Irregularly-shaped Grains Research Articles

Photocatalytic activity (dye degradation) of pristine and doped LaFeO3 (dopant Y at a site and Ni at B site) by impedance spectroscopy

Lanthanum iron oxide (LaFeO3) nanoparticles, doped with yttrium (Y) at the A-site and nickel (Ni) at the B-site, were synthesized using a sol-gel method at 600 °C. This study focuses on the synthesis of nanocrystalline La1−xYxFeO3 (Y doped LaFeO3), LaFe1−xNixO3 (Ni doped LaFeO3) and La1−xYxFe1−xNixO3 (Y/Ni doped LaFeO3) materials, where x = 0.01. The Synchrotron-based XRD analysis confirmed the single-phase formation of orthorhombic LaFeO3 (Pbnm space group) in each sample. The characterization through scanning electron microscopy and EDX revealed grains of irregular shape with an average particle size of around 200 nm. Optical properties were explored using UV–Visible spectroscopy, indicating a band gap of 1.7 eV for the pure sample. Additionally, the photocatalytic properties of the synthesized nanoparticles were evaluated for dye degradation. Electrical properties were systematically examined using impedance spectroscopy across a frequency range of 1 Hz–10 MHz at room temperature. The effect of doping on crystal structure and possible implications on dielectric and photocatalytic properties were studied. The complex impedance diagram displayed a depressed semicircle, suggesting non-Debye relaxation processes. A correlation was established between impedance and UV–Vis spectroscopy. However, the current literature lacks a comprehensive investigation for isovalent i.e. +3 substitution at A and B site simultaneously for dye degradation properties of LaFeO3-based materials. This study addresses this research gap by systematically exploring the influence of separate as well as simultaneous Y+3 and Ni+3 doping on the structural, optical, electrical, and photocatalytic characteristics of LaFeO3 nanoparticles, thereby providing valuable insights for the development of advanced functional materials for environmental applications. It was found that Y+3 dopants had a notable impact on the dye degradation properties for Mythlene blue dye at room temperature.

Wear-resistant CrCoNi-(Ti, Al) medium-entropy alloy coatings prepared by laser cladding on CrCoNi medium-entropy alloy and their microstructural characteristics

Three medium-entropy alloy (MEA) coatings (CrCoNi, CrCoNi-Ti and CrCoNi-Al) were prepared by laser cladding on a CrCoNi MEA alloy to obtain enhanced surface wear resistance. The CrCoNi coating is composed of columnar grains (face centered cubic (FCC) structure) with typical epitaxial growth features, while the CrCoNi-Ti coating is mainly comprised of FCC irregularly-shaped grains with high-density substructures. As for the CrCoNi-Al coating, it consists of lamellar structures with alternating equiaxed and columnar grains, both of which mainly correspond to BCC phase with a small amount of FCC phase. Compared to the substrate, the hardnesses of the CrCoNi, CrCoNi-Ti, and CrCoNi-Al coatings are enhanced by 7.3 %, 79.1 %, and 209.6 %, respectively. Wear experiments show that the CrCoNi coating is less wear-resistant than the substrate, while there are 14.1 % and 39.7 % enhancements for the CrCoNi-Ti and CrCoNi-Al coatings, respectively. Characterizations of the worn surfaces suggest that all the specimens involve three wear mechanisms: adhesive, abrasive and oxidation wear. Comprehensive analyses suggest that the superior surface properties of the CrCoNi-Ti and CrCoNi-Al coatings can be associated with the solid-solution, second-phase, grain-boundary, and heterostructure-induced strengthening after adding Ti and Al.

Structural and luminescence characterization of β-Ga2O3 nanopowders obtained via high-energy ball milling

β-Ga2O3 nanocrystals have been successfully obtained by the high-energy ball milling method. The obtained nanocrystalline powders have been characterized using X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and luminescent spectroscopy. X-ray diffraction patterns show a single gallium oxide structure formed in the milling process with a small amount of α-Ga2O3 phase. The grains of irregular shape were identified with the TEM technique. HRTEM images confirmed the formation of the β-Ga2O3 nanocrystals with a size distribution of 50–80 nm. Three luminescence bands peaked at about 2.52, 2.91, and 3.26 eV were observed in photoluminescence spectra. The gradual blue shift of the emission maxima at the excitation in the fundamental absorption edge under the different milling conditions was detected.

