Influence of Crystallization Temperature on Structural, Ferroelectric, and Ferromagnetic Properties of Lead-Free Bi_0.5(Na_0.8K_0.2)_0.5TiO₃ Multiferroic Films

Abstract

Lead-free Bi0.5(Na0.8K0.2)0.5TiO3 (abbreviated as BNKT) films have been synthesized via a sol-gel technique on Pt/Ti/SiO2/Si substrates, and the dependence of the physical properties in BNKT films were investigated as a function of the crystallization temperature. The BNKT films were annealed at different temperatures (600, 650, 700, and 750°C) for 60 min in the air. The results of this study showed that the optimal crystallization temperature is 700°C. At this, the BNKT films exhibited a single perovskite phase structure and high-dense surface. Besides, the remanent (Pr) and maximum (Pm) polarization reached their highest values of 9.2 µC/cm2 and 30.6 µC/cm2, respectively. All the films showed a weak ferromagnetic behavior with the maximum saturated magnetization (Ms) of 2.1 emu/cm3. These values are equivalent to the highest Pr and Pm values in previous reports on lead-free films.

Influence of Crystallization Time on Energy-Storage Density and Efficiency of Lead-Free Bi0.5(Na0.8K0.2)0.5TiO3 Thin Films

“…With the surpassed intensity, the (111) orientation located at 2 ∼ 39.8 ∘ is the mixture of orientations, deriving from the Pt coated substrate. All other peaks belong to a single-phase perovskite structure with no other impurity phases detected, which agrees with our recent report [25] on influence of crystallization temperature on multiferroic behaviour of BNKT films. This observation also matches our previous works [26,27] where they indicated that BNKT thin films possess simultaneously the rhombohedral and tetragonal symmetries.…”

“…The wavenumber differences may be caused by the residual stress formed by film/substrate interface. Similar behaviour is also observed in our recent works [25,32].…”

Effect of Structural Deficiencies on Bi-Ferroic Behaviors of Lead-Free Bi0.5 Na0.40K0.10TiO3 Films

“…It reached to the best value of 2.3 emu/cm 3 for film S60. The magnetic dipole moments originated by the oxygen deficiencies were attributed to contribute to the improvement of the ferromagnetic behavior within the BNKT films [2,40]. Theoretically, Stoneham et al [41] proved that magnetic orders also are related to point deficiencies like cation or anion vacancies.…”

“…Multiferroic materials, new generation materials are being paid more attention because have potential for applications as magnetic field sensors, actuators, new types of electronic memory devices, and switches [1]. Multiferroic materials own unique property as magnetoelectricity (ME) stemmed from the existence of a coupling between electric dipolar and magnetic orders at room temperature [2]. Thanks to their special properties, multiferroics are studied largely for several technological applications, like magnetoelectric (ME) recording, magnetoelectric random access memories (MERAM), and electrically tunable microwave devices [3,4].…”

Influence of Excess Potassium on Structural and Ferroelectric Properties of Lead-Free Bi0.5K0.5TiO3 Thin Films

“…In previous works, the influence of the processing conditions, such as the film thickness, annealing temperature and crystallization time on the electric properties of BKT-based films [18][19][20][21], were investigated. Via modifying A or B-site in the perovskite structure, we have enhanced significantly the electric properties of BKT-based films [22][23][24][25].…”