Tatyana Koutzarova | Bulgarian Academy of Sciences (original) (raw)

Papers by Tatyana Koutzarova

Research paper thumbnail of Magnetic Properties of Nanosized Ba2Mg2Fe12O22 Powders Obtained by Auto-combustion

Journal of Superconductivity and Novel Magnetism, 2011

Research paper thumbnail of Differences in the structural and magnetic properties of nanosized barium hexaferrite powders prepared by single and double microemulsion techniques

Journal of Alloys and Compounds, 2013

Barium hexaferrite powders of nanometer particle size synthesized via two variants of the microem... more Barium hexaferrite powders of nanometer particle size synthesized via two variants of the microemulsion technique, namely, single microemulsion and double microemulsion, were studied. The influence was explored of the type of microemulsion technique on the microstructure and on the magnetic properties of the barium hexaferrite powders. The average particle size of the barium hexaferrite powders was in the range from 110 nm to 442 nm depending on the method and conditions of synthesis. The particles with size below 150 nm had irregular shapes between spherical and platehexagonal; the bigger ones had an almost perfect hexagonal shape. The powders obtained by single microemulsion had better magnetic characteristics (saturation magnetization of 65.12 emu/g and coercivity field of 3.6 Â 10 5 A/m) than those obtained by double microemulsion.

Research paper thumbnail of Data supporting the results of the characterization of the phases and structures appearing during the synthesis process of Ba0.5Sr1.5Zn2-xNixFe12O22 by auto-combustion

Research paper thumbnail of <strong>Study of the Properties of Co-Substituted Ba<sub>2</sub>Mg<sub>2</sub>Fe<sub>12</sub>O<sub>22</sub> Hexaferrites</strong>

Proceedings of The 3rd International Electronic Conference on Materials Sciences, May 17, 2018

We present results from a study on the influence of the substitution of Mg 2+ cations in the Y-ty... more We present results from a study on the influence of the substitution of Mg 2+ cations in the Y-type Ba2Mg2Fe12O22 hexaferrite with magnetic cations, such as Co 2+ , on its structural and magnetic properties. The Ba2Mg0.4Co1.6Fe12O22 powder was synthesized by sonochemical co-precipitation method. The XRD pattern of the powders showed the characteristic peaks corresponding to the Ytype hexaferrite structure as a main phase and some CoFe2O4 impurity (< 2%) as a second phase. This result was also confirmed by Mössbauer spectroscopy measurements. The magnetization values at 50 kOe were 30 emu/g at 4.2 K and 26.6 emu/g at 300 K, respectively. The ZFC and FC magnetization curves were measured at magnetic fields of 50 Oe, 100 Oe and 500 Oe, which revealed a magnetic phase transition around 200 K from ferrimagnetic-to-helical spin order. This is considered as a precondition for the material to exhibit multiferroic properties.

Research paper thumbnail of Study of the Structural and Magnetic Properties of Co-Substituted Ba2Mg2Fe12O22 Hexaferrites Synthesized by Sonochemical Co-Precipitation

Materials, 2019

Ba2Mg0.4Co1.6Fe12O22 was prepared in powder form by sonochemical co-precipitation and examined by... more Ba2Mg0.4Co1.6Fe12O22 was prepared in powder form by sonochemical co-precipitation and examined by X-ray diffraction, Mössbauer spectroscopy and magnetization measurements. Careful XRD data analyses revealed the Y-type hexaferrite structure as an almost pure phase with a very small amount of CoFe2O4 as an impurity phase (about 1.4%). No substantial changes were observed in the unit cell parameters of Ba2Mg0.4Co1.6Fe12O22 in comparison with the unsubstituted compound. The Mössbauer parameters for Ba2Mg0.4Co1.6Fe12O22 were close to those previously found (within the limits of uncertainty) for undoped Ba2Mg2Fe12O22. Isomer shifts (0.27–0.38 mm/s) typical for high-spin Fe3+ in various environments were evaluated and no ferrous Fe2+ form was observed. However, despite the indicated lack of changes in the iron oxidation state, the cationic substitution resulted in a significant increase in the magnetization and in a modification of the thermomagnetic curves. The magnetization values at 50 ...

