Color-tunable and white emission of Tm3+ doped transparent zinc silicate glass-ceramics embedding ZnO nanocrystals

Tm³⁺ doped zinc silicate glass-ceramics composed of SiO₂-Al₂O₃-ZnO-K₂O-Tm₂O₃ embedded with ZnO nanocrystals were successfully fabricated by melt-quenching method with subsequent heat treatment. Tm³⁺ ions and ZnO nanocrystals were introduced as blue and yellow luminescence centers, respectively. The effects of heat treatment, excitation wavelength and Tm³⁺ doping concentration on the photoluminescence behaviors of these glass-ceramics were studied. Short-time (5 minutes) heat treatment was considered as the optimal heat treatment time, which facilitates simultaneously emitting narrow blue peak located at 453 nm and a broad yellow band centered at 580 nm. Blue and yellow emissions could be attributed to the ¹D₂ → ³F₄ transition of Tm³⁺ and Zn_i/O_i-related defect emission of ZnO nanocrystals, respectively. The combination of these two emissions allows the realization of white light emitting in the glass-ceramic samples. Furthermore, tunable luminescent color and chromaticity coordinates, including yellow, white and blue, can be realized by varying the pumping wavelengths as well as the content of Tm³⁺ dopant in the glass matrix. Nearly perfect white light emission with Commission Internationale de l'Eclairage coordinate (x = 0.33, y = 0.32) was achieved for the 0.05 mol% Tm³⁺ doped glass-ceramic embedding ZnO nanocrystals by heat treatment at 750°C for 5 minutes under the excitation of 360 nm. These luminescent glass-ceramics doped with Tm³⁺ ion and ZnO nanocrystals could be a promising candidate for white light emitting devices under near-ultraviolet excitation.     

Structure,Raman and luminescence characteristics of Zn1-xHfxO (0≤x≤0.1) nanocrystals prepared via N-(methyl)mercaptoacetamide assisted microwave approach

A series of Zn_1-xHf_xO (0 ≤ x ≤ 0.1) nanocrystals was synthesized via the N-(methyl)mercaptoacetamide assisted microwave approach. The influence of the Hf dopant on the crystal structure, Raman lattice vibrations, and luminescent emission spectra was studied. XRD measurements revealed that the inclusion of the Hf dopant in the Zn cites instigated the expansion of the ZnO lattice while preserving its hexagonal structure. The XRD, SEM and DLS measurements demonstrated that the Hf dopant increased the size of ZnO nanocrystals from 2.5 ± 0.1 nm to 11.5 ± 0.1 nm. The EDS spectra confirmed the stoichiometry of the prepared samples. The zeta potential measurement revealed that the Hf dopant is incorporated within the ZnO nanostructure. The Raman spectra showed that the Hf dopant was efficiently incorporated into the ZnO crystals without altering its internal structure. The UV–vis. spectroscopy indicated that the partial substitution of Zn atoms by Hf atoms leads to modulation of the optical bandgap. Luminescence measurements revealed that the inclusion of the Hf dopant in the Zn cites resulted in suppression of the ZnO crystal defects. The XPS measurements confirmed that the inclusion of Hf dopant in the Zn cites resulted in a reduction of the amount of oxygen vacancy which actes as a trap centers for the photogenerated electrons. Therefore, a modulation of the visible spectra occurred, while the Hf dopant did not affect the intensity of UV-emission band of ZnO nanocrystals. Therefore, the Zn_1-xHf_xO (0 ≤ x ≤ 0.1) nanocrystals are favorable as potential candidates for both catalytic and luminescent device applications.     

