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Papers by Bostjan Jancar, PharmaHemp

Research paper thumbnail of Thermal Evolution of Cation Distribution/Crystallite Size and Their Correlation with the Magnetic State of Yb-Substituted Zinc Ferrite Nanoparticles

The Journal of Physical Chemistry C, 2013

Research paper thumbnail of Tem analyses of the local crystal and domain structures in (na<sub>1-x</sub>k<sub>x</sub>)<sub>0.5</sub>bi<sub>0.5</sub>tio<sub>3</sub> perovskite ceramics

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2011

Research paper thumbnail of Microwave dielectric properties and microstructure of Sm(Mg0.5Ti0.5−xSnx)O3 ceramics

Ceramics International, 2014

Research paper thumbnail of Microstructural Characterization of CaTiO 3-NdAlO 3-Based Ceramics

Ceramics based on CaTiO 3-NdAlO3 solid solutions were synthesized in order to study their dielect... more Ceramics based on CaTiO 3-NdAlO3 solid solutions were synthesized in order to study their dielectric microwave properties. Microstructural analysis was performed with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) using different analytical methods such as energy-dispersive X-ray spectroscopy (EDXS). It was observed that the heating conditions during sintering and cooling strongly affect the microstructural development of CaTiO 3NdAlO3-based ceramics. Various types and concentrations of structural defects were identified, for example, dislocations, twins and/or antiphase boundaries. All such defects resulted in a degradation of the dielectric microwave properties, in particular the quality factor Q. Dielectric properties of CaTiO3-NdAlO3-based ceramics can be improved by an appropriate thermal treatment of ceramics which results in a decrease in the concentration of the identified microstructural defects.

Research paper thumbnail of Nano-engineering the Antimicrobial Spectrum of Lantibiotics: Activity of Nisin against Gram Negative Bacteria

Research paper thumbnail of Domain-wall conduction in ferroelectric BiFeO3 controlled by accumulation of charged defects

Nature Materials, 2016

Mobile charged defects, accumulated in the domain-wall region to screen polarization charges, hav... more Mobile charged defects, accumulated in the domain-wall region to screen polarization charges, have been proposed as the origin of the electrical conductivity at domain walls in ferroelectric materials. Despite theoretical and experimental efforts, this scenario has not been directly confirmed, leaving a gap in the understanding of the intriguing electrical properties of domain walls. Here, we provide atomic-scale chemical and structural analyses showing the accumulation of charged defects at domain walls in BiFeO3. The defects were identified as Fe(4+) cations and bismuth vacancies, revealing p-type hopping conduction at domain walls caused by the presence of electron holes associated with Fe(4+). In agreement with the p-type behaviour, we further show that the local domain-wall conductivity can be tailored by controlling the atmosphere during high-temperature annealing. This work has possible implications for engineering local conductivity in ferroelectrics and for devices based on domain walls.

Research paper thumbnail of Nanocrystalline Ti02 Thin Films Fabricated Via a Polyelectrolyte Multilayer-Assisted Sol-Gel Reaction

Journal of the American Ceramic Society, 2010

Research paper thumbnail of Mo6S3I6 nanowires

Research paper thumbnail of EPR Study of TiO2 Based Nanotubes and NO2 Adsorption

Research paper thumbnail of SYNTHESIS OF TITANIA BASED NANOTUBES AND ADSORBTION STUDY OF NO 2 (g) ON THIS NANOSTRUCTURES

Research paper thumbnail of NiO/Ni nanocomposite (micro)structure evolution induced by thermal annealing and milling

Acta Crystallographica Section A Foundations of Crystallography, 2011

Research paper thumbnail of (Micro)structure determination of ferrite nanoparticles using multiple techniques

Acta Crystallographica Section A Foundations of Crystallography, 2011

Research paper thumbnail of Synthesis and dielectric and nonlinear properties of BaTi1 − x Zr x O3 ceramics

Inorganic Materials, 2014

We have studied the formation of BaTi1 − xZrxO3 solid solutions with the perovskite structure. Th... more We have studied the formation of BaTi1 − xZrxO3 solid solutions with the perovskite structure. The phase composition, microstructure, and electrical properties of the BaTi1 − xZrxO3 materials have been investigated. The results demonstrate that their dielectric permittivity (ɛ) and loss tangent (tan δ) decrease with increasing zirconium content. At the same time, their nonlinearity coefficient (nR) remains large (nR = 30–50%) in relatively low fields (E = 30–50 kV/cm). The present data suggest that the materials studied here are potentially attractive for use in creating nonlinear devices of modern microelectronics.

