Crystal structure and dielectric properties of La(Mg_(0.5)Ti_(0.5))O_3-Ca_(0.8)Sm_(0.4/3)TiO_3 solid solution system at microwave frequencies

摘要

The crystal structure and the dielectric properties of (1 -x)La(Mg_(0.5)Ti_(0.5))O_3-xCa_(0.8)Sm_(0.4/3)TiO_3 ceramics have been investigated. Ca_(0.8)Sm_(0.4/3)TiO_3 was employed as a τ_f compensator and was added to La(Mg_(0.5)Ti_(0.5))O_3 to achieve a temperature-stable material. The formation of (1 -x)La(Mg_(0.5)Ti_(0.5))O_3-xCa_(0.8)Sm_(0.4/3)TiO_3 solid solutions were confirmed by the XRD results and the measured lattice parameters for all compositions. The dielectric properties are strongly correlated to the sintering temperature and the compositional ratio of the specimens. Although the ε_r of the specimen could be boosted by increasing the amount of Ca_(0.8)Sm_(0.4/3)TiO_3, it would instead render a decrease in the Q x f. The τ_f value is strongly correlated to the compositions and can be controlled by the existing phases. A new microwave dielectric material 0.45La(Mg_(0.5)Ti_(0.5))O_3-0.55Ca_(0.8)Sm_(0.4/3)TiO_3, possessing a fine combination of microwave dielectric properties with an ε_r of 47.83, a Q x f of 26,500 GHz (at 6.2 GHz) and a τ_f of-1.7ppm/°C, is proposed as a very promising candidate material for today's 3G applications.