Impact of pH Value on Structural,Thermal, Optical and Raman Studies of Neodymium Phosphate (NdP) Nanoparticles Synthesized by Co-Precipitation Technique

Abstract

The present study deals with the impact of pH value on neodymium phosphate (NdP) nanoparticles which have been successfully synthesized via wet chemical co precipitation technique. PXRD revealed the formation of monoclinic phase, purity and crystallinity. TEM reveals spherical morphology with the formation of slight agglomeration and grain size decrease at low pH as compared to high pH. TGA/DTA suggests that as synthesized nanoparticle shows phase transition above 800^°C. FTIR and Raman spectroscopy signifies slight shifting of bands towards lower wave number at high pH and gives relevant peaks of phosphates (PO₄^3?) group. Optical absorption with selected value of pH were studied in UV-VIS spectrophotometer and showed a strong absorbance with a tendency towards blue shift.     

Concentration Effect of Gd3+ on the Structural,Optical and Spectroscopic Properties of NdVO4 Nanoparticles

Abstract

Neodymium vanadate with concentration of gadolinium as 3% and 5% having general formulae Gd_xNd_1-xVO₄ where x?=?0.03 and 0.05 was prepared by chemical route technique. The effect of concentration of gadolinium on the structural, optical and spectroscopic properties was explained by various characterization techniques. Powder X-ray diffraction study suggests tetragonal zircon structure; various parameters such as crystallite size, volume and X-ray density were calculated. A change in morphology with the change in concentration of gadolinium was observed through scanning electron microscopy. Ultraviolet absorption spectroscopy shows various transitions from ground state to various excited state within 4f shell, and variation in the optical band gap calculated by Tauc plot is due to the incorporation of Gd³⁺ ions.     

Neodymium doped bismuth telluride alloys using chemical reflux method for thermoelectric application

ABSTRACT

This work reports synthesis of pure and neodymium (Nd) doped bismuth telluride (Bi₂Te₃) alloys (Bi_2-xNd_xTe₃, x = 0, 0.5), using reflux method. The X-ray powder diffraction for the as-synthesized Bi₂Te₃ indicates phase purity and crystallographic structure, and agrees well with the prescribed JCPDS data # 000–60601. The Bi_2-xNd_xTe₃ alloys were characterized by pursuing various imaging and spectroscopic techniques including, scanning electron microscope, and UV-Vis absorption spectroscopy. After Nd doping, the micrographs show formation of a new contrast (white phase) with the prominent (201) plane of a hexagonal crystal structure.     

Mesophase configurations and optical properties of mesoporous TiO2 thin films

Highly ordered mesoporous TiO₂ thin films have been successfully synthesized via a copolymer templating sol-gel route. A configuration transition from hexagonal, to cubic, and then to a channel-like structure was observed when the copolymer-templated thin film was thermally annealed from 110 to 450^∘C. In the mesoporous TiO₂ film annealed at 450^∘C, mesopores were merged in a preferential direction, forming a channel-like structure consisting of a semicrystalline (anatase) framework. These films exhibit excellent optical transparency with transmittance higher than 85% in the visible region. A blue shift in UV-Vis absorption onset was shown for the mesoporous TiO₂ films, indicating a size quantization effect of nanocrystalline titania.     

Investigation on structural and electrical properties of BZT ceramics synthesized at low temperature

Abstract

Due to environmental concerns, lead free ceramics such as KNN- NBT and BT have growing interest in applications such as actuators and sensors. Among them Barium Zirconate Titanate (BZT) has become most attractive because it is derived from two perovskite lattice i.e. Barium Titanate (BaTiO₃) and Barium Zirconate (BaZrO₃). It has been reported that Zirconium substitution in titanium lattice enhances the material properties. In the present paper BZT was prepared using solid state route. By adding a mixture of Li₂CO₃ as a sintering aid, the sample could be sintered at 1150?°C having around 94% of the theoretical density. Prepared samples were then subjected to XRD analysis. X-ray diffraction revealed the formation of single phase material. It is observed that the electrical properties of such low-temperature sintered samples are comparable with BZT samples prepared via conventional sintering at a high temperature. It is also observed that the curie temperature shift towards room temperature for a samples sintered at low temperature.     