Synthesis and characterization of new multiferroic (BiBa)(FeTi2)O8

The present communication reports the study of various properties (i.e., structural, electrical, dielectric, ferroelectric, and magnetic) of new multiferroic: (BiBa)(FeTi2)O8 synthesized by a mixed oxide reaction route. The analysis of the X-ray diffraction profile at room temperature ensures its phase formation in the orthorhombic crystal structure. The micrographic study divulges irregular shape grains (mostly rectangular) with an average grain size of 3.5 μm. The compositional study displays the desired stoichiometry. The study of electrical (impedance, modulus, and conductivity) and dielectric properties (dielectric constant and tangent loss) of the sample at different temperatures (RT – 773 K) and electric field frequency (1 kHz-1MHz) provides many new experimental data, and insight mechanisms. The temperature dependence of the dielectric constant exhibits a dielectric anomaly around 523 K that may be due to the combined effect of oxygen vacancy mediated redox reaction (Fe3+→Fe2+ and Ti4+→Ti3+) and Maxwell-Wagner polarization. The loss tangent follows a similar trend to that of the dielectric constant except for an additional low-frequency relaxation peak of about 543 K. The dielectric loss tangent exhibits low value in low temperature and high-frequency regions, indicating that the sample can be a potential candidate for data storage devices. The ferroelectric recording shows a non-linear PE loop at room temperature. The room temperature magnetic recordings show evidence of weak ferromagnetism due to suppression of spiral spin structure as opposed to the antiferromagnetic nature of BiFeO3. The coexistence of these unique features enables the synthesized sample to be used in voltage-controlled data storage devices.

Quick and enhanced separation of Eosin Yellow dye from aqueous solution by FeCl3 interaction: thermodynamic study and treatment cost analysis

ABSTRACT Dyes and their metabolites have noxious and carcinogenicity potential and are known to be hazardous for human beings and other living organisms. The discharge of untreated wastewater comprising wide varieties of synthetic dyes into the water resources is one of the vital environmental problems. Therefore, in this study, the efficacy of the chemical coagulation method was explored using ferric chloride as a coagulant to remove the toxic dye Eosin Yellow (EY) from aqueous solution. The interaction between FeCl3 and EY dye was quick and profound at a solution pH of 2.2, yielding the brownish precipitate with a dye removal efficiency of more than 98%. An extremely high dye removal capacity of 1263 mg/g is reported for 100 mg/L of EY dye concentration at optimum experimental conditions. The possible chemical interaction between FeCl3 and EY dye can be attributed to the formation of polymeric complex, as oxygen atoms of carbonyl, phenolate and carboxylate groups of EY dye molecule interact strongly with Fe3+ ions. The presence of various coexisting anions could reduce the EY dye removal efficiency by 2%–5%; however, the required FeCl3 dose has increased from 64 to 170 mg/L. Thermodynamic studies showed that the interaction of EY dye with FeCl3 was exothermic and spontaneous in nature. The investigation of real industrial wastewater samples has exhibited a 90%–215% increase in the required FeCl3 dose as compared to the control experiment for the initial EY dye concentration from 100 to 750 mg/L. Sludge volume index analysis indicates that FeCl3 generated highly dense sludge with good settling characteristics. X-ray diffraction and field emissionscanning electron microscopy characterisation of the generated sludge indicate the polycrystalline nature with a combination of spherical and irregular shape grains of the sludge. Treatment cost analysis revealed that the cost involved in dye removal is in the range of 0.99–3.60 USD ($)/kg of dye removed.

