鉍層結構鐵電體(BLSFs)因為具有特殊的晶格結構，可以在加上電壓後改變其極化方向與極化量，適用於製作鐵電記憶體(FeRAM)的材料，而受到廣泛的研究。就現今的鐵電記憶體而言，具備有切換速度快、低功率操作與非壞性讀取的優點，然而所面臨的挑戰有耐久性、絕緣層特性、介電係數的要求等問題。本論文針對三種不同系列的含鉍鐵電材料採用固相反應法製程，分別透過晶格結構、表面形態與介電係數，探討不同的製程參數對其物性及介電性的影響。
第一個系列為SrBi2Ta2O9-based的鐵電材料，其中一者為SrBi2Ta2O9 + x wt% Bi2O3 (x=0, 2, and 4)的組成，添加超量的2wt%或4wt% Bi2O3可降低燒結溫度約100°C，可抑制二次相SrBi2O4與BiTaO4的生成，且在晶相中只生成SrBi2Ta2O9單一相，添加超量的Bi2O3促進此組成的晶粒成長與緻密度、改善介電係數(dielectric constant)以及提高鐵電性極化量。另一者為SrBi2Ta2-xVxO9 (x=0.1, 0.2, 0.3, and 0.4) 的組成，以V2O5取代Ta2O5，改變了鐵電體的極化指向；燒結溫度可降到約1000°C。
第二個系列為SrBi4Ti4O15-based的鐵電材料其中一者為(Sr1-xBax)Bi4Ti4O15 (x=0, 005, 0.1, 0.15, and 0.02)的組成，以掺雜BaO取代SrO，居理溫度會隨BaO的含量增加而略微升高；燒結溫度在1150°C時，介電係數以x=0.01的組成為最大。另一者為SrBi4Ti4O15+x Bi2O3, (x= -0.04, -0.02, 0, 0.02, and 0.04) 的組成，鉍缺乏的組成(x= -0.04, -0.02)有二次相Bi2Ti2O7與 SrTiO3生成，使介電係數降低；當燒結溫度高於1100°C時，介電係數隨Bi2O3的添加量增加而升高。
第三個系列為(Na0.5Bi0.5)TiO3-BaTiO3-based的鐵電材料。其中一者為0.95 (Na0.5Bi0.5)TiO3-0.05 BaTiO3 + x wt% Bi2O3(x= 0, 1, 2, and 3)的組成，透過兩種不同的粉體混合製程，(第一種粉體混合製程:先將原始粉末混合，在850°C與1100°C分別煅燒出(Na0.5Bi0.5)TiO3與BaTiO3，再將(Na0.5Bi0.5)TiO3與BaTiO3當作粉體，依照組成進行混合燒結，第二種粉體混合製程是採用傳統的固相燒結。) 以x=1 wt%過量掺雜Bi2O3的組成介電係數最大；運用Bi2O3的液相燒結特性燒結不同Bi2O3添加量的組成，可知適量的Bi2O3添加對微結構中的孔隙減少與晶粒成長才有最大助益，相同燒結溫度以第二種製程製造出的鐵電材料介電係數較高，但是採用第一種製程製造出的鐵電材料，對溫度與頻率的敏感度較低。另一者為(1-x) (Na0.5Bi0.5)TiO3-x BaTiO3 (x= 0.03, 0.05, and 0.07) 的組成，依照上述兩種不同的粉體混合製程，發現這個系列的介電係數隨BaTiO3的含量增加而上升，在頻率10 kHz.~1MHz變化量微小，呈現穩定值，是一種寬頻的材料。

