Large piezoelectric response of Bi_0.5(Na_(1 − x)K_x)_0.5TiO₃ thin films near morphotropic phase boundary identified by multi-peak fitting

Abstract

Bi0.5(Na(1 − x)K x )0.5TiO3 (BNKT100x) (x = 0.11, 0.13, 0.15, 0.17, 0.19) thin films were deposited on Pt/Ti/SiO2/Si(1 0 0) substrates by metal-organic decomposition, and the effects of potassium content on the microstructure and ferroelectric/piezoelectric properties were investigated in detail. The coexistence of typical rhombohedral and tetragonal phases can be identified by multi-peak fitting in grazing incidence x-ray diffraction patterns, which indicates that morphotropic phase boundary (MPB) can be obtained for BNKT100x thin films. The results show that all the thin films are of single-phase perovskite structure and there is intimate coexistence of two phases in the potassium content range x = 0.13–0.17. The BNKT17 thin film is of the largest effective piezoelectric coefficient (d 33eff = 98 pm V−1), which is attributed to a high degree of alignment of ferroelectric domains in the MPB region and its largest grain size. The BNKT17 thin film exhibits the classical diffuse phase transition of a relaxor ferroelectric, which is discussed by compositional inhomogeneity and polar nanoregions. This study offers useful guidelines to identify MPB of ferroelectric thin films with improved piezoelectric performance.

Structural and microstructural features of lead‐free BNT–BT thin films: Nanoscale electromechanical response analysis

“…In BNT-based systems, for instance, the evaporation of Na, K, and Bi may result in many nonstoichiometric structural defects to form secondary phases during the thermal processes. 80 As a consequence, a noticeable imprint behavior could be expected, as indeed observed for the pure BNLBT-0 sample. Nevertheless, taking into account that donor doping does mainly introduce immobile defect dipoles, the inclusion of the La 3+ cation, which suppresses the formation of oxygen vacancies, could have led to a decrease in the mobile defect-dipole concentration and, therefore, to a reduction in imprint, as observed for the La-doped concentrations (BNLBT-2 and BNLBT-3).…”

In situ X-ray diffraction studies on the piezoelectric response of PZT thin films

“…3(c)). Such behavior was observed and explained for different materials including different compositions of PZT [21,26,35,36]. The asymmetry of the loops may originate from an uncomplete switching of the polarization domains [26] or from a selfpolarization of the film [13].…”

“…Compared to the piezoelectric strain induced by the electric field, the thermal lattice expansion is a factor of 5 less over a time period of 10 min. The studied sample contains Au and Pt electrodes whose thermal expansion coefficients are much higher than those for piezo ceramics [36] making them ideal as a reference for detecting heating effects. Hence, the evolution of the Pt 111 Bragg peak was studied as a function of the applied potential (not shown here) revealing a variation of~10 −3 degrees in its 2θ-position, which is close to the resolution limit of this experimental approach.…”

Approaching Piezoelectric Response of Pb-Piezoelectrics in Hydrothermally Synthesized Bi0.5(Na1–xKx)0.5TiO3 Nanotubes

“…Although many BNKT thin films − and bulk ceramics − have been reported, recently a new class of functionalized one-dimensional (1D) morphologies (or generally low-dimensional systems) such as nanotubes and nanofibers which demonstrate excellent figures of merit for piezoelectric and thermoelectric applications is gaining significant interest. These superior properties arise from the large surface to volume ratio , of the 1D materials, in comparison with their bulk counterparts, in addition to possessing a unique density of electronic state leading to higher magnetic, optical, and electrical properties. , Particularly, 1D piezoelectric materials are ideal for energy harvesting owing to their high mechanical strength and sensitivity to mechanical movements .…”