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Relaxor ferroelectrics of Pb(Zn1/3Nb2/3)0.5(Zr0.47Ti0.53)0.5O3 (0.5PZN-0.5PZT) were prepared using the conventional oxide mixing method. Both x-ray diffraction analysis and Raman spectroscopy indicate that the amounts of rhombohedral phase are close to tetragonal phase, implying the presence of the morphotropic phase boundary (MPB) in the system of 0.5PZN-0.5PZT, and this result was further confirmed by transmission electron microscopy (TEM) micrographs. At MPB composition, the excellent piezoelectric properties, such as kp (0.66) and d33 (425pC/N), were obtained due to the more possible polarization directions of domains and high dc resistivity of 6.5
1010 Ocm. Meanwhile, the dielectric studies revealed that the indicator of the degree of diffuseness g value is 1.73, implying the relaxor nature of the 0.5PZN-0.5PZT ceramic. The activation energy related to the dc conductivity was estimated from a linear fitting of the Arrhenius law. The value of 0.09 and 1.04 eV for low and high temperature range corresponds well to the activation energies of migration and first ionization of the oxygen vacancies.

I. INTRODUCTION

Much attention has been paid to relaxor ferroelectrics for its high dielectric permittivity, broad ferroelectricparaelectric transition, and strong frequency dependency of the dielectric properties.1 Among all the lead-based relaxor ferroelectrics, lead zinc niobate, Pb(Zn1/3Nb2/3)O3 (PZN), in the perovskite structure exhibits a high Curie temperature of 140  C and excellent piezoelectric as well as dielectric properties. However, pure perovskite structure PZN is difficult to prepare by conventional oxide mixing methods, due to its inherently low tolerance factor and small electronegativity difference between cations.2 To stabilize the perovskite structure of PZN, addition of other perovskite materials, such as BaTiO3, PbTiO3, or Pb (Zr,Ti)O3 (PZT), is an effective method.3 Among all the additives, PZT is one of the most important piezoelectric materials. It has been found that by adding a certain amount of PZT to the PZN matrix, the formation of pyrochlore phase was suppressed effectively. Conversely, compared with binary PZT, adding PZN can extend the stability region of the morphotropic phase boundary (MPB) from one point to line.4 Furthermore, due to the lower sintering temperature (approximately 900  C) of PZN compared with that of PZT, the densified temperature would be lowered after adding PZN to PZT. a)

Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2009.0246 J. Mater. Res., Vol. 24, No. 6, Jun 2009

http://journals.cambridge.org

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It has been reported that Pb(Zn1/3Nb2/3)0.5(Zr0.47Ti0.53)0.5 O3 (0.5PZN-0.5PZT) exhibits more excellent properties because it is at MPB composition.5–7 In our previous work, the effect of sintered temperature and Li2CO3 doping on the properties 0.5PZN-0.5PZT have also been reported.8,9 In spite of these intensive investigations, the studies of phase structure related to MPB composition through differ