利用同步輻射分析技術研究添加劑對低膨脹Li2O-Al2O3-SiO2玻璃陶瓷的顯微結構發展之影響

Effect of Various Dopants on the Microstructure Evolution of Low Thermal Expansion Li2O-Al2O3-SiO2 Glass-ceramic Materials Studied by Synchrotron Radiation Techniques

吳宇瀚(Yu-Han Wu)

指導教授 ： 李志浩

國立清華大學/原子科學院/工程與系統科學系/博士(2012年)

摘要

此研究探討添加B2O3, P2O5, ZnO, MgF2 and Fe2O3在商業化配方的低膨脹鋰鋁矽酸鹽玻璃陶瓷中，使該材料顯微組織的發展於不同熱處理條件下所呈現的變化。可以觀察到不同種類的添加劑會使顯微組織與電子結構的發展產生不盡相同的變化。試樣由一般的玻璃塊材淬冷法製備並經1階段或2階段熱處理而析出晶相。材料的顯微結構發展經由X光繞射、X光近吸收邊結構、紅外光吸收光譜術等方法來鑑別。主要結果條列如下：
(1)玻璃失透過程中，鈦離子(成核劑)的配位數由4與5轉變為6。
(2)在具商業配方的高度結晶試樣中，鋅離子傾向位於類似尖晶石結構的周遭環境當中；在簡化的配方當中，鋅離子較常處於類似纖鋅礦的結構中。
(3)在低添加濃度時 (~<0.2%)，大部分鐵離子於結晶化過程處於較無序的環境；在高添加濃度時，部分鐵離子會進入較有序的結構中，例如:主晶相的鋰位置。
(4)這些添加劑通常使得試樣的結晶化溫度以及主晶相相變溫度降低，然而添加較高含量氧化鐵時(~>0.6%)例外。
(5)對於添加氧化磷、氟化鎂與氧化鐵的試樣，其顯微組織的均勻性因為添加濃度的提高而降低。因此，這些試樣的抗折強度也隨之下降。
添加劑造成的玻璃黏度、化學劑量比、以及陽離子力場強度等變化被認為是可能造成上述現象的機構。

關鍵字

鋰鋁矽酸鹽 ； 玻璃陶瓷 ； X光吸收光譜術 ； X光粉末繞射 ； 顯微結構 ； 添加劑 ； 機械強度

並列摘要

The effects of additives, such as B2O3, P2O5, ZnO, MgF2 and Fe2O3, on the microstructure evolution under different thermal treatment conditions in a low thermal expansion lithium aluminosilicate glass-ceramic material with commercial-like compositions are studied. It can be found that the effects on micro- and electronic structural development accompanied with different types of additives are varied. Samples are prepared by the standard bulk quench method and heated by one or two-step thermal programs to achieve vitreous to crystalline phase transition. The analytical work is emphasized on the results obtained from these techniques: X-ray powder diffraction, X-ray absorption near edge structure and IR absorption spectroscopy. A few results can be summarized as follows:
(1)During the devitrification process, the coordination number of Ti (the nucleation agent) changes from 4 and 5 to 6;
(2)For highly crystalline samples with commercial-like composition, Zn ions tend to have spinel-like local environments; while in a simplified composition, Zn ions favor hexagonal ZnO-like surroundings;
(3)At low doping level (~<0.2%), most of Fe ions remain in disorder states during devitrification process; at high doping level(~>0.6%), some of these ions migrate into order environments, such as the Li site of the main crystalline phase;
(4)The crystallization and main phase transformation temperatures are often lowered for samples with these additives; while these phase change temperatures are increased for samples with high Fe2O3 doping concentration (~>0.6%);
(5)The microstructural uniformity becomes irregular as the doping level of P2O5, MgF2 or Fe2O3 is increased. As a result, the flexural strengths of these samples are decreased.
The possible mechanisms of changes by the additives in viscosity, stoichiometry and cation field strength are proposed to be responsible for the above phenomenon.

並列關鍵字

lithium aluminosilicate ； glass ceramic ； X-ray absorption spectroscopy ； X-ray powder diffraction ； microstructure ； additives ； mechanical strength

參考文獻

References of Chapter 1

[1.4] W. Holand, G. Beall, Glass-ceramic Technology, The American Ceramic Society, (2002).

References of Chapter 2

[2.1] F. A. Hummel, “Thermal expansion properties of some synthetic lithia minerals”, Journal of the American Ceramic Society, vol.34, pp.235-239, (1951)

[2.2] P. G. Debenedetti and Frank H. Stillinger,” Supercooled liquids and the glass transition”, Nature, vol.410, (2001).