Structure and luminescence properties of Eu3+ doped TiO2 nanocrystals and prolate nanospheroids synthesized by the hydrothermal processing

We report on a new approach to the synthesis of Eu³⁺ doped TiO₂ nanocrystals and prolate nanospheroids. They were synthesized by shape transformation of hydrothermally treated titania nanotubes at different pH and in the presence of Eu³⁺ ions. The use of nanotubes as a precursor to the synthesis of Eu³⁺ doped TiO₂ nanocrystals and prolate nanospheroids opens the possibility of overcoming the problems related to molecular precursors. The shapes and sizes of the nanotubes, Eu³⁺ doped TiO₂ nanocrystals and prolate nanospheroids were characterized by transmission electron microscopy (TEM) technique. Crystal structures of the resultant powders were investigated by X-ray diffraction (XRD) analysis. The percentage ratio of Eu³⁺ to Ti⁴⁺ ions in doped nanocrystals was determined using inductively coupled plasma atomic emission spectroscopy. The optical characterization was done by using fluorescence and ultraviolet-visible reflection spectroscopies. An average size of faceted Eu³⁺ doped TiO₂ nanocrystals was 13 nm. The lateral dimensions of Eu³⁺ doped TiO₂ prolate nanospheroids varied from 14 to 20 nm, while the length varied from 40 to 80 nm, depending on precursor concentrations. The XRD patterns revealed the homogeneous anatase crystal phase of Eu³⁺ doped TiO₂ nanocrystals and prolate nanospheroids independently of the amount of dopant. A postsynthetic treatment (filtration or dialysis) was applied on the dispersions of the doped nanoparticles in order to study the influence of the dopant position on photoluminescence (PL) spectra. In the red spectral region, room temperature PL signals associated with ⁵D₀ → ⁷F_J (J = 1–4) transitions of Eu³⁺ were observed in all samples. The increased contribution of dopants from the interior region of dialyzed nanocrystals to photoluminescence was confirmed by the increase of R value.     

Structural,optical, morphological properties of silver doped cobalt oxide nanoparticles by microwave irradiation method

The synthesis of silver doped cobalt oxide nanoparticles by microwave-assisted method and their structural, optical, antibacterial activities are presented in this study. The doping concentrations were chosen as 5, 10, 15, and 20 wt percentages. The sample was undergone powder X-ray diffraction studies and the result shows the good crystalline nature of the sample. Also, the average crystallite size increases from 13.95 nm, 21.26 nm, 26.13 nm, and 28.35 nm with different doping concentrations. The transmission electron microscopy image shows cubic and spherical morphology. The optical properties were tested by UV–vis–NIR absorption spectrum. It indicates the decrease of band gap value. From the antibacterial activity studies, the 20 wt % Ag doped nanoparticles exhibit better activity.     

Structural,morphological, and optical properties of strontium doped lead-free BCZT ceramics

We report the synthesis of Sr²⁺ doped Ba_0.9-xCa_0.1Sr_xTi_0.8Zr_0.2O₃ nano-ceramics by the conventional solid-state reaction method. Phase formation of single-phase orthorhombic ABO₃ type structure with space group P2mm was confirmed through X-ray diffraction (XRD). The crystallite size increased with increasing doping concentration from 25.46 nm to 52.96 nm as calculated by the Scherrer formula and from 47.1 nm to 88.5 nm by the Williamson-Hall method. The lattice parameter, dislocation density, and apparent density decreased with doping, except for when x = 0.05. The porosity was found to increase up to 16.8% with increasing doping. Field emission scanning electron microscopy (FESEM) shows that samples exhibit a flake-like structure. X-ray photoelectron spectroscopy (XPS) analysis confirms that Sr-ions occupy the Ca-site, for x = 0.05, and force the Ca ions to occupy the Ti-sites. For the higher concentration of Sr, i.e. x ≥ 0.15, no more forced substitution is observed and Sr-ions occupy the Ba-site only, which decreases oxygen vacancies. Diffused rings observed in selective area electron diffraction (SAED) patterns indicate the high crystalline order of the samples. The Fourier-transformed infrared spectroscopy (FTIR) measurements show a single broad peak between 544 and 594 cm^?1 for all the compositions, while two prominent peaks are observed for the composition x = 0.05 at 528 cm^?1 and 592 cm^?1. The Raman spectra show a shift in the most prominent peak, observed approximately 517 cm^?1.     

