Structural evolution and electromechanical properties of SrTiO3-modified Bi0.5Na0.5TiO3?BaTiO3 ceramics prepared by sol-gel and hydrothermal methods

This article reports structural evolution and electromechanical properties of lead-free (1-x)(0.965Bi0.5Na0.5TiO30.035BaTiO3)-xSrTiO3 (BNTBT-100xST with x = 0.00?0.30) ceramics synthesized by sol-gel and hydrothermal methods. The crystal structure investigation shows a compositionally-driven phase transition from the dominant rhombohedral (R) phase to the tetragonal (T) phase. However, the physical properties revealed that BNTBT converts from normal ferroelectric to relaxor ferroelectric due to the disruption of long-range ferroelectric order with ST modifications. Highest electric field-induced strain coefficient (d33* = 320 pm/V) for the optimum composition was attributed to the crystal structure morphotropic phase boundary of the R and T phases. A phenomenological explanation from the ferroelectric properties strongly supports the argument of the high piezoelectric strain response. A phase diagram was developed based on the crystal structure, dielectric, ferroelectric and piezoelectric properties that provide a systemic correlation and better elucidation of the BNTBT100xST ceramic system.

Automated summary

This study investigated the structural evolution and physical properties of lead-free BNTBT-100xST ceramics and found the transition from normal ferroelectric to relaxor ferroelectric behavior. The highest electric field-induced strain coefficient was attributed to the crystal structure morphotropic phase boundary between the rhombohedral and tetragonal phases, supporting a high piezoelectric strain response. A phase diagram was developed to systematically correlate the crystal structure, dielectric, ferroelectric, and piezoelectric properties of the BNTBT-100xST ceramic system.