SBN thin film growth by pulsed laser deposition and study of nonlinear optical properties

Abstract

Strontium barium niobate (Sr_xBa_1?xNb₂O₆) thin films were grown by PLD and characterized as to their structure, composition, and both linear and nonlinear optical properties. Attempted composition of very nearly x'0.61 was achieved, as shown within experimental error of RBS and PIXE techniques. Films deposited with high growth rates and at 700°C substrate temperature resulted polycrystalline on (001)-cut MgO and amorphous on fused silica, while those grown on MgO at lower growth rates were very well oriented with the substrate. A considerable blue shift in the absorption band edge was observed for the disordered SBN:61 films, compared to that for bulk SBN:61 crystal. A broad luminescence band was observed to occur, similar to that for bulk SBN. Degenerate four-wave-mixing techniques were used to study the nonlinear optical response of the amorphous films. A considerable enhancement, by 2 orders of magnitude, of the third order nonlinear susceptibility χ⁽³⁾ in transverse alignment was found to occur with respect to bulk values. A significant squeezing of the coherent response signal was observed in the SBN films.     

LOW-TEMPERATURE MONOCLINIC PHASE IN EPITAXIAL (001) BARIUM TITANATE ON (001) CUBIC SUBSTRATES

ABSTRACT

The possibility of the existence of a low temperature monoclinic phase in epitaxial (001) BaTiO₃ films on a (001) compressive substrate is analyzed theoretically and compared to recent experimental data from literature. There is good agreement between the theoretical findings and the experimentally observed behavior. The formation of the monoclinic phase arises from the point group reduction due to the rotation of the polarization vector commensurate with the variations in the in-plane strain state.     

Dielectric,ferroelectric, and piezoelectric properties of lead-free Ba0.95Ca0.05Ti1-xZrxO3 ceramics

Abstract

Ba_0.95Ca_0.05Ti_1-xZr_xO₃ (BCTZO) ceramics were prepared by a solid state reaction method. The samples were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and X-ray absorption near edge structure (XANES). The ceramics exhibit a pure perovskite structure. The average grain size gradually decreases with increasing Zr concentration. XANES results indicate that the intensities of pre-edge peaks dropped with increasing Zr concentration. The BCTZO ceramic of x?=?0.05 has the optimum electrical properties with the maximum dielectric constant (ε'_m), remanent polarization (2P_r), coercive electric field (2E_c) and piezoelectric charge constant (d₃₃) of 7,244, 12.54 (μC/cm²), 5.29 (kV/cm) and 288 (pC/N), respectively.     

Asymmetric capacitance-voltage characteristics of (Bi3.25, La0.75)Ti3O12 thin films grown on Si

Abstract

Electrical properties of Lamodified bismuth titanate Bi_3.25La_0.75Ti₃O₁₂) thin films for a metal-ferroelectric-insulator-semiconductor (MFIS) structure were investigated with capacitance-voltage (C-V). The MFIS structure exhibits progressively increasing C-V memory window with a sweep voltage due to ferroelectric polarization with suppressed charge injection. Moreover, the asymmetric shift of threshold voltage with a sweep voltage was observed. The flat-band voltage (V_fb2) at the negative sweep was gradually increased with a sweep voltage. The flatband voltage (V_fb1) at the positive sweep decreased at low sweep voltages and then increased at further high voltages (i.e., V_fb1 shift toward the positive direction rather than the negative direction). The asymmetric behavior of C-V characteristics was attributed to negative trapped charges by electron injection from Si.     

Tuning the Wavelength Drift of PZT/PAT Composite Structure

The reflection and absorption performance of orderly porous Pb(Zr_0.52Ti_0.48)O₃ (PZT) on porous alumina template (PAT) structure are investigated, PZT ferroelectric film were deposited on PAT substrate by RF magnetron sputtering process. By controlling the specifications of PZT/PAT nanopores, we could implement the amplitude modulation of absorption edge and reflection. With the decrease of the nanopore size, absorption edge are red shift and the amplitude of the reflection are lower. The wavelength drift between the reflection and absorption has been optimized by changing the thickness of PZT film and structure. This provides an excellent reference to the device of absorption edge/stripe requiring careful tuning.     

Materials Characterization of Cobalt Antimonide Nanostructures as Thermoelectric Material

Abstract

Cobalt antimonide (CoSb₃) nanoparticles, a binary skutterudite structure, are synthesized by following solvothermal method using water as solvent. The solvothermally processed powders are annealed to remove the excess Sb to achieve single phase CoSb₃ nanoparticles, and are examined by X-ray diffraction (XRD) indicating the formation of cubic phase of CoSb₃. The structural analysis by selected area electron diffraction (SAED) and the elemental composition of 1:3 for Co and Sb using energy dispersive X-ray spectrophotometer (EDX) predicts formation of high purity crystalline CoSb₃ nanoparticles. Morphology of the annealed CoSb₃ powders observed using field emission scanning electron microscope (FESEM) and transmission electron microscopy (TEM) indicates particle size of 50-100?nm. The ultraviolet–visible (UV-Vis) absorption spectroscopy estimates an energy gap of 3?eV. The nanosized CoSb₃ skutterudites are potential intermediate-temperature thermoelectric materials with further application in developing efficient thermoelectric modules.     

