Structural change in polar nanoregion in alkali niobate added Pb(Zn <inf>1/3</inf>Nb <inf>2/3</inf>) <inf>0.95</inf>Ti <inf>0.05</inf>O <inf>3</inf> single crystal and its effect on ferroelectric properties

Abstract

Pb(Zn 1/3Nb 2/3) 0.95Ti 0.05O 3 (PZNT) single crystals with 5 mol.% alkali niobate such as LiNbO 3 (LN), NaNbO 3 (NN), and KNbO 3 (KN) were fabricated by using a flux method to investigate the effect of A-site cation radius on the structure and ferroelectric properties of PZNT under electric field (E-field). Their structure and properties showed different electric field dependence. Polarization versus electric field and strain versus electric field curves of PZNT-0.05LN showed E-field induced phase transition from a relaxor state to a normal ferroelectric state. However, only relaxor behavior was observed in PZNT-0.05NN and PZNT-0.05KN. The effect of A-site ion doping is attributed to the change in local lattice distortion and polar nano-region. When smaller cation such as Li ion substitutes Pb ion, the off-center displacement of Nb ion stabilizes rhombohedral lattice distortion. They, in turn, facilitate the development of macro-domains under electric field (E-field) in PZNT-0.05LN. In contrast, the substitution of Pb with larger cations such as Ni and K decreases the rhombohedral distortion of PZNT, which leads to the disappearance of unique E-field induced phase transition from rhombohedral to tetragonal phase in PZNT. Therefore, non-linear electrostrictive behavior of relaxor ferroelectrics is found in PZNT-0.05NN and PZNT-0.05KN. © 2012 American Institute of Physics