Showing papers by "S. B. Majumder published in 2011"

Improved Dielectric Properties and Their Temperature Insensitivity in Multilayered Ba0.8Sr0.2TiO3/ZrO2 Thin Films

Abstract: The electrical and dielectric properties of Ba0.8Sr0.2TiO3 thin films and Ba0.8Sr0.2TiO3/ZrO2 multilayer thin films deposited on Pt/Ti/SiO2/Si substrates by sol-gel method are studied. The temperature dependence of the dielectric properties for pure Ba0.8Sr0.2TiO3 film and Ba0.8Sr0.2TiO3/ZrO2 multilayer films has been studied in the temperature range from 90 to 500 K. Both dielectric constant and dielectric loss exhibit minimal dispersion as a function of temperature in this range. It is observed that dielectric constant, dielectric loss, and tunability are reduced for multilayer thin films. Additionally, the ferroelectricity disappears in multilayer thin films. Our results show that the multilayered Ba0.8Sr0.2TiO3/ZrO2 design has excellent dielectric properties and they are stable over a broad temperature range (90–500 K), thereby making them excellent candidates for the next generation of enhanced performance temperature stable microwave devices.

Nanocomposite thin films for miniaturized multi-layer ceramic capacitors prepared from barium titanate nanoparticle based hybrid solutions

Abstract: In the present work a flexible approach for the wet chemical processing of nanocomposite functional thin films is demonstrated. Barium titanate (BTO) based nanocomposite thin films for future miniaturized multi-layer ceramic capacitors are chosen as model systems to introduce the concept of “hybrid solutions” which consist of stabile mixtures of reverse micelle derived BTO nanoparticle dispersions and conventional molecular precursor solutions of either the same (BTO:BTO) or a specifically different material such as zirconia (BTO:ZrO2). While in the case of using BTO:BTO hybrid solutions an interesting mode of microstructure control is found, the use of BTO:ZrO2 hybrid solutions with various BTO : ZrO2 ratios leads to nanocomposite films. BTO:BTO hybrid solutions yield columnar grown films with excellent permittivities up to 1050 with a significantly reduced number of coating steps at 700 °C. Low values of the temperature coefficient of capacitance are realized in the BTO–ZrO2 nanocomposite thin films. The observed dielectric behavior of these films is explained based on the formation of a core–shell type microstructure on the nanoscale. A detailed high resolution transmission electron microscopy study combined with Raman spectroscopy and X-ray diffraction gives evidence for the proposed BTO–ZrO2 nanocomposite character of these thin films.

Magnetoelectric coupling in sol-gel synthesized dilute magnetostrictive-piezoelectric composite thin films

Abstract: Multiferroic lead lanthanum titanate–cobalt iron oxide nano-composite thin films are synthesized by sol-gel route. A percolative distribution of cobalt iron oxide phase, with percolation threshold ∼8 vol%, is identified in these films. Large magnetoelectric coupling coefficient (∼250 mV/cm.Oe) is found in the composite films with cobalt iron oxide volume contents in the vicinity of its percolation threshold. The composite films with dilute magnetostrictive volume contents yield superior multiferroic properties to its counterparts with relatively higher magnetostrictive volume contents.