Influence of Cobalt Doping on the Physical Properties of Zn<Subscript>0.9</Subscript>Cd<Subscript>0.1</Subscript>S Nanoparticles

Zn_0.9Cd_0.1S nanoparticles doped with 0.005–0.24 M cobalt have been prepared by co-precipitation technique in ice bath at 280 K. For the cobalt concentration >0.18 M, XRD pattern shows unidentified phases along with Zn_0.9Cd_0.1S sphalerite phase. For low cobalt concentration (≤0.05 M) particle size, d _XRD is ~3.5 nm, while for high cobalt concentration (>0.05 M) particle size decreases abruptly (~2 nm) as detected by XRD. However, TEM analysis shows the similar particle size (~3.5 nm) irrespective of the cobalt concentration. Local strain in the alloyed nanoparticles with cobalt concentration of 0.18 M increases ~46% in comparison to that of 0.05 M. Direct to indirect energy band-gap transition is obtained when cobalt concentration goes beyond 0.05 M. A red shift in energy band gap is also observed for both the cases. Nanoparticles with low cobalt concentrations were found to have paramagnetic nature with no antiferromagnetic coupling. A negative Curie–Weiss temperature of −75 K with antiferromagnetic coupling was obtained for the high cobalt concentration.     

B-site acceptor doped AgNbO3 lead-free antiferroelectric ceramics: The role of dopant on microstructure and breakdown strength

B-site aliovalent modification of AgNbO₃ with a nominal composition of Ag(Nb_1-xM_x)O_3-x/2 (x = 0.01, M = Ti, Zr and Hf) was prepared. The effects of dopants on microstructure, dielectric, ferroelectric and conduction properties were investigated. The results indicate that the introduction of acceptor dopant does not lead to grain coarsening. Zr⁴⁺ and Hf⁴⁺ doping are beneficial to stabilize the antiferroelectric phase of AgNbO₃. Among all the samples, Ti⁴⁺ doped AgNbO₃ has the minimum resistivity while Hf⁴⁺ doped AgNbO₃ has the maximum resistivity, therefore, Hf⁴⁺ doped AgNbO₃ has high BDS. The XPS results indicate that the conduction behaviour is associated with the concentration of oxygen vacancies. This work hints that acceptor dopant is also effective on the microstructure control and chemical modification of AgNbO₃-based ceramics.     

Effect of silver (Ag) ions irradiation on the structural,optical and photovoltaic properties of Mn doped TiO2 thin films based dye sensitized solar cells

Dye sensitized solar cell (DSSC) is an emerging energy harvesting tool which converts direct sunlight into electrical energy. These cells have much better properties in contrast with silicon based solar cells because of their flexible nature, light weight, low cost, environment friendly nature, and involvement of a simple manufacturing process. Since, a photoanode is the backbone of DSSC, we synthesized a pure and 1% manganese (Mn) doped titanium dioxide (TiO₂) films by sol-gel method which are irradiated with silver (Ag) ions at two different concentrations (2 × 10¹⁴ and 4 × 10¹⁴) ions-cm^?2. X-ray diffraction revealed that Mn doping followed by Ag irradiation transformed TiO₂ from pure anatase to rutile phase. Ultraviolet–visible spectroscopy exposed the reduction in band gap of TiO₂ film during this doping and irradiation process. Therefore, absorption is enhanced with red shift in UV-range. When these films are used as a photoanode in DSSC, 1% Mn doped TiO₂ film exposed with Ag at the concentration of (2 × 10¹⁴) ions-cm^?2 exhibited maximum efficiency of 2.40%.     

