Crystalline structure and dielectric properties of Li_1+x-yNb_1-x-3yTi_x+4yO₃ M-phase solid solutions

The structure and dielectric properties of the so-called M-phase solid solutions in the Li₂O-Nb₂O₅-TiO₂ system have been investigated. Detailed studies of the lattice parameters of these phases agree well with structure models based on intergrowths of LiNbO₃ slabs with a titanium-rich corundum-type layer. The relative permittivity ranges from ∼80 to ∼55; microwave quality factors increase with the titanium content, reaching values of Q×f = 9000 at 6 GHz. The temperature coefficient of the resonant frequency changes sign within the solid solution region, thus permitting tunability to a zero value. All the compositions can be sintered to high density at temperatures ≤1100°C.