Research paper thumbnail of Magnetic properties of nanosized MgFe2O4 powders prepared by auto-combustion

Journal of Physics: Conference Series, 2012

Targets were prepared to be used for magnetron sputtering and laser ablation and their microstruc... more Targets were prepared to be used for magnetron sputtering and laser ablation and their microstructural and magnetic properties were investigated. The base material was nanosized MgFe 2 O 4 powder produced by citrate auto-combustion synthesis. The auto-combusted powders were annealed at temperatures in the range 600 -1000 o С in air to study the effect of temperature on thofe formation MgFe 2 O 4 . The saturation magnetization М s was 24.30 emu/g at room temperature.

Research paper thumbnail of Modified ferrite plating of Fe3O4 and CuFe2O4 thin films

Journal of Magnetism and Magnetic Materials, 2000

ABSTRACT The present work proposes a modification of the ferrite plating method for synthesizing ... more ABSTRACT The present work proposes a modification of the ferrite plating method for synthesizing ferrite thin films from aqueous solutions at low temperatures about 97°C. Our approach combines spin-spray deposition from aqueous solutions at low temperature with co-precipitation. We were thus able to produce isotropic polycrystalline Fe3O4 and CuxFe3−xO4 films with thicknesses from 100 to 1000 nm. The modified ferrite plating enabled us to produce CuFe-oxide films with cubic and tetragonal crystalline structure and Jahn–Teller effect have been observed. The spectra showed that the films of magnetite were isotropic while the heat-treated samples of CuxFe3−xO4 films showed anisotropic behavior and coercivity of 1000 Oe.

Research paper thumbnail of ChemInform Abstract: Structural and Magnetic Properties and Preparation Techniques of Nanosized M-Type Hexaferrite Powders

Research paper thumbnail of Influence of the scanning conditions on the characteristics of the nanostructures fabricated by laser ablation in liquid

18th International School on Quantum Electronics: Laser Physics and Applications, 2015

Research paper thumbnail of Magnetic properties of nanosized MgFe 2 O 4 powders prepared by auto-combustion

Journal of Physics: Conference Series, 2012

Targets were prepared to be used for magnetron sputtering and laser ablation and their microstruc... more Targets were prepared to be used for magnetron sputtering and laser ablation and their microstructural and magnetic properties were investigated. The base material was nanosized MgFe2O4 powder produced by citrate auto-combustion synthesis. The auto-combusted powders were annealed at temperatures in the range 600 - 1000°C in air to study the effect of temperature on thofe formation MgFe2O4. The saturation magnetization Ms was 24.30 emu/g at room temperature.

Research paper thumbnail of Magnetic Properties of Nanosized Ba2Mg2Fe12O22 Powders Obtained by Auto-combustion

Journal of Superconductivity and Novel Magnetism, 2012

We studied the magnetic properties of nanosized Ba2Mg2Fe12O22 powder obtained by citrate auto-com... more We studied the magnetic properties of nanosized Ba2Mg2Fe12O22 powder obtained by citrate auto-combustion synthesis. The powder consists of agglomerates with mean crystallite size of 100 nm. The magnetic properties of the powder were investigated at 4.2 K and at room temperature. The values measured of the magnetization M at a magnetic field of 60 kOe are 22.78 emu/g and 30.47 emu/g at room temperature and

Research paper thumbnail of Investigation of DyBa 2 Cu 3 O 7− d superconducting domains grown by the infiltration technique starting with small size Dy-211 particles

Superconductor Science and Technology, 2005

An infiltration and growth process is here used as an alternative to the classical top-seeded mel... more An infiltration and growth process is here used as an alternative to the classical top-seeded melt-textured growth process for the production of Dy-123 single-domains with finely dispersed small size Dy-211 particles. The starting materials are the 211-particles and a barium and copper rich liquid phase precursor. The infiltration and growth process allows for controlling both the spatial and size distribution of the 211-particles in the final superconducting 123-single-domain. The main parameters (set-ups, maximum processing temperature with respect to the peritectic temperature, nature of reactant, porosity of the 211 -preform) of the infiltration and growth process are discussed. Moreover, different processes of chimie douce are shown in order to produce Dy-211 particles with controlled shape and size, particles that can be used as precursors for the infiltration and growth process.

