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In this paper, new results on the degradation of losartan potassium (LP, (1)), in the absence and presence of excipients, which was induced by UV light, the acid character of phosphate buffer solution (PBS) and alkaline medium, respectively, are reported through correlated studies of FTIR spectroscopy, photoluminescence and dielectric spectroscopy. The photoluminescence (PL) spectra of LP and the drug marked under the name Lorista (LO) are characterized by intense emission bands, peaking at 378 nm and 380 nm, respectively, accompanied by low intensity bands with a maximum at ~450–460 nm. Photodegradation of LO in a solid state is evidenced by a decrease in the intensity of the PL band at 380 nm, a variation that originates both in the adsorption of water vapors from the air and in the interaction of LP with excipients such as cornstarch, silicon dioxide and cellulose. The LP-water interaction is described, taking into account the main electrical parameters, i.e., complex dielectric permittivity and electrical conductivity. Photodegradation of LP and LO also induces an increase in the intensity of the emission band, at ~450–460 nm. The influence of acid and alkaline medium on the LO degradation is analyzed using phosphate buffer (PBS) and NaOH solutions, respectively. In both cases, a decrease in the intensity of the PL band, at 380 nm, is reported. The intensity diminution of the PL spectra of NaOH-reacted LP and LO is the result of the formation of the photodegradation product N-methanolamide-{[2′-(1H-tetrazol-5-yl)(1,1′-biphenyl)-4-yl]methyl} (2). This compound was proven by the studies of FTIR spectroscopy achieved on LP and NaOH-reacted LP. The appearance of the IR band at 1740 cm−1 and the increase in the absorbance in the IR band at 1423 cm−1 indicate that the photodegradation product (2) contains the C=O and C-OH functional groups. [ABSTRACT FROM AUTHOR]

Neodymium and gallium codoped barium titanate (BaNdGaTiO, x = 0.03, 0.05, 0.07, 0.1 and y = 0.03) were prepared by sol-gel method in order to investigate its dielectric and photoluminescence properties. The structure and morphology of BaNdGaTiO powders calcined at 1100 °C and sintered ceramics by spark plasma sintering (SPS) technique were analyzed using X-ray diffraction and scanning electron microscope, respectively. The photoluminescence and dielectric properties of Nd doped BaGaTiO, (y = 0.03) as a function of Nd concentration and sintering temperature were also investigated. The influence of Ga and Nd dopants on the crystalline phases, sintering process by SPS and macroscopic properties of BaNdGaTiO ceramics was analyzed, as well as a weak hot emission from the 4F5/2 level. The sintered ceramics showed high dielectric constant and moderate dielectric losses. The highest value of the permittivity obtained for BaNdGaTiO ceramics was ɛ = 5890 at room temperature, 1 kHz and x = y = 0.03. This study shown that Nd decreases the density of the pellets, increases the dielectric losses and decreases the dielectric constant of BaGaTiO ceramics. Therefore, the values of dielectric properties, at room temperature, of BaTiO doped with 3 at.% Ga and ≤7 at.% Nd are higher than those of undoped BaTiO ceramic. [ABSTRACT FROM AUTHOR]

The As2S3-Cu interface was studied by dielectric spectroscopy measurements on Cu-As2S3-Cu thin film heterostructure samples to assess the charge carriers' contribution to the electrical properties of such an interface. Three-dimensional printed masks ensured good reproducibility during the PLD deposition of heterostructure samples. The samples were tested for electrical conductivity and AC photoconductivity by dielectric spectroscopy measurements. DC bias voltages and light were applied to the samples. The electrical capacity of the thin film heterostructure can be modified electrically and optically. We observed long-term photoconductivity with a time dependency that was not exponential, and a quick change of the electrical capacity, indicating the potential of the heterostructure cells as photodetector candidates. [ABSTRACT FROM AUTHOR]

We obtained a new system containing nematic liquid crystal doped with nanostructured copolymer-clay particles. The clay (Cloisite-type) was modified by copolymerization of maleic anhydride and divinyl benzene and the nanocomposite has intercalated structure. Current-voltage characteristics of the liquid crystal/copolymer-clay systems were analyzed and the electro-optical response at heating -cooling cycles for different applied electric fields is discussed. Dielectric spectroscopy measurements in the low frequency domain have shown different regimes of its temperature dependence as function of the sample nature and the applied voltage. Comparison is made with the bulk liquid crystal. Changes of the phase transition temperature are thus revealed. [ABSTRACT FROM AUTHOR]

