Viorica Stancu - Academia.edu (original) (raw)
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Papers by Viorica Stancu
A new method for the preparation of PbS/PZT composite materials is proposed. The PZT matrix has b... more A new method for the preparation of PbS/PZT composite materials is proposed. The PZT matrix has been obtained using the sol-gel method on Pt-coated Si substrates. The PbS (nano) crystals were subsequently obtained by dipping the porous PZT matrix in Pb(NO3)2 and Na2S solutions at room temperature. The XRD spectra show the presence of the tetragonal phase of PZT. The microstructure of the film was analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The size of the PbS (nano)-particles at the sample's surface is about 25 nm, estimated from the AFM analysis. The roughness of the sample's surface is about 5 nm. The porosity of the composite, estimated from the SEM analysis in cross-section is smaller than for the reference PZT porous matrix. The equivalent dielectric constant of the composite increases by a factor of 4-5 in comparison with the porous PZT reference and does not depend on the thickness of the surface PbS (nano)-crystalline layer. The saturated polarization (Ps) value for the PZT-PbS composite is smaller than that corresponding to the bulk PZT but higher than for the reference porous PZT. We attribute these effects to the partial filling of the pores in the PZT matrix with PbS.
Processing and Application of Ceramics
Ba0.75Sr0.25TiO3 (BST) and PbZr0.68Fe0.14Nb0.14Ti0.04O3 (PZFNT) ceramic pellets were obtained by ... more Ba0.75Sr0.25TiO3 (BST) and PbZr0.68Fe0.14Nb0.14Ti0.04O3 (PZFNT) ceramic pellets were obtained by ceramic technology and their structural, ferroelectric and pyroelectric properties were investigated. The relative density of BST and PZFNT is about 93% and 90%, respectively, with an average grain size of 102 ?m and 6.45 ?m. Both materials have similar room temperature dielectric constants (~2000), but PZFNT shows higher remnant polarization (~15?C/cm2) and better pyroelectric properties (~1.69?10?4 C/m2K), which recommend it for pyroelectric detectors, infrared radiation- and laser pulse energy-meters.
Applied Surface Science, 2011
The paper presents the influence of pulsed laser deposition (PLD) parameters on the structural an... more The paper presents the influence of pulsed laser deposition (PLD) parameters on the structural and optical properties of PZT thin films grown on platinum substrate. X-ray diffraction (XRD), spectroscopic ellipsometry (SE) and X-ray photoelectron spectroscopy (XPS) are used to determine the thin film properties. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) are employed to get additional information. By changing the distance between target and substrate, different crystalline orientations of PZT are obtained. The thin film thickness and its roughness, as well as the refractive index are also influenced by the chosen distance.
A new method for the preparation of PbS/PZT composite materials is proposed. The PZT matrix has b... more A new method for the preparation of PbS/PZT composite materials is proposed. The PZT matrix has been obtained using the sol-gel method on Pt-coated Si substrates. The PbS (nano) crystals were subsequently obtained by dipping the porous PZT matrix in Pb(NO3)2 and Na2S solutions at room temperature. The XRD spectra show the presence of the tetragonal phase of PZT. The microstructure of the film was analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The size of the PbS (nano)-particles at the sample's surface is about 25 nm, estimated from the AFM analysis. The roughness of the sample's surface is about 5 nm. The porosity of the composite, estimated from the SEM analysis in cross-section is smaller than for the reference PZT porous matrix. The equivalent dielectric constant of the composite increases by a factor of 4-5 in comparison with the porous PZT reference and does not depend on the thickness of the surface PbS (nano)-crystalline layer. The saturated polarization (Ps) value for the PZT-PbS composite is smaller than that corresponding to the bulk PZT but higher than for the reference porous PZT. We attribute these effects to the partial filling of the pores in the PZT matrix with PbS.
Processing and Application of Ceramics
Ba0.75Sr0.25TiO3 (BST) and PbZr0.68Fe0.14Nb0.14Ti0.04O3 (PZFNT) ceramic pellets were obtained by ... more Ba0.75Sr0.25TiO3 (BST) and PbZr0.68Fe0.14Nb0.14Ti0.04O3 (PZFNT) ceramic pellets were obtained by ceramic technology and their structural, ferroelectric and pyroelectric properties were investigated. The relative density of BST and PZFNT is about 93% and 90%, respectively, with an average grain size of 102 ?m and 6.45 ?m. Both materials have similar room temperature dielectric constants (~2000), but PZFNT shows higher remnant polarization (~15?C/cm2) and better pyroelectric properties (~1.69?10?4 C/m2K), which recommend it for pyroelectric detectors, infrared radiation- and laser pulse energy-meters.
Applied Surface Science, 2011
The paper presents the influence of pulsed laser deposition (PLD) parameters on the structural an... more The paper presents the influence of pulsed laser deposition (PLD) parameters on the structural and optical properties of PZT thin films grown on platinum substrate. X-ray diffraction (XRD), spectroscopic ellipsometry (SE) and X-ray photoelectron spectroscopy (XPS) are used to determine the thin film properties. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) are employed to get additional information. By changing the distance between target and substrate, different crystalline orientations of PZT are obtained. The thin film thickness and its roughness, as well as the refractive index are also influenced by the chosen distance.