Research paper thumbnail of Phase relations in the Fe-Bi-O system under hydrothermal conditions

EMC 2008 14th European Microscopy Congress 1–5 September 2008, Aachen, Germany, 2008

ABSTRACT The phases appearing during a hydrothermal reaction in the Fe-Bi-O system were investiga... more ABSTRACT The phases appearing during a hydrothermal reaction in the Fe-Bi-O system were investigated, with the aim to optimize the conditions for the syntheses of nanostructured bismuth ferrite. BiFeO3 is a multiferroic material; hence it is ferroelectric and antiferromagnetic at room temperature [1]. Since the spins in this material take the form of a long-wavelength (62 nm) the spiral linear magnetoelectric effect averages to zero. One of the ways to recover this linear effect is with thin-film epitaxial constraints. Thus, we expect the same effects in nanostructured BiFeO3.

Research paper thumbnail of Magnetite/Mn-ferrite nanocomposite with improved magnetic properties

Materials Letters

Magnetic nanocomposites can show enhanced properties compared to their single phase counterparts.... more Magnetic nanocomposites can show enhanced properties compared to their single phase counterparts. Novel soft ferrite Fe3O4/soft ferrite MnFe2O4 nanocomposite, as well as pure MnFe2O4 and Fe3O4 for the sake of comparison, were synthesized by co-precipitation method. The spinel type of structure (space group Fd (3) over barm) of the samples was confirmed by XRPD and SAED. Samples are composed of spherical particles with size in the range 5-15 nm. Nanocomposite (92 wt%) MnFe2O4/(8 wt%) Fe3O4 exert single phase like magnetic behavior. Saturation magnetization (M-S) of Fe3O4/MnFe2O4 is 26% greater than M-S of MnFe2O4 and even 50% than M-S of Fe3O4. At the same time coercivity field of the nanocomposite is twice less value (H-C=180 Oe) than in binary ferrites (H-C=360 Oe). Magnetization enhancement and softening in Magnetite/Mn-ferrite is discussed related to particle interactions among two different ferrites and intrinsic properties of nanoparticles. Tailoring phase ratio and synthesis c...

Research paper thumbnail of Cu and CuO/titanate nanobelt based network assemblies for enhanced visible light photocatalysis

Langmuir : the ACS journal of surfaces and colloids, Jan 29, 2014

3D network configurations of copper(II) oxide/titanate nanobelt (CuO/TiNBs) and copper/titanate n... more 3D network configurations of copper(II) oxide/titanate nanobelt (CuO/TiNBs) and copper/titanate nanobelt (Cu/TiNBs) were formed using a two-step polyelectrolyte-assisted synthesis and assembly approach. The photoactivity of the TiNB/CuO and Cu/TiNB composite networks is significantly enhanced as compared to the activity of 3D structures formed of pristine TiNB. An efficient, UV-vis-light-induced electron transfer at the two-component interface achieved by the intimate coupling of TiNB with p-type semiconducting CuO and plasmonic Cu nanoparticles in composite heterostructures facilitates control over the system's exciton dynamics, which results in highly efficient UV-vis photocatalytic performance of heterostructures. The superior photocatalytic activity of the metal and semiconductor/semiconductor nanocomposite structures in the visible region is discussed, highlighting the role of interfacial electron-charge transfer (IFCT) in semiconductor-semiconductor (CuO/TiNB) and surface ...

Research paper thumbnail of The synthesis, crystal structural study and microwave dielectric properties of Ba 6 WNb 2 O 14

Acta Crystallographica Section A Foundations of Crystallography, 2008

Research paper thumbnail of Na0.5Bi0.5TiO3-Based Voltage-Tunable Materials

We have investigated the dielectric tunability of the Na0.5Bi0.5TiO3 relaxor ferroelectric, modif... more We have investigated the dielectric tunability of the Na0.5Bi0.5TiO3 relaxor ferroelectric, modified with additions of Li3xLa(2/3)-xTiO3 (0.03lesxges0.167) and NaTaO3. These two additives have characteristics similar to incipient antiferroelectric and ferroelectric materials, respectively. The phase relations in the Na0.5Bi0.5TiO3-Li3xLa(2/3)-xTiO3 system were determined; however, this was made difficult by the slow kinetics and the thermodynamic instability of the compounds from the system.

Research paper thumbnail of A-site deficient perovskites Ba(M2+1/3Nb2/3)O3: microstructural attributes for a high quality factor

Research paper thumbnail of Effect of Zn2TiO4 and ZnB2O4 additions on the microstructure and dielectric properties of AgNb1 − xTaxO3 solid solutions

... decomposes, which is accompanied by the formation and subse quent vaporization of silver meta... more ... decomposes, which is accompanied by the formation and subse quent vaporization of silver metal nanoinclusions [7]. As shown by Valant et al. ... 1239 The phase composition of the synthesized materi als was determined by X ray diffraction (XRD) on a DRON 4 07 diffractometer ...

