectric constants increased from 39.7 to 60.0, while the quality factors decreased from 8300 to 1500. At x = 40%, a near-zero temperature coefficient of +2.2ppm/°C was achieved. The presence of pores, Ti³⁺ and Ti²⁺ was proposed to be the cause of the deviation from calculated dielectric properties.