P. B. Joshi

Fabrication of Nanocrystalline TiO 2 Thin Film Ammonia Vapor Sensor

Nanocrystalline titanium oxide thin films have been deposited by spin coating technique and then have been analyzed to test their application in NH3 gas-sensing technology. In particular, spectrophotometric and con-ductivity measurements have been performed in order to determine the optical and electrical properties of titanium oxide thin films. The structure and the morphology of such material have been investigated by X ray diffraction, Scanning microscopy, high resolution electron microscopy and selected area electron diffrac-tion. The X-ray diffraction measurements confirmed that the films grown by this technique have good crys-talline tetragonal mixed anatase and rutile phase structure The HRTEM image of TiO2 thin film showed grains of about 50-60 nm in size with aggregation of 10-15 nm crystallites. Selected area electron diffraction pattern shows that the TiO2 films exhibited tetragonal structure. The surface morphology (SEM) of the TiO2 film showed that the nanoparticles are fine The optical band gap of TiO2 film is 3.26 eV. Gas sensing proper-ties showed that TiO2 films were sensitive as well as fast in responding to NH3. A high sensitivity for ammo-nia indicates that the TiO2 films are selective for this gas.

Synthesis and characterization of Ba0.7Sr0.3TiO3, BaZr0.3Ti0.7O3 thin film heterostructures

The paper presents synthesis of Ba0.7Sr0.3TiO3 (BST), Ba0.7Sr0.3TiO3 (BZT) thin films and BZT/BST heterostructures using modified Pechini method. The La0.7Sr0.3MnO3 has been used as a conducting bottom layer to form metal ferroelectric metal capacitor. The thin films are spin coated on SiO2/n-Si (100) substrates. The thin films thus deposited are characterized for crystal structure, morphology, dielectric and complex impedance properties. The results show that BZT/BST heterostructures show reduced loss tangent tan δ and useful value of figure of merit γ in RF range of frequencies. The results on dielectric properties could be analyzed in terms of the Maxwell–Wagner Model and contribution due to superlattice effects.

Investigations on Fe doped Ba0.95Sr0.05TiO3 single phase magnetodielectric compounds

The paper reports synthesis, crystal structure, dielectric properties, P–E hysteresis loops, M–H hysteresis loops and magnetodielectric properties of Fe doped Ba0.95Sr0.05TiO3 (0.05BST) single phase magnetodielectric compositions. The parent and doped 0.05BST compositions are synthesized via ceramic route of synthesis. The studies on crystal structure show that the parent composition (0.05BST) show a tetragonal crystal structure, while the substitution of Fe is observed to exhibit a cubic crystal structure with a tetragonal distortion. The investigations on dielectric properties show that the Fe doped 0.05BST show a diffused phase transition and Tc approaches room temperature as the level of doping is increased. The studies on P–E and M–H hysteresis loops are carried out to confirm simultaneous presence of both the ferroelectric and ferromagnetic orders in a Fe doped 0.05BST. All the Fe doped compositions are found to exhibit a significant magnetodielectric coupling at room temperature.

Dielectric properties of sol–gel synthesized SrTiO3/(Ba0.7Sr0.3)TiO3 and SrTiO3/Ba(Zr0.3Ti0.7)O3 thin film heterostructures

The paper presents synthesis of Ba0.7Sr0.3TiO3 (BST), BaZr0.3Ti0.7O3 (BZT) and SrTiO3 (ST) thin films and their heterostructures using modified Pechini method. The La0.7Sr0.3MnO3 has been used as a conducting bottom layer to form metal ferroelectric metal capacitor. The thin films are spin coated on SiO2/n-Si(100) substrates. The thin films thus deposited are characterized for crystal structure, morphology, dielectric, complex impedance and admittance properties. Deposition of surface layer ST is observed to reduce loss tangent tan δ of BST and BZT thin films, still maintaining equivalent magnitude of figure of merit γ. The results on dielectric properties are analyzed in terms of the Maxwell–Wagner model and Koop’s phenomenological theory.

Structural, magnetic and magnetodielectric characteristics of Ni doped Ba0.95Sr0.05TiO3 single phase multiferroic compound

Abstract Synthesis of Ni doped Ba0.95Sr0.05TiO3 (BST) was carryout by solid state reaction method. The influence of doping amount of Ni on BST was investigated. The XRD confirmed the single phase crystalline structure. Scanning electron microscopy image was also employed to observe surface morphology. The dielectric constant and dielectric loss of BST0.05 are obviously influenced by nickel addition content. The Curie temperature Tc decreases with increasing nickel doping content. The studies on P–E and M–H hysteresis loops are carried out to confirm simultaneous presence of both the ferroelectric and ferromagnetic orders in a Ni doped BST.