製備方式對Nd2Ti3O8.7陶瓷結構特性之影響

Abstract

本研究採用兩種方法來製備Nd2O3-TiO2 系統介穩態 化合物(metastable compound)：Nd2Ti3O8.7(此化合物無法經由Nd2O3與TiO2的混和直接以固態反應法得到)，這兩種方法分別是：1.添加PbO於Nd4Ti9O24，以固態反應法使Nd4Ti9O24相變化成 (PbxNd2-x)Ti3O8.7； 2.利用化學反應法的共沈法 (coprecipitation)，直接得到Nd2Ti3O8.7。以XRD及DTA 分析由這兩種方法製備得的Nd2Ti3O8.7原始粉末其相變化歷程、生成相隨PbO添加量改變的變化及 PbO 添加所造成的晶格常數變化，進而製作 900℃下的 PbO-Nd2O3-TiO2三元相圖。 由方法1.製備得的(PbxNd2-x)Ti3O8.7，在 1300℃/4hr. 的燒結條件下 達 到 緻 密 (99﹪理論密度) 且不含雜相； 由方法2. 製備得的Nd2Ti3O8.7 ， 則需 1400℃/4hr.燒結緻密(99﹪理論密度) ，但有雜相Nd2Ti2O7 出現。 並以 EDS半定量分析，分析此兩種陶瓷燒結塊材它們的組成元素比例變化，進而討論Nd2Ti3O8.7結構內部的原子取代機制及點缺陷結構(point defect structure)。

In this study , the author makes use of two methods to fabricate the metastable compound, Nd2Ti3O8.7 ,in the Nd2O3-TiO2 system which cannot be obtained by the conventional solid-state reaction method. The first method is doping PbO into Nd4Ti9O24 to make phase transformation take place from Nd4Ti9O24 to Nd2Ti3O8.7 , and the second is to fabricate Nd2Ti3O8.7 directly by the chemical reaction method , coprecipitation , which is often used to fabricate pure compounds in many other researches. The history of phase transformation , the changes in phase obtained as the doping quantity varie , and the lattice parameter variation arising from different PbO doping quantity , are investigated by XRD and DTA in this study. The ternary phase diagram of PbO-Nd2O3-TiO2 at 900℃ is also reported by the author. The bulks, in the shape of cylinder, of compound Nd2Ti3O8.7 which is fabricated by method 1 can be sintered to densification ( up to 99﹪theoretical density ) without any undesired phase at 1300℃for 4 hours. Those fabricated by method 2 can be sintered to densification (up to 99﹪theoretical density) at 1400℃for 4 hours but the impurity phase Nd2Ti2O7 appears in the final phase . The variation of the molar ratio of the constitutional elements in the two kinds of bulks above is analyzed by the EDS Semi-Quantification analysis. According to the data obtained , the substitutive mechanism of atoms inside the structure of Nd2Ti3O8.7 and the point defects structure are discussed by the author.