研究目的
To explore the relevance between phase transition and electrical properties in (Sr1/3Nb2/3)4+ doped Bi0.5(Na0.82K0.18)0.5Ti1-x(Sr1/3Nb2/3)xO3 ceramics, focusing on modifications to phase structure, dielectric behavior, strain, and energy storage density.
研究成果
The SN complex-ion doping effectively modifies the phase structure of BNKT ceramics, promoting a transition from ferroelectric to ergodic relaxor phase, with a critical point at x=0.035. This leads to enhanced energy storage density (up to 0.754 J/cm3) and high bipolar strain (0.25%) with low hysteresis. The dielectric properties show broadened peaks and decreased transition temperature, indicating improved relaxor characteristics. These findings clarify the relationship between phase structure and electrical properties in BNT-based ceramics.
研究不足
The energy storage density and strain properties, while improved, are lower than those achieved by special fabrication methods such as texture or spark plasma sintering. The mechanisms of large strain are not fully unified, and further investigations are needed.
1：Experimental Design and Method Selection:
The study used the conventional ceramic process to fabricate lead-free BNKT-xSN ceramics with varying SN content (x = 0.02–0.045). The rationale was to investigate the effects of (Sr1/3Nb2/3)4+ complex-ion doping on phase transitions and electrical properties. Theoretical models included perovskite structure analysis and relaxor ferroelectric behavior.
2：02–045). The rationale was to investigate the effects of (Sr1/3Nb2/3)4+ complex-ion doping on phase transitions and electrical properties. Theoretical models included perovskite structure analysis and relaxor ferroelectric behavior.
Sample Selection and Data Sources:
2. Sample Selection and Data Sources: Ceramic samples were prepared using high purity powders (≥99.9%) including Bi2O3, Na2CO3, K2CO3, SrCO3, Nb2O5, and TiO2, selected based on stoichiometric formulas.
3：9%) including Bi2O3, Na2CO3, K2CO3, SrCO3, Nb2O5, and TiO2, selected based on stoichiometric formulas.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment included an X-ray diffractometer (XRD, AXS D8-ADVANCE, Bruker) for phase structure characterization, scanning electron microscopy (SEM, JSM-5610LV, JEOL) for surface morphology, a DXR microprobe system (Thermo Fisher Scientific DXR, America) for Raman spectroscopy, a ferroelectric test system (TF Analyzer 2000HS, aixACCT) for polarization, current, and strain measurements, and an impedance analyzer (4294A, Agilent) for dielectric properties. Materials were the raw powders and polyvinyl alcohol binder.
4：Experimental Procedures and Operational Workflow:
Powders were ground in ethanol for 24h, calcined at 880°C for 2h, mixed with binder, compacted into discs under 40 MPa, sintered at 1130°C for 2h, polished, and electrodes applied. Measurements were conducted at room temperature and varying electric fields up to 80 kV/cm.
5：Data Analysis Methods:
Data analysis involved Gaussian-Lorentzian fitting for Raman spectra, calculation of energy storage density and efficiency from P-E loops, and use of the diffuseness degree formula for dielectric relaxor behavior.
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