Evidence of multiferroic behavior in sintered BaTiO3 obtained from high-energy ball-milled powders

Published: 29 October 2024| Version 1 | DOI: 10.17632/4k763zdwd3.1
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Description

Multiferroic BaTiO3 exhibiting ferroelectric and ferromagnetic behavior was synthesized via the high-energy ball milling of pure BaTiO3 (BTO) powders for durations ranging from 15 to 60 min, followed by pressing and sintering at 1200 ◦C X-ray diffraction patterns of all synthesized samples predominantly revealed a BTO phase with a tetragonal structure and a secondary Ba12Fe28Ti15O84 (BFTO) phase. The BFTO phase was formed after milling for more than 30 min because of chemical interactions between the BTO powder and milling media. Vibrating sample magnetometry confirmed the ferromagnetic nature of the sintered pellets. The specific magnetization increased with increasing milling duration, reaching a maximum value of 1.15 emu/g after 60 min of milling. This increase can be attributed to the distortion of the crystal structure and presence of a secondary phase, as confirmed by scanning electron microscopy and energy-dispersive X-ray spectroscopy. Additionally, electrical characterization revealed the dielectric nature of the materials, with relative permittivity ranging from 500 to 1800, maximum spontaneous polarization from 9.77 to 11.31 μC/cm2, coercive field from 3.86 to 11.12 kV/cm, and AC conductivity from 1 × 10􀀀 6 to 1 × 10􀀀 3 S/cm. The method described in this study is a simple and cost effective approach to produce multiferroic materials with ferroelectric and relaxor ferroelectric behavior at room temperature, broadening their potential for technological applications.

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BTO powder (Sigma-Aldrich, 99.9 % purity) was used as the precursor to investigate the effect of milling duration on the multiferroic properties of BTO. Briefly, 1 g of pure BTO powder and 45 μL of methanol as a control agent were placed into cylindrical steel vials (60 ×103 mm3) containing steel balls with a diameter of 6.3 mm, maintaining a ball:powder weight ratio of 60:1. The powder was milled for different durations—0, 15, 30, 45, and 60 min—under an air atmosphere using a shaker mixer mill (SPEX, model 8000D). Subsequently, the milled powders were pressed uniaxially under a pressure of 1000 MPa to form disk-shaped pellets. The pellets were sintered at 1200 ◦C for 4 h under an air atmosphere using a tube furnace (Lindberg/Blue M, model STF54459C). This procedure was repeated five times to ensure the reproducibility of the results. The crystal structures of the sintered pellets were analyzed using an X-ray diffractometer (XRD) (Bruker, model D8 Advance) with CuKα1 radiation (λ =1.15418 Å) in a 2θ range from 20◦to 80◦with a step size of 0.01◦. Rietveld refinement of the XRD patterns was performed using MAUD software to quantify the phases in the pellets, as well as to determine the weight percentage of each phase, cell parameters, crystallite size, and microstrain. The crystallographic data were obtained in the PDF from the Crystallography Open Database (COD). The surface morphology and microstructure of the sintered pellets were examined using a scanning electron microscope (SEM) (HITACHI, model TM3030). An energy-dispersive X-ray spectrometer (EDS; integrated with SEM) (QUANTAX, model 75) was used for chemical analysis. Magnetic hysteresis loops were recorded at room temperature using a vibrating sample magnetometer (MicroSense, model EV7) with a maximum magnetic field of ±18 kOe. Dielectric characterization was conducted at room temperature using an inductance, capacitance, and resistance (LCR) meter (HIOKI, model Hi-Tester 3532–50) in the frequency range from 50 to 5 ×106 Hz. Before electrical characterization, both sides of the pellets were coated with silver paste to ensure electrical continuity. In addition, ferroelectric hysteresis loops were obtained at room temperature using a ferroelectric test system (Radiant Technologies, model Premier II) at 10 Hz and voltage amplification of up to 10 kV.

Institutions

Universidad Autonoma del Estado de Hidalgo, Instituto Politecnico Nacional

Categories

Powder Milling, Barium Titanate, Ferroelectricity, Ferromagnetism, Multiferroic Material

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