Elaboration and piezoelectric properties of high-density ceramics of the system Li_0.85Ca_0.15Ta_0.85Zr_0.15O₃–SiO₂

Abstract

Lithium tantalate (LiTaO 3 ) single crystals are relevant as surface acoustic wave filters due to their high electromechanical coupling factor. However, LiTaO 3 and related-compound ceramics reported so far have low relative density and therefore cannot be sufficiently poled to be used as lead-free piezoelectric materials. In the present work we succeeded in elaborating rather dense ceramics within the binary diagram (1-x)Li 0.85 Ca 0.15 Ta 0.85 Zr 0.15 O 3 -x wt% SiO 2 with   x 0 1 . 0 .This system tended to behave as a continuous solid solution for   x 0 1 . 0 . However due to the great difference between the size of Si 4+ and that of Li + , Ca 2+ , Zr 4+ and Ta 5+ , such a solid solution could not be explained by a substitution mechanism as Si 4+ cannot fit the size of larger cations. CZS0.3 (x = 0.3) of the highest density had a resonance characteristic of the radial-extensional mode with a phase shift of 74.2°in the inductive region and a Q m value as high as 8024 was achieved.