Research paper thumbnail of Investigation of DyBa2Cu3O7-d superconducting domains grown by the infiltration technique starting with small size Dy-211 particles

Superconductor Science & Technology, 2005

An infiltration and growth process is here used as an alternative to the classical top-seeded mel... more An infiltration and growth process is here used as an alternative to the classical top-seeded melt-textured growth process for the production of Dy-123 single-domains with finely dispersed small size Dy-211 particles. The starting materials are the 211-particles and a barium and copper rich liquid phase precursor. The infiltration and growth process allows for controlling both the spatial and size distribution

Research paper thumbnail of Microwave properties of polymer composites containing combinations of micro- and nano-sized magnetic fillers

Journal of nanoscience and nanotechnology, 2008

We investigated the microwave absorbing properties of composite bulk samples with nanostructured ... more We investigated the microwave absorbing properties of composite bulk samples with nanostructured and micron-sized fillers. As magnetic fillers we used magnetite powder (Fe3O4 with low magnetocrystalline anisotropy) and strontium hexaferrite (SrFe12O9 with high magnetocrystalline anisotropy). The dielectric matrix consisted of silicone rubber. The average particle size was 30 nm for the magnetite powder and 6 micro/m for the strontium hexaferrite powder. The micron-sized SrFe12O19 powder was prepared using a solid-state reaction. We investigated the influence of the filler concentration and the filler ratio (Fe3O4/SrFe12O19) in the polymer matrix on the microwave absorption in a large frequency range (1 / 18 GHz). The results obtained showed that the highly anisotropic particles become centers of clusterification and the small magnetite particles form magnetic balls with different diameter depending on the concentration. The effect of adding micron-sized SrFe12O19 to the nanosized Fe...

Research paper thumbnail of Study of Quasi-Monophase Y-Type Hexaferrite Ba<sub>2</sub>Mg<sub>2</sub>Fe<sub>12</sub>O<sub>22</sub> Powder

Micro and Nanosystems, 2014

Research paper thumbnail of Influence of the agglomeration in the initial suspension (ferrofluid) on the oriented magnetic structure

Journal of Physics: Conference Series, 2014

ABSTRACT The process was studied of preparation of oriented BaFe12O19 films via deposition of BaF... more ABSTRACT The process was studied of preparation of oriented BaFe12O19 films via deposition of BaFe12O19 nanoparticles from a suspension in a magnetic field. The films&#39; structural, microstructural and magnetic properties were investigated by X-ray diffraction, scanning electron microscopy and magnetic measurements. The influence was explored of the particles&#39;s agglomeration in the ferrofluid on the films&#39; properties and microstructure. Using time delay deposition, we obtained thick films with a high degree of orientation and good density.

Research paper thumbnail of Effect of different technological approaches on the optical properties of ZnO sol-gel thin films

Journal of Physics: Conference Series, 2014

The work presents a sol-gel approach with two types of solvents for ZnO films deposition in view ... more The work presents a sol-gel approach with two types of solvents for ZnO films deposition in view of varying the films' structural and optical properties. The ZnO films were characterized by X-Ray diffraction (XRD) and found to have a polycrystalline wurtzite phase structure. The grain sizes and the lattice parameters were determined; it was established that the ZnO crystallites' size increases with the annealing temperatures from 25 nm to 36 nm. The ZnO films possess high transmittance in the visible spectral range. Further, the optical band gap values were estimated. The material's vibration properties were analyzed by Fourier Transform Infrared (FTIR) spectroscopy. The two technological sol-gel approaches for deposition of ZnO films, using two different solvents, proved to be successful in producing structures with different structural and optical properties. The thin films fabricated were very smooth and uniform and exhibited a high transparency in the visible spectral range.

