Tetragonal Crystal Structure Research Articles

Dielectric, piezoelectric and energy storage properties of large grain Ba1−xSrxTiO3 (BST) ceramic system for 0.17 ≤ x ≤ 0.26

The ferroelectric, energy storage, piezoelectric, and electrostrictive properties of the Ba1-xSrxTiO3 (BST) ceramic system for different Sr contents was synthesized using the solid-state reaction technique. At room temperature, pure tetragonal crystal structure was confirmed for the large grain ceramics, by the X-ray diffraction study for all compositions with coexistence of phases for x = 0.26. The dielectric measurement showed the maximum values of the dielectric constant, εr = 6434.33 at the Curie temperature, Tc = 42°C for x = 0.26. The maximal polarization (Pmax = 11.15μC/cm2) and remnant polarization (Pr = 4.67μC/cm2) was obtained with the low value of coercive field Ec = 317 V/cm. Increasing the Sr content, Wtot and Wrec reach 91.67 mJ/cm3 and 79.36 mJ/cm3, and a maximal energy storage efficiency (η) of 86.57% was achieved for x = 0.26, also the electrostrictive coefficient was calculated as 0.048 m4/C2 with a conversepiezoelectric coefficient 220 pm/V.

Evolution of morphological, crystal structure, and electrical properties of Ba-Pb-Bi-O superconducting materials

Bismuthate superconductor material has a transition from a semiconductor/conductor to a superconductor. Research on this transition temperature has attracted many researchers' attention to reveal this material's superconducting properties. We synthesized the materials by the solid-state reaction method. Samples were synthesized with variations in sintering temperature and also with variations in Bi-doping. X-ray diffractometer (XRD), scanning electron microscope (SEM), and resistivity versus temperature measurements were used to analyse the crystal structure, morphology, and electrical characteristics, respectively. Based on SEM results, there were no significant changes with the increase in sintering temperature. However, from x = 0 to 0.40 there was a change in the crystallization properties which changed according to the amount of doping of the Bi element. Based on the XRD results, the major phases were Ba4Bi(PbO4)3 with a tetragonal crystal structure and P4/mmm space group, and BaPbO3 with a cubic crystal structure and Pm-3m space group . The increase in the sintering temperature causes a change in the insulator-metal-insulator properties. In the variation of Bi composition, the evolution of phase formation of Ba4Bi(PbO4)3 starts at x = 0.20 and then decreases drastically when x = 0.40. TC was detected at a value of x less than 0.35, indicating that the effect of Bi composition below x = 0.35 does not significantly affect the electrical properties. The increase in the Bi composition causes changes in the metal-insulator-metal properties. At x = 0.2 to 0.25, there is a change in the crystal structure which is thought to cause the semiconductor properties to be above the TC.

Solvothermal synthesis of TiO2 nanospheres for non-volatile memory and synaptic learning applications

In this study, we used the one-pot solvothermal method to synthesize the TiO2 nanospheres (NSs) and used them for non-volatile memory and neuromorphic computing applications. Several analytical tools were used to understand the structural, optical, morphological, and compositional characteristics of synthesized TiO2 NSs. The tetragonal crystal structure of anatase TiO2 was formed, according to the Rietveld refined x-ray diffraction results. The NS morphology was confirmed by field emission scanning electron microscopy and transmission electron microscopy images. X-ray photoelectron spectroscopy was probed to understand the elemental composition and electronic states of the TiO2 NSs. We specifically looked at the impact of reaction time on the structural, optical, morphological, compositional, and resistive switching (RS) properties of TiO2 NSs. The fabricated devices (Ag/TiO2 NSs/FTO) exhibit bipolar RS behavior. The optimized RS device shows good endurance (5000 cycles) and memory retention (5000 s) properties. Moreover, fabricated devices showed double-valued charge-flux characteristics, whereas charge transport was caused by the Ohmic and space charge-limited current mechanisms. Additionally, the optimized device can mimic various synaptic characteristics including potentiation-depression, excitatory post-synaptic current, and paired-pulse facilitation.