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Single-phased samples of the medium-entropy BiSbTe1.5Se1.5 (low-temperature thermoelectric with electron con- ductivity) and PbSnTeSe (mid-temperature thermoelectric with hole conductivity) compounds have been prepared by reactive spark plasma sintering of powder mixtures consisting of relevant elemental metals. The samples prepared are grained. Plate- like grains with average grain size of ∼ 3.3 μm are observed in BiSbTe1.5Se1.5, whereas irregularly-shaped grains with average grain size of ∼ 18.9 μm are typical for PbSnTeSe. Highest value of the thermoelectric figure-of-merit of the samples is equal to ∼ 0.43 (at 500 K for BiSbTe1.5Se1.5) and ∼ 0.35 (at 725 K for PbSnTeSe).

Mechanical and Chemical Studies of Al2O3-Ti Composites for Their Use as a Bone Substitute

Alumina-based composites reinforced with titanium were manufactured by powder techniques. Characterizations indicate that titanium content affects densification which in turn causes positive effects on hardness and toughness. Microstructure presents grains of irregular shape and small sizes. Electrochemical impedance spectroscopy indicates that additions of titanium on Al2O3 enhance its corrosion resistance.

A cost-effective computational approach based on molecular dynamics for generating 3D packs of irregularly-shaped grains in a container of complex geometry

The reliable modelling of irregular grain shapes and generating realistic particle packs still remain urgent problems limiting the application of the particle-based numerical techniques in many industries dealing with granular materials. An effective computational approach for generating irregular three-dimensional (3D) grains by dynamic agglomeration of a large number of movable and interacting particles is proposed. The constructed grains are then randomly packed within an arbitrary-shaped container. The molecular dynamics-based concept is used for producing the grains with realistically complex configurations and adjustable shape morphology. The identical molecular dynamics technique coupled with the full six-degree-of-freedom rigid-body dynamics of the agglomerates is applied for grain packing. A database of 3D models of unduplicated irregular particles has been created. Several examples are considered to demonstrate the computational efficiency and controllability of the presented algorithms. The numerically reconstructed packings qualitatively and quantitatively satisfy the desirable properties of the real one in terms of the morphological features, void ratio, size distribution, and generally accepted shape characteristics of the grains (such as aspect ratio, sphericity, roundness, and roughness). Not only statistical, but also physical correspondence is established through the numerical reproduction of the angle of repose tests. An experimental verification of the model is performed.

Structure and electrical properties characterization of NiMn2O4 NTC ceramics

Spinel-type NiMn2O4 negative temperature coefficient (NTC) ceramic compound was successfully prepared by the co-precipitation technique. The structure, microstructure, and transport properties are examined for the thermistors application. X-ray diffraction pattern illustrates the formation of spinel structure with cubic crystal symmetry. The scanning electron micrograph shows irregular shape grains with an average size of less than 100 nm. The observed microstructure is mainly due to the low-temperature synthesis and occupancy of Mn3+ at octahedral sites. The dielectric loss was very less in low-temperature regions and increase exponentially at higher temperatures indicating an improvement in electrical conductivity. Similar behavior was observed for relative permittivity and indicates temperature-dependent dielectric polarization along with high-temperature phase transition. The Cole-Cole graph shows a decrease in an area of semicircular with an increase in temperature confirming the improvement of electrical conductivity. The dc-resistivity measurement shows a decrease in resistivity with increasing temperature typically observed in NTC materials.

Fahlbands of the Keret archipelago, White Sea: the composition of rocks and minerals, ore mineralization

This paper presents a complex mineralogical and geochemical characteristic (based on SEM-EDS, ICP-MS analysis) of the fahlband rocks of the Kiv-Guba-Kartesh occurrence within the White Sea mobile belt (WSMB). The term “fahlband” first appeared in the silver mines of Kongsberg in the 17th century. Now fahlbands are interlayers or lenses with sulfide impregnation, located in the host, usually metamorphic rock. The level of sulfide content in the rock exceed the typical accessory values, but at the same time be insufficient for massive ores. Fahlbands are weathered in a different way than the host rocks, so they are easily distinguished in outcrops due to their rusty-brown color. The studied rocks are amphibolites, differing from each other in garnet content and silicification degree. Ore mineralization is represented mainly by pyrrhotite and pyrite, and pyrrhotite grains are often replaced along the periphery by iron oxides and hydroxides, followed by pyrite overgrowth. At the same time, the rock contains practically unaltered pyrrhotite grains of irregular shape with fine exsolution structures composed of pentlandite, and individual pyrite grains with an increased Ni content (up to 5.4 wt.%). A relatively common mineral is chalcopyrite, which forms small grains, often trapped by pyrrhotite. We have also found single submicron sobolevskite and hedleyite grains. The REE composition of the fahlband rocks suggests that they are related to Archean metabasalts of the Seryakskaya and Loukhsko-Pisemskaya structures of the WSMB, rather than with metagabbroids and metaultrabasites common in the study area.

