Crystal growth and piezoelectricity of BaTiO[sub 3]–CaTiO[sub 3] solid solution (original) (raw)
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Spinodal Decomposition in Lead-free Piezoelectric BaTiO3–CaTiO3–BaZrO3 Crystals
Crystal Growth & Design
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
Journal of Asian Ceramic Societies, 2019
Dense Ba 1-x Pb x TiO 3 (x = 0-0.20) samples (>90% TD) were fabricated through a solid-state reaction route involving wet ball milling for 24 h and calcination at 1150°C for 4 h, followed by sintering at 1300°C for 4 h. XRD results for all the samples revealed a tetragonal perovskite (P4mm) crystal structure. Increased substitution of Pb caused monotonic growth in the tetragonality character of the perovskite phase. Although, the value of ε r ʹ dropped from an initial value of 3000 for x = 0 (pure BaTiO 3) to 400 for x = 0.20 samples, the losses (tanδ) interestingly declined almost to half. A substantial increase in the Curie temperature from 120°C for x = 0°C to 180°C for x = 0.15 samples was noted. P-E loop analysis revealed an increase in the saturation polarization by almost 1.5 times, moreover, in the remnant polarization by six times with Pb-substitution. The d 33 values demonstrated an increase from 95 pC/N for pure BaTiO 3 samples to 220 pC/N for x = 0.15 samples.
Journal of Crystal Growth, 2011
High quality 95Na 1/2 Bi 1/2 TiO 3-5BaTiO 3 (NBT-5BT) single crystals of 10 mm  10 mm  3 mm in size were fabricated by the solid state single crystal growth technique involving the sintering of proportioned powder compacts in contact with a seed. Structural studies with X-ray diffraction and Raman spectroscopy revealed that the as-grown single crystals have a rhombohedral (pseudo-cubic) single phase. The (0 0 1) cubic-oriented single crystals showed excellent dielectric and piezoelectric properties: e r ¼ 723, tan d¼0.01 (1 kHz at 25 1C), d 33 ¼ 207 pC/N, and k 33 ¼ 0.5. These values are comparable to the best reported properties of melt-grown single crystals.
RSC Adv., 2014
This study provides a fundamental understanding of the enhanced piezoelectric instability in ABO 3 perovskite based lead-free piezoelectric materials. For this we synthesized (1 À x)BaTiO 3-xA(Cu 1/3 Nb 2/3) O 3 (A: Sr, Ba and Ca and x ¼ 0.0-0.03) solid solutions exhibiting high piezoelectric response. The piezoelectric instability in these compositions was found to increase with x despite monotonous decrease in the long range polar ordering. High energy X-ray diffraction coupled with atomic pair distribution functions (PDF)s indicated an increase in local polarization. Raman scattering and EPR analysis revealed that substitutions on A and B sites both substantially perturbed the local octahedral dynamics and resulted in localized nano polar regions which imparted the high piezoelectric response.
RSC Advances, 2014
This study provides a fundamental understanding of the enhanced piezoelectric instability in ABO 3 perovskite based lead-free piezoelectric materials. For this we synthesized (1 À x)BaTiO 3-xA(Cu 1/3 Nb 2/3) O 3 (A: Sr, Ba and Ca and x ¼ 0.0-0.03) solid solutions exhibiting high piezoelectric response. The piezoelectric instability in these compositions was found to increase with x despite monotonous decrease in the long range polar ordering. High energy X-ray diffraction coupled with atomic pair distribution functions (PDF)s indicated an increase in local polarization. Raman scattering and EPR analysis revealed that substitutions on A and B sites both substantially perturbed the local octahedral dynamics and resulted in localized nano polar regions which imparted the high piezoelectric response.
Bulletin of Materials Science
We prepared a lead-free ceramic (Ba 0.85 Ca 0.15)(Ti 1−x Zr x)O 3 (BCTZ) using the conventional mixed oxide technique. The samples were prepared by an ordinary mixing and sintering technique. In this study we investigated how small amounts of Zr 4+ can affect the crystal structure and microstructure as well as dielectric and piezoelectric properties of BaTiO 3. X-ray diffraction analysis results indicate that no secondary phase is formed in any of the BCTZ powders for 0 ≤ x ≤ 0.1, suggesting that Zr 4+ diffuses into BaTiO 3 lattices to form a solid solution. Scanning electron microscopy micrographs revealed that the average grain size gradually increased with Zr 4+ content from 9.5 μm for x = 0.02 to 13.5 μm for x = 0.1; Curie temperature decreased due to the small tetragonality caused by Zr 4+ addition. Owing to the polymorphic phase transition from orthorhombic to tetragonal phase around room temperature, it was found that the composition x = 0.09 showed improved electrical properties and reached preferred values of d 33 = 148 pC N −1 and K p = 27%.
Lead-free Bi 0.5 Na 0.5 TiO 3 (BNT)-Bi 0.5 K 0.5 TiO 3 (BKT)-BaTiO 3 (BT) piezoelectric thin films with compositions near the morphotropic phase boundary (MPB) were deposited by metal-organic solution deposition on Pt/Ti/SiO 2 /Si (1 0 0) substrates. The compositional dependences of their microstructure and ferroelectric/piezoelectric properties were investigated. The results indicated that all the thin films have a single-phase perovskite structure and show outstanding electrical properties at room temperature. We found that the thin film with a composition of 0.884BNT-0.08BKT-0.036BT showed the best structural and electrical properties, with a dielectric constant, remnant polarization, and effective piezoelectric constant of 638,638, 638,27 lC/cm 2 and $79 pC/N, respectively. We suggest that these superior properties are due to this sample's high degree of alignment of ferroelectric domains in the MPB region and largest grain size.
Applied Physics Letters, 2015
We present a general rule for the perovskite oxide ceramics: "A large piezoelectric constant in ABO 3 perovskite ceramics can be obtained by tuning the weight ratio of A and B sites, W A / W B or W B / W A , to 3. Piezoelectric constant decreases significantly when W A / W B or W B / W A is in the range of 0.5-2.0, termed as forbidden zone." A comparative analysis was conducted for broad range of materials demonstrating the applicability of proposed rule. Further based on this rule optimized compositions in BaTiO 3 and alkali niobate based systems were developed. Polycrystalline ceramics in modified BaTiO 3 system were found to exhibit longitudinal piezoelectric coefficient ͑d 33 ͒ of 330 pC/N, while alkali niobate ceramics showed d 33 of 294 pC/N.
Journal of Sol-Gel Science and Technology, 2019
In this work, lead-free 0.965Bi 0.5 Na 0.5 TiO 3-0.035BaTiO 3 (BNT-BT) piezoelectric ceramics were synthesized by a sol-gel process. X-ray diffraction pattern of the BNT-BT samples revealed that powder calcined at 600°C, exhibit a pure perovskite structure. Scanning electron microscopy (SEM) was used to find the surface morphology and grain size of the investigated ceramics. At an optimized sintering temperature of 1150°C, well-saturated ferroelectric (P-E) hysteresis loops with high remnant polarization (P r = 34.8 µC/cm 2) and low corrosive field (E c = 23 kV/cm) were obtained. Electric field-induced strain of 0.137% with a dynamic piezoelectric coefficient (d 33 * = 196 pm/V) was observed under 75 kV/cm drawing field. In addition, high static piezoelectric constant (d 33 = 138 pC/N) was recorded for the sample sintered at 1150°C. This value of d 33 is comparable to that of BNT-based bulk piezoelectric ceramics.