研究目的
Investigating the evolution of local electromechanical and capacitive properties of a representative relaxor material lead lanthanum zirconate across the phase transition from a ferroelectric to relaxor state using contact Kelvin probe force microscopy (cKPFM) and machine learning.
研究成果
The study successfully used cKPFM and k-means clustering to identify the origin of local functional response in PLZT across the transition from ferroelectric to relaxor state. The phase transition was found to occur near 50°C for all grains, manifested as collapsing bands in cKPFM response. The findings provide insight into the development of local electromechanical and electrostatic response across the ferroelectric – relaxor transition temperature and aid interpretation of PFM and cKPFM data of similar materials.
研究不足
The study is limited by the inherent artefacts of piezoresponse force microscopy and associated switching spectroscopy caused by signal contributions emanating from electrostatic interactions between tip and sample. Additionally, the technique's sensitivity to local topography due to changes in the tip – sample contact could affect the measured cKPFM signal.
1：Experimental Design and Method Selection:
Contact Kelvin probe force microscopy (cKPFM) spectroscopy was performed on PLZT of 8/65/35 composition across a temperature range from 5°C to 95°C. The technique harnesses electrostatic forces by controlling them through a Vdc sweep applied sequentially during read steps in multiple cycles.
2：Sample Selection and Data Sources:
A platelet-shaped sample of
3：0 mm thickness and a surface area of ca. 3х3 mm2 was polished to optical quality. List of Experimental Equipment and Materials:
An Asylum Research Cypher atomic force microscopy equipped with a temperature stage was used for all measurements. A conductive Budgetsensor Multimode probe (nominal force constant = 3 N/m, nominal resonance frequency = 75 kHz) was used.
4：Experimental Procedures and Operational Workflow:
cKPFM maps of 10x10 pixels were obtained upon varying the temperature from 5 °C to 95 °C in 7 steps. The cKPFM waveform consists of 40 write steps between +/- 45 V and 9 read steps between +/- 7 V. For AC excitation, a signal of 3 V and a frequency band centered around the contact resonance was applied.
5：Data Analysis Methods:
The obtained response was fitted using a simple harmonic oscillator model to extract amplitude, phase, resonance frequency and Q- factor. Data processing and analysis was partially performed using pycroscopy.
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