Nontrivial Phenomena in Magnetic Nanocomposites Co/Al2O3 and Co/SiO2

Magnetic nanocomposites (MNC), in which nanoparticles of ferromagnetic metals are distributed in wide-gap dielectric matrices (Al2O3 or SiO2), are prospective materials for electronics due to their amenability to technological control of the concentration and size of ferromagnetic nanoparticles. Co/Al2O3 and Co/SiO2 MNC layers with Co concentrations below the percolation threshold were deposited on polycor substrates using electron-beam deposition in a vacuum (EB-PVD). Scanning electron microscopy showed the presence of tightly packed Co grains of irregular shape with sizes of 5–50 nm in MNC. Low-temperature measurements of the magnetization for MNC Co/Al2O3 were made in the temperature range 4–300 K and magnetic fields up to 10 kOe. The ‘magnetic exchange bias’ has been detected, and it increases with a rise in Co concentration. By studying the electrical properties of the MNC Co/Al2O3 and Co/SiO2 in the temperature range of 77–280 K, the Mott type electron transport hopping mechanism was established. We first observed the effect of a giant positive thermoelectric power in a magnetic field in MNC Co/Al2O3 and the effect of a negative magnetothermoelectric power in a Co/SiO2.Magnetic nanocomposites (MNC), in which nanoparticles of ferromagnetic metals are distributed in wide-gap dielectric matrices (Al2O3 or SiO2), are prospective materials for electronics due to their amenability to technological control of the concentration and size of ferromagnetic nanoparticles. Co/Al2O3 and Co/SiO2 MNC layers with Co concentrations below the percolation threshold were deposited on polycor substrates using electron-beam deposition in a vacuum (EB-PVD). Scanning electron microscopy showed the presence of tightly packed Co grains of irregular shape with sizes of 5–50 nm in MNC. Low-temperature measurements of the magnetization for MNC Co/Al2O3 were made in the temperature range 4–300 K and magnetic fields up to 10 kOe. The ‘magnetic exchange bias’ has been detected, and it increases with a rise in Co concentration. By studying the electrical properties of the MNC Co/Al2O3 and Co/SiO2 in the temperature range of 77–280 K, the Mott type electron transport hopping mechanism was established. We...

Tracking the occurrence of anthropogenic magnetic particles and potentially toxic elements (PTEs) in house dust using magnetic and geochemical analyses

The influence of anthropogenic outdoor sources on the geochemical composition of house dust material in large cities is poorly understood. In this study, we investigate the magnetic signature and the concentrations of potentially toxic elements (PTEs) in randomly selected house dust samples from the metropolitan area of Athens, the most populated city in Greece. Environmental magnetic measurements, including isothermal remanent magnetization and thermomagnetism, indicated that the main magnetic mineral is coarse-grained low-coercivity magnetite. Detailed microscopic observations of the magnetically extracted material revealed the presence of three different kinds of Fe-rich particles deriving from both combustion-related and non-exhaust vehicular sources: irregularly-shaped grains and spherules of Fe-oxides, and particles consisting of metallic Fe. Further study of the morphology of single anthropogenic magnetic spherules (size > 30 μm) identified the presence of magnetite spherical particles, typically formed by industrial combustion processes. Enrichment factors (EFs) for the PTEs calculated against the Athens urban soil showed that the house dusts were very highly enriched in Cd, Cu, Zn and significantly enriched in Pb (median EF values of 34.1, 26.2, 25.4 and 10.3, respectively). The oral bioaccessibility of PTEs in the house dust, evaluated using a simulated gastric solution (0.4 M glycine), was in the order Pb > Zn > Mn > Cd > Ni > Cu > Cr > Fe. Concentrations of Pb increased with the house age. Principal component and cluster analysis demonstrated the close association of anthropogenic Cu, Pb and Zn with the magnetic susceptibility of the house dusts. We conclude that both traffic-related and industrial sources trigger the occurrence of magnetic Fe/PTEs- rich particles in house dust. These results reinforce the use of environmental magnetism determinations for assessing anthropogenic contamination of PTEs in the indoor environment in large cities.