Research paper thumbnail of Study of sol-gel Cu-doped Al 2 O 3 thin films: structural and optical properties

Journal of Physics: Conference Series, 2014

ABSTRACT We present a study of of copper-doped Al2O3 films prepared by sol-gel deposition. The fi... more ABSTRACT We present a study of of copper-doped Al2O3 films prepared by sol-gel deposition. The films were spin-coated on Si and quartz substrates and a high-temperature treatment was conducted in the range 500 – 800 °C in oxygen or nitrogen. The impact was followed of the annealing procedures on the AlxCu1-xO3 films&#39;s properties. XRD was used to determine the films&#39; structure; it revealed a mixture of amorphous and crystalline phases. Optical characterization was performed by UV-VIS spectroscopy. The sol-gel films prepared are very transparent. The band gaps of the Al-Cu-O films were estimated from the optical data, with the values ranging from 3.4 to 4.8 eV depending on the Cu content, the annealing and the gas ambients.

Research paper thumbnail of Sol–gel nanocrystalline ZnO:Ag films: Structural and optical properties

Superlattices and Microstructures, 2014

ABSTRACT The paper presents a sol-gel approach for deposition of ZnO:Ag composite films. The film... more ABSTRACT The paper presents a sol-gel approach for deposition of ZnO:Ag composite films. The films are obtained by spin coating method on quartz and Si substrates. The effect of the annealing temperatures (500-800°C) and the gas ambient (oxygen, nitrogen) has been studied by X-Ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR). Optical properties are investigated by UV-VIS spectroscopy. The transmittance spectra of ZnO:Ag films are differed from ZnO spectra and manifest absorption features due to silver nanoparticles formation.

Research paper thumbnail of Investigation of DyBa 2 Cu 3 O 7− d superconducting domains grown by the infiltration technique starting with small size Dy-211 particles

Superconductor Science and Technology, 2005

An infiltration and growth process is here used as an alternative to the classical top-seeded mel... more An infiltration and growth process is here used as an alternative to the classical top-seeded melt-textured growth process for the production of Dy-123 single-domains with finely dispersed small size Dy-211 particles. The starting materials are the 211-particles and a barium and copper rich liquid phase precursor. The infiltration and growth process allows for controlling both the spatial and size distribution of the 211-particles in the final superconducting 123-single-domain. The main parameters (set-ups, maximum processing temperature with respect to the peritectic temperature, nature of reactant, porosity of the 211 -preform) of the infiltration and growth process are discussed. Moreover, different processes of chimie douce are shown in order to produce Dy-211 particles with controlled shape and size, particles that can be used as precursors for the infiltration and growth process.

Research paper thumbnail of Magnetic Properties of Nanosized Ba2Mg2Fe12O22 Powders Obtained by Auto-combustion

Journal of Superconductivity and Novel Magnetism, 2011

Research paper thumbnail of Differences in the structural and magnetic properties of nanosized barium hexaferrite powders prepared by single and double microemulsion techniques

Journal of Alloys and Compounds, 2013

Barium hexaferrite powders of nanometer particle size synthesized via two variants of the microem... more Barium hexaferrite powders of nanometer particle size synthesized via two variants of the microemulsion technique, namely, single microemulsion and double microemulsion, were studied. The influence was explored of the type of microemulsion technique on the microstructure and on the magnetic properties of the barium hexaferrite powders. The average particle size of the barium hexaferrite powders was in the range from 110 nm to 442 nm depending on the method and conditions of synthesis. The particles with size below 150 nm had irregular shapes between spherical and platehexagonal; the bigger ones had an almost perfect hexagonal shape. The powders obtained by single microemulsion had better magnetic characteristics (saturation magnetization of 65.12 emu/g and coercivity field of 3.6 Â 10 5 A/m) than those obtained by double microemulsion.

Research paper thumbnail of Data supporting the results of the characterization of the phases and structures appearing during the synthesis process of Ba0.5Sr1.5Zn2-xNixFe12O22 by auto-combustion

Research paper thumbnail of <strong>Study of the Properties of Co-Substituted Ba<sub>2</sub>Mg<sub>2</sub>Fe<sub>12</sub>O<sub>22</sub> Hexaferrites</strong>

Proceedings of The 3rd International Electronic Conference on Materials Sciences, May 17, 2018

