研究目的
To investigate the effects of Ca and Pb co-doping on the structure, ferroelectric, dielectric, and magnetic properties of BiFeO3 ceramics, aiming to improve leakage current, ferroelectric polarization, and magnetization.
研究成果
Ca and Pb co-doping in BiFeO3 ceramics induces a structural transition from rhombohedral to cubic phase, with Pb ions in tetravalent state. This co-doping significantly improves dielectric properties, reduces leakage current by two orders of magnitude compared to Sr/Pb co-doping, enhances ferroelectric polarization, and increases magnetization due to suppressed spiral spin structure and enhanced double exchange interactions. The method effectively modifies multiferroic properties, but ferroelectric polarization remains a limitation for practical use.
研究不足
The ferroelectric polarization of Ca/Pb co-doped BFO ceramics is still small compared to some reports, possibly due to weakened off-center effect of Bi ions and structural transition. The study is limited to bulk ceramics and specific doping ranges; thin films or other forms were not explored. The leakage current improvement, while significant, may not be sufficient for all practical applications, and further optimization is needed.
1：Experimental Design and Method Selection:
A rapid two-stage solid-state reaction method was used to synthesize polycrystalline Bi1-x(Ca1/2Pb1/2)xFeO3 ceramics with x = 0, 0.1, 0.2, 0.3. The design rationale was to study the impact of Ca/Pb co-doping on structural and multiferroic properties.
2：1, 2, The design rationale was to study the impact of Ca/Pb co-doping on structural and multiferroic properties.
Sample Selection and Data Sources:
2. Sample Selection and Data Sources: Samples were prepared using high-purity oxides (Bi2O3, Fe2O3, CaCO3, PbO) as starting materials. Selection criteria were based on stoichiometric ratios to achieve desired doping concentrations.
3：List of Experimental Equipment and Materials:
Equipment included an agate mortar for grinding, alumina crucibles for annealing, a Rigaku TTR III X-ray diffractometer for XRD, a JY LABRAM-HR Raman spectrometer for Raman spectra, a Sirion200 FESEM for microstructure analysis, an ESCALAB25Xi XPS for chemical composition, an HP 4294A impedance analyzer for dielectric measurements, a Precision Premier II for P-E and J-E measurements, and a SQUID MPMS for magnetic measurements. Materials were high-purity oxides and carbonates.
4：Experimental Procedures and Operational Workflow:
Starting oxides were ground, annealed at 825°C for 30 min, milled, pressed into pellets, sintered at 920°C for 15 min, and quenched to room temperature. Characterization involved XRD, Raman, FESEM, EDX, XPS, dielectric measurements, ferroelectric and leakage current measurements, and magnetic measurements.
5：Data Analysis Methods:
XRD data were analyzed for phase identification and lattice parameters, Raman spectra for structural changes, XPS for valence states, dielectric data for constant and loss, ferroelectric loops for polarization, and magnetic data for magnetization and hysteresis.
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