Macro- and microstructure of lead perovskite ternary piezoelectric single crystals after direct current and alternating current poling

Piezoelectric single crystal (SC) plates of ternary system 0.24Pb(In1/2Nb1/2)O3-0.46Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 manufactured by the continuous-feeding Bridgman method with excellent uniformity were subjected to direct current poling (DCP) and alternating current poling (ACP) processes. And the relationship between their piezoelectric properties and microstructures was investigated using a scanning electron microscope. The dielectric constant (ε33T/ε0) and piezoelectric constant (d33) of the DCP SC were 5500 and 1800 pC/N, respectively, while the microstructure was a uniform random domain structure. Under optimum ACP conditions, the SC had ε33T/ε0 of 7500 and d33 of 2300 pC/N. Four types of 109° domains with stripes ranging from 1 to 3 µm were observed. The under-poled SC had ε33T/ε0 of 1700–6000 and, d33 of 600–2000 pC/N, and a large abnormal microstructure of approximately 25 × 150 µm2 was observed along with 109° stripe-like fine domains. Also, in all SC samples, unclear microstructure layers of approximately 20 µm were observed in the area directly below the top and bottom electrodes. These results indicate that the microstructure of piezoelectric SC is non-uniform between small areas (less than 20 µm2 in a plate), and that precision is essential when discussing the correlation between piezoelectric properties and the microstructure of SCs.