Microwave dielectric properties of MO–La₂O₃–TiO₂ (M = Ca, Sr, Ba) ceramics

Single-phase polycrystalline ceramics in the MO–La₂O₃–TiO₂ (M = Ca, Sr, Ba) system, such as cation-deficient hexagonal perovskites CaLa₄Ti₄O₁₅, SrLa₄Ti₄O₁₅, BaLa₄Ti₄O₁₅, and Ca₂La₄Ti₅O₁₈ and the orthorhombic phases CaLa₄Ti₅O₁₇ and CaLa₈Ti₉O₃₁, were prepared through the solid-state ceramic route. The phases and structure of the ceramics were analyzed through x-ray diffraction and scanning electron microscopy. The microwave dielectric properties of the ceramics were studied using a network analyzer. The investigated ceramics show high ε_r in the range 42 to 54, high quality factors with Q ×f in the range 16,222 to 50,215 GHz, and low T_f in the range –25 to +6 ppm / °C. These high dielectric constant materials with high Q × f up to 50,215 GHz are suitable for applications where narrow bandwidth and extremely low insertion loss is necessary, especially at frequencies around 1.9 GHz.