Electronic, electrical and thermoelectric properties of Ba0.95Ca0.05Ti0.95Y0.05O2.975 compound: Experimental study and DFT-mBJ calculation

This article explores the impact of co-doping BaTiO3 ceramics with Ca2+ and Y3+ using solid-state reactions to improve its dielectric constant and decrease losses. The oxide BCTYO (Ba0.95Ca0.05Ti0.95Y0.05O2.975) exhibits a tetragonal crystal structure, characterized by a space group of P4mm. By examining the behavior of the doped BaTiO3 sample and performing simulations, researchers can better understand the underlying mechanisms and optimize material properties for specific applications. DFT study shows a semiconductor behavior with an indirect gap (Eg = 2.5 eV). The partial DOS proves that the hybridization between the orbitals Ti 3d, Y 3d, and O 2p is responsible for the band gap and the hopping processes. The analysis of conductivity curves provides evidence for the semiconductor characteristics of the material under investigation. By determining the activation energy (Ea) through analyzing Ln(fmax) and conductivity as a function of 1000/T, the interconnection between conduction and relaxation phenomena is demonstrated. The study of the real part of the dielectric permittivity (ε′) shows a transition at Tc = 380 K. The obtained results are promising and indicate that the studied material has the potential for various electronic applications (energy storage and diode fabrication …). Moreover, the thermal, electrical, and thermoelectric characteristics were examined utilizing the semi-classical Boltzmann theory. The findings revealed an intriguing result, suggesting that Ba0.95Ca0.05Ti0.95Y0.05O2.975 holds promise as a potential candidate for application in thermoelectric devices.

A Highly Active and Reusable Multicomponent high Entropy Metal Oxide Catalyst for Nitroarenes Hydrogenation

It is well known that multicomponent catalysts can improve catalytic performance, however their rational design and precise control of catalytic activities by varying the composition of the elements is challenging. Herein, we present a facile and scalable synthetic strategy for production of senary and septenary metal oxide nanoparticles with a chemical composition of MSbOx and MSb2Ox (M: Fe, Ni, Co, Cu, and Zn). All samples were formed in a tetragonal crystal structure with space group 136 and crystallographic symmetry P42/mnm while the details of their constituent unit cells are different, belonging to rutile or trirutile structures. These nanocomposites have an oxygen vacancy-rich construction with uniform elemental distributions that produce various surface functionalities. They showed instantaneous hydrogenation catalytic performance for reduction of 4-nitrophenol to 4-aminophenol at room temperature. Among our samples, the senary catalyst with MSbOx chemical composition showed better durability and reusability owning to its morphological and microstructural properties. It showed 100% conversion of 4-nitrophenol to 4-aminophenol within 4 min at the 18th run without any by-products.

Jahn–Teller-driven phase segregation in MnxCo3−xO4 spinel thin films

Transition metal spinel oxides comprised of earth-abundant Mn and Co have long been explored for their use in catalytic reactions and energy storage. However, understanding functional properties can be challenging due to differences in sample preparation and the ultimate structural properties of the materials. Epitaxial thin film synthesis provides a novel means of producing precisely controlled materials to explore the variations reported in the literature. In this work, MnxCo3−xO4 samples from x = 0 to x = 1.28 were synthesized through molecular beam epitaxy and characterized to develop a material properties map as a function of stoichiometry. Films were characterized via in situ x-ray photoelectron spectroscopy, x-ray diffraction, scanning transmission electron microscopy, and polarized K-edge x-ray absorption spectroscopy. Mn cations within this range were found to be octahedrally coordinated, in line with an inverse spinel structure. Samples largely show mixed Mn3+ and Mn4+ character with evidence of phase segregation tendencies with the increasing Mn content and increasing Mn3+ formal charge. Phase segregation may occur due to structural incompatibility between cubic and tetragonal crystal structures associated with Mn4+ and Jahn–Teller active Mn3+ octahedra, respectively. Our results help in explaining the reported differences across samples in these promising materials for renewable energy technologies.