Ultra-rapid microwave-assisted synthesis of gallium doped zinc oxide for enhanced photocurrent generation

Ultra-rapid microwave-assisted hydrothermal synthesis was performed, zinc oxide nanoparticles were fabricated and doped with gallium. Different times (5, 15, and 30 min) and concentrations of doped Ga (1, 3, and 6%) were used to improve their characteristic properties. In addition, the relation between time/dopant was analyzed. The samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and UV–Vis diffuse reflectance spectroscopy. Photoluminescence (PL) to verify number of defects. SEM analysis showed the formation of nanorods morphology even with a short synthesis time. The X-ray diffractograms and Raman spectra suggest the successful insertion of Ga into the ZnO lattice. The crystallite size obtained by doping was between 36 and 50 nm. The lattice parameters determined by the Rietveld refinement confirmed the formation of a wurtzite hexagonal structure. The band gap range found was 3.12–3.22 eV, which increases the potential of ZnO for optical applications. The presence of defects as result of doping was confirmed by PL. The microstructural changes of the material are enhanced by doping, which causes the photocurrent to increase from 0,002 to 0.012 mA/cm² in doped ZnO. The synthesis time and Ga doping facilitated the production of ZnO nanoparticles with improved properties.     

Preparation of Gadolina Stabilized Bismuth Oxide Doped with Boron via Electrospinning Technique

In this study, boron doped and undoped poly (vinyl) alcohol/bismuth–gadolina acetate (PVA/Bi–Gd) nanofibers were prepared using electrospinning technique then calcinated at 800 °C for 2 h. The originality of this study is the addition of boron to metal acetates. The effects of boron doping were investigated in terms of solution properties, morphological changes and thermal characteristics. The characteristics of the fibers were investigated with FT-IR, XRD, SEM and BET. The addition of boron did not only increase the thermal stability of the fibers, but also their diameters, which yielded stronger fibers. XRD analyses showed that boron doping increased the peak intensities and indicated that the boron doping enhanced the crystallite size. Moreover, no shifts were noticed in diffraction angles for boron doped and undoped samples. Therefore, boron doping did not significantly alter the lattice spacing. The SEM micrograph of the fibers showed that the addition of boron resulted in the formation of cross-linked bright-surfaced fibers. The average fiber diameter for boron doped and undoped fiber mats were 204 and 123 nm, respectively. Also, grain diameters of boron doped and undoped nanocrystalline sintered powders were measured as 140 and 118 nm, respectively. The BET results showed that boron undoped and doped Bi₂O₃–La₂O₃ nanocrystalline powder ceramic structures sintered at 800 °C have surface areas of 59.72 and 39.80 m²/g, respectively.     

How different dopants leads to difference in photocatalytic activity in doped TiO2?

This study explores the significance of dopant location in a doped TiO₂ nanostructure in ascertaining its photocatalytic properties. The un-doped TiO₂, boron-doped TiO₂ (B–TiO₂) and nitrogen-doped TiO₂ (N–TiO₂) photocatalysts were synthesized (with variable dopant concentrations) via sol-gel method. The photocatalysts were further characterized for structural, surface, and physico-chemical properties in reference to their influence on photocatalytic properties. The results of X-ray diffraction (XRD), micro Raman, Energy dispersive X-ray technique (EDX), X-ray photoelectron spectroscopy (XPS), and Fourier Transform infrared spectroscopy (FTIR) confirmed the existence of B and N atoms in the TiO₂ crystal lattice. The results also indicated that the B and N doping promoted the formation of rutile phase in doped TiO₂. Further, B doping leads to decrease in the surface area whereas N doping leads to increase in surface area of TiO₂. The UV–Vis DRS analysis revealed that a red shift in absorption band edge occurs upon B and N doping. The band gap values also decreased to 2.96 and 2.27 eV in B–TiO₂ and N–TiO₂, respectively in comparison to 2.98 for un-doped TiO₂. The photocatalytic degradation studies of diclofenac sodium (DCLF) were conducted to examine the effect of dopant role on the efficiency of doped photocatalyst. B–TiO₂ exhibited maximum photocatalytic activity by degrading 98% of DCLF in comparison to N–TiO₂, which showed 95% degradation.     

