Synthesis, Crystal Structure, and Characterization of Ba(Ti1/2Mn1/2)O3: A High Permittivity 12R-Type Hexagonal Perovskite
详细信息 查看全文
- 作者：Gillian M. Keith ; Caroline A. Kirk ; Kumaravinothan Sarma ; Neil McN. Alford ; Edmund J. Cussen ; Matthew J. Rosseinsky ; and Derek C. Sinclair
- 刊名：Chemistry of Materials
- 出版年：2004
- 出版时间：May 18, 2004
- 年：2004
- 卷：16
- 期：10
- 页码：2007 - 2015
- 全文大小：144K
- 年卷期：v.16,no.10(May 18, 2004)
- ISSN：1520-5002
文摘
A 12R-type hexagonal perovskite, Ba(Ti1/2Mn1/2)O3, has been prepared by a mixed oxideroute at 1250 
C in air and the crystal structure established by a joint Rietveld refinementof powder X-ray and neutron diffraction data at room temperature [space group R
m, a =5.69135(2) Å, and c = 27.91860(15) Å]. The structure consists of a (hhcc)3 stacking sequenceof BaO3 close-packed layers along the c-axis with face sharing M3O12 trimers connected bya vertex sharing octahedron. Partial ordering of the Ti+IV and Mn+IV ions occurs in the B-sitesubstructure; Mn+IV ions occupy the central octahedral site in the trimers, Ti+IV ions occupythe octahedral site in the vertex sharing octahedron, and both ions occupy the outeroctahedral site of the trimers. Impedance spectroscopy and microwave dielectric resonancemeasurements on dense pellets (>97% of the theoretical X-ray density) show the titlecompound to be a modest dielectric insulator at room temperature with high permittivity,
r ~ 45 (at both radio and microwave frequencies); a modest unloaded quality factor, Qu ~2026 (at ~5.75 GHz); and a temperature coefficient of resonant frequency, TCf = -4 ppmK-1.
C in air and the crystal structure established by a joint Rietveld refinementof powder X-ray and neutron diffraction data at room temperature [space group Rm, a =5.69135(2) Å, and c = 27.91860(15) Å]. The structure consists of a (hhcc)3 stacking sequenceof BaO3 close-packed layers along the c-axis with face sharing M3O12 trimers connected bya vertex sharing octahedron. Partial ordering of the Ti+IV and Mn+IV ions occurs in the B-sitesubstructure; Mn+IV ions occupy the central octahedral site in the trimers, Ti+IV ions occupythe octahedral site in the vertex sharing octahedron, and both ions occupy the outeroctahedral site of the trimers. Impedance spectroscopy and microwave dielectric resonancemeasurements on dense pellets (>97% of the theoretical X-ray density) show the titlecompound to be a modest dielectric insulator at room temperature with high permittivity,r ~ 45 (at both radio and microwave frequencies); a modest unloaded quality factor, Qu ~2026 (at ~5.75 GHz); and a temperature coefficient of resonant frequency, TCf = -4 ppmK-1.