Peculiar properties of a high Curie temperature Pb(In1/2Nb1/2)O-3-PbTiO3 single crystal grown by the modified Bridgman technique

(1 - x)Pb(In1/2Nb1/2)O-3-xPbTiO(3) single crystal near the morphotropic phase boundary has been grown directly from the melt by the modified Bridgman technique, in which an allomeric PMNT 69/31 seed crystal was used. It was found the use of seed crystal has some advantages for the control of spontaneous nucleation, parasitic growth and for restraining the formation pyrochlore phase. The electric properties of the single crystals oriented along [001] axis have been characterized. It exhibited an abnormal high permittivity (epsilon(33)/epsilon(0)) of more than 4000 at room temperature, Curie temperature (T-c) higher than 200 degreesC, piezoelectric constant (d(33)) > 2000 pC/N, and electromechanical coupling factor k(33) approximate to 92%, k(t) = 59.2%. Our results show that the peculiar properties e.g. the larger dielectric constant at room temperature and lower T-c than that of previous reports should attribute to the diffuseness of magnesium ion into the PINT single crystal during crystal growth. X-ray fluorescence analysis revealed the composition of the crystals was in the range of 0.23Pb(Mg1/3Nb2/3)O-3-0.46Pb(In1/2Nb1/2)O-3-0.31PbTiO(3) to 0.19Pb(Mg1/3Nb2/3)o(3)-0.46Pb(In1/2Nb1/2)O-3-0.35PbTiO(3). It implied that the ternary system of xPb(Mg1/3Nb2/3)O-3-yPb(In1/2Nb1/2)O-3-(1 - x - y)PbTiO3 (PMINT) should have good perovskite phase thermal stability, larger dielectric constant at room temperature, and ultrahigh piezoelectric properties. (C) 2002 Published by Elsevier Science Ltd.