Optimizing SAW Device Performance Using Titanium-Doped Lithium Niobate Substrates

This study introduces a new theoretical framework for the ferroelectric phase transition in lithium niobate (LiNbO3), which explicitly incorporates electrostatic interactions between both first and second nearest-neighbor ions. This extended model is applied to estimate the inverse quality factor (Q−1), the equivalent mechanical resistance (Rm), and the Curie temperature (Tc) of pure and titanium-doped lithium niobate (LiNbO3:Ti). The proposed analytical expression for Tc is given by: TC*=2−p*3cos(θ*3)−B*32−p3cos(θ3)−B3 TC. The analysis reveals that variations in Q−1 and Tc are governed by factors such as ionic mass, charge, and defect structure. The theoretical predictions show good agreement with experimental data reported in the literature—particularly for Q−1 in pure LiNbO3 and for Tc in Ti-doped LiNbO3—thus validating the reliability of the proposed model. Moreover, at constant temperature, both the inverse quality factor and the equivalent mechanical resistance decrease as the Ti concentration increases. This trend highlights that titanium doping enhances the acoustic performance of LiNbO3 substrates, making them more suitable for high-performance surface acoustic wave (SAW) device applications.