Aqueous Solution Preparation,Structure, and Magnetic Properties of Nano-Granular ZnxFe3?xO4 Ferrite Films

This paper reports a simple and novel process for preparing nano-granular Zn_xFe_3−xO₄ ferrite films (0 ≤ x ≤ 0.99) on Ag-coated glass substrates in DMAB-Fe(NO₃)₃-Zn(NO₃)₂ solutions. The deposition process may be applied in preparing other cations-doped spinel ferrite films. The Zn content x in the Zn _x Fe_3−x O₄ films depends linearly on the Zn²⁺ ion concentration ranging from 0.0 to 1.0 mM in the aqueous solutions. With x increasing from 0 to 0.99, the lattice constant increases from 0.8399 to 0.8464 nm; and the microstructure of the films changes from the non-uniform nano-granules to the fine and uniform nano-granules of 50–60 nm in size. The saturation magnetization of the films first increases from 75 emu/g to the maximum 108 emu/g with x increasing from 0 to 0.33 and then decreases monotonously to 5 emu/g with x increasing from 0.33 to 0.99. Meanwhile, the coercive force decreases monotonously from 116 to 13 Oe.     

Effect of lanthanide doping on crystal phase and near-infrared to near-infrared upconversion emission of Tm doped KF–YbF3 nanocrystals

Tm³⁺ doped KF–YbF₃ nanocrystals were synthesized by a hydrothermal method using oleic acid as a stabilizing agent at 190 °C. The influence of Gd³⁺ and Sm³⁺ content on the phase structure and upconversion (UC) emission of the final products was investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and UC spectra. XRD analyses and TEM observations evidence that the phase and size of the as prepared Tm³⁺ doped KF–YbF₃ nanocrystals are closely related to the Gd³⁺ doping content. Without Gd³⁺ impurity, the undoped nanocrystals crystallize in orthorhombic KYb₂F₇ with an average diameter of 42 nm. When the Gd³⁺ doping is below 10 mol%, the orthorhombic KYb₂F₇ nanocrystals grow up. However, with Gd³⁺ addition beyond about 30 mol%, the complete phase transformation from orthorhombic KYb₂F₇ to cubic KGdF₄ occurs in the final products. Under the excitation of a 980 nm laser diode, the as prepared Tm³⁺ doped nanocrystals exhibit strong near-infrared UC emission at 800 nm. Particularly, the intensity of high energy UV and blue UC emissions of Tm³⁺ ions in Tm³⁺ doped KYb₂F₇ nanocrystals are selectively reduced compared to the NIR emission at 800 nm by co-doping a small amount of Sm³⁺ ions into the host matrix. Possible dynamic processes for UC emissions in Tm³⁺ doped nanocrystals are discussed in detail.     

Synthesis of Ni doped barium hexaferrite by microemulsion route to enhance the visible light-driven photocatalytic degradation of crystal violet dye

The pristine and Ni doped BaNi_xFe_12-xO₁₉ (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) NPs have been fabricated via facile microemulsion approach and the impact of dopants was explored based dielectric, optical, structural and the photocatalytic properties of BaNi_xFe_12-xO₁₉ nanoparticles. X-ray diffraction and Raman study confirmed the formation of regular hexagonal geometry with space group P6₃/mmc with crystallite size in 32–50 nm range. Functional groups were identified using FTIR analysis. The remanence (Pr), saturation polarization (Ps) and coercivity (Hc) was explored by P-E loop analysis and the value of Pr and Ps was enhanced with the concentration of dopant. According to PL spectra, highly doped materials had a higher charge separation (e^?- h⁺) and low recombination rate, which resulted in higher photocatalytic degradation activity of fabricated nanomaterials. The optical band gap was found to be 1.78 eV versus undoped (2.60 eV for pristine BaFe₁₂O₁₉). Due to polarizations, the dielectric loss, dielectric constant and tangent loss values were declined, while AC conductivity was enhanced. Photocatalytic performance of doped and undoped samples under visible right irradiation was studied for crystal violet dye. For 100 min exposure to visible light, the highly doped catalyst exhibits 97% degradation versus 60% in case of pristine this is attributed to efficient electron-hole pair separation. Furthermore, quenching effect of different scavengers indicated that hydroxyl radical had a main role, and e^? or h⁺ played a minimal role in CV dye degradation. The enhanced properties due to doping make BaNi_xFe_12-xO₁₉ a potential candidate for photocatalytic applications under visible light irradiation.     

