Nanostructured barium titanate prepared through a modified reverse micellar route: Structural distortion and dielectric
- PDF / 1,938,856 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 23 Downloads / 196 Views
Gnanasundaram Kavitha and Chandrabhas Narayana Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064, India
Ashok K. Gangulia) Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi 110016, India (Received 25 October 2004; accepted 12 January 2005)
A modified and convenient route using microemulsions (avoiding Ba-alkoxide) was evolved for the synthesis of uniform and monodisperse nanoparticles of BaTiO3 at low temperature (800 °C). X-ray line broadening and transmission electron microscopy studies show that the particle size varies in the range of 20–25 nm. Evidence for tetragonal distortion was found in these nano-sized (20–25 nm) particles of barium titanate from careful x-ray diffraction studies as well as from Raman spectroscopy. Our study showed that the critical size of the cubic to tetragonal transition in barium titanate may be much lower than suggested theoretically. The grain size showed an increase on sintering of 35 nm at 900 °C to 120 nm at 1100 °C, which was much lower than the grain size obtained at this temperature by the normal solid state route. The dielectric constant depends on sintering temperature and was found to increase from 210 (900 °C sintering) to 520 (1100 °C sintering) at 100 kHz. The dielectric constant was highly stable with temperature as well as frequency.
I. INTRODUCTION
BaTiO3 is a high-dielectric-constant material and is widely used in the manufacture of multilayer ceramic capacitors (MLCC). For increased miniaturization and volumetric efficiency of these multilayer capacitors, the thickness of the ceramic capacitor films must be decreased. There is also interest in reducing the sintering temperature of BaTiO3 to enable the use of more inexpensive non-noble metal electrodes. Both the above aspects put a greater emphasis on novel low-temperature synthetic approaches. Oxide powders produced by the high-temperature solid-state reaction route have problems due to chemical inhomogeneity and reactivity. In addition it gives a wide range of grain sizes (normally in the 0.5–3 m range) and very little control is possible on the size, shape and agglomeration of particles. Thus alternate routes to synthesis based on novel low-temperature processes are of significance to yield high-purity ultrafine powders with
a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2005.0189 J. Mater. Res., Vol. 20, No. 6, Jun 2005
http://journals.cambridge.org
Downloaded: 26 Aug 2014
controlled morphology and size of the particles. Various low temperature routes involving organometallic precursors like alkoxides, acetates, oxalates, nitrates, citrates of Ba and Ti have been used in the past to obtain BaTiO3.1–3 Apart from these methods, sol-gel, sol-precipitation, hydrothermal, and organic polymeric precursor routes have been used for the preparation of BaTiO3 powders.4–7 In recent years, there has been a lot of interest in preparing nano-sized particles of metals, ox
Data Loading...