Investigation of the effects of milling ceramic targets on the optical and electrical properties of BST thin films deposited by RF sputtering

Abstract

The RF sputtering method was utilized to deposit thin films of Ba_1-xSr_xTiO₃ (BST). The targets utilized in these experiments were prepared from ceramic powders with different particle size. The goal of this work is to examine whether the particle size distribution of the target can affect the properties of the thin films fabricated by the sputtering method. The Atomic Force Microscope (AFM) was used to examine the grain size in the thin films. The composition of the thin films and the bulk materials were examined by Fourier Transform Infrared (FTIR) spectroscopy. The dielectric properties of the thin films were measured and compared to its bulk counterparts. It was found that on lattice matched electrodes of SrRuO₃ on LaAlO₃ substrates, the thin films deposited from ceramic targets manufactured from ball-milled powders had finer grain size than those deposited from targets made from unmilled powders. However, this phenomenon was not observed in the case of polycrystalline films deposited on platinized silicon wafers.     

High quality BaxSr1-xTiO3 films grown by mocld and novel ferroelectric/ferrite structures for dual-tuning microwave devices

Abstract

Excellent single crystal Ba_xSr_1-xTiO₃ (BST) films were grown on LaAlO₃ substrates using the metal-organic chemical liquid deposition (MOCLD) method. Very low losses (tanδ ∽0.002-0.008) were measured from these films at 400 KHz. Biaxially oriented BST films were successfully grown on polycrystalline YIG substrates using both MOCLD and pulsed laser deposition methods with biaxially oriented MgO and YSZ buffer layers. The dielectric losses of the films range from 0.005 to 0.015 while 25% of dielectric constant change was observed with 40V bias voltage up to 10 MHz. Both the dissipation and dielectric constant of the films remained nearly constants over a wide temperature range (77 K to 380 K). A dual-tuning microwave coplanar phase shifter using a BST film grown on a MgO buffered polycrystalline YIG substrate was fabricated. A significant phase shift was observed in GHz frequency range when an electric bias or a magnetic field was applied to the device.     

Qualitative identification of nitrate nitrogen in compound fertilizers by infrared spectroscopy

ABSTRACT

In this study, NPK compound fertilizers containing nitrate nitrogen were tested by Fourier transform infrared spectroscopy (FTIR), and the relative contents of nitrate nitrogen and qualitative comparison were qualitatively identified. The raw materials of compound fertilizers: agricultural ammonium nitrate (AN), potassium nitrate (KNO₃) and ammonium phosphate (NH₄)₂HPO₄ were analyzed by infrared spectroscopy respectively. The results showed that the absorption peaks of nitrate (NO₃^?1) in solid agricultural fertilizers were 1384 cm^?1, 825 cm^?1. Furthermore, the NPK compound fertilizer with 4%, 5.5%, 6% and 9.5% nitrate nitrogen content were respectively tested by infrared spectroscopy. The results showed that with the increase of nitrate nitrogen content in the compound fertilizers, the relative intensity of the infrared absorption peaks of nitrate increased as well. Moreover, the relative intensity of the absorption peaks at 1384 cm^?1 and 825 cm^?1 are proportional to the content of nitrate in the nitro-compound fertilizer-containing ammonium nitrogen and nitrate nitrogen.     

Structural study of (1-x)BNKLT-xBZT ceramics using XRD,Raman spectroscopy and XAS

Abstract

The aim of this work is to study the structural phase of (1-x)Bi_0.5(Na_0.74K_0.16Li_0.10)_0.5TiO₃–xBaZr_0.05Ti_0.95O₃ ((1-x)BNKLT-xBZT) ceramics with various x content between 0.025 and 0.150?mol% synthesized via the combustion method. The X-ray diffraction (XRD), Raman spectroscopy and X-ray absorption spectroscopy (XAS), including X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), were used to investigate the structural phases of all samples. The XRD pattern and Raman spectra revealed coexisting phases of rhombohedral (R) and tetragonal (T) in all compositions. As the BZT content increased, the phase formation in these samples exhibited higher tetragonality. The quantity of each phase in (1-x)BNKLT-xBZT ceramics can be determined by the XAS technique with Ti K-edge measurements. Increasing the BZT content from 0 to 0.15?mol% caused the R phase to suddenly deceased from 60.9% to 20% while the T phase rapidly increased from 39.1% to 80%. The phase of the structural was determined by several alternative strategies including XRD, Raman and XAS techniques.     

