化学包覆法制备Ho~(3+)掺杂钛酸钡基X8R细晶陶瓷
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摘要
采用化学包覆法将Ho_2O_3包覆在纳米级钛酸钡粉体表面,通过烧结将Ho~(3+)扩散到钛酸钡晶粒中,调节其介电性能,研究了不同Ho~(3+)掺杂量对Ba Ti O3基陶瓷相组成、微观结构和介电性能的影响。X射线衍射和扫描电子显微镜分析结果表明:Ho~(3+)改性陶瓷样品均为赝立方相,Ho~(3+)的加入能抑制晶粒生长,改善陶瓷微观结构,有利于制备均匀的细晶陶瓷。透射电子显微镜观察显示,包覆层的厚度约为2 nm,包覆Ho_2O_3有助于陶瓷烧结过程中形成"核-壳"结构晶粒,能显著改善钛酸钡基陶瓷的介电温度稳定性,提高绝缘电阻。当Ho~(3+)掺杂量为2.0%时,陶瓷的相对介电常数为1 612,ΔC/C(-55~150℃)<±15%,满足EIA X8R电容器的温度特性。
Ho_2O_3 was coated on the surface of nanosized barium titanate powder by a chemical coating method. Ho~(3+) ions were diffused into BaTiO_3 grains in a ceramic sintering process to adjust the dielectric properties. The effect of doped Ho~(3+) ionic content on the composition, microstructure and dielectric constant of ceramics at various temperatures were investigated. Based on the results by X-ray diffraction and scanning electron microscopy, Ho~(3+) ions-doped ceramics show a pseudo-cubic crystalline phase. The addition of Ho~(3+) ions can inhibit the grain growth, modify the microstructure, and form the homogeneous fine-grain structure. The results by transmisson electron microscopy indicate that the thickness of the coating layer is approximately 2 nm. The coating of Ho_2O_3 favors the formation of the core-shell grain structure during sintering, thus improving the temperature stability of dielectric constant, and enhancing the insulative resistance. The dielectric constant of is 1 612, ΔC/C(-50~150 ℃) <±15% at the Ho~(3+) ionic concentration of 2%, which meet the requirements of EIA X8 R for the temperature-dependent ceramic capacitors.
Ho_2O_3 was coated on the surface of nanosized barium titanate powder by a chemical coating method. Ho~(3+) ions were diffused into BaTiO_3 grains in a ceramic sintering process to adjust the dielectric properties. The effect of doped Ho~(3+) ionic content on the composition, microstructure and dielectric constant of ceramics at various temperatures were investigated. Based on the results by X-ray diffraction and scanning electron microscopy, Ho~(3+) ions-doped ceramics show a pseudo-cubic crystalline phase. The addition of Ho~(3+) ions can inhibit the grain growth, modify the microstructure, and form the homogeneous fine-grain structure. The results by transmisson electron microscopy indicate that the thickness of the coating layer is approximately 2 nm. The coating of Ho_2O_3 favors the formation of the core-shell grain structure during sintering, thus improving the temperature stability of dielectric constant, and enhancing the insulative resistance. The dielectric constant of is 1 612, ΔC/C(-50~150 ℃) <±15% at the Ho~(3+) ionic concentration of 2%, which meet the requirements of EIA X8 R for the temperature-dependent ceramic capacitors.
引文
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[3]HWANG J H,CHOI S K,HAN Y H.Dielectric properties of Ba Ti O3codoped with Er2O3 and Mg O[J].Jpn J Appl Phys,2001,40(8):4952–4955.
[4]CHANG C Y,WANG W N,HUANG C Y.Effect of Mg O and Y2O3doping on the formation of core–shell structure in Ba Ti O3 ceramics[J].J Am Ceram Soc,2013,96(8):2570–2576.
[5]PARK J S,HAN Y H.Effects of Mg O coating on microstructure and dielectric properties of Ba Ti O3[J].J Eur Ceram Soc,2007,27(2):1077–1082.
[6]KISHI H,OKINO Y,HONDA M,et al.The effect of Mg O and rare-earth oxide on formation behavior of core–shell structure in Ba Ti O3[J].Jpn J Appl Phys,1997,36(9):5954–5957.
[7]TIAN Zhibin,WANG Xiaohui,ZHANG Yichi,et al.Formation of core–shell structure in ultrafine-grained Ba Ti O3-based ceramics through nanodopant method[J].J Am Ceram Soc,2010,93(1):171–175.
[8]WANG Yan,CUI Bin,LIU Yu,et al.Fabrication of submicron La2O3-coated Ba Ti O3 particles and fine-grained ceramics with temperature-stable dielectric properties[J].Scripta Mater,2014,s90–91(16):49–52.
[9]BASSANO A,BUSCAGLIA V,SENNOUR M,et al.Nanocrystalline oxide(Y2O3,Dy2O3,Zr O2,Ni O)coatings on Ba Ti O3 submicron particles by precipitation[J].J Nanopart Res,2010,12(2):623–633.
[10]BUSCAGLIA M T,VIVIANI M,ZHAO Z,et al.Synthesis of Ba Ti O3core-shell particles and fabrication of dielectric ceramics with local graded structure[J].Chem Mater,2006,18(17):4002–4010.
[11]ZHANG Yichi,WANG Xiaohui,Kim J Y,et al.High performance Ba Ti O3-based BME–MLCC nanopowder prepared by aqueous chemical coating method[J].J Am Ceram Soc,2012,95(5):1628–1633.
[12]LI Tao,LI Longtu,ZHAO Jianqiang,et al.Modulation effect of Mn2+on dielectric properties of Ba Ti O3-based X7R materials[J].Mater Lett,2000,44(1):1–5.
[13]YAO Guofeng,WANG Xiaohui,LI Longtu.Study on occupation behavior of Y2O3 in X8R nonreducible Ba Ti O3-based dielectric ceramics[J].Jpn J Appl Phys,2011,50(12R):121501.
[14]KIM C H,PARK K J,YOON Y J,et al.Role of yttrium and magnesium in the formation of core–shell structure of Ba Ti O3 grains in MLCC[J].J Eur Ceram Soc,2008,28(6):1213–1219.
[15]ATKIN R B,FULRATH R M.Point defects and sintering of lead zirconate–titanate[J].J Am Ceram Soc,2006,54(5):265–270.
[16]ZHANG Baolin,WU Shunhua.Effect of calcinating temperature and Mn doping on dielectric properties of temperature–stable Ba Ti O3-based X8R ceramics[J].Int J Appl Ceram Technol,2013,10(s1):E57–E63.
[17]YAO Guofeng,WANG Xiaohui,ZHANG Yichi,et al.Nb-modified0.9Ba Ti O3–0.1(Bi0.5Na0.5)Ti O3 ceramics for X9R high–temperature dielectrics application prepared by coating method[J].J Am Ceram Soc,2012,95(11):3525–3531.
[18]PARK Y,KIM Y H,KIM H G.The effect of grain size on dielectric behavior of Ba Ti O3 based X7R materials[J].Mater Lett,1996,28(1/3):101–106.