介電陶瓷材料之拉曼光譜研究
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2006
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在這篇論文中利用拉曼光譜，來量測微觀狀態下 perovskite structure 和cubic pyrochlore structure的微波介電陶瓷材料結構性質與其微波性質之關連性。本文主要討論的 perovskite 陶瓷材料的是ABO3中之1：1結構，也就是 A(B’1/2B”1/2)O3和 A2B2O6O’的cubic pyrochlore 陶瓷材料是以bismuth、zinc和 niobium三種離子為主其中主要探討的部份包含： Qxf 值與氧八面體結構之關係，以及微波介電係數是否受到陶瓷perovskite材料中陰陽離子間距的影響。
我們利用兩組樣品來探討上述的微波特性與晶體結構的相關性。第一組樣品是改變A晶體位置的樣品。利用這一個系列的樣品來說明A位置取代對微波介電參數的影響。
第一組樣品為xCaSc1/2Nb1/2O3 + Ba(1-x) Sc1/2Nb1/2O3 ，這組樣品是針對改變A位置的離子，探討結構與微波關連性。我們發現第一組樣品中，圍繞在A位置周圍的O離子所形成的氧八面體結構對於Qxf值有極強烈相關性，而Ca離子大小以及極化率與O離子的距離對於介電係數之也有影響。當x增加時，即Ca離子在A位置上的含量越來越多時，氧八面體會越趨於鬆散，也就是Ca離子距O離子的距離越來越大，同時介電係數也有此趨勢，由此我們可以證明介電係數確實與陰陽離子的間距相關。
第二組樣品是一系列cubic pyrochlore structure樣品，他們分別為是減少Bi離子及O離子的Bi1.5-xZn1.0Nb1.5O7-1.5x、減少Zn離子及O離子Bi1.5Zn1.0-xNb1.5O7-x、減少Nb離子及O離子Bi1.5Zn1.0Nb1.5-xO7-2.5x、由Ta離子取代Nb離子的Bi1.5Zn0.5Nb1.5-xTaxO7以及由Ti離子取代Zn和Nb離子的(Bi1.5Zn0.5)(Zn0.5-x/3TixNb1.5-2x/3)O7共五組樣品的結果可看出，可以看出在低頻區域有個exponential 的背景隨著濃度下降而變弱，由此可以求出在哪些特徵溫度的時候exponential 的背景才會有強烈的影響。此外發現B位置周圍的O離子所形成的氧八面體結構對於tanδ值有極強烈相關性，同時介電係數也有也會應此有所改變，由此我們可以證明介電係數確實與陰陽離子的間距相關。
In this thesis, we adopted the Raman scattering techniques to detect the micro-structure of a series of perovskite and cubic pyrochlore microwave materials the correlation with microwave dielectric properties were also investigated. The size of oxygen-octahedrons in perovskite ceramics can be revealed by these measurements, and can be directly correlated with the microwave dielectric properties. The Raman measurements of xCaSc1/2Nb1/2O3 + Ba(1-x) Sc1/2Nb1/2O3 with calcium and barium ions as A sites ions revealed the structural properties of the oxygen-octahedrons. The rigid oxygen-octahedrons give the loose oxygen bonds with the increasing concentration of the calcium ions because the radius of calcium is smaller than barium. In addition, the distance between cations and anions is enlarged with the increasing concentration of calcium ions. There are five series samples in this thesis. They are Bi1.5-xZn1.0Nb1.5O7-1.5x, Bi1.5Zn1.0-xNb1.5O7-x, Bi1.5Zn1.0Nb1.5-xO7-2.5x, Bi1.5Zn0.5Nb1.5-xTaxO7, and (Bi1.5Zn0.5)(Zn0.5-x/3TixNb1.5-2x/3)O7. The Raman measurement of cubic pyrochlore structure exhits exponential background is getting stronger with the increasing temperature. In this way, we can find the critical temperature. In addition, we also find the characteristic of the rigid oxygen-octahedrons is well-defined to the correlation of the dielectric properties.
In this thesis, we adopted the Raman scattering techniques to detect the micro-structure of a series of perovskite and cubic pyrochlore microwave materials the correlation with microwave dielectric properties were also investigated. The size of oxygen-octahedrons in perovskite ceramics can be revealed by these measurements, and can be directly correlated with the microwave dielectric properties. The Raman measurements of xCaSc1/2Nb1/2O3 + Ba(1-x) Sc1/2Nb1/2O3 with calcium and barium ions as A sites ions revealed the structural properties of the oxygen-octahedrons. The rigid oxygen-octahedrons give the loose oxygen bonds with the increasing concentration of the calcium ions because the radius of calcium is smaller than barium. In addition, the distance between cations and anions is enlarged with the increasing concentration of calcium ions. There are five series samples in this thesis. They are Bi1.5-xZn1.0Nb1.5O7-1.5x, Bi1.5Zn1.0-xNb1.5O7-x, Bi1.5Zn1.0Nb1.5-xO7-2.5x, Bi1.5Zn0.5Nb1.5-xTaxO7, and (Bi1.5Zn0.5)(Zn0.5-x/3TixNb1.5-2x/3)O7. The Raman measurement of cubic pyrochlore structure exhits exponential background is getting stronger with the increasing temperature. In this way, we can find the critical temperature. In addition, we also find the characteristic of the rigid oxygen-octahedrons is well-defined to the correlation of the dielectric properties.
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拉曼, Raman, Pyrochlore, Pervoskite