Influence of Cr and Fe doping on the structure,magnetic and optical properties of nano CuCo2O4

Nano CuCo_2-xM_xO₄ (x = 0, 0.1, 0.2, M = Cr or Fe) samples were synthesized by hydrothermal method. Synchrotron x-ray diffraction data obtained for the samples were subjected to phase analysis and manifested a single-phase cubic spinel structure for Cr-doped samples, while for Fe-doped samples two phases were identified. Cation distribution and cell parameter (a) were obtained from Rietveld X-ray diffraction analysis. FTIR analysis affirmed the formation of the cubic spinel and the cation distribution obtained. The nano nature of the samples and the particle morphology were examined by high-resolution transmission electron microscope (HRTEM) with selected area electron diffraction (SAED). UV-diffuse reflectance revealed that all samples have two optical energy gaps. For all Fe doped samples, the optical band gaps decreased, while for Cr-content x = 0.1 the bandgaps increased then reduced for x = 0.2. Doped samples exhibited a blue or red shift depending on the kind and amount of the dopant ions. The PL intensity and the emitted colors depended on the kind and amount of the dopant ions. Magnetic measurements disclosed the paramagnetic nature of CuCo₂O₄, while a weak ferromagnetic is revealed for CuCo_2-xCr_xO₄ and a ferromagnetic nature for CuCo_2-xFe_xO₄. Lowering the bandgap upon doping could make better mobility of lattice oxygen and enhancing the catalyst reducibility. Thus, the Cr and Fe-doped samples are expected to have better catalytic activity than the pristine one.     

Hydrothermal formation and up‐conversion luminescence of Er3+‐doped GdNbO4

The effect of concentration of Er³⁺ on the up‐conversion and photoluminescence properties of Gd_1.00?xEr_xNbO₄, x=0‐0.50 which has monoclinic fergusonite‐type structure as a main phase has been investigated, using a processing technique based on hydrothermal method. Under weakly basic hydrothermal condition at 240°C for 5 hours, a single phase of fergusonite‐type Gd_1.00?xEr_xNbO₄ solid solution was directly formed as nanocrystals by the substitutional incorporation of Er³⁺ into GdNbO₄ because of the gradual and linear decrease in the lattice parameters of the monoclinic phase corresponding to the Vegard's Law. The gadolinium niobate doped with 2 mol% Er³⁺, Gd_0.98Er_0.02NbO₄ after heating at 1300°C for 1 hour, which has nanocrystalline structure whose crystallite size is around 29 nm, exhibits the highest photoluminescence intensity in the green spectral region, 515‐560 nm under excitation at wavelength of 254 nm. On the other hand, the up‐converted luminescence intensity of the niobate nanocrystals becomes the maximum at the concentration of 20 mol% Er³⁺, Gd_0.80Er_0.20NbO₄ under excitation at 980 nm. These results demonstrate that the material, Er³⁺‐doped GdNbO₄ nanocrystals prepared through hydrothermal route and postheating has potential for up‐converting phosphor.     