Study of brush coating and spin coating on stannic oxide thin film for the electron transport layer in a perovskite solar cell

This work addresses the challenges associated with using brush coating as a cost-effective and rapid method for large-scale deposition instead of applying a spin coating for the large-scale production of solar cells. This study used brush coating and spin coating techniques to coat a 0.1 M precursor solution onto a cleaned glass substrate. Brush coating utilized a fibril brush, followed by thermal annealing at 180 °C for 1 min, while the spin coating was performed at 1000 RPM for 10 s. Compositional analysis was conducted using Electron Diffraction X-ray (EDAX), and structural analysis employed X-ray Diffraction (XRD). The EDAX analysis confirmed the presence of stannic oxide and XRD data indicated a tetragonal crystal structure of SnO 2, matched with standard data. Scanning Electron Microscopy (SEM) examination revealed that the spin-coated film surface morphology was more effective than the brush-coated film. Additionally, the brush-coated sample demonstrated superior morphology and crystallinity compared to previous research. The optical bandgap, conduction band and valence band edge potentials were determined by UV-spectroscopy. The spin-coated sample exhibited values of 4.02, −1.33 and 2.69 eV, respectively, while the brush-coated sample showed values of 3.98, −1.31 and 2.67 eV, respectively. The valence band maximum and conduction band minimum binding energies were determined using the core level binding energy in the XPS spectroscopy data. Overall, brush coating and spin coating exhibited similarities with minor differences. We may infer that the main drawback of this approach lies in the surface morphology, which can be mitigated through careful management of the coating rate and heat treatment.

CoMn2O4 and Cu0.5Co0.5Mn2O4 spinels as efficient protective coating layers on SUS430 for SOFC interconnect

In this study, CoMn2O4 and Cu0.5Co0.5Mn2O4 spinels are examined as protective coatings for chromium diffusion in metallic interconnect of solid oxide fuel cell. Both spinels are prepared by co-precipitation technique in order to obtain high temperature conducting spinels. The spinels obtained after 4 h of calcinations in air at 500 °C exhibit tetragonal crystal structure with average grain size between 90 and 100 nm. Cu0.5Co0.5Mn2O4 spinel exhibits superior electrical conductivity over CoMn2O4 and both display NTCR (negative temperature co-efficient of resistance) behavior illustrating their use as a protective layer on interconnects for fuel cells operating at higher temperatures. Doctor-blade employed spinel coating over SUS430 alloy exhibits good adhesion between protective spinel layer and metallic alloy. Cross section micrographs reveal presence of nanosized and highly dense grains capable to resist the outflow of chromium ions present in SUS430. Mass gain and diffusion rate constant (Kp) was high for CoMn2O4 coated SUS430 illustrating Cu0.5Co0.5Mn2O4 spinel as a better protective coating layer for interconnect application. Chromium outflow is restricted and the same is evident from all cross-section micrographs of spinel coated SUS430 specimens subjected for oxidation up to 1000 h. Estimated thickness of Cr2O3 layer was ∼15 nm for CoMn2O4 whereas Cu0.5Co0.5Mn2O4 coated SUS430 specimen had ∼12.5 μm thickness at the SUS430/spinel interface demonstrating superior resistance to chromium outflow. The area specific resistance was lowest for Cu0.5Co0.5Mn2O4 coated specimen (between 14 mΩcm2 – 15 mΩcm2) followed by CoMn2O4 coated specimen reiterating Cu0.5Co0.5Mn2O4 as efficient protective coating material for SUS430 SOFC interconnect.

Bio‐Templated Chiral Zeolitic Imidazolate Framework for Enantioselective Chemoresistive Sensing

AbstractChiral metal–organic frameworks (MOFs) have gained rising attention as ordered nanoporous materials for enantiomer separations, chiral catalysis, and sensing. Among those, chiral MOFs are generally obtained through complex synthetic routes by using a limited choice of reactive chiral organic precursors as the primary linkers or auxiliary ligands. Here, we report a template‐controlled synthesis of chiral MOFs from achiral precursors grown on chiral nematic cellulose‐derived nanostructured bio‐templates. We demonstrate that chiral MOFs, specifically, zeolitic imidazolate framework (ZIF), unc‐[Zn(2‐MeIm)2, 2‐MeIm=2‐methylimidazole], can be grown from regular precursors within nanoporous organized chiral nematic nanocelluloses via directed assembly on twisted bundles of cellulose nanocrystals. The template‐grown chiral ZIF possesses tetragonal crystal structure with chiral space group of P41, which is different from traditional cubic crystal structure of I‐43 m for freely grown conventional ZIF‐8. The uniaxially compressed dimensions of the unit cell of templated ZIF and crystalline dimensions are signatures of this structure. We observe that the templated chiral ZIF can facilitate the enantiotropic sensing. It shows enantioselective recognition and chiral sensing abilities with a low limit of detection of 39 μM and the corresponding limit of chiral detection of 300 μM for representative chiral amino acid, D‐ and L‐ alanine.

