Space Group Pnma Research Articles

UVB emitting phosphors based on singly and co-doped Ce3+, Gd3+ in Li4ZrF8 phosphors

Preparation of Li4ZrF8:Ce3+ and Li4ZrF8:Ce3+,Gd3+ phosphors is described. Data on luminescence characteristics are presented. Hydrothermal route was employed for the synthesis. Li4ZrF8 crystallizes in orthorhombic system with Pnma space group. Li atoms are distributed over two sites, both having same coordination of six. Zr is also similarly distributed over two 8 coordinated sites. Li4ZrF8:Ce3+ emits a broad band UVB light, while the emission of Li4ZrF8:Ce3+,Gd3+ is in form of a narrow line around 311 nm attributed to 6P7/2 → 8S7/2. Both phosphors exhibited a broad excitation spectrum with a peak at 253 nm. The excitation and emission properties are thus adequate enough to obtain UVB light sources using a conventional high pressure mercury vapour lamp or an ultraviolet LED.

Crystal Structure and Microwave Dielectric Characteristics of Novel Ba(Eu1/5Sm1/5Nd1/5Pr1/5La1/5)2Ti4O12 High-Entropy Ceramic

High-permittivity Ba(Eu1/5Sm1/5Nd1/5Pr1/5La1/5)2Ti4O12 (BESNPLT) high-entropy ceramics (HECs) were synthesized via a solid-state route. The microstructure, sintering behavior, phase structure, vibration modes, and microwave dielectric characteristics of the BESNPLT HECs were thoroughly investigated. The phase structure of the BESNPLT HECs was confirmed to be a single-phase orthorhombic tungsten-bronze-type structure of Pnma space group. Permittivity (εr) was primarily influenced by polarizability and relative density. The quality factor (Q×f) exhibited a significant correlation with packing fraction, whereas the temperature coefficient (TCF) of the BESNPLT HECs closely depended on the tolerance factor and bond valence of B-site. The BESNPLT HECs sintered at 1400 °C, demonstrating high relative density (>97%) and optimum microwave dielectric characteristics with TCF = +38.9 ppm/°C, Q×f = 8069 GHz (@6.1 GHz), and εr = 87.26. This study indicates that high-entropy strategy was an efficient route in modifying the dielectric characteristics of tungsten-bronze-type microwave ceramics.

Green synthesis of calcium nanoferrites using leaf extract of Brassica oleracea for photocatalysis of malachite green dye

The calcium ferrite nanoparticles were made by the sol–gel process. X-ray diffraction, a scanning electron microscope, and UV–vis spectroscopy were used to analyze the material. There is an orthorhombic phase in the space group Pnma. There were four techniques used to calculate the average crystallite size. Using ImageJ software, the particles were aggregated and their size was ascertained. Using energy-dispersive X-ray (EDX) analysis, the composition of the material was ascertained. 2.29 eV was determined to be the band gap. Vibrating test magnetometer (VSM) provided an explanation for the materials’ magnetic property. A decreased band gap energy is responsible for the 90% degradation of malachite green dye at a concentration of 15 mg/L in 150 min, with a four-cycle reusability.

Two Perovskite Modifications of BiFe0.6Mn0.4O3 Prepared by High-Pressure and Post-Synthesis Annealing at Ambient Pressure

BiFeO3-related perovskite-type materials attract a lot of attention from the viewpoint of applications and fundamental science. In this work, we prepared two modifications of heavily Mn-doped BiFeO3 with the composition of BiFe0.6Mn0.4O3. A high-pressure (HP) modification was prepared at about 6 GPa and 1400 K. An ambient pressure (AP) modification was prepared by heating the HP modification at 780 K in the air at AP (post-synthesis annealing). Crystal structures of both modifications and in situ transformation were investigated with synchrotron powder X-ray diffraction. The transformation started at about 700 K and finished at about 780 K. The HP modification crystallized in space group Pnma with a = 5.57956 Å, b = 15.70576 Å, and c = 11.22557 Å, and the AP modification crystallized in space group Pbam with a = 5.63839 Å, b = 11.2710 Å, and c = 7.75923 Å (all parameters were at room temperature). Post-synthesis annealing of the HP modification (conversion polymorphism) is the only way to prepare the Pbam modification of oxygen stoichiometric BiFe0.6Mn0.4O3. Magnetic properties of both modifications have been reported. The Néel temperatures are TN = 350 K (HP) and TN = 335 K (AP). HP modification shows larger spin canting. Both modifications show negative magnetization phenomena at low temperatures in low magnetic fields.

Flux Crystal Growth, Structure, and Optical Properties of LiLa3Ti2S3O6: An Oxysulfide Phase Derived from K2NiF4-Type Structure.

Single crystals of a new titanium oxysulfide, LiLa3Ti2S3O6, were grown from a KI molten salt. Single-crystal X-ray diffraction analysis revealed that LiLa3Ti2S3O6 crystallizes in the space group Pnma with lattice parameters of a = 11.7319(4) Å, b = 3.94787(14) Å, and c = 20.6885(6) Å. In this structure, the one-dimensional chains of corner-sharing TiO5S octahedra are further corner-linked via equatorial and apical oxygen atoms to form unique corrugated two-dimensional perovskite-type layers in the ab plane with one octahedral thickness. These layers were intervened along the c-axis by the LaS rock-salt layers corrugated concomitantly with the perovskite-type layers, and LiO2S2 tetrahedral chains were located between these two types of two-dimensional layers. LiLa3Ti2S3O6 can be viewed as a modified K2NiF4-type structure with TiO5S octahedral layers stacked in a zigzag manner along the c axis. The oxysulfide has a direct-type band gap of 1.85 eV, based on UV-vis-NIR diffuse reflectance measurements. First-principles calculations showed that the conduction band minimum mainly consists of Ti 3d orbitals, and the valence band maximum consists of S 3p, O 2p, and Li 2s orbitals. The electronic structures near the Fermi level are similar to those of the structurally related photocatalytic oxysulfides Y2Ti2S2O5 and La5Ti2CuS5O7.

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The pressure-induced structural changes in the perovskite-type (ABO3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document}) ferroelectric solid solution (1-x)Na0.5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{0.5}$$\\end{document}Bi0.5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{0.5}$$\\end{document}TiO3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document}-xBaTiO3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document} (NBT-xBT) at the morphotropic phase boundary (MPB) (xMPB=0.048\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$x_{\ ext {MPB}}=0.048$$\\end{document}) have been analyzed up to 12.3 GPa by single-crystal x-ray diffraction with synchrotron radiation. A pressure-induced phase transition takes place between 4.4 and 5.0 GPa, where the pseudocubic low-pressure phase transforms into an orthorhombic high-pressure phase with space group Pnma. The high-pressure phase is comprised of mixed BO6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_6$$\\end{document} tilts and anti-polar A-cation displacements, without exhibiting coherent off-centered shifts of the B-site Ti4+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{4+}$