Investigation of Piezoelectric Resonators Excited By Lateral Electric Field

During last years the disigners of acoustic liquid sensors concentrate special attention on piezoelectric resonators with lateral electric field. The main problem of their development is the supression of unwanted oscillations. For achievement of this aim there exist at least two variants. Firstly, the choice of optimal shape of electrodes and exact their orientation respectively to crystallographic axes of plate. However the shape and dimensions of electrodes depend on shape of plate and its sizes. Secondly, the deposition of the damping layer around the electrodes including the certain part of electrodes. The paper is devoted to the experimental study of the influence of width of gap between electrodes and width of area of electrodes covered by damping layer on the frequency and $Q$ - factor of series and parallel resonances and electromecanical coupling coefficient. Electrodes of rectangular shape with dimensions 5 $\times$ 10 mm were deposited on the plate of lithium niobate of $X$ – cut with thickness of 0.5 mm. The width of the gap between electrodes and width of their coating area were changed from 1 to 5 mm. The lateral electric field was oriented along axis $Y$. It has been shown that the resonance was achieved on the longitudinal acoustic wave propagating along axis $X$ between electrodes. It has been found that changes in width of gap between electrodes and width of coating area vary frequencies of series and parallel resonances in the range of $\sim$1\%. At that the values of $Q$ – factor of series and parallel resonances change in ranges 500 - 13000 and 500 - 1800, respectively. The change in electromechanical coupling coefficient lies in range 1 - 4\%.