Effect of Li addition in (Pb,Ca)(Ti,W,Co)O3 piezoelectric ceramics

(Pb,Ca)(Ti,W,Co)O3 + x Li2CO3 preparation and properties are reported. We have found that the substitutions of 24 at% of Pb2+ ions in A-site positions by Ca2+ and 5 at% of Ti4+ by cobalt and tungsten ions decrease the transition temperature to around about 300oC. A further decrease is obtained by Li addition of to the Pb0.76Ca0.24Ti0.95W0.025Co0.025O3 basic composition. A sintering process at relatively low temperatures (1000-1050oC) has been employed. The effect of Li content (x wt% Li2CO3, x = 0, 0.14 and 0.28) and sintering temperature on structural, dielectric and piezoelectric properties and their temperature dependence has been investigated. The grain growth process and densification of samples with x = 0.28 Li addition was stabilized at a lower sintering temperature compared to those without Li addition. In both cases similar microstructure and physical properties were obtained . However, in samples with x = 0.14, it seems that the presence of lithium ions reduces the sintering temperature, but favours the abnormal growth of the grains and defects formation in the crystalline lattice, thus leading to very different physical properties.