Ferroelectric and piezoelectric properties of novel relaxor ferroelectric single crystals PMNT

Relaxer ferroelectric single crystals PMNT with the size of phi 40 mmX80 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 epsilon of about 3 400, a dielectric loss of tans <0.7%, a piezoelectric constant d(33) Of 980 pC/N, an electromechanical coupling factor k(t) of 0.55 and T-c of about 110 degrees C. Whereas the properties of PMNT67/33 single crystals on (001) cut were better: epsilon Of about 5 300, tan delta <0.6%, d(33) UP to 3 000 pC/N, k(t) 0.64, k(33) 0.93 and T-c of about 150 degrees 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.