本研究利用了X光繞射、掃瞄及穿透式電子顯微鏡及背向散射電子繞射的分析方法，針對無壓燒結固態反應生成的LaGaO3陶瓷材料做有系統的微結構分析。鈣鈦礦結構的LaGaO3隨著溫度降低時，會在145oC發生一固態相變化，其結晶結構由菱形晶 (空間群R c) 轉變為正方晶 (空間群Pnma) 過程中而衍生出雙晶。我們一共觀察及分析了四種形式的雙晶，包括有{101}、{121}、

Pressureless-sintered lanthanum gallate (LaGaO3) ceramics have been analyzed using X-ray diffractometry (XRD), scanning electron and transmission electron microscopy (SEM and TEM), and electron-backscatter diffraction (EBSD). Transformation-induced twin domains are generated by solid-state phase transition upon cooling from the rhombohedral (r, space group R c) to orthorhombic (o, space group Pnma) symmetry at 145oC. Four types of transformation twins {101}, {121},

中文摘要 …………………………………………………....…………………………..….. I
Abstract …………………………………………………….……………………...…...… III
Contents ………………………………………………….………...…………………….. VI
List of Tables …………………………………………………………………………... XII
List of Figures ……………………………………………………………………….... XIV

Chapters:
1 Introduction ………………………….……………………………………………... 1
1.1 Research background ……….…………………………………………….…….. 1
1.2 Objective of research ……………………………………………….…………... 4

2 Literature review …………………………………………………………………... 6
2.1 Structures of perovskites …………...…………………………………………… 7
2.1.1 Ideal cubic perovskite ………………………..…………………………. 7
2.1.2 Distorted perovskites …………………………...……………………... 11
2.1.3 Octahedral tilting ……………………………………………………… 14
2.1.4 The sequences of structural phase transitions in perovskites ……….…. 19
2.2 Phase transformation in solids ...………….…………………………………… 22
2.2.1 Fundamentals of phase transformation ….……….……………………. 22
2.2.2 Symmetry breaking transformations ……….………………………….. 31
2.2.3 Phase transformation-induced domain structures …………………..…. 32
2.2.4 Transformation twins ……………………………...………………...… 36
2.2.4.1 Twins ……...…………………………….………………...…. 36
2.2.4.2 Twin interfaces ………………………………………...…….. 40
2.2.4.3 Reflection twins and rotation twins ………………………..... 49
2.2.4.4 Identification of reflection twin and 180o rotation twin …….. 54
2.2.5 Phase transformations and transformation twins in perovskites ………. 58
2.2.5.1 Cubic-to-tetragonal transition (4/m 2/m

Aleksandrov, K. S., “The sequences of structural phase transitions in perovskites,” Ferroelectrics, 14, 801