Research paper thumbnail of Thermal Evolution of Cation Distribution/Crystallite Size and Their Correlation with the Magnetic State of Yb-Substituted Zinc Ferrite Nanoparticles

The Journal of Physical Chemistry C, 2013

Research paper thumbnail of Tem analyses of the local crystal and domain structures in (na<sub>1-x</sub>k<sub>x</sub>)<sub>0.5</sub>bi<sub>0.5</sub>tio<sub>3</sub> perovskite ceramics

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2011

Research paper thumbnail of Microwave dielectric properties and microstructure of Sm(Mg0.5Ti0.5−xSnx)O3 ceramics

Ceramics International, 2014

Research paper thumbnail of Microstructural Characterization of CaTiO 3-NdAlO 3-Based Ceramics

Ceramics based on CaTiO 3-NdAlO3 solid solutions were synthesized in order to study their dielect... more Ceramics based on CaTiO 3-NdAlO3 solid solutions were synthesized in order to study their dielectric microwave properties. Microstructural analysis was performed with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) using different analytical methods such as energy-dispersive X-ray spectroscopy (EDXS). It was observed that the heating conditions during sintering and cooling strongly affect the microstructural development of CaTiO 3NdAlO3-based ceramics. Various types and concentrations of structural defects were identified, for example, dislocations, twins and/or antiphase boundaries. All such defects resulted in a degradation of the dielectric microwave properties, in particular the quality factor Q. Dielectric properties of CaTiO3-NdAlO3-based ceramics can be improved by an appropriate thermal treatment of ceramics which results in a decrease in the concentration of the identified microstructural defects.

Research paper thumbnail of Nano-engineering the Antimicrobial Spectrum of Lantibiotics: Activity of Nisin against Gram Negative Bacteria

Research paper thumbnail of Domain-wall conduction in ferroelectric BiFeO3 controlled by accumulation of charged defects

Nature Materials, 2016

Mobile charged defects, accumulated in the domain-wall region to screen polarization charges, hav... more Mobile charged defects, accumulated in the domain-wall region to screen polarization charges, have been proposed as the origin of the electrical conductivity at domain walls in ferroelectric materials. Despite theoretical and experimental efforts, this scenario has not been directly confirmed, leaving a gap in the understanding of the intriguing electrical properties of domain walls. Here, we provide atomic-scale chemical and structural analyses showing the accumulation of charged defects at domain walls in BiFeO3. The defects were identified as Fe(4+) cations and bismuth vacancies, revealing p-type hopping conduction at domain walls caused by the presence of electron holes associated with Fe(4+). In agreement with the p-type behaviour, we further show that the local domain-wall conductivity can be tailored by controlling the atmosphere during high-temperature annealing. This work has possible implications for engineering local conductivity in ferroelectrics and for devices based on domain walls.

Research paper thumbnail of Nanocrystalline Ti02 Thin Films Fabricated Via a Polyelectrolyte Multilayer-Assisted Sol-Gel Reaction

Journal of the American Ceramic Society, 2010

Research paper thumbnail of Mo6S3I6 nanowires

Research paper thumbnail of EPR Study of TiO2 Based Nanotubes and NO2 Adsorption

Research paper thumbnail of SYNTHESIS OF TITANIA BASED NANOTUBES AND ADSORBTION STUDY OF NO 2 (g) ON THIS NANOSTRUCTURES

Research paper thumbnail of NiO/Ni nanocomposite (micro)structure evolution induced by thermal annealing and milling

Acta Crystallographica Section A Foundations of Crystallography, 2011

Research paper thumbnail of (Micro)structure determination of ferrite nanoparticles using multiple techniques

Acta Crystallographica Section A Foundations of Crystallography, 2011

Research paper thumbnail of Synthesis and dielectric and nonlinear properties of BaTi1 − x Zr x O3 ceramics

Inorganic Materials, 2014

We have studied the formation of BaTi1 − xZrxO3 solid solutions with the perovskite structure. Th... more We have studied the formation of BaTi1 − xZrxO3 solid solutions with the perovskite structure. The phase composition, microstructure, and electrical properties of the BaTi1 − xZrxO3 materials have been investigated. The results demonstrate that their dielectric permittivity (ɛ) and loss tangent (tan δ) decrease with increasing zirconium content. At the same time, their nonlinearity coefficient (nR) remains large (nR = 30–50%) in relatively low fields (E = 30–50 kV/cm). The present data suggest that the materials studied here are potentially attractive for use in creating nonlinear devices of modern microelectronics.

