  We report the phase diagram of (Ba1-xCax)(Zr0.1Ti0.9)O3 solid solution. It is
found that substitution of smaller Ca ions for Ba ions can slightly increase
the cubic-tetragonal(T) para-ferroelectric phase transition temperature and
strongly decrease the T-orthorhombic (O) and O-rhombohedral (R) transition.
This unique ferroelectric phase evolution is attributed to Ca off-centering
effects. More importantly, lowering of the T-O or O-R phase transitions allows
us to prepare the piezoelectric ceramics with a strain response as high as
S/E~800 pm/V (E=10 kV/cm) over a wide range of compositions with x~0.1 - 0. 18
at room temperature, which may be interesting for piezoelectric applications.