Optimization of Opto-Electrical and Photocatalytic Properties of SnO<Subscript>2</Subscript> Thin Films Using Zn<Superscript>2+</Superscript> and W<Superscript>6+</Superscript> Dopant Ions

Abstract  

A series of Zn²⁺ and W⁶⁺ doped tin oxide (SnO₂) thin films with various dopant concentrations were prepared by spray pyrolysis deposition, and were characterized by X-ray diffraction, atomic force microscopy, contact angle, absorbance, current density–voltage (J–V) and photocurrent measurements. The results showed that W⁶⁺ doping can prevent the growth of nanosized SnO₂ crystallites. When Zn²⁺ ions were used, the crystallite sizes were proved to be similar with the undoped sample due to the similar ionic radius between Zn²⁺ and Sn⁴⁺. Regardless of the dopant ions’ type or concentration, the surface energy has a predominant dispersive component. By using Zn²⁺ dopant ions it is possible to decrease the band gap value (3.35 eV) and to increase the electrical conductivity. Photocatalytic experiments with methylene blue demonstrated that with zinc doped SnO₂ films photodegradation efficiencies close to 30% can be reached.     

Smooth and highly-crystalline Ag-doped CIGS films sputtered from quaternary ceramic targets

Sputtering with copper indium gallium selenide (CIGS) ceramic targets could produce smooth CIGS thin films that are preferred for preparing two-terminal tandem devices. However, grain sizes prepared in this way are small and device efficiency was low. To increase the grain size, in this report, an Ag layer was pre-sputtered beneath CIGS. The Ag doping layer increased the grain size and improved the crystalline alignment. Consequently, the Ag-doped films exhibited improved charge mobility. From X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy characterizations, we obtained an optimized Ag thickness of 15 nm. Short-circuit current density (J_SC), open-circuit voltage (V_OC), and fill factor (FF) were all improved after doping with 15-nm Ag. Increasing the annealing temperature from 550 °C to 575 °C, the grains was enlarged further, with the power conversion efficiency (PCE) increasing to 14.33% and V_OC to 545 mV. Upon the smooth CIGS film, a thin conformal perovskite layer was fabricated without polishing. This work demonstrates a simple way to fabricate smooth and highly-crystalline CIGS films that can be used for tandem solar cells.     

Effects of Mn-Doping on the Properties of BaBi4Ti4O15 Bismuth Layer Structured Ceramics

Bismuth-layer-structured (Ba_1−x Mn _x )Bi₄Ti₄O₁₅ (0.0 ≤ x ≤ 0.8) ceramics were prepared by a Sol–Gel method. The effects of the amount of Mn-doped on the phase structure, the dielectric as well as piezoelectric properties of BaBi₄Ti₄O₁₅ ceramics were studied. The X-ray diffraction results revealed that the introduction of Mn resulting in distortion of lattice, which contributes to the crystallization of the layered structure grains. The densification, dielectric and piezoelectric properties of the (Ba_1−x Mn _x )Bi₄Ti₄O₁₅ ceramics were significantly promoted by the Mn substitution of Ba. When the value of doping amount Mn is 0.4, the (Ba_0.6Mn_0.4)Bi₄Ti₄O₁₅ ceramic exhibited a high piezoelectric constant (d ₃₃ = 7.5 pC/N), a big relatively dielectric constant (ε _r  = 764.26) and a small dielectric loss (tanδ = 0.0124).     

Enhanced photocatalytic activity of Ag doped TiO2 nanoparticles synthesized by a microwave assisted method

Pure anatase TiO₂ photocatalyst with different Ag contents was prepared via a controlled and energy efficient microwave assisted method. The prepared material was further characterized by several analytical techniques like X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), surface area measurement (BET), Fourier transform-infrared spectroscopy (FT-IR), diffused reflectance spectroscopy (DRS), and thermogravimetric–differential thermal analysis (TGA–DTA). A 10 nm average crystallite size with nano-crystals of pseudo-cube like morphology was obtained for optimal (0.25 mol%) Ag doped TiO₂. The present research work is mainly focused on the enhancement of degradation efficiency of methyl orange (MO) by doping of Ag in TiO₂ matrix using UV light (365 nm). A 99.5% photodegradation efficiency of methyl orange was achieved by utilizing 0.25 mol% Ag doped TiO₂ (1 g/dm³) at pH=3 within 70 min. Recyclability of photocatalyst was also studied, with the material being found to be stable up to five runs.