研究目的
To investigate the role of oxygen partial pressure on the structure and phase transitions of PMN-28PT, focusing on how changes in oxygen content affect structural properties and electrical impedance.
研究成果
Oxygen content in PMN-28PT can be controlled by oxygen partial pressure during heat treatment, leading to structural changes and affecting electrical impedance. Low oxygen partial pressure promotes disorder and diffuse phase transitions, suggesting potential for property control in piezoelectric applications.
研究不足
Temperature control tolerances (±5°C for thermal analyzer, ±2°C for Raman chamber) and potential baseline drift in thermogravimetric tests. The use of a borosilicate glass tube in XRD reduced peak-to-background ratios, affecting chi-squared factors.
1：Experimental Design and Method Selection:
The study uses thermal analysis (TGA/DSC), in-situ high-temperature X-ray diffraction (XRD), and in-situ high-temperature Raman spectroscopy to monitor structural changes and oxygen content variations during thermocycles.
2：Sample Selection and Data Sources:
PMN-28PT single crystals grown by Bridgman-Stockbarger technique were used.
3：List of Experimental Equipment and Materials:
Simultaneous Thermal Analyzer (SDT Q600-TA Instruments), GADDS/D8 diffractometer (Bruker) with Apex Smart CCD detector and molybdenum rotating anode, Ar ion laser (Spectra Physics Model 177), CCD detector HoloSpec f/l.8i, compact split tube furnace (MTI Corporation), HP4194A Impedance/Gain Analyzer, and various gases (compressed dried air, argon).
4：Experimental Procedures and Operational Workflow:
Samples underwent thermocycles between 250-300°C under oxidizing (CDA) or reducing (Ar) atmospheres, with in-situ XRD and Raman measurements at various temperatures. Heat treatments were conducted at 80°C for 10 hours under Ar.
5：Data Analysis Methods:
Rietveld refinement (HighScore Plus 4.7), Raman spectra fitting (Fityk software), and impedance analysis.
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