1. 電子陶瓷研究室 中國材料科學學會年會 ( 台北科技大學 ) 2008 年 11 月 21 日 - 22 日，台灣，台北市。 Synthesis and properties of Ba 4 La(Sn 0.75 Ti 0.25 )Nb 3 O 15 ceramics by a reaction-sintering process Ba 4 La(Sn 0.75 Ti 0.25 )Nb 3 O 15 (BLSTN) microwave dielectric ceramics prepare using a reaction-sintering process were investigated. The mixture of raw materials was pressed and sintered directly without any calcination stage involved. Phases with similar structure of Ba 4 LaTiNb 3 O 15 and Ba 4 LaSnNb 3 O 15 were found in BLSTN. Density reached 6.35g/cm 3 for 4 h sintering at 1470 o C. keyword ： reaction sintering process 、 microwave dielectric ceramics 、 Ba 4 La(Sn 0.75 Ti 0.25 )Nb 3 O 15 Results and discussion Fig. 1 shows the XRD patterns of BLSTN ceramics produced using the reaction- sintering process. Phases with similar structure of Ba 4 LaTiNb 3 O 15 and Ba 4 LaSnNb 3 O 15 were found in BLSTN. The patterns were based on hexagonal perovskite structure. Therefore, the reaction sintering process is a simple and effective process to prepare BLSTN ceramics even the calcination stage was bypassed. The shrinkage percentage for sintered BLSTN pellets are shown in Fig. 2. 1430 o C is not high enough for densification. Values between 23% and 26% are found in BLSTN sintered at 1450-1500 o C. In Fig. 3, the density values of BLSTN ceramics increases with sintering temperature and reaches a maximum value 6.35 g/cm 3 in 1470 o C/4 h sintering pellets. Fang et al. obtained Ba 4 LaTiNb 3 O 15 with 98.6% of theoretical density 6.223 g/cm 3 and Ba 4 LaSnNb 3 O 15 with 97.3% of 6.49g/cm 3 after being calcined at 1200–1300 o C/4 h and sintered at 1450 o C/4 h and 1480 o C/4 h respectively. BLSTN sintered at 1470 o C/4 h reached 97.9% of theoretical density 6.48g/cm 3. Therefore, the reaction-sintering process is effective to produce BLSTN ceramics with high density even without the calcination stage and the addition of sintering aid. Fig. 1. The XRD patterns of BLSTN ceramics sintering 2 h at different temperature. (A)Ba 4 LaTiNb 3 O 15 (ICDD-00-056-0400) (B)Ba 4 LaSnNb 3 O 15 (ICDD-00-056-1047) Fig. 2. Shrinkage percentages for BLSTN ceramics sintered at various temperatures. Fig. 3. Density values for BLSTN ceramics sintered at various temperatures. SEM photographs of as fired BLSTN ceramics are shown in Fig. 4 and 5. Porous pellets are found in 1430 o C/2 h sintering BLSTN. Pores decreased and grain size increased with the sintering temperature and soak tine. It is in good agreement with the shrinkage and density values in Fig. 2 and 3. Morphology in microstructure of BLSTN is different from the morphology observed in Ba 4 LaTiNb 3 O 15 and Ba 4 LaSnNb 3 O 15 investigated by Fang et al. 2-20μm grains could be found in those pellets and many rectangular grains formed. In Fig. 4 and Fig. 5, packed hexagonal grains are seen. More uniform grains could be obtained. Conclusion Reaction-sintering process is a simple and effective method to obtained Ba 4 La(Sn 0.75 Ti 0.25 )Nb 3 O 15 ceramics even the calcination stage is bypassed. Density of BLSTN ceramic increases with sintering temperature and reaches a maximum value 6.35 g/cm 3 at 1470 o C/4 h. Uniform packed hexagonal grains formed in BLSTN ceramics. Acknowledgements The authors would like to thank Dr. Min-Hang Weng from National Nano Device Laboratories (NDL) for help in obtaining the SEM photos. Fig. 4. SEM photographs of BLSTN ceramics sintered at (A)1430 o C, (B) 1450 o C, (C) 1470 o C and (D) 1500 o C for 2 h. Fig. 5. SEM photographs of BLSTN ceramics sintered at (A) 1430 o C, (B) 1450 o C, (C) 1470 o C and (D) 1500 o C for 4 h. Yi Cheng Liou ( 劉依政 ), *Chi Yang Liu ( 劉冀陽 ) Department of Electronic Engineering, Kun Shan University 崑山科技大學電子工程系