Abstract: Some special features in dielectric, piezoelectric properties and phase transition behavior of (1-x)Pb(Mg_1/3Nb_2/3)O_3-xPbTiO_₃ (PMN-PT) (x=0.24, 0.3, 0.33 and 0.35)
single crystals grown by Bridgman method were outlined: 1) Extremely high piezoelectric constant d₃₃ (up to 3000 pC/N) and
coupling factors k₃₃ and k_t (up to 0.94 and 0.62 respectively), low mechanical factor of merit (Q_m～60), large dielectric constant
ε(～5000). 2) Strong orientation dependence of piezoelectric properties. 3) with increasing PT content, the system becomes less relaxational,
but at least upto x=0.35, the system still partly exhibites relaxor feature: for x=0.33 and 0.35. ε～T curves look sharp enough to show
a normal ferroelectric like feature, however when T>T_m the ε～T relation does not obey Curie-Weiss law, but follows Smolenskii’s relation.
The piezoelectric properties of PMN-PT ceramics are similar to PZT-5H, but with higher ε and k₃₁.

Key words: Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃, piezoelectric property, relaxor