We present results from a study on the influence of the substitution of Mg 2+ cations in the Y-ty... more We present results from a study on the influence of the substitution of Mg 2+ cations in the Y-type Ba2Mg2Fe12O22 hexaferrite with magnetic cations, such as Co 2+ , on its structural and magnetic properties. The Ba2Mg0.4Co1.6Fe12O22 powder was synthesized by sonochemical co-precipitation method. The XRD pattern of the powders showed the characteristic peaks corresponding to the Ytype hexaferrite structure as a main phase and some CoFe2O4 impurity (< 2%) as a second phase. This result was also confirmed by Mössbauer spectroscopy measurements. The magnetization values at 50 kOe were 30 emu/g at 4.2 K and 26.6 emu/g at 300 K, respectively. The ZFC and FC magnetization curves were measured at magnetic fields of 50 Oe, 100 Oe and 500 Oe, which revealed a magnetic phase transition around 200 K from ferrimagnetic-to-helical spin order. This is considered as a precondition for the material to exhibit multiferroic properties.

Research paper thumbnail of Study of the Structural and Magnetic Properties of Co-Substituted Ba2Mg2Fe12O22 Hexaferrites Synthesized by Sonochemical Co-Precipitation

Materials, 2019

Ba2Mg0.4Co1.6Fe12O22 was prepared in powder form by sonochemical co-precipitation and examined by... more Ba2Mg0.4Co1.6Fe12O22 was prepared in powder form by sonochemical co-precipitation and examined by X-ray diffraction, Mössbauer spectroscopy and magnetization measurements. Careful XRD data analyses revealed the Y-type hexaferrite structure as an almost pure phase with a very small amount of CoFe2O4 as an impurity phase (about 1.4%). No substantial changes were observed in the unit cell parameters of Ba2Mg0.4Co1.6Fe12O22 in comparison with the unsubstituted compound. The Mössbauer parameters for Ba2Mg0.4Co1.6Fe12O22 were close to those previously found (within the limits of uncertainty) for undoped Ba2Mg2Fe12O22. Isomer shifts (0.27–0.38 mm/s) typical for high-spin Fe3+ in various environments were evaluated and no ferrous Fe2+ form was observed. However, despite the indicated lack of changes in the iron oxidation state, the cationic substitution resulted in a significant increase in the magnetization and in a modification of the thermomagnetic curves. The magnetization values at 50 ...

Research paper thumbnail of Magnetic properties of nanosized MgFe2O4 powders prepared by auto-combustion

Journal of Physics: Conference Series, 2012

Targets were prepared to be used for magnetron sputtering and laser ablation and their microstruc... more Targets were prepared to be used for magnetron sputtering and laser ablation and their microstructural and magnetic properties were investigated. The base material was nanosized MgFe 2 O 4 powder produced by citrate auto-combustion synthesis. The auto-combusted powders were annealed at temperatures in the range 600 -1000 o С in air to study the effect of temperature on thofe formation MgFe 2 O 4 . The saturation magnetization М s was 24.30 emu/g at room temperature.

Research paper thumbnail of Modified ferrite plating of Fe3O4 and CuFe2O4 thin films

Journal of Magnetism and Magnetic Materials, 2000

ABSTRACT The present work proposes a modification of the ferrite plating method for synthesizing ... more ABSTRACT The present work proposes a modification of the ferrite plating method for synthesizing ferrite thin films from aqueous solutions at low temperatures about 97°C. Our approach combines spin-spray deposition from aqueous solutions at low temperature with co-precipitation. We were thus able to produce isotropic polycrystalline Fe3O4 and CuxFe3−xO4 films with thicknesses from 100 to 1000 nm. The modified ferrite plating enabled us to produce CuFe-oxide films with cubic and tetragonal crystalline structure and Jahn–Teller effect have been observed. The spectra showed that the films of magnetite were isotropic while the heat-treated samples of CuxFe3−xO4 films showed anisotropic behavior and coercivity of 1000 Oe.

Research paper thumbnail of ChemInform Abstract: Structural and Magnetic Properties and Preparation Techniques of Nanosized M-Type Hexaferrite Powders

Research paper thumbnail of Influence of the scanning conditions on the characteristics of the nanostructures fabricated by laser ablation in liquid

18th International School on Quantum Electronics: Laser Physics and Applications, 2015

Research paper thumbnail of Magnetic properties of nanosized MgFe 2 O 4 powders prepared by auto-combustion

Journal of Physics: Conference Series, 2012

Targets were prepared to be used for magnetron sputtering and laser ablation and their microstruc... more Targets were prepared to be used for magnetron sputtering and laser ablation and their microstructural and magnetic properties were investigated. The base material was nanosized MgFe2O4 powder produced by citrate auto-combustion synthesis. The auto-combusted powders were annealed at temperatures in the range 600 - 1000°C in air to study the effect of temperature on thofe formation MgFe2O4. The saturation magnetization Ms was 24.30 emu/g at room temperature.