Barium titanate (BaTiO) has been doped in situ with 5 mol% thulium by a sol-gel method. The as-prepared gel powder consists of nanosized grains (20-30 nm) and crystallizes on the cubic BaTiO lattice, at 700°C. BaTmTiO ceramics derived from this powder have tetragonal perovskite structure and contain a small amount of TmTiO pyrochlore phase. These ceramics exhibit dielectric constants of 4282-3240 and dielectric loss (tan δ) of 0.1077-0.0161 at Curie temperature T=132°C and at 10 Hz-100 kHz, respectively. For a drive voltage of 400 V, the hysteresis loop recorded at the frequency of 100 Hz shows a remnant polarization ( P) value of 76 μC/cm and a coercive field ( E) of 124 V and for 1 kHz a remnant polarization ( P) value of 58 μC/cm and a coercive field ( E) of 116 V. [ABSTRACT FROM AUTHOR]

Holmium-doped BaTiO3 with composition Ba0.97Ho0.03TiO3 was prepared by sol-gel combustion method. A molar ratio of citrate/nitrate (CA/NO3− = 1.3) was used to prepare nanopowders of (Ba,Ho)TiO3. The structure and microstructure of (Ba,Ho)TiO3 powders and ceramics were investigated. The ceramics exhibit a dielectric constant of about 4400 and dielectric loss (tan d = 0.267) at 10 Hz, and at the Curie temperature (Tc = 132 °C). The remanent polarization and the coercive field of Ba0.97Ho0.03TiO3 ceramics, at 1 kHz, were Pr = 6 µC/cm2 and EC = 0.75 kV/cm. The dielectric and ferroelectric behavior of the holmium-doped BaTiO3 is influenced by the amphoteric character of Ho3+ ions. [ABSTRACT FROM AUTHOR]

A two-step sintering approach composed of spark-plasma-sintering (SPS) technique at 1000 °C for 1 min and under a uniaxial pressure of 63 MPa followed by conventional sintering at 1400 °C for 3 h is proposed for synthesis of dense Ba(Ti0.87Sn0.13)O3 ceramics. Starting powders had grain size of about 90 nm and were obtained by co-precipitation. The SPS pellets consist of submicron (300–500 nm) grains. X-ray diffraction analysis of as-prepared Ba(Ti0.87Sn0.13)O3 ceramic shows the occurrence of cubic and tetragonal phase coexistence for the pellets obtained after SPS processing and the presence of only tetragonal phase in the samples after the second (conventional) sintering. Grain uniformity in the final product is high, with average size of ~2 μm. The apparent densities of the sintered pellets at temperature of 1400 °C were ~92% of the theoretical value of Ba(Ti0.87Sn0.13)O3. The ceramics exhibit a high relative dielectric constant of 6,550 and a dielectric loss (tan δ) = 0.078 at Curie temperature of 63 °C and 10 Hz. [ABSTRACT FROM AUTHOR]

This paper prepared composites under the free membranes form that are based on thermoplastic polymers of the type of polyurethane (TPU) and polyolefin (TPO), which are blended in the weight ratio of 2:1, and ceramic nanoparticles (CNs) such as BaSrTiO3 and SrTiO3. The structural, optical, and conductive properties of these new composite materials are reported. The X-ray diffraction studies highlight a cubic crystalline structure of these CNs. The main variations in the vibrational properties of the TPU:TPO blend induced by CNs consist of the following: (i) the increase in the intensity of the Raman line of 1616 cm−1; (ii) the down-shift of the IR band from 800 to 791 cm−1; (iii) the change of the ratio between the absorbance of IR bands localized in the spectral range 950–1200 cm−1; and (iv) the decrease in the absorbance of the IR band from 1221 cm−1. All these variations were correlated with a preferential adsorption of thermoplastic polymers on the CNs surface. A photoluminescence (PL) quenching process of thermoplastic polymers is demonstrated to occur in the presence of CNs. The anisotropic PL measurements have highlighted a change in the angle of the binding of the TPU:TPO blend, which varies from 23.7° to ≈49.3° and ≈53.4°, when the concentration of BaSrTiO3 and SrTiO3 CNs, respectively, is changed from 0 to 25 wt. %. Using dielectric spectroscopy, two mechanisms are invoked to take place in the case of the composites based on TPU:TPO blends and CNs, i.e., one regarding the type of the electrical conduction and another specifying the dielectric–dipolar relaxation processes. [ABSTRACT FROM AUTHOR]

