New microwave dielectric ceramics BaLn₂(MoO₄) ₄ (Ln = Nd and Sm) with low loss

In the present work, a pure monoclinic phase of BaNd₂(MoO ₄)₄ and BaSm₂(MoO₄)₄ was formed at 850°C and 600°C, respectively, via a solid-state reaction method. The ceramic samples were found to be well densified at 960°C. Dense and homogeneous microstructures were revealed from the scanning electron microscopy. The microwave dielectric behaviors were studied as a function of sintering temperature and characterized in the temperature range 25°C-120°C. The best properties were obtained in ceramics sintered at 960°C with a permittivity ∼11.7, a Q × f value of 45 000 GHz and a temperature coefficient of frequency about -41 ppm/°C for BaNd ₂(MoO₄)₄ ceramic at 9.9 GHz, and a permittivity ∼11.8, a Q × f value of 20 000 GHz, and a temperature coefficient of frequency about -34 ppm/°C for BaSm₂(MoO₄)₄ ceramic at 9.7 GHz, respectively.