Spinodal Decomposition in Lead-free Piezoelectric BaTiO3 –CaTiO3 –BaZrO3 Crystals

Gabriel Buse (1) , Cong Xin (1) , Pascal Marchet (2) , Ana Borta-Boyon (3) , Maï Pham-Thi (3, 4) , Hughes Cabane (4) , Emmanuel Véron (5) , Michaël Josse (1) , Matias Velázquez (1) , Michel Lahaye (6) , Eric Lebraud (1) , Mario Maglione (1) , Philippe Veber (7, 1)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
2 IRCER-AXE3 - IRCER - Axe 3 : organisation structurale multiéchelle des matériaux
3 Thales Research and Technology [Palaiseau]
4 Cristallinov
5 CEMHTI - Conditions Extrêmes et Matériaux : Haute Température et Irradiation
6 PLACAMAT - Plateforme Aquitaine de Caractérisation des Matériaux
7 ILM - Institut Lumière Matière [Villeurbanne]

Polycrystals and centimeter-sized BaTiO3-based single crystals were grown by top seeded solution growth from the BaTiO3–CaTiO3–BaZrO3 system. High effective partition coefficients of Zr ranging from 15 to 6 with small Zr content have been calculated from Castaing microprobe measurements, whereas those of Ca increase slightly from 0.45 to 0.7. A spinodal decomposition mechanism is emphasized during the growth leading to the emergence of two phases with close compositions. Chemical analysis displayed periodical Zr and Ca content fluctuations within the whole boules, and Rietveld measurements highlighted two phases belonging to perovskite structures with tetragonal P4mm and orthorhombic Amm2 space groups. Samples with various calcium and zirconium contents were characterized by means of dielectric and piezoelectric measurements. Most efficient samples are indistinctly polycrystals or oriented single crystals where electromechanical performances are compositional-dependent. Polycrystalline samples and single crystals oriented along (001)pc and (110)pc displayed Curie temperatures ranging from 50 to 111 °C. Electromechanical coupling factor up to 58% and piezoelectric charge coefficient d33 = 496 pC·N–1 were obtained at room temperature. The miscibility gap between the two perovskite solid solutions as well as Ca and Zr element content variation in single crystals lower crystal piezoelectric response that remains nonetheless of the same efficiency compared to that of ceramics of the same composition.

Domaines: Chimie; Matériaux

Gabriel Buse, Cong Xin, Pascal Marchet, Ana Borta-Boyon, Maï Pham-Thi, et al.. Spinodal Decomposition in Lead-free Piezoelectric BaTiO3 –CaTiO3 –BaZrO3 Crystals. Crystal Growth & Design, 2018, 18 (10), pp.5874-5884. ⟨10.1021/acs.cgd.8b00596⟩. ⟨hal-01891394⟩