Some New Ceramics and Thin Films of Pb(B 3+ ,Nb)TiO 3 -PbTiO 3 System

The structure, dielectric, and electromechanical properties of (1-x)Pb(B 3+ ,Nb)TiO 3 -xPbTiO 3 binary systems (B=Lu,Er,To,Ho) are reported. High values of the electromechanical coupling coefficients k p =0.66, k t =0.48, k 31 =0.36 are attained in lead lutecium niobate-titanate (PLuNT) near the morphotropic phase boundary (MPB) between tetragonal P4mm and pseudomonoclinic phases at x=0.41. The crystallographic features at the MPB are discussed with respect to electro-mechanical properties. The heterovalent substitution of Pb 2+ by La 3+ either in both components or maintaining the PbTiO 3 unmodified shifts the MPB to the pseudomonoclinic M side of phase diagram. The initial unmodified material "softens"- coercive field E c decreases up to 15,9 kV/cm in the first case and below 10 kV/cm in the second case; simultaneously high values of maximum polarization P m = 50.3 w C/cm 2 and remnant polarization P r ; 40.3 w C/cm 2 are characteristic. The films of PLuNT with composition near the MPB formed by in situ pulsed laser deposition onto LSCO/(100)MgO exhibited ferroelectric behaviour with P m ; 29 w C/cm 2 , P r ; 14 w C/cm 2 , E c ; 70 kV/cm. The zero-field dielectric permittivity l = 300-450 at room temperature, and demonstrate a relaxor type broad peak around 350°C.

Keywords:

• Binary Systems
• Phase Diagram
• Morphotropic Phase Boundary
• Electromechanical Coupling
• La Doping