Bismuth layer structure ferroelectrics (BLSFs) have attracted intensive investigation for the potential use in nonvolatile ferroelectric random access memory (NvRAM/FeRAM) and high temperature piezoelectric devices. In this thesis, there are three kinds of Bi-layered structure ferroelectric ceramics materials prepared by solid-state reaction methods. Investigations have been made on the crystal structure, surface morphology, and dielectric properties of these ferroelectric materials.
In the chapter3 of this thesis, ferroelectric materials are SrBi2Ta2O9-based ceramics. One of the materials is SrBi2Ta2O9 composition with excess x wt% Bi2O3 (x=0, 2, and 4). Even 1280oC is used as the sintering temperature of stoichiometric SrBi2Ta2O9 composition, the X-ray diffraction patterns will show that the SrBi2Ta2O9 phase is coexisted with the raw material of Ta2O5 and the secondary phases of SrBi2O4 and BiTaO4. For SrBi2Ta2O9 composition with excess 2wt%- or 4wt%-Bi2O3-doped and sintered at 1040oC, the Ta2O5, SrBi2O4, and BiTaO4 phases are eliminated and only the SrBi2Ta2O9 phase is observed in the X-ray diffraction patterns. The other of SrBi2Ta2O9-based ceramics was doped with V2O5. V2O5 is used to substitute Ta2O5 of the SrBi2Ta2O9 ceramics to form SrBi2Ta2-xVxO9 composition, where x=0.1, 0.2, 0.3, and 0.4. For all SrBi2Ta2-xVxO9 composition, the crystal intensities of the (00l) planes (l =6, 8, 10, 12, and 14) increase with the increase of sintering temperature and saturate at 1050oC-sintered ceramics, and the increase in the crystal intensities of the (008) and (0010) planes are more obvious. For the same sintering temperature, the crystal intensities of the (00l) planes increase with the increase of V2O5 content and saturate at SrBi2Ta1.7V0.3O9 ceramics.
In the chapter4, ferroelectric materials are SrBi4Ti4O15-based ceramics. One of the materials is (Sr1-xBax)Bi4Ti4O15 (x=0, 005, 0.1, 0.15, and 0.02), and BaO is used to substitute SrO. Dielectric properties were investigated in the temperature of 25oC~ 805oC at 1MHz. It is found that Curie temperatures are shifted to higher temperature as the BaO content increased. For (Sr1-xBax)Bi4Ti4O15 ceramics sintered at 1150oC, the Curie temperature for x=0, 0.05, 0.1, 0.15, and 0.2 are 645oC, 665oC, 705oC, 725oC, and 745oC, respectively. The other is non-stoichiometric compositions SrBi4Ti4O15+x Bi2O3, (x= -0.04, -0.02, 0, 0.02, and 0.04). From the observations of SEM, the SrBi3.92Ti4O14.88 and the SrBi3.96Ti4O14.94 ceramics reveal a two-phased grain growth, the bar-typed and the irregularly disk-typed grains coexist; The other ceramics will reveal the irregularly disk-typed grains. From the X-ray diffraction patterns, Bi2Ti2O7 and SrTiO3 phases are observed in the SrBi3.92Ti4O14.88 and the SrBi3.96Ti4O14.94 ceramics. Except the SrBi3.96Ti4O14.94 ceramics, the other ceramics have revealed an unapparent splitting peak in the (119) plane.
In the chapter5, ferroelectric materials are (Na0.5Bi0.5)TiO3-BaTiO3-based ceramics. The 0.95 (Na0.5Bi0.5)TiO3-0.05 BaTiO3 + x wt% Bi2O3 (x= 0, 1, 2, and 3) ceramics were fabricated by two different processes. The first process is that (Na0.5Bi0.5)TiO3 and BaTiO3 composition was calcined at 850oC and 1100oC, respectly, and then the calcined (Na0.5Bi0.5)TiO3 and BaTiO3 powders were mixed in according to 0.95 (Na0.5Bi0.5)TiO3-0.05 BaTiO3 + x wt% Bi2O3 compositions. The second process was that the raw materials were mixed in accordance to the 0.95 (Na0.5Bi0.5)TiO3-0.05 BaTiO3 + x wt% Bi2O3 compositions and then calcined at 900oC. The sintering process was carried out in air for 2h from 1120oC to 1240oC. As the sintering temperatures are higher than 1160oC, the maximum dielectric constants of ceramics made by the second method are higher than those of ceramics by the first method, and the maximum dielectric constant of this ceramics will reveal in the x =1 ceramics. Both ceramics reveal a broaden dielectric constant-temperature curves. The other is (1-x) (Na0.5Bi0.5)TiO3-x BaTiO3 compositions, where x= 0.03, 0.05, and 0.07, formatted by two different methods given above. The dielectric-temperature curves of (1-x) (Na0.5Bi0.5)TiO3-x BaTiO3-based ceramics are almost unchanged as the measured frequency changed from 10 kHz to 1MHz.

Abstract (Chinese) Ⅰ
Abstract (English) Ⅲ
knowledgements Ⅵ
Contents Ⅶ
List of Figures Ⅹ

Chapter 1 Introduction………...……...…………………..…….................…….. 1
1.1 Motivation………………………………………………………………….1
1.2 Ferroelectric materials………………………………………………….…..4
1.3 Crystal structure of Perovskite ABO3-type Compounds……………….…..5
1.4 Crystal structure of Aurivillius layer-structure Compounds……………….6
1.5 Solid solutions……………………………………………………………..7
1.5.1 Substitution and Additions…………………...……………………..7
1.5.2 Non-stoichiometry Compounds……………...……………………..9
1.5.3 Influence of Chemical Reaction on Sintering.……………………...9
1.6 Dielectric Properties of Ceramic Materials………...……………………..10
1.7 Dielectric Properties of Ferroelectric Materials…...………………….…..12

