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

Abstract

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 micro-probe 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 contents 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°C 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 elements content variation in single

Single crystal growth of BaZrO3 from the melt at 2700 °C using optical floating zone technique and growth prospects from BaB2O4 flux at 1350 °C

“…we can reasonably conclude that the effective segregation coefficient of Sr in the A site of BaZrO 3 perovskite is higher than 1, similarly to what can be deduced from the sign of the solidus and liquidus curves of the BaTiO 3 -SrTiO 3 perovskite system [44]. In the same way, effective segregation coefficients of Hf, Ca and Ti are lower than 1, as previously referenced for Ca and Ti in BaZrO 3 -based perovskite solid solutions [45]. Figure 3 shows the transmittance of the three samples BZO1, 2 and 3.…”

Lead-free piezoelectric crystals grown by the micro-pulling down technique in the BaTiO3–CaTiO3–BaZrO3 system

“…were investigated. Substantial lower effective partition coefficients of Ca and Zr in µ-PD grown crystals were calculated and discussed with those calculated in already reported 15 TSSG-grown crystals. Strong chemical inhomogeneity is highlighted through Laser-Induced Breakdown Spectroscopy (LIBS).…”

“…N -1 as predicted by Liu et al 11 . Recently, growth attempt of BCTZ single crystals in BaTiO 3 -CaTiO 3 -BaZrO 3 pseudo-ternary solid-solution were reported [13][14][15][16][17][18] with various calcium (Ca) and zirconium (Zr) contents. However, high partition coefficients have been measured in these single crystals grown by Top Seeded Solution Growth (TSSG) method 15 .…”

“…Recently, growth attempt of BCTZ single crystals in BaTiO 3 -CaTiO 3 -BaZrO 3 pseudo-ternary solid-solution were reported [13][14][15][16][17][18] with various calcium (Ca) and zirconium (Zr) contents. However, high partition coefficients have been measured in these single crystals grown by Top Seeded Solution Growth (TSSG) method 15 . This phenomenon induces strong elemental content variations within the crystals and is detrimental for their piezoelectric performances.…”

Lattice dynamics and Raman spectrum of BaZrO3 single crystals

“…As a functional material, BaZrO 3 has attracted attention as a high-temperature proton conductor [3]; it can be used in solid oxide fuel cells [4] and sensors [5], or as nanoparticles for increasing the vortex pinning in iron-based superconductor thin films [6]. It is also of interest as one of the end-members of the (Ba,Ca)(Ti,Zr)O 3 system for high-performance leadfree piezoelectrics [7][8][9][10]. At a fundamental level, its lattice dynamics and stability were found more complex than anticipated, which has drawn attention to its low-temperature structure and properties.…”