Bio-Templated Chiral Zeolitic Imidazolate Framework-8 for Enantioselective Chemoresistive Sensing.

Chiral metal-organic frameworks (MOFs) have gained rising attention as ordered nanoporous materials for enantiomer separations, chiral catalysis, and sensing. Among those, chiral MOFs are generally obtained through complex synthetic routes by using a limited choice of reactive chiral organic precursors as the primary linkers or auxiliary ligands. Here, we report a template-controlled synthesis of chiral MOFs from achiral precursors grown on chiral nematic cellulose-derived nanostructured bio-templates. We demonstrate that chiral MOFs, specifically, zeolitic imidazolate framework-8 (ZIF-8), can be grown from regular precursors within nanoporous organized chiral nematic nanocelluloses via directed assembly on twisted bundles of cellulose nanocrystals. The template-grown chiral ZIF-8 possesses tetragonal crystal structure with chiral space group of P41, which is different from traditional cubic crystal structure of I-43m for freely grown conventional ZIF-8. The uniaxially compressed dimensions of the unit cell of templated ZIF-8 and crystalline dimensions are signatures of this structure. We observe that the templated chiral ZIF-8 can facilitate the enantiotropic sensing. It shows enantioselective recognition and chiral sensing abilities with a low limit of detection of 39 µM and the corresponding limit of chiral detection of 300 µM for representative chiral amino acid, D- and L- alanine.

Dielectric Spectroscopy Studies and Modelling of Piezoelectric Properties of Multiferroic Ceramics

Compounds and solid solutions of bismuth ferrite (BiFeO3)—barium titanate (BaTiO3) system are of great scientific and engineering interest as multiferroic and potential high-temperature lead-free piezoelectric materials. In the present paper, the results of research on the synthesis and characterisation of 0.67Bi1.02FeO3–0.33BaTiO3 (67BFBT) ceramics in terms of crystal structure and dielectric and piezoelectric properties are reported. It was found that the produced 67BFBT ceramics were characterised by a tetragonal crystal structure described by the P4mm space group, an average crystallite size <D> ≈ 80 nm, and an average strain <ε> = 0.01%. Broad-band dielectric spectroscopy (BBDS) was employed to characterise the dielectric response of polycrystalline ceramics. The frequency range from ν = 10−1 Hz to ν = 105 Hz was used to characterise the influence of the electric field strength on dielectric response of the ceramic sample at room temperature. The dielectric spectra were checked for consistency with the Kramers–Kronig test, and the high quality of the measurements were confirmed. The electric equivalent circuit method was used to fit the dielectric spectra within the frequency range that corresponded to the occurrence of the resonant spectra of the radial mode for thin disk sample, i.e., from ν = 105 Hz to ν = 107 Hz and the temperature range from T = −20 °C to T = 50 °C. The electric equivalent circuit [RsCPE1([L1R1C1]C0)] was used, and good fitting quality was reached. The relevant calculations were performed, and it was found that the piezoelectric charge coefficient exhibited a value of d31 = 35 pC/N and the planar coupling factor was kp = 31% at room temperature. Analysis of impedance spectra performed in terms of circumferential magnetic field made it possible to establish an influence of magnetic field on piezoelectric parameters of 67BFBT multiferroic ceramics. Additionally, the “magnetic” tunability of the modulus of the complex dielectric permittivity makes 67BFBT a sensing material with vast potential.

Green synthesis of strontium-doped tin dioxide (SrSnO2) nanoparticles using the Mahonia bealei leaf extract and evaluation of their anticancer and antimicrobial activities

