球磨對鈦酸鋇粉體物性、燒結特性及其介電特性之影響

積層陶瓷電容器(MLCCs)廣泛的使用於電子產品中，隨著電子產品小型化發展，MLCC也朝著多層數且薄層化而發展，藉此提高電容值。為了製作較薄的陶瓷介電層，則必須使用微奈米之鈦酸鋇粉末，微奈米之鈦酸鋇粉末通常可藉由各種合成方法製得，但其成本較高。因此在MLCCs產業界常常使用微米之鈦酸鋇粉，再以機械研磨將粉末磨細，一方面可以有效的控制粒徑大小與分佈，另一方面可以降低成本。在機械研磨製程中，會添加許多添加物，藉此調整介電陶瓷之特性，因此機械研磨在MLCCs製程中扮演相當重要之角色。本研究使用市售水熱法(BT01)法與草酸法(BT02)之鈦酸鋇粉末，經由不同的球磨時間後，針對鈦酸鋇之物理特性，如粒徑、粒徑分布、晶體結構、B.E.T.比表面積、鋇鈦比、晶格常數(c/a比)與鋯汙染等做一探討。此外將粉末以單軸成型機製作成生胚後燒結，觀察球磨對燒結後之特性與介電特性之影響。本研究結果，粉末粒徑隨球磨時間增加下降，於球磨48 h時可得最小粒徑BT01為0.53 μm，BT02為0.64 μm，且粒徑分佈呈單峰常態分佈；經球磨後，鈦酸鋇晶體仍屬於正方晶結構(tetragonal)，但其c/a比隨著球磨時間增加而並無變化；B.E.T.比表面積隨著球磨時間增加而上升，於球磨48 h時，BT01為2.47 m2/g，BT02粉末為1.96 m2/g；鋇鈦比隨著球磨時間增加並無變化，其鋇鈦比＜1；隨著球磨時間增加鋯離子析出量增加，於球磨48 h時達75 ppm；純鈦酸鋇粉末，介電常數隨著球磨時間增加而下降，於球磨48 h時，BT01粉末之介電常數為1978，BT02粉末之介電常數為4697；添加X7R配方之鈦酸鋇粉末，介電常數隨著球磨時間增加而上升，於球磨48 h時，BT01之介電常數為1768，BT02之介電常數為1881；添加X7R配方之鈦酸鋇粉末，其介電損失隨球磨時間增加而下降，於球磨48 h時，BT01之介電損失為2.17%，BT02之介電損失為1.08%。

關鍵字

MLCCs ；鈦酸鋇；球磨；水熱法；草酸法

並列摘要

Mutil-Layer Ceramic Capacitors (MLCCs) are widely used in the electronic products. With the development of miniaturization of electronic products, MLCCs also towards the development of multi and thin dielectric ceramics layer, which result in capacitance increased. In order to produce thin dielectric ceramics layer, we must use the micro-nano barium titanate powders. The micro-nano barium titanate powders are normally prepared by various synthesis methods, which are expensive. Therefore, the mechanical grinding is often used to reduce the micro barium titanate powders in the MLCCs industry. These methods not only control the particle size and distribution, but also reduce the cost. This process will be added with many kinds of additives to adjust the characteristics of the dielectric ceramics. Therefore, the mechanical grinding plays an important role in the MLCCs process. In this study, we use commercial hydrothermal and oxalic acid synthesis barium titanate powders for grinding with different milling times, and investigate the physical properties of the barium titanate powders, such as particle size, particle size distribution, crystal structure, B.E.T specific surface area, Ba/Ti ratio, lattice constant (c/a ratio) and the pollution of Zr+. In addition, the barium titanate powders is pressed to the disk by uniaxial forming machine followed by sintering. The effects of milling on the properties of sintering and dielectric are investigated. The results of this study reveal the particle size decreases with increasing milling time and the particle size distribution is normal distribution. After milling for different periods, the crystal structure of BaTiO3 powders is still tetragonal and c/a ratio does not change. The Ba/Ti ratio and the precipitation of Zr ions increase with increasing milling time. The dielectric constant of undoped-BaTiO3 powders decreases with increasing milling time. The dielectric constant of BaTiO3 powders doped with X7R increases with increasing milling time, and the dielectric loss decreases with increasing milling time.

並列關鍵字

MLCCs ； BaTiO3 ； Ball Milling ； Hydrothermal ； Oxalic Acid

參考文獻

[1]B. Jaffee, W. R. Cool, and h. Jaffaee, “Piezoelectric ceramics,” Academic Press, New York (1971).

[2]Z. X. Chen, C. G. Liu, “Theoretical investigation on BaTiO3 with periodic density functional theory BLYP method,” Chem. Phys., 270 253-261 (2001).

[5]D. E. Rase, R. Roy, “Phase equilibria in the system BaO-TiO2,” J. Am. Ceram. Soc., 38 [3] 102-113 (1995).

[6]Y. H. Hu, M. P. Harmer, D. M. Smyth, “Solubility of BaO in BaTiO3,” J. Am. Ceram. Soc., 68 [7] 372-376 (1985).

[7]R. K. Sharma, N. H. Chan, D. M. Smyth, “Solubility of TiO2 in BaTiO3,” J. Am. Ceram. Soc., 64 [8] 448-451 (1955).

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球磨對鈦酸鋇粉體物性、燒結特性及其介電特性之影響

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