共沉澱法合成細顆粒鈦酸鋇; Synthesis of Barium Titanate Fine Powders by Coprecipitation

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Title:	共沉澱法合成細顆粒鈦酸鋇;Synthesis of Barium Titanate Fine Powders by Coprecipitation
Authors:	余文懷;Wen-Hwai Yu
Contributors:	化學工程與材料工程研究所
Keywords:	擴散;草酸;共沉澱;鈦酸鋇;形狀和顆粒大小控制;morphology and particle size control;coprecipitation;Barium titanate;diffusion;BTO
Date:	2002-06-17
Issue Date:	2009-09-21 12:21:02 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	摘要自從Clabaugh 等人在1956年，首先發現將BaTiO(C2O4)2?4H2O (BTO) 於800℃下鍛燒，可以得到高純度的鈦酸鋇 (BaTiO3)。許多相關的研究也於其後陸續發表，然而大部份的研究者都將研究重心放在BTO的熱分解機構上，對於探討影響BTO顆粒大小和形狀的研究並不多。本研究主要探討影響BTO顆粒大小和形狀的因素，包括不同反應溫度、進料速度、pH值以及進料混合方式等;並利用擴散以及不同醇水比等方式製備BTO，以期得到細顆粒的鈦酸鋇粉末，並對其形狀做一定的控制。使用SEM分析沉澱的顆粒大小和形狀，使用XRD和TGA等儀器分析沉澱物的晶相和熱分解機構。研究發現BTO可於800℃鍛燒後得到立方晶相的鈦酸鋇，但聚集形狀卻和原BTO類似。進料速度愈快所得到的BTO 顆粒愈大，高溫下容易得到大顆粒的BTO沉澱。改變進料混合方式雖可以得到細顆粒(0.2μm)且分散的沉澱，但於800℃鍛燒後卻有BaTi2O5的雜相存在。另外以擴散方式可以得到類似葉片狀的BTO，並可利用快速攪拌得到顆粒約0.5 μm的BTO。在乙醇/水比等於1時，可以得到片狀的BTO沉澱，而在丙醇/水比大於1下所得沉澱於800℃鍛燒後會有BaT2iO5存在。本研究並指出BTO應為Ti(OH)22+嵌入Ba(HC2O4)2?2H2O的結構中，並和極性水分子反應所得到的錯和物Ba(HC2O4)2?2H2O－TiO(OH)2。此外在pH大於4之下所得到的沉澱應該是BaC2O4和TiO(OH)2的混合物。 Abstract Many research reports had been reported that high purity of barium titanate (BaTiO3) could be prepared by calcined BaTiO(C2O4)2?4H2O (BTO) at 800℃.However, most of the researchers put the emphasis on the mechanism of the thermal decomposition of BTO, only a few researchers discussed the morphology and particle size of BTO. In this study, several experiments had been conducted to investigate the factor that affected the morphology and particle size of BTO. The effect of investigated different reaction-temperature, adding rate, pH values, and adding order were used. BTO was also prepared by way of diffusion and different alcohol/water ratios in order to control the morphology and to obtain small particle size of BTO. SEM was used to examine the morphology and particle size of the precipitates. XRD and TGA were used to study the phase and thermal decomposition mechanism of the precipitates. It has been found that cubic barium titanate could be prepared by calcining BTO at 800℃, the particle size and morphology of agglomerated barium titanate was similar to that of BTO. The faster the adding rate the bigger the particle size of BTO. It is easy to form BTO with larger particle size at higher reaction temperature. Small particle size (0.2 μm) and dispersed BTO could be prepared by changing the adding order, however some BaTi2O5 was present after calcining the precipitates at 800℃. Furthermore, leaf-like BTO could be prepared by diffusion without stirring. BTO with particle size of 0.5 μm could be prepared by diffusion with vigorous stirring. Flake-like BTO could be prepared at ethanol/water of 1, and some BaTi2O5 was present after calcining the precipitates which were prepared at propanol/water>1. In this study, it was also found that BTO might be a compound which Ba(HC2O4)2 inserted with TiO(OH)22+, and then reacted with dipole molecular H2O to form the compound Ba(HC2O4)2?2H2O－TiO(OH)2. Besides, the precipitates prepared at pH>4 were the mixture of BaC2O4 and TiO(OH)2.
Appears in Collections:	[National Central University Department of Chemical & Materials Engineering] Electronic Thesis & Dissertation

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