Chapter 2 Experimental Details ………...…………………………..…………..18
2.1 Preparation of SrBi2Ta2O9-based Ferroelectric Ceramics….....…………..18
2.1.1 Preparation of Excess Bi2O3 Doped SrBi2Ta2O9 Ceramics………..18
2.1.2 Preparation of V2O5 Doped SrBi2Ta2O9 Ceramics…….............…..18
2.2 Preparation of SrBi4Ti4O15 –based Ferroelectric Ceramics…...............…..19
2.2.1 Preparation of (Sr,Ba)Bi4Ti4O15 Ceramics….............................…..19
2.2.2 Preparation of SrBi4Ti4O15+x Bi2O3 Ceramics….......................…..19
2.3 Preparation of (Na0.5Bi0.5)TiO3-BaTiO3–based Ferroelectric Ceramics......20
2.3.1 Preparation of Excess Bi2O3 Doped
0.95(Na0.5Bi0.5)TiO3-0.05BaTiO3 Ceramics.....………………..…..20
2.3.2 Preparation of (1-x) (Na0.5Bi0.5)TiO3-x BaTiO3 Ceramics……..…..21
2.4 X-ray Diffraction Analysis (XRD)......………………………………..…..22
2.5 Scanning Electron Microscope (SEM) ……………………………….…..22
2.6 Temperature–dependent Capacitance-Voltage (C-V) Measurements.…....22

Chapter 3 Results and Discussion of SrBi2Ta2O9 -based Ferroelectric Ceramics.....……………..…………………..………………….…....33
3.1 The Effect of Excess Bi2O3 Content on the Properties of SrBi2Ta2O9 Ceramics. ………………………………………………………………....33
3.1.1 Microstructure Analysis…………………………………………....33
3.1.2 Dielectric Properties Analysis………………………………..……34
3.2 The Influence of the Substitution Ta+5 by V+5 on Characteristics of SrBi2(Ta2-xVx)O9 Ceramics……….……………………………..………...36
3.2.1 Microstructure Analysis…………………………………..………..36
3.2.2 Dielectric Properties Analysis…………………………..…..……..37

Chapter 4 Results and Discussion of (Sr,Ba)Bi4Ti4O15 and SrBi4Ti4O15+ x Bi2O3 Ferroelectric Ceramics………………………………….….....……..51
4.1 The Influence of the Substitution of Sr+2 by Ba+2 on Characteristics of (Sr1-xBax)Bi4Ti4O15 Ceramics………………………………….…..……...51
4.1.1 Microstructure Analysis……………………………….…..…….....51
4.1.2 Dielectric Properties Analysis………………………..…..……......52
4.2 Development of Non-Stoichiometric SrBi4+2xTi4O15+3x Ceramics..…..…..53
4.2.1 Microstructure Analysis………………………..….........................53
4.2.2 Dielectric Properties Analysis………………..…............................55

Chapter 5 Results and Discussion of (Na0.5Bi0.5)TiO3-BaTiO3-based Ferroelectric Ceramics………………..…..........................................67
5.1 The Influence of Different Fabrication Processes on Characteristics of Excess Bi2O3-doped 0.95(Na0.5Bi0.5)TiO3-0.05 BaTiO3 Ceramics..............67
5.1.1 Microstructure Analysis....................................................................67
5.1.2 Dielectric Properties Analysis..........................................................71
5.2 The Influence of Different Fabrication Processes on Characteristics of
(1-x) (Na0.5Bi0.5)TiO3-x BaTiO3 Ceramics............................................... 73
5.2.1 Microstructure Analysis.................................................................. 73
5.2.2 Dielectric Properties Analysis......................................................... 76

Chapter 6 Conclusions......................................................................................... 98
6.1 SrBi2Ta2O9- based Ferroelectric Ceramics................................................. 98
6.1.1 Excess Bi2O3 Doped SrBi2Ta2O9 Ceramics..................................... 98
6.1.2 V2O5 Doped SrBi2Ta2O9 Ceramics.................................................. 98
6.2 SrBi4Ti4O15 –based Ferroelectric Ceramics................................................ 99
6.2.1 (Sr,Ba)Bi4Ti4O15 Ceramics............................................................... 99
6.2.2 SrBi4Ti4O15+x Bi2O3Ceramics......................................................... 99
6.3 (Na0.5Bi0.5)TiO3-BaTiO3–based Ferroelectric Ceramics........................... 100
6.3.1 Excess Bi2O3 Doped 0.95(Na0.5Bi0.5)TiO3 -0.05BaTiO3 Ceramics 100
6.3.2 (1-x) (Na0.5Bi0.5)TiO3-x BaTiO3 Ceramics..................................... 101

References.......................................................................................................... 102

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