Research paper thumbnail of Phase relations in the Fe-Bi-O system under hydrothermal conditions

EMC 2008 14th European Microscopy Congress 1–5 September 2008, Aachen, Germany, 2008

ABSTRACT The phases appearing during a hydrothermal reaction in the Fe-Bi-O system were investiga... more ABSTRACT The phases appearing during a hydrothermal reaction in the Fe-Bi-O system were investigated, with the aim to optimize the conditions for the syntheses of nanostructured bismuth ferrite. BiFeO3 is a multiferroic material; hence it is ferroelectric and antiferromagnetic at room temperature [1]. Since the spins in this material take the form of a long-wavelength (62 nm) the spiral linear magnetoelectric effect averages to zero. One of the ways to recover this linear effect is with thin-film epitaxial constraints. Thus, we expect the same effects in nanostructured BiFeO3.

Research paper thumbnail of Magnetite/Mn-ferrite nanocomposite with improved magnetic properties

Materials Letters

Magnetic nanocomposites can show enhanced properties compared to their single phase counterparts.... more Magnetic nanocomposites can show enhanced properties compared to their single phase counterparts. Novel soft ferrite Fe3O4/soft ferrite MnFe2O4 nanocomposite, as well as pure MnFe2O4 and Fe3O4 for the sake of comparison, were synthesized by co-precipitation method. The spinel type of structure (space group Fd (3) over barm) of the samples was confirmed by XRPD and SAED. Samples are composed of spherical particles with size in the range 5-15 nm. Nanocomposite (92 wt%) MnFe2O4/(8 wt%) Fe3O4 exert single phase like magnetic behavior. Saturation magnetization (M-S) of Fe3O4/MnFe2O4 is 26% greater than M-S of MnFe2O4 and even 50% than M-S of Fe3O4. At the same time coercivity field of the nanocomposite is twice less value (H-C=180 Oe) than in binary ferrites (H-C=360 Oe). Magnetization enhancement and softening in Magnetite/Mn-ferrite is discussed related to particle interactions among two different ferrites and intrinsic properties of nanoparticles. Tailoring phase ratio and synthesis c...

Research paper thumbnail of Cu and CuO/titanate nanobelt based network assemblies for enhanced visible light photocatalysis

Langmuir : the ACS journal of surfaces and colloids, Jan 29, 2014

3D network configurations of copper(II) oxide/titanate nanobelt (CuO/TiNBs) and copper/titanate n... more 3D network configurations of copper(II) oxide/titanate nanobelt (CuO/TiNBs) and copper/titanate nanobelt (Cu/TiNBs) were formed using a two-step polyelectrolyte-assisted synthesis and assembly approach. The photoactivity of the TiNB/CuO and Cu/TiNB composite networks is significantly enhanced as compared to the activity of 3D structures formed of pristine TiNB. An efficient, UV-vis-light-induced electron transfer at the two-component interface achieved by the intimate coupling of TiNB with p-type semiconducting CuO and plasmonic Cu nanoparticles in composite heterostructures facilitates control over the system's exciton dynamics, which results in highly efficient UV-vis photocatalytic performance of heterostructures. The superior photocatalytic activity of the metal and semiconductor/semiconductor nanocomposite structures in the visible region is discussed, highlighting the role of interfacial electron-charge transfer (IFCT) in semiconductor-semiconductor (CuO/TiNB) and surface ...

Research paper thumbnail of The synthesis, crystal structural study and microwave dielectric properties of Ba 6 WNb 2 O 14

Acta Crystallographica Section A Foundations of Crystallography, 2008

Research paper thumbnail of Na0.5Bi0.5TiO3-Based Voltage-Tunable Materials

We have investigated the dielectric tunability of the Na0.5Bi0.5TiO3 relaxor ferroelectric, modif... more We have investigated the dielectric tunability of the Na0.5Bi0.5TiO3 relaxor ferroelectric, modified with additions of Li3xLa(2/3)-xTiO3 (0.03lesxges0.167) and NaTaO3. These two additives have characteristics similar to incipient antiferroelectric and ferroelectric materials, respectively. The phase relations in the Na0.5Bi0.5TiO3-Li3xLa(2/3)-xTiO3 system were determined; however, this was made difficult by the slow kinetics and the thermodynamic instability of the compounds from the system.

Research paper thumbnail of A-site deficient perovskites Ba(M2+1/3Nb2/3)O3: microstructural attributes for a high quality factor

Research paper thumbnail of Effect of Zn2TiO4 and ZnB2O4 additions on the microstructure and dielectric properties of AgNb1 − xTaxO3 solid solutions

... decomposes, which is accompanied by the formation and subse quent vaporization of silver meta... more ... decomposes, which is accompanied by the formation and subse quent vaporization of silver metal nanoinclusions [7]. As shown by Valant et al. ... 1239 The phase composition of the synthesized materi als was determined by X ray diffraction (XRD) on a DRON 4 07 diffractometer ...