Abstract In this study, a simple green method was employed to produce strontium (Sr)-doped-tin-dioxide (SnO2) nanoparticles (SrSnO2 NPs) using the Mahonia bealei leaf extract. The synthesized NPs were characterized with XRD, FE-SEM, FTIR, and PL spectroscopy measurements. SrSnO2 NPs were analysed for antimicrobial and anticancer activities. The XRD analysis revealed that the synthesized samples exhibited a tetragonal rutile crystal structure type of tin oxide. The EDX spectrum conforms to the chemical composition and elemental mapping of SrSnO2 NP synthesis. At 632 cm−1, the O–Sn–O band was observed and chemical bonding was confirmed using an FTIR spectrum. The PL spectrum identified surface defects and oxygen vacancies. The SrSnO2 NPs were tested against both Gram-positive and Gram-negative human pathogens. The synthesized nanoparticles exhibited effective antibacterial properties. The anticancer effects of SrSnO2 nanoparticles were also assessed against MCF-7 cells, and growth was decreased with increasing concentrations of the nanoparticles. Dual staining revealed high apoptosis in SrSnO2 NP-treated MCF-7 cells, proving its apoptotic potential. To conclude, we synthesized and characterized potential SrSnO2 nanoparticles using a green approach from the Mahonia bealei leaf extract. Further, green SrSnO2 nanoparticles showed significant antibacterial and anticancer properties against breast cancer cells (MCF-7) through apoptosis, which suggests a healthcare application for these nanoparticles.

Low-temperature antiferromagnetic order in orthorhombic CePdAl3

We report the magnetization, ac susceptibility, and specific heat of optically float-zoned single crystals of ${\mathrm{CePdAl}}_{3}$. In comparison to the properties of polycrystalline ${\mathrm{CePdAl}}_{3}$ reported in the literature, which displays a tetragonal crystal structure and no long-range magnetic order, our single crystals exhibit an orthorhombic structure ($Cmcm$) and antiferromagnetic order below a N\'eel temperature ${T}_{1}=5.6$ K. The specific heat at zero field shows two anomalies, namely, a broad transition at ${T}_{1}=5.6$ K followed by a $\ensuremath{\lambda}$-anomaly at ${T}_{2}=5.4$ K. A conservative estimate of the Sommerfeld coefficient of the electronic specific heat, $\ensuremath{\gamma}=121\phantom{\rule{0.28em}{0ex}}\mathrm{mJ}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}2}\phantom{\rule{0.16em}{0ex}}{\mathrm{mol}}^{\ensuremath{-}1}$, indicates a moderately enhanced heavy-fermion ground state. A twin microstructure evolves in the family of planes spanned by the basal plane lattice vectors ${\mathbf{a}}_{\mathrm{o}}$ and ${\mathbf{c}}_{\mathrm{o}}$ , with the magnetic hard axis ${\mathbf{b}}_{\mathrm{o}}$ common to all twins. The antiferromagnetic state is characterized by a strong a${}_{\mathrm{o}}$, c${}_{\mathrm{o}}$ easy-plane magnetic anisotropy where the a${}_{\mathrm{o}}$ direction is the easy axis in the easy plane. A spin-flop transition induced under magnetic field along the easy directions, results in complex magnetic phase diagrams. Taken together, our results reveal a high sensitivity of the magnetic and electronic properties of ${\mathrm{CePdAl}}_{3}$ to its structural modifications.

High-pressure synthesis and magnetic properties of tetragonal R2BaCuO5 (R = Sm and Eu).

We report the experimental discovery of a new structural phase of well-known orthorhombic R 2BaCuO5 (R = Sm and Eu), exhibiting a tetragonal crystal structure with space group . The high-pressure tetragonal phase is isostructural with the brown phase R 2BaCuO5 (R = La, Pr, and Nd). In this structure, the Cu ions form an isolated square planar environment, contrary to the orthorhombic phase, where the Cu ions are located in a distorted square pyramid. Magnetization and specific heat measurements reveal the long-range antiferromagnetic order of the Cu2+ and/or Sm3+ moments for the Sm-sample, with the magnetic specific heat accounting for only 35% of the magnetic entropy. Interestingly, the Eu-sample remains paramagnetic down to the lowest temperature. The high Curie-Weiss temperature of -140K and magnetic entropy of 3% of the expected value indicates that the system is highly frustrated. We estimated the isothermal entropy change and investigated the magnetocaloric effect for Eu2BaCuO5, and the maximum entropy change detected at a field of 70kOe at 3K reaches 5.6Jkg-1K-1.

