New Piezoelectric Ceramics with Zero Temperature Coefficients for Acoustic Wait Applications

Lead titanate (PbTi03) ceramics having zero temperature coefficients in various acoustic wave modes are developed by addition of Nd2O3, and Mn02. The chemical formulae of these ceramics are generally expressed by (Pbl 3,+lZNd,) (Til-y-zM”yInz)03. These ceramics have very small surface wave delay time temperature coefficients (less than 1 x 10-6/OC) over a wide temperature range (-loo to +6OoC) with appropriate compositions. Furthermore, it is possible to reduce the resonance frequency temperature coefficients in bulk wave modes (radial mode, thickness mode, flexure mode) to the same order as for surface waves by appropriately changing the combination of Nd, Mn, In concentrations. These modified PbTi03 ceramics are thus potential materials for acoustic wave applications. As application examples, SAW filters (60, ~OOMHZ), tuning fork resonators (3OkHz), and thickness mode resonators (4wz) are fabricated using these ceramics. In203