Crystal growth and dielectric characterization of crystals derived from the solid-solution Ba_(1−x)Na_xTi_(1−x)Nb_xO₃ (BTNN)

Lakhdar Gacem (1, 2) , Djamel Ouadjaout (3) , Jean-Pierre Chaminade (1) , Mario Maglione (1) , Régnault von Der Mühll (1) , Stanislav Pechev (1)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
2 Département de physique
3 UDTS - Unité de Développement de la Technologie du Silicium

Single crystals of (1 − x)BaTiO₃ + xNaNbO₃ (BTNN) for x = 0.84 were obtained by high temperature solution growth using Na₂B₄O₇ as solvent. The room temperature crystal structure of BTNN 16/84-phase was determined from X-ray single crystal diffraction data, in the tetragonal system with space group P4bm. The refinement from 246 independent reflections led to the following parameters: a = b = 5.5845(3) Å, c = 3.9453(2) Å, V = 123.041(11) Å³, Z = 2, with final cR_wp = 0.150 and R_B = 0.041. The structure of BTNN 16/84-phase can be described as a three-dimensional framework built up from (Nb–Ti)O₆ octahedra with Na and Ba in the dodecahedral site of perovskite-like type. Some mm³-sized crystals have been selected and various dielectric measurements (ferroelectric, pyroelectric, and piezoelectric) have been performed. Transition from paraelectric to ferroelectric state at around 460 K has been observed to be in good agreement with ceramics of closer composition. Dielectric, piezoelectric and pyroelectric measurements on crystal confirm the ferroelectric behaviour of BTNN 16/84.

Mots clés: Oxides; Crystal growth; Crystal structure; Dielectric properties; Ferroelectricity; Piezoelectricity; Phase transition

Domaines: Matériaux

Lakhdar Gacem, Djamel Ouadjaout, Jean-Pierre Chaminade, Mario Maglione, Régnault von Der Mühll, et al.. Crystal growth and dielectric characterization of crystals derived from the solid-solution Ba_(1−x)Na_xTi_(1−x)Nb_xO₃ (BTNN). Materials Research Bulletin, 2009, 44 (12), pp.2240-2245. ⟨10.1016/j.materresbull.2009.07.019⟩. ⟨hal-00442636⟩