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 Er in the range 42 to 54, high quality factors with Q x f in the range 16,222 to 50,215 GHz, and low tau(f) in the range -25 to +6 ppm/degreesC. These high dielectric constant materials with high Q x 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.