4. Conclusions
Low temperature sintering of BNKT ceramics was
examined by doping CuO as a sintering aid. It was found
that the addition of excess CuO was quite effective to lower Ts
of BNKT ceramics by 200 8C even at a doping level as low as
1 mol% although their piezoelectric properties were degraded
with CuO doping. However, the electric-field-induced strain
was markedly enhanced by further addition of Nb2O5 with CuO
even at a low Ts of 975 8C. A large normalized strain Smax/Emax
of 427 pm/V was observed in a specimen co-doped with
0.02 mol CuO and 0.02 mol Nb2O5 in excess, which is very
promising for its application to low cost MLAs.