Herein we report on novel multiferroic core–shell nanostructures of cobalt ferrite (CoFe2O4)–bismuth, sodium titanate doped with barium titanate (BNT–BT0.08), prepared by a two–step wet chemical procedure, using the sol–gel technique. The fraction of CoFe2O4 was varied from 1:0.5 to 1:1.5 = BNT–BT0.08/CoFe2O4 (molar ratio). X–ray diffraction confirmed the presence of both the spinel CoFe2O4 and the perovskite Bi0.5Na0.5TiO3 phases. Scanning electron microscopy analysis indicated that the diameter of the core–shell nanoparticles was between 15 and 40 nm. Transmission electron microscopy data showed two–phase composite nanostructures consisting of a BNT–BT0.08 core surrounded by a CoFe2O4 shell with an average thickness of 4–7 nm. Cole-Cole plots reveal the presence of grains and grain boundary effects in the BNT–BT0.08/CoFe2O4 composite. Moreover, the values of the dc conductivity were found to increase with the amount of CoFe2O4 semiconductive phase. Both X-ray photoelectron spectroscopy (XPS) and Mössbauer measurements have shown no change in the valence of the Fe3+, Co2+, Bi3+ and Ti4+ cations. This study provides a detailed insight into the magnetoelectric coupling of the multiferroic BNT–BT0.08/CoFe2O4 core–shell composite potentially suitable for magnetoelectric applications. [ABSTRACT FROM AUTHOR]

Nano-sized lanthanum doped barium titanate Ba 1-x La x TiO 3 (0.00 ≤ x ≤ 0.08) powders were prepared by sol-gel method. These powders with perovskite BaTiO 3 cubic single phase structure, obtained after calcinations of gels precursors at 1100 °C, 3 h in air, were pressed and sintered by spark plasma technique in order to obtain dense ceramics. The optimal sintering temperatures used for Ba 1-x La x TiO 3 powders were dependent on lanthanum amount added to barium titanate and decrease from 1300 °C to 1160 °C when the La concentration increases from 0 to 8 at.% La. An additional annealing treatment was made in air at 900 °C for all the sintered pellets for oxidize and remove the contaminant graphite which migrated in ceramics from the graphite die during the sintering process. The effect of lanthanum concentration on the densification behavior, structure, microstructure, photoluminescence and dielectric properties of the Ba 1-x La x TiO 3 ceramics was investigated in this work. The results shown that as the lanthanum content increases, the grain size of the powders and ceramics increases accompanied by decrease of density of the samples. Also, increase of La amount inserted in BaTiO 3 lattice leads to significant decrease of the dielectric losses and Curie temperature and, increase of dielectric permittivity but the luminescence properties seem to be less affected. [ABSTRACT FROM AUTHOR]

• Ba 1–x Tb x TiO 3 x = 0.00, 0.01 and 0.05 powders were synthesized by hydrothermal route. • Ba 1–-x Tb x TiO 3 ceramics were sintered at 1325 °C, for x = 0.00, 0.01 and 0.05, respectively. • Ba 1–x Tb x TiO 3 ceramics exhibited good permittivity and low dielectric losses. • The band gap energy of BaTiO 3 decreases with the Tb–doping. Multifunctional materials integrating optical and electric properties into a composite or into a doped single–phase material have attracted much attention from scientists for future optoelectronic devices. In this work, polycrystalline Ba 1–x Tb x TiO 3 , x = 0.00, 0.01 and 0.05 materials were synthesized by hydrothermal route and their photoluminescence and dielectric properties were studied. The as–prepared powders showed a microstructure consisting of grains with the shape of cube; and average particle size ranging from 75 nm to 150 nm. The investigated temperature dependence of dielectric permittivity of Ba 1–x Tb x TiO 3 ceramics revealed a decrease of the Curie temperature (Tc) with increasing terbium content, and a more pronounced degree of diffuseness of phase transition. The resistivity at room temperature was discussed in terms of positive temperature coefficient of resistance (PTRC) effect. UV–vis reflectance spectra of Ba 1–x Tb x TiO 3 samples showed a decrease of the band gap energy with the increase of Tb amount, due to the band–gap narrowing effect. The photoluminescence spectra recorded for Tb doped BaTiO 3 materials, at 80 K, evidenced the typical f–f luminescence lines of the Tb3+ accompanied the broad luminescence band at about 425 nm due to self–trapped exciton recombination. These results demonstrated that the terbium enhances the dielectric properties and photoluminescence simultaneously, being suitable for electronic applications. [ABSTRACT FROM AUTHOR]