Research paper thumbnail of Magnetic Properties of Nanosized Ba2Mg2Fe12O22 Powders Obtained by Auto-combustion

Journal of Superconductivity and Novel Magnetism, 2012

We studied the magnetic properties of nanosized Ba2Mg2Fe12O22 powder obtained by citrate auto-com... more We studied the magnetic properties of nanosized Ba2Mg2Fe12O22 powder obtained by citrate auto-combustion synthesis. The powder consists of agglomerates with mean crystallite size of 100 nm. The magnetic properties of the powder were investigated at 4.2 K and at room temperature. The values measured of the magnetization M at a magnetic field of 60 kOe are 22.78 emu/g and 30.47 emu/g at room temperature and

Research paper thumbnail of Investigation of DyBa 2 Cu 3 O 7− d superconducting domains grown by the infiltration technique starting with small size Dy-211 particles

Superconductor Science and Technology, 2005

An infiltration and growth process is here used as an alternative to the classical top-seeded mel... more An infiltration and growth process is here used as an alternative to the classical top-seeded melt-textured growth process for the production of Dy-123 single-domains with finely dispersed small size Dy-211 particles. The starting materials are the 211-particles and a barium and copper rich liquid phase precursor. The infiltration and growth process allows for controlling both the spatial and size distribution of the 211-particles in the final superconducting 123-single-domain. The main parameters (set-ups, maximum processing temperature with respect to the peritectic temperature, nature of reactant, porosity of the 211 -preform) of the infiltration and growth process are discussed. Moreover, different processes of chimie douce are shown in order to produce Dy-211 particles with controlled shape and size, particles that can be used as precursors for the infiltration and growth process.

Research paper thumbnail of Investigation of DyBa2Cu3O7-d superconducting domains grown by the infiltration technique starting with small size Dy-211 particles

Superconductor Science & Technology, 2005

An infiltration and growth process is here used as an alternative to the classical top-seeded mel... more An infiltration and growth process is here used as an alternative to the classical top-seeded melt-textured growth process for the production of Dy-123 single-domains with finely dispersed small size Dy-211 particles. The starting materials are the 211-particles and a barium and copper rich liquid phase precursor. The infiltration and growth process allows for controlling both the spatial and size distribution

Research paper thumbnail of Microwave properties of polymer composites containing combinations of micro- and nano-sized magnetic fillers

Journal of nanoscience and nanotechnology, 2008

We investigated the microwave absorbing properties of composite bulk samples with nanostructured ... more We investigated the microwave absorbing properties of composite bulk samples with nanostructured and micron-sized fillers. As magnetic fillers we used magnetite powder (Fe3O4 with low magnetocrystalline anisotropy) and strontium hexaferrite (SrFe12O9 with high magnetocrystalline anisotropy). The dielectric matrix consisted of silicone rubber. The average particle size was 30 nm for the magnetite powder and 6 micro/m for the strontium hexaferrite powder. The micron-sized SrFe12O19 powder was prepared using a solid-state reaction. We investigated the influence of the filler concentration and the filler ratio (Fe3O4/SrFe12O19) in the polymer matrix on the microwave absorption in a large frequency range (1 / 18 GHz). The results obtained showed that the highly anisotropic particles become centers of clusterification and the small magnetite particles form magnetic balls with different diameter depending on the concentration. The effect of adding micron-sized SrFe12O19 to the nanosized Fe...

