Ferroelectric and piezoelectric properties of novel relaxor ferroelectric single crystals PMNT

Relaxor ferroelectric single crystals PMNT with the size of Φ40 mm 80 mm have been grown by a modified Bridgman method and their ferroelectric and piezoelectric properties have been characterized. The properties varied with the compositions and cut types. On the (001) cut, PMNT76/24 single crystals exhibited a dielectric constant e of about 3 400, a dielectric loss of tan δ <0.7%, a piezoelectric constant d₃₃ of 980 pC/N, an electromechanical coupling factor k_t of 0.55 and T_c of about 110 . Whereas the properties of PMNT67/33 single crystals on (001) cut were better: ε of about 5 300, tan δ 0.6%, d₃₃ up to 3 000 pC/N, k_t 0.64, k₃₃ 0.93 and T_c of about 150°C . The piezoelectric properties on other cuts such as (110) and (111) were much lower than those on the (001) cut. The rhombohedral PMNT crystals grown by this method showed more excellent piezoelectric properties than those grown by high temperature solution method and higher value of k_t than the rhombohedral PZNT single crystals. It has also been found that the fluctuation in ferroelectric and piezoelectric properties was related to such factors as composition uniformity and poling degree.