氧化物與碳酸鹽之間的固態反應對於工業上生產許多功能陶瓷粉末相當的重要，藉由了解鹼土金屬碳酸鹽與氧化物間反應的機制，不僅可降低其反應溫度，同時亦可避免產物粒子形成凝聚與粗化，以合成出高純度奈米級粉末。由於反應的過程同時牽涉碳酸鹽的分解以及氧化物間物質擴散的過程，許多矛盾的說法以及不明的實驗結果目前仍無法被合理地解釋。因此本研究藉由合成SrAl2O4以及BaTiO3兩種材料系統的固態反應過程，深入探討碳酸鹽與氧化物之固態反應機制，進而了解鹼土碳酸鹽與氧化物進行固態反應的過程中可能包含的反應機構以及物質擴散之現象。
由SrCO3與Al2O3合成SrAl2O4的實驗中，發現反應過程可能同時包含SrO與Al2O3兩種擴散機制。在部分CO2的氣氛下，其反應之DTG結果顯示四個階段的失重變化，由低溫至高溫分別推測為SrO擴散主導的SrAl2O4生成反應，Al2O3擴散主導的SrAl2O4生成反應，SrO擴散主導的Sr3Al2O6生成反應，以及SrCO3獨自分解的反應，其中Al2O3擴散進入SrAl2O4的結構時，產生的氧空缺會造成靜電排斥力，而將高溫相hexagonal SrAl2O4穩定於室溫中，此外，在SrCO3相變的過程中，亦可能會發生Hedvall effect而促進Al2O3擴散進入SrCO3的結構，進而產生內應力將高溫相hexagonal SrCO3穩定於室溫下。
由BaCO3與TiO2合成BaTiO3的實驗中，其反應與前述擴散機構類似。在部分CO2氣氛下，反應之DTG結果顯示三個階段的失重變化，由低溫至高溫分別推測為BaO擴散主導的BaTiO3生成反應、TiO2擴散主導的BaTiO3生成反應，以及BaO擴散主導的Ba2TiO4生成反應。然而在空氣氣氛下進行熱處理時，其第三階段的反應可能會與第二階段的反應發生重疊，因此一般不容易觀察到TiO2擴散的現象。
使用介面活性劑、小粒徑或不同晶體結構的起始原料均對反應會造成明顯的影響。在SrCO3與Al2O3生成SrAl2O4的固態反應中，使用γ-Al2O3可於反應初期生成較多的SrAl2O4產物，而當縮小SrCO3粒徑時，可以幫助反應較容易獲得純相SrAl2O4產物。在BaCO3與TiO2生成BaTiO3的固態反應中，利用聚乙烯亞胺(PEI)對於BaCO3的表面進行改質，可以有效地提高反應物間的混合均勻度，有助於BaTiO3生成反應的發生，而使用小粒徑BaCO3除了可以增加反應接觸面積，且可提供較短的擴散距離而有利於TiO2的擴散，因此可於800oC的低溫下長時間反應得到幾乎為純相的BaTiO3產物。

The conventional solid-state synthesis is usually used to prepare many important functional ceramics, especially the solid state reaction between oxides and alkaline earth carbonates. However, the reaction mechanism related to the decomposition of carbonates and the diffusion of oxides is complicated and is still unclear. This study conducted the solid-state synthesis of SrAl2O4 from SrCO3 and Al2O3, and BaTiO3 from BaCO3 and TiO2 to evaluate the complex reaction mechanism, culminating in the presentation of phase evolution and material diffusion model.
In the synthesis of SrAl2O4, the dual diffusion mechanism of SrO and Al2O3 was observed. The diffusing Al2O3 not only reacts with SrCO3 to form SrAl2O4, but also plays a viable role in stabilizing the metastable species by generation of lattice strains and oxygen vacancies. The excess Al2O3 ions existing in the SrAl2O4 structure can result in the increase of oxygen vacancy concentration, providing some clues to the stabilization of the hexagonal SrAl2O4 at room temperature. In addition, a small amount of Al2O3 ions may enter the certain specific positions of the SrCO3 structure that causes the lattice strain to stabilize the hexagonal SrCO3 at room temperature as well. In the synthesis of BaTiO3, the reaction mechanism is similar to the synthesis of SrAl2O4. But the overlapping of each reaction makes it difficult to observe the TiO2 diffusion when the calcination is in air.
The solid state syntheses could be influenced by adding surfactants, reducing the raw material size and the variation of the raw material crystal structure. Compared to χ-Al2O3 and α-Al2O3, using γ-Al2O3 can promote the formation of SrAl2O4 in the initial stage. Besides, using small SrCO3 is helpful to obtain pure SrAl2O4 products. PEI addition can improve the mixing homogeneity of reactants that facilitate the formation reaction of BaTiO3. Meanwhile using small BaCO3, nearly pure BaTiO3 product with particle sizes less than 50nm was obtained at 800oC.

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