稀土錳氧化物奈米棒之尺寸效應與介電性質研究

Size effect on dielectric properties of rare earth multiferroics nanorods

林亮劼(Liang-Chieh Lin)

指導教授 ： 楊仲準

中原大學/理學院/物理研究所/碩士(2017年)

https://doi.org/10.6840/cycu201700646

摘要

本研究利用水熱法製作GdMn2O5¬奈米棒樣品，以熱退火燒結出不同尺寸之奈米棒。樣品透過X光粉末繞射儀、場發穿透式電子顯微鏡(FE-TEM)、電性量測儀器、多功能物理測量儀(PPMS)等儀器，對於結構、樣品表面樣貌、磁性、電性、尺寸等方面分析。
本研究中奈米棒尺寸=80nm 溫度40K時具有磁化率峰，溫度27K時變溫XRD量測繞射峰異常，顯示臨界尺寸造成錳氧鍵長產生突變，指初期發生磁有序之尺寸維=80nm 與=67nm之間。

關鍵字

多鐵奈米棒 ； 介電係數

並列摘要

GdMn2O5 nanorods were prepared by hydrothermal method, and different sizes of nanorods were sintered by thermal annealing. The samples were characterized by X-ray powder diffractometer, field emission electron microscopy (FE-TEM), electrical measuring instrument and physical property measuring instrument (PPMS).
A magnetic susceptibility peak was found at 40 K as sample larger than 80nm. Varied temperature XRD experiments show an anomaly peak at 27.3º in =80 nm but not in 67 nm sample as temperature cooling down to 27 K. This is not expected in orthorhombic Pbnm structure. We believe this is correlated with the magnetic and structural critical size in between = 80 nm and = 67 nm. The peak value of ferroelectric phase transition for all samples are at 43 K, and the peak value of ferroelectric phase of 210 nm is 35 K, while the peak of 80 nm and 67 nm is 27 K. This shows that the ordering of ferroelectrics begins to change between = 210 nm and 80 nm.

並列關鍵字

multiferroics nanorods ； dielectric constant

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