Research paper thumbnail of Study of Quasi-Monophase Y-Type Hexaferrite Ba<sub>2</sub>Mg<sub>2</sub>Fe<sub>12</sub>O<sub>22</sub> Powder

Micro and Nanosystems, 2014

Research paper thumbnail of Influence of the agglomeration in the initial suspension (ferrofluid) on the oriented magnetic structure

Journal of Physics: Conference Series, 2014

ABSTRACT The process was studied of preparation of oriented BaFe12O19 films via deposition of BaF... more ABSTRACT The process was studied of preparation of oriented BaFe12O19 films via deposition of BaFe12O19 nanoparticles from a suspension in a magnetic field. The films&#39; structural, microstructural and magnetic properties were investigated by X-ray diffraction, scanning electron microscopy and magnetic measurements. The influence was explored of the particles&#39;s agglomeration in the ferrofluid on the films&#39; properties and microstructure. Using time delay deposition, we obtained thick films with a high degree of orientation and good density.

Research paper thumbnail of Effect of different technological approaches on the optical properties of ZnO sol-gel thin films

Journal of Physics: Conference Series, 2014

The work presents a sol-gel approach with two types of solvents for ZnO films deposition in view ... more The work presents a sol-gel approach with two types of solvents for ZnO films deposition in view of varying the films' structural and optical properties. The ZnO films were characterized by X-Ray diffraction (XRD) and found to have a polycrystalline wurtzite phase structure. The grain sizes and the lattice parameters were determined; it was established that the ZnO crystallites' size increases with the annealing temperatures from 25 nm to 36 nm. The ZnO films possess high transmittance in the visible spectral range. Further, the optical band gap values were estimated. The material's vibration properties were analyzed by Fourier Transform Infrared (FTIR) spectroscopy. The two technological sol-gel approaches for deposition of ZnO films, using two different solvents, proved to be successful in producing structures with different structural and optical properties. The thin films fabricated were very smooth and uniform and exhibited a high transparency in the visible spectral range.

Research paper thumbnail of Study of sol-gel Cu-doped Al 2 O 3 thin films: structural and optical properties

Journal of Physics: Conference Series, 2014

ABSTRACT We present a study of of copper-doped Al2O3 films prepared by sol-gel deposition. The fi... more ABSTRACT We present a study of of copper-doped Al2O3 films prepared by sol-gel deposition. The films were spin-coated on Si and quartz substrates and a high-temperature treatment was conducted in the range 500 – 800 °C in oxygen or nitrogen. The impact was followed of the annealing procedures on the AlxCu1-xO3 films&#39;s properties. XRD was used to determine the films&#39; structure; it revealed a mixture of amorphous and crystalline phases. Optical characterization was performed by UV-VIS spectroscopy. The sol-gel films prepared are very transparent. The band gaps of the Al-Cu-O films were estimated from the optical data, with the values ranging from 3.4 to 4.8 eV depending on the Cu content, the annealing and the gas ambients.

Research paper thumbnail of Sol–gel nanocrystalline ZnO:Ag films: Structural and optical properties

Superlattices and Microstructures, 2014

ABSTRACT The paper presents a sol-gel approach for deposition of ZnO:Ag composite films. The film... more ABSTRACT The paper presents a sol-gel approach for deposition of ZnO:Ag composite films. The films are obtained by spin coating method on quartz and Si substrates. The effect of the annealing temperatures (500-800°C) and the gas ambient (oxygen, nitrogen) has been studied by X-Ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR). Optical properties are investigated by UV-VIS spectroscopy. The transmittance spectra of ZnO:Ag films are differed from ZnO spectra and manifest absorption features due to silver nanoparticles formation.

Research paper thumbnail of Investigation of DyBa 2 Cu 3 O 7− d superconducting domains grown by the infiltration technique starting with small size Dy-211 particles

Superconductor Science and Technology, 2005

An infiltration and growth process is here used as an alternative to the classical top-seeded mel... more An infiltration and growth process is here used as an alternative to the classical top-seeded melt-textured growth process for the production of Dy-123 single-domains with finely dispersed small size Dy-211 particles. The starting materials are the 211-particles and a barium and copper rich liquid phase precursor. The infiltration and growth process allows for controlling both the spatial and size distribution of the 211-particles in the final superconducting 123-single-domain. The main parameters (set-ups, maximum processing temperature with respect to the peritectic temperature, nature of reactant, porosity of the 211 -preform) of the infiltration and growth process are discussed. Moreover, different processes of chimie douce are shown in order to produce Dy-211 particles with controlled shape and size, particles that can be used as precursors for the infiltration and growth process.