Belousovite, KZn(SO4)Cl, a new sulfate mineral from the Tolbachik volcano with apophyllite sheet-topology.

ABSTRACTBelousovite, ideally KZn(SO4)Cl, was found in a Yadovitaya fumarole of the Second scoria cone of the North Breach of the Great Tolbachik Fissure Eruption (1975–1976), Tolbachik volcano, Kamchatka Peninsula, Russia. Belousovite occurs as irregularly-shaped grains and in the form of microcrystalline masses associated with kamchatkite, langbeinite, euchlorine, anglesite and zincite. Belousovite is monoclinic,P21/c,a= 6.8904(5),b= 9.6115(7),c= 8.2144(6) Å, β = 96.582(2),V= 540.43(7) Å3andZ= 4 (from single-crystal diffraction data). The eight strongest lines of the powder X-ray diffraction pattern are [dmeasÅ(I)(hkl)]: 6.8451(100)(100), (3.6401)(71)($\bar{1}$21), (3.1592)(84)(1$\bar{1}$2), (3.1218)(41)($\bar{2}$11), (3.1140)(52)(022), (2.9812)(41)(031), (2.9121)(44)(130) and (2.0483)(19)($\bar{3}$12). The chemical composition determined by the electron-microprobe analysis is (wt.%): K2O 19.55, Rb2O 0.58, ZnO 34.85, SO334.65, Cl 14.77, –O = Cl23.34, total 101.06. The empirical formula based on O + Cl = 5 apfu is K0.97Rb0.01Zn1.00S1.01O4.03Cl0.97. The simplified formula is KZn(SO4)Cl. The crystal structure was solved by direct methods and refined toR1= 0.029 on the basis of 1965 independent observed reflections. The structure of belousovite consists of infinite [ZnSO4Cl]–layers and K+ions. [ZnSO4Cl]–layers are formed by corner sharing mixed-ligand ZnO3Cl tetrahedra and SO4tetrahedra. The topology of [ZnSO4Cl]–layers in belousovite is identical to [Si4O10]4–layers in the minerals of the apophyllite group. A review of mixed-ligand ZnOmClncoordination polyhedra in minerals and inorganic compounds is given.

Registration of ShunMai Triplet Wheat for Flower Development Studies and Embryogenesis Research

ShunMai Triplet (Reg. No. GS‐189, PI 678624) is a winter wheat (Triticum aestivum L.) that was developed using conventional selection as an F4:5 progeny line derived from bulked crosses and is of unknown pedigree. ShunMai Triplet has three unique embryogenesis characteristics: (i) between one lemma and one palea, there are three ovaries (a large one and two equally small ones) and three anthers, giving rise to one to three grains in one floret; (ii) it often produces a twin spikelet at one node in the middle part of the rachis, usually with one to two twin spikelets per spike; and (iii) nearly 0.1 to 0.2% (average 0.168%) of the seeds give rise to twin shoots without doubled primary roots during germination. The triplet trait is controlled by a single dominant gene and could be useful for wheat embryology research as well as for flower development studies. ShunMai Triplet has medium maturity, with an average plant height of 80 ± 5 cm. It has a clavate head, white awns about 10 to 11 cm in length, a pale auricle, a pale ligule, pale green glumes with an oblique shoulder, a glume beak approximately 0.9 to 1.1 cm long, white grains of irregular shape, kernel weight of 27 ± 5 mg, broader leaves, thicker stems, moderate resistance to yellow rust, and moderate sensitivity to powdery mildew based on visual observations in the field.