Synthesis and characterization of mixed iodide–bromide methylammonium lead perovskite

Abstract

The research field of perovskite based solar cells has recently been developed as the most promising candidate for next-generation because of their high efficiency solar cell technology that is compatible with low-cost, low-temperature processing, long-term stability and simple structure of solar cells production such as the hybrid halide perovskite CH₃NH₃PbI₃ in solar cells have high power conversion efficiency exceeding 22%. However, the unstable nature of perovskite was observed when exposing it to continuous moisture, illumination and high temperature obstructing the commercial development in the long run and thus becoming the main problem that needs to be solved immediately. In this work, the preparation of organic – inorganic halide perovskite by mixing halide group between iodide with bromide, CH₃NH₃PbI_xBr_3-x compound under the annealing temperature condition was investigated. The structure of the product was identified by X-ray diffraction (XRD). In addition, High Resolution SEM image was used to study the presence morphology of crystalline domains within the sample. We examine the thermal properties of samples using Thermogravimetric analysis (TGA) and Simultaneous Thermal Analyzer (STA). To check the variation of optical properties in these compounds, we measured the UV-visible absorption spectroscopy and X-ray Photoelectron Spectroscopy (XPS) which showed the survival of organic group. It is concluded that the annealing affects phase formation and thermal stability of CH₃NH₃PbI_xBr_3-x compounds. A small powder amount of lead bromide (PbBr₂), a product of the degradation, was observed with increasing annealing temperature. Accordingly, appropriate annealing temperature should be chosen to produce a high efficiency photovoltaic.     

Investigation of the Effects of Acid Content and Annealing on the Properties of Nanostructured TiO2 Sol

Abstract

Titanium dioxide (TiO₂) sol was prepared using tetrabutyl titanate as a precursor via an acid catalyzed sol-gel process. Investigation of the effects of acid content and annealing on the properties of nanostructured TiO₂ materials. The influence of acid content on the sol density, viscosity, stability and particle size were studied and based on the kinematic viscosity data, Gibbs energies of activation for viscous flow (ΔG*) were also calculated. Furthermore, the prepared samples were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and ultraviolet-visible (UV-Vis) spectrophotometer. The results showed that the increase of acid content nearly had no obvious influence on the chemical structure of TiO₂ sol. With the increase of annealing temperature, titanium dioxide changes from amorphous phase to crystalline phase, anatase coexists with rutile at 600?°C, sample absorbance increases, and the edge of UV-Vis spectra shows red shift. Ti-O-Ti bond is the main structure of TiO₂ sol, and the formed TiO₂ molecule has linear structure.     

Thin film BaxSr1-xTiO3 ku- and k-band phase shifters grown on MgO substrates

Abstract

We report measurements of gold circuits fabricated on four Ba_xSr_1-xTiO₃ ferroelectric films doped with 1% Mn grown on MgO substrates by laser ablation. Low frequency (1 MHz) measurements of σ_T and tanδ on interdigital capacitors are compared with high frequency measurements of phase shift and insertion loss on coupled microstrip phase shifters patterned onto the same films. The variation in temperature of both high and low frequency device parameters is compared. Annealed with amorphous buffer layer and unannealed films are compared. Room temperature figures of merit of phase shift per insertion loss of up to 58.4°/dB at 18 GHz and 400 V dc bias were measured.     

Preparation and physical properties of Nano-ZnSe/SiO2 mesoporous composite for assembly system

A novel synthesis route of ZnSe/gel-glass mesoporous composite was described. $ {\text{SeO}}_{4} ^{{2 - }} $ and Zn²⁺ were loaded into the porous framework of silica gel-glasses by immersion. Followed by drying and the reductive thermal treatment, the transparent, homogeneous ZnSe/SiO₂ samples with the color of light yellow were prepared. The specific surface area, grain size, structure and phase properties of nano-sized ZnSe/SiO₂ mesoporous composites were studied by powder X-ray diffraction, nitrogen sorption, SEM. The effects of pore structure properties and loading solution concentration on the optical absorption of ZnSe/SiO₂ were investigated by UV-vis absorption. It is found that the optical absorption edges of ZnSe nanoparticles in mesoporous silica shift to the red as ZnSe loading concentration increases, which is attributed to the quantum size effect. The nonlinear optical property of these samples was presented by the open aperture z-scan technique. This method has some potential advantages in comparison to the conventional methods.