posted on 2018-09-06, 00:00authored byGabriel Buse, Cong Xin, Pascal Marchet, Ana Borta-Boyon, Mai Pham-Thi, Hughes Cabane, Emmanuel Veron, Michael Josse, Matias Velazquez, Michel Lahaye, Eric Lebraud, Mario Maglione, Philippe Veber
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.