Structure, morphology and optical-luminescence investigations of spinel ZnGa2O4 ceramics co-doped with Mn2+ and Eu3+ ions

The polycrystalline zinc gallate ZnGa2O4: Mn2+ and ZnGa2O4: Mn2+, Eu3+ samples have been synthesized via high-temperature solid-state reaction ceramic technique. The obtained ceramics have been characterized employing the methods of X-ray diffraction analysis, transmission electron microscopy, energy-dispersive X-ray spectroscopy, positron annihilation lifetime spectroscopy and optical-luminescent spectroscopy. The XRD analysis testified in favor of successful formation of spinel structure in the prepared samples with small amount of additional phase observed in the ZnGa2O4: Mn2+, Eu3+ ceramics. The grains of irregular shape with a homogeneous distribution of Eu3+ ions in a volume were identified with TEM technique. The band gap of ZnGa2O4: Mn2+ spinel was estimated from optical absorption spectra in UV–Vis range. The characteristic bands related to electronic transitions of Mn2+ and Eu3+ ions were found in optical absorption and excitation spectra. The photoluminescence emission spectra exhibited matrix luminescence along with emission band of Mn2+ ions and narrow lines of Eu3+ ions in blue, green and red spectral region, respectively. The intensity ratio of Eu3+ emission lines confirms the high asymmetry around Eu3+ ions. These findings correlate well with results of positron annihilation lifetime spectroscopy showing intense reduction of positron trapping rate deeply in ceramics grains due to Eu3+ ions penetration.

Performance evaluation of the grinding wheel with aggregates of grains in grinding of Ti-6Al-4V titanium alloy

The results of grinding are highly dependent on conditions of workpiece removal process. The material is removed by an unspecified number of abrasive grains of irregular shape and random distribution on the grinding wheel active surface. The interaction between the abrasive grain and the workpiece can be divided into three stages: (i) rubbing, (ii) ploughing and (iii) chip formation. Reciprocal contribution of each stage is dependent on the properties of the workpiece, the grinding parameters, the friction condition between the abrasive grain and the workpiece and the shape of the grains. In the article, the results of numerical and experimental process in the analysis of grinding of Ti-6Al-4V titanium alloy, using a conventional grinding wheel and a newly developed grinding wheel with aggregates of grains, were presented. The analysis of influence of the geometric parameters of the abrasive aggregates and the abrasive grains on the effectiveness of the workpiece removal process is presented. The effects of the geometrical parameters of grains and abrasive aggregates in direction of motion as well as in transversal direction on the size of ridges were determined. It has been observed that increase of the length of sideway material displacement results in the decrease of ridge formation. The results of a numerical analysis were confirmed by experimental research. The analysis of the impact of utilization of abrasive aggregates on the grinding forces, grinding-specific energy and surface roughness was performed. The impact of abrasive aggregates on the decrease of grinding forces and specific energy and the increase of quality of ground surface was observed.

Morphological characteristics in polycrystalline tungsten diselenide regulating transport properties lead to predominant thermoelectric performance

We studied a polycrystalline p-type WSe2 semiconductor for thermoelectric applications. The polycrystalline WSe2 nanocompound was prepared via a thermal reaction process of tungsten and selenium elements and it was sintered to produce a bulk structure using spark plasma sintering equipment. The resulting bulk specimen showed different morphological aspects, in which we observed irregularly-shaped grains along the direction perpendicular to the sintering pressing direction (i.e., along transversal direction) while finding thin layers along the parallel direction (i.e., along longitudinal direction). The specimen recorded a significantly low longitudinal thermal conductivity possibly because longitudinal phonon transport should be hindered due to the thin layers. Electron transport along the longitudinal direction might not be greatly interrupted by the morphological characteristics because the specimen recorded high carrier mobility along the direction resulting in lower electrical resistivity than that of a single crystalline equivalent. The specimen also showed moderate carrier concentration, which led to a plausible Seebeck coefficient. Since the specimen exhibited the significantly low thermal conductivity with the electrical properties, it recorded a higher figure of merit than the equivalent, which is the highest thermoelectric performance for p-type WSe2 in bulk phase ever developed.

