Enhanced Piezoelectric, Ferroelectric, and Electrostrictive Properties of Lead-Free (1-x)BCZT-(x)BCST Electroceramics with Energy Harvesting Capability.

Next-generation electronics and energy technologies can now be developed as a result of the design, discovery, and development of novel, environmental friendly lead (Pb)-free ferroelectric materials with improved characteristics and performance. However, there have only been a few reports of such complex materials' design with multi-phase interfacial chemistry, which can facilitate enhanced properties and performance. In this context, herein, novel lead-free piezoelectric materials (1-x)Ba 0.95 Ca 0.05 Ti 0.95 Zr 0.05 O 3 -(x)Ba 0.95 Ca 0.05 Ti 0.95 Sn 0.05 O 3 , are reported, which are represented as (1-x)BCZT-(x)BCST, with demonstrated excellent properties and energy harvesting performance. The (1-x)BCZT-(x)BCST materials are synthesized by high-temperature solid-state ceramic reaction method by varying x in the full range (x = 0.00-1.00). In-depth exploration research is performed on the structural, dielectric, ferroelectric, and electro-mechanical properties of (1-x)BCZT-(x)BCST ceramics. The formation of perovskite structure for all ceramics without the presence of any impurity phases is confirmed by X-ray diffraction (XRD) analyses, which also reveals that the Ca 2+ , Zr 4+ , and Sn 4+ are well dispersed within the BaTiO 3 lattice. For all (1-x)BCZT-(x)BCST ceramics, thorough investigation of phase formation and phase-stability using XRD, Rietveld refinement, Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and temperature-dependent dielectric measurements provide conclusive evidence for the coexistence of orthorhombic + tetragonal (Amm2 + P4mm) phases at room temperature. The steady transition of Amm2 crystal symmetry to P4mm crystal symmetry with increasing x content is also demonstrated by Rietveld refinement data and related analyses. The phase transition temperatures, rhombohedral-orthorhombic (T R-O ), orthorhombic- tetragonal (T O-T ), and tetragonal-cubic (T C ), gradually shift toward lower temperature with increasing x content. For (1-x)BCZT-(x)BCST ceramics, significantly improved dielectric and ferroelectric properties are observed, including relatively high dielectric constant ε r ≈ 1900-3300 (near room temperature), ε r ≈ 8800-12 900 (near Curie temperature), dielectric loss, tan δ ≈ 0.01-0.02, remanent polarization P r ≈ 9.4-14 µC cm -2 , coercive electric field E c ≈ 2.5-3.6 kV cm -1 . Further, high electric field-induced strain S ≈ 0.12-0.175%, piezoelectric charge coefficient d 33 ≈ 296-360 pC N -1 , converse piezoelectric coefficient ( d 33 ∗ ) ave ${( {d_{33}^*} )}_{{\rm{ave}}}$ ≈ 240-340 pm V -1 , planar electromechanical coupling coefficient k p ≈ 0.34-0.45, and electrostrictive coefficient (Q 33 ) avg ≈ 0.026-0.038 m 4 C -2 are attained. Output performance with respect to mechanical energy demonstrates that the (0.6)BCZT-(0.4)BCST composition (x = 0.4) displays better efficiency for generating electrical energy and, thus, the synthesized lead-free piezoelectric (1-x)BCZT-(x)BCST samples are suitable for energy harvesting applications. The results and analyses point to the outcome that the (1-x)BCZT-(x)BCST ceramics as a potentially strong contender within the family of Pb-free piezoelectric materials for future electronics and energy harvesting device technologies.