Fabrication of micro patterns on BaTiO3:Er3+/Yb3+ perovskite films by femtosecond laser micromachining

Femtosecond lasers currently show much promise as potential sources for the fabrication of optical and photonic devices, displaying high performance due to their high resolution, excellent geometric flexibility, and low collateral damage. In particular, devices displaying high performance based on BaTiO3:Er3+/Yb3+ (BTEY) films have been widely investigated, promising for the innovation of perovskite patterning applications. Herein, we fabricated BTEY perovskite films by spin coating at room temperature. XRD pattern and Raman spectroscopy analysis of the BTEY films revealed a tetragonal crystal structure. The study of Williamson-Hall's method calculated the strain and crystallite size for the BTEY film. Different parameters in the exploiting cylindrical focusing of an fs-laser were adopted to modulate the crater cavity of patterning, which gives the opportunities to evaluate their impact on the energy ablation threshold (Eth). It was found that cavity radius is proportional to the energy cross-section, thus providing wide range dependence of damaged spot size versus pulse energy. The Eth was measured using Liu's method, determining a value of Eth that decreased from 33.4 nJ to 22.4 nJ when the number of applied laser pulses per spot increased. It is found that the number of pulses per spot low possesses the best performance, successfully producing highly uniform patterning. Moreover, the evolution with the number of pulses also revealed changes in the surface morphology of the crater cavity via AFM and scanning confocal fluorescence microscopy (SCFM) analysis. These results are crucial for determining the Eth required to damage the material, understating the driving mechanism of formations of cavity profile surfaces, and changes in their optics properties in the edges owing to the balling effects and structural defects.

Exploration of crystal structure, and luminescence behaviors of Terbium-activated CaWO4 phosphor

This manuscript includes structural, optical, photoluminescence, and thermoluminescence behaviors of Terbium incorporated CaWO4 samples with nominal compositions of Ca1-xTb2x/3WO4 (x = 0.01, 0.02, 0.03, 0.04, 0.05) prepared by the traditional solid-state reaction route. Results found from the Rietveld refinements of X-ray diffraction patterns confirmed that all the samples have tetragonal crystal structures with I41/a space group. The variation of unit cell volume with the compositions shows an anomaly at x = 0.03. Band gap energy values of these synthesized samples are found from the UV–Visible absorbance spectra with increasing order. Photoluminescence behaviors, as well as the FWHM values, are analyzed from the excitation along with the emission spectra. Critical quenching concentration at x = 0.03 with a critical energy transfer distance of ∼ 20 Å caused by the dipole-dipole interactions is found in these spectra. CIE Chromaticity coordinates are indicated the green emission color of all the prepared samples with high color purity, correlated color temperature, color rendering index, and luminous efficiency of radiation values. Quantum efficiency of the material with x = 0.03 Tb concentration is observed under 255 nm excitation wavelength. PL decay analyses of the phosphors are carried out and the average lifetime values are calculated. Thermoluminescence spectroscopy of x = 0.03 irradiating by 15 min of UV dose is described as the lower UV dosimetry and second-order kinetics of the material.

Strontium Free Cu-Doped La2NiO4 Oxides as Promising Oxygen Electrodes for Solid Oxide Electrolysis Cells

In this work, strontium-free copper-doped nickelates, La2Ni1-xCuxO4 (x=0.1-0.3), were synthesized using solid state synthesis method and tested as potential oxygen electrodes in solid oxide electrolysis cells (SOEC). Similar to the parent compound, the Ruddlesden-Popper (RP) La2NiO4 oxide, the Cu-doped compositions were confirmed to crystallize with tetragonal crystal structure with I4/mmm space group. The electrochemical performance of La2Ni1-xCuxO4 electrodes was studied using Ni-YSZ electrode-supported button cells in SOEC mode and compared to the state-of-the-art (La0.6Sr0.4)0.95Co0.0.8O3-δ (LSCF)-doped ceria composite electrodes. Electrochemical tests were conducted at 750oC with the Ni-YSZ hydrogen electrode exposed to 50% steam in hydrogen. The polarization resistance of SOEC with the La2Ni0.8Cu0.2O4 (LNCuO-20) electrode was lower than that with LSCF. LNCuO-20 showed stable current density output over 800 hours tested, while cell with LSCF showed more degradation.

Surface Vertical Multi-Emission Laser with Distributed Bragg Reflector Feedback from CsPbI3 Quantum Dots.

