研究目的
To investigate the in situ characterization of non-isothermal densification behavior of zinc oxide under simultaneous application of thermal and electric field by energy dispersive X-ray diffraction, aiming to understand the sintering mechanism during flash sintering.
研究成果
The study achieved high densification (99.3% density) of ZnO at lower temperatures (588–843 °C) and short times (42 s) using electric field assisted sintering, with no significant grain growth. In-situ EDXRD revealed abnormal unit cell expansion and peak broadening singularities, indicating correlations with power absorption and defect rearrangement, supporting mechanisms involving Joule heating and defect dynamics in flash sintering.
研究不足
The measurement of specimen temperature was not possible during the in-situ experiment, relying on external thermocouple readings which may not accurately reflect internal temperatures due to Joule heating. The study used a specific electric field and current limit, which may not cover all possible sintering conditions. The analysis of defect structures is inferred from peak broadening and lattice parameter changes without direct measurement of defect types or concentrations.
1：Experimental Design and Method Selection:
The study used energy dispersive X-ray diffraction (EDXRD) for in situ observation of lattice parameters during flash sintering of ZnO under thermal and electric fields. The experiment was designed to monitor densification behavior non-isothermally with a heating rate of 25 °C/min and an applied electric field of 50 V/mm.
2：Sample Selection and Data Sources:
ZnO powder (96479-Sigma Aldrich) with 1 μm median particle size was compacted into 12 mm diameter disks with
3：65 mm thickness without binder. Data were collected from the body center of the specimen using synchrotron X-ray diffraction at the Advanced Photon Source. List of Experimental Equipment and Materials:
Equipment includes a portable furnace, power source for electric field application, thermocouple for temperature measurement, pycnometer (AccuPyc II 1340) for density measurement, Zeiss Σigma field emission scanning electron microscope (FESEM) for microstructure analysis, and synchrotron X-ray diffraction setup at Beamline 6BM-A of the Advanced Photon Source. Materials include ZnO powder and platinum wires for electrical connections.
4：Experimental Procedures and Operational Workflow:
The sample was heated at 25 °C/min with an electric field of 50 V/mm applied from room temperature. Voltage, current, and temperature were recorded concomitantly with diffraction data. The current was limited to
5：5 A to prevent excessive Joule heating. Data were collected with a time resolution of 2 s. The power supply was cut off when the system switched to current control. Data Analysis Methods:
Lattice parameters were computed using equations for energy dispersive X-ray diffraction, with calibration using LaB6, CeO2, and Au standards. Peak broadening and unit cell volume changes were analyzed to infer defect formation and densification mechanisms.
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