Concentration-driven structural stability and dielectric dispersion in lead free (Ba1−xSc2x/3)Zr0.3Ti0.7O3 ceramics

Lead free scandium doped barium zirconate titanate (Ba1−xSc2x/3)(Zr0.3Ti0.7)O3 abbreviated as (BScZT) (x = 0.02, 0.04, 0.06, 0.08, 0.10) ceramics were prepared by the conventional solid state reaction route and their structural, microstructural and electrical properties were investigated experimentally. X-ray diffraction and Rietveld refinement analysis are indexed by considering cubic symmetry having space group Pm-3 m. Scandium ion (Sc3+) substitution induced A-site vacancies and distortion in three dimensional cation-oxygen networks leads to disorder in the local symmetry as identified in Raman spectra. The microstructural image shows formation of smaller grains of irregular shape and sizes along with aggregative characteristic with successive increase in Sc concentration. Lorentz type quadratic behavior in dielectric dispersion follows modified Curie–Weiss law and indicates a relaxor behavior with diffuse type of phase transition. A non-Debye type of relaxation behavior is observed in these materials. Variation of relaxation strength and diffuse parameters obey the Vogel–Fulcher relation. The ac conductivity highlights the hopping of bound charge carriers between the localized environment at lower temperature and translation hopping at higher temperature is modeled through universal dielectric response.

Optimized substrate temperature range for improved physical properties in spray pyrolysis deposited Tin Selenide thin films

Tin diselenide (SnSe2) thin films have been deposited on glass substrate using the spray pyrolysis technique by varying substrate temperatures (Tsub) from 250 °C to 400 °C. These films were characterized for structural, morphological, electrical and thermoelectric properties by using X-ray Diffraction, Field Emission Scanning Electron Microscopy (FESEM), four probe resistivity/conductivity and thermoelectric measurement respectively. X-Ray Diffraction patterns revealed that substrate temperature plays a critical role in phase formation and a single phase SnSe2 film were formed at a critical temperature range 275–375 °C. FESEM study of single phase film at 300 °C shows uneven and irregular shape grains throughout the film and the EDX shows the stoichiometric ratio of deposit. The variations of the micro-structural parameters, such as crystallite size (D), dislocation density (δ), and micro-strain (ε), were investigated for all films. The results showed that the crystallite sizes increase with an increase in substrate temperature, whereas the dislocation density and micro-strain decreases with increasing substrate temperature. The resistivity (ρ) of SnSe2 film was found to be decreasing with increasing temperature and also with substrate temperature. The predefined substrate temperature range (275–375 °C) was further narrowed down using 4-probe resistivity measurement. It shows that, although 275–375 °C is enough formation of single phase SnSe2, but there is a small temperature range 325–375 °C where one will get low resistive sample, which influence the flow of charge carrier. Low electrical resistance or inversely high electrical conductivity is one of the prime requirements of thermoelectric samples. The 4-probe resistivity measurement of single phase thin films shows that the lowest electrical resistance obtained for substrate temperature of 350 °C. Thermoelectric measurement confirms that the coated films were n-type semiconductor materials and the thermo-emf increases with an increase in substrate temperature. Among all the films the film with substrate temperature of 350 °C shows enhanced behaviour to be used in industrial applications.

Improvement of Ferroelectric Properties of PZT Ceramics by SBT Addition

(1−x)PZT-xSBT ceramics were prepared by a solid-state mixed oxide method. Phase characteristics of (1−x)PZT-xSBT ceramics showed a PZT phase and new phase in the compositions with 0.1 ≤ x ≤ 0.3, while a mainly new phase was observed in the composition with x = 0.5. The tetragonality (c/a) of PZT phase decreased with increasing in SBT content up to x = 0.3. SEM micrographs of the sample surface showed equiaxed grains of the PZT phase and irregularly-shaped grains of the new phase in samples with 0.1 ≤ x ≤ 0.3. The 0.5PZT-0.5SBT sample showed mainly irregularly-shaped grains of the new phase. The ferroelectric properties of these samples showed that the addition of small amounts of SBT (x = 0.1) into PZT increased the remanent polarization.