Co mpositional proximity to a morphotropic t ransformation between two ferroelectric solid-solution phases seems to yie ld ceramic transducers having desirable properties over a wide range of te mperature. Examples of t his phenomenon were observed in the systems PbTi03-PbZr03, PbTi03-PbO:Sn02, PbTi03-PbZr03-PbO:SnO" and PbTi03-PbHf03. The dielectric and piezoelectric properties of ceramics having compositions in these syste ms and in t he system PbZr03-PbO:Sn02 are described . The composition Pb (Ti .. 5Zr .5,) 0 3 ex hibits a high radial coupli ng coefficient, greater than 0.3, for temperatures as high as 275 0 C and has t he highest g31 constant, 1l .7 X 103 volt -meters per ne\\·toll . For the ser ies of compositions containing 30 percent PbO:SnO, in the ternary system PbTi03-PbZr03-PbO:Sn02 the tetragonal composition nearest the morphotropic boundary has the highes t d31 value, 74 X 1012 coulombs per newton . The rhombohedral composition nea rest. the morphotropic boundary sho\\'s the least change of frequency co nstant with temperature, a 2 perce nt variat ion over t he range of 25 0 to 225 0 C.