The influence of nickel substitutions on the local structure, dielectric and magnetic properties of Ba hexaferrites is investigated in this study for use as rare earth free permanent magnets and microwave devices, especially. For this purpose, BaNi x Fe 12–x O 19 (x = 0.0, 0.2, 0.5, 0.8 and 1.0) powders were prepared by auto–combustion of their citrate–nitrate gels precursor whilst spark plasma sintering and conventional sintering techniques were used in order to prepare BaNi x Fe 12–x O 19 sintered ceramics samples. Structure, microstructure, dielectric and magnetic properties of BaNi x Fe 12–x O 19 materials were investigated by X-ray diffraction, scanning electron microscopy (SEM), dielectric measurements, Mössbauer spectroscopy and SQUID magnetometry. X-ray diffraction analyses indicated that BaNi x Fe 12–x O 19 , x = 0.0–1.0crystallized on the hexagonal BaFe 12 O 19 structure and, the lattice parameters a and c , decrease as the Ni content increases. Raman spectroscopy analysis confirmed the formation of the BaFe 12 O 19 phase. The presence of Fe in the +3 oxidation state (Fe3+) and of Ni2+ is confirmed by X-ray photoelectron spectroscopy (XPS). The SEM investigations on BaNi x Fe 12–x O 19 powders showed the change of the morphology from a granular-like structure to a platelet-like structure with increasing the nickel content which influences the dielectric and magnetic properties of these materials. Dielectric measurements performed on BaFe 12−x Ni x O 19 ceramics showed consistent differences between the two sintering methods. Impedance analysis shows a contribution of grains and grain boundaries in all samples. The Mössbauer spectroscopy results evidenced the five Wyckoff crystallographic iron positions and their site occupancy with respect to Ni substitutions content. The permanent magnet characteristics of the hexaferrites were confirmed by the high values of coercive field (up to ∼ 1.7 kOe) and remanence (∼28 emu/g), while the saturation magnetization values are found up to 95 emu/g at low temperatures and 70 emu/g at room temperature (for x = 0.8). The coercive field, remanence and maximum energy product decrease with nickel content, while the saturation magnetization behaves unmonotonically due to the specific variation of the site occupancy. More insight into the link between local structure and magnetic properties of Ni substituted Ba hexaferrite was given. • BaNi x Fe 12–x O 19 (x = 0.0–1.0) hexaferrites were prepared by gel auto–combustion. • Dielectric properties are influenced by different sintering methods. • Magnetic moments are sensitive to the local structure of Fe ions. • Ni2+ ions have an improper crystallographic occupation, affecting M S. • Ni2+ substitution caused decrease of H C , M R and (BH) max. [ABSTRACT FROM AUTHOR]

Herein we report on novel multiferroic core-shell nanostructures of cobalt ferrite (CoFe 2 O 4 )-bismuth, sodium titanate doped with barium titanate (BNT-BT 0.08 ), prepared by a two-step wet chemical procedure, using the sol-gel technique. The fraction of CoFe 2 O 4 was varied from 1:0.5 to 1:1.5 = BNT-BT 0.08 /CoFe 2 O 4 (molar ratio). X-ray diffraction confirmed the presence of both the spinel CoFe 2 O 4 and the perovskite Bi 0.5 Na 0.5 TiO 3 phases. Scanning electron microscopy analysis indicated that the diameter of the core-shell nanoparticles was between 15 and 40 nm. Transmission electron microscopy data showed two-phase composite nanostructures consisting of a BNT-BT 0.08 core surrounded by a CoFe 2 O 4 shell with an average thickness of 4-7 nm. Cole-Cole plots reveal the presence of grains and grain boundary effects in the BNT-BT 0.08 /CoFe 2 O 4 composite. Moreover, the values of the dc conductivity were found to increase with the amount of CoFe 2 O 4 semiconductive phase. Both X-ray photoelectron spectroscopy (XPS) and Mössbauer measurements have shown no change in the valence of the Fe 3+ , Co 2+ , Bi 3+ and Ti 4+ cations. This study provides a detailed insight into the magnetoelectric coupling of the multiferroic BNT-BT 0.08 /CoFe 2 O 4 core-shell composite potentially suitable for magnetoelectric applications.