鎳錳鐵氧體之鉻摻雜電性與磁性性質研究

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Title:	鎳錳鐵氧體之鉻摻雜電性與磁性性質研究 Study of the electrical and magnetic properties of Cr doped Ni-Mn
Authors:	蘇駿翔
Contributors:	化學工程與材料工程學系奈米材料碩士班
Keywords:	鎳錳鐵氧體 Neel鬆弛行為
Date:	2017
Issue Date:	2017-03-29 13:16:04 (UTC+8)
Abstract:	本研究利用固態反應法合成Ni0.9Mn0.1CrxFe2-xO4 (x=0.0, 0.1, 0.2, 0.3, 與0.5) 陶瓷，用於研究化合物的介電性質與隨溫度變化的Neel鬆弛行為。經由XRD分析陶瓷體粉末發現所有摻雜鉻與未摻雜的樣品皆具有立方尖晶石結構，由於鉻離子半徑較小因此單位晶格常數的a軸長隨著摻雜量增加而減少。藉由光學顯微鏡觀察顯示鎳錳鐵氧體樣品隨著燒結溫度增加，晶粒尺寸跟著上升，但隨著鉻濃度的增加晶粒大小逐漸下降。利用節距法計算出光學顯微圖像中樣品的晶粒大小。室溫下的VSM測量結果顯示，非磁性離子的鉻濃度增加，使飽和磁化強度下降，分析低溫交流磁導分析儀測量結果，顯示所有的樣品都遵守Neel鬆弛行為，可利用Debye鬆弛模型計算出共振頻率(f0)，並且利用ln f0與溫度倒數做圖計算出磁異向能。在1623K燒結溫度摻雜鉻的樣品，其磁異向能隨著鉻摻雜濃度逐漸增加而增加。Ni0.9Mn0.1Cr0.1Fe1.9O4樣品除了最低溫燒結的樣品，磁異向能數值隨著燒結溫度的增加逐漸減少。室溫下的介電性能測量顯示介電常數隨著鉻離子摻雜濃度增加而降低，介電損耗隨著燒結溫度的增加而變大。我們可藉由塊材或粉體樣品利用測量不同溫度下交流磁導率的變化推算出磁異向能，其樣品的介電性質可通過燒結溫度與鉻離子摻雜濃度變化進行控制。 In this work, The Ni0.9Mn0.1CrxFe2-xO4 (x=0.0, 0.1, 0.2, 0.3, and 0.5) ceramics have been synthesized with the solid-state method to study the dielectric property and temperature dependent of the Neel relaxation behavior in these compounds. All un-dopant and Cr-doped samples were formed spinel cubic structure, which has been checked by powder X-ray diffraction and a-axis the lattices constant was decreased with Cr-doped level increasing due to smaller Cr-ion radii. The OM pictures in the Ni-Mn ferrite samples are shown that the grain size is increasing with sintering temperature increasing, but decreasing with Chromium concentration increasing. The grain size has been counted by the intercept technique through the OM images. Room temperature VSM measurement is showed that saturation magnetization is decreasing with Cr concentration increasing due to nonmagnetic Cr-ion increasing. AC magnetic susceptibility measurement is showed that all samples obey Neel magnetic relaxation behavior. Low temperatures AC magnetic susceptibility has been measured vary temperature, which was fitted the Debye relaxations model to calculate the resonance frequency (f0), and the magnetic anisotropy energy can be computed by the lnf0 versus reciprocal temperature plot. The magnetic anisotropy energy of 1623K sintering temperature of Cr-doped samples is gradually increasing with Cr-doped level x increasing except un-dopant sample. The amplitude magnetic anisotropy energy of Ni0.9Mn0.1Cr0.1Fe1.9O4 samples is gradually decreasing with sintering temperature increasing except 1473K sintering temperature sample. Room temperature dielectric property measurement is showed that dielectric constant is decreasing with Cr-doped level increasing and dielectric loss is increasing with sintering temperature increasing. We reported that bulk or powder samples’ magnetic anisotropy energy can measure by temperature dependent AC susceptibility method, and dielectric property can improve by Cr-doped processing and sintering temperature control.
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