Quantum dots (QDs) laser has become an important way to solve micro-application problems in many fields. However, single wavelength distributed Bragg reflector (DBR) has many limitations in practical applications, such as signal transmission. How to realize multiwavelength DBR lasing output simply is a challenge. To achieve a stable multi-wavelength quantum dots laser in the near-infrared region, the perovskite CsPbI3 QDs laser with DBR structure is developed in this paper. A tetragonal crystal structure with complete bonding information and no defect is explained by X-ray diffractions (XRD) and Raman spectrum. The cross-section morphology of the DBR laser and the surface morphology of QDs is measured by scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. An elliptical light propagation field and a double wavelength laser radiation are obtained from the finite-difference time-domain (FDTD) simulation. The output of the three wavelength lasers at 770 nm, 823 nm, and 873 nm is measured. The emission time of a DBR laser is about 2 h, and the average fluorescence quantum yield is 60%. The cavity length selection and energy level model are put in place to clearly see the working mechanism. All the results suggest that an effective and stable CsPbI3 quantum dots DBR laser is realized.

Effect of Li+/K+/Zn2+ doping on the optical and temperature sensing properties of Tm3+ and Yb3+ doped YVO4 phosphor

The Pechini sol-gel reaction technique has been used to produce Tm3+, Yb3+ co-doped YVO4 and Li+/K+/Zn2+ codoped YVO4: Tm3+,Yb3+ phosphors. Post-heat treatment (at 800 °C) was given to all the samples to strengthen the material's structural and optical characteristics. Prepared phosphors exhibit blue and near-infrared (NIR) light. The crystalline structure and morphology of the prepared phosphors were studied by using powder X-ray diffraction (PXRD), Fourier transform Infrared spectroscopy (FTIR) and scanning electron microscope (SEM). All prepared phosphors crystallise in the tetragonal crystal structure having space group I41/amd. Prepared phosphors, when pumped with the laser at 980 nm, give strong upconversion emission in blue and NIR regions that correspond to Tm3+ transitions 1G4→3H6 and 3H4→3H6, respectively. Li+/K+/Zn2+ co-doping enhances the luminescence intensity significantly. Among Li+/K+/Zn2+ ions, Zn2+ co-doping increases the upconversion emission intensity mostly compared to others, the blue emission intensity get increased by ∼7 times and the NIR by ∼6 times. The main cause of enhancement in the emission intensity may be primarily due to the charge imbalance and asymmetry in the crystal field.Further, optical temperature sensing was also investigated by using the fluorescence intensity ratio (FIR) of the transitions (3F2,3→3H6) and (3H4→3H6). Co-doping of Li+/K+/Zn2+ ions also affects the temperature sensitivity. The relative sensitivity and absolute sensitivity of the samples were also calculated. This study indicates that this phosphor is a suitable candidate as a blue phosphor for display devices, WLEDs and optical temperature-sensing probes.

Piezoelectric, structural, vibration and optical properties of lead free based 0.5Ba(Ti0.8Zr0.2)O3-0.5(Ba0.7Ca0.3)TiO3 ceramic sample

The single-phase solid solution of 0.5 {Ba (Zr0.2Ti0.8) O3}− 0.5 {(Ba0.7Ca0.3) TiO3} ceramic sample was prepared by solid state method. The X-ray diffraction study confirmed the mixed phases of tetragonal and rhombohedral crystal structure. The average crystallite size was ∼ 90 nm measured from the Williamson Hall plot method. An estimated average grain size ∼ 4.2 µm is obtained from scanning electron microscopy and well-defined grains separated by clear grain boundaries. The band gap for the sample was found ∼2.8 eV from absorption spectra. The red shifting of vibration B1/E(TO3)/E(LO2) mode at low temperature causes the phase transition from tetragonal to rhombohedral and the band E(TO)+A1(TO) at ∼523 cm−1 becomes more broadening and disappears above 300 °C. So sample transfer from tetragonal to cubic phase. The absence of A(LO1) and the softening of A(TO3) modes are attributed to transfer from tetragonal to rhombohedral above − 100 °C at low temperature. The temperature dependence of permittivity value further supports the phase transition from orthorhombic-tetragonal ∼50° C and tetragonal–cubic ∼ 250 °C. The PL spectra revealed disorder and three distinct green peaks (2.85 eV, 2.75 eV, 2.65 eV and 2.54 eV) evidence of rhombohedral structure. P∼E loop exhibits a soft and ferroelectric in nature. A maximum strain of 0.45% field-induced and a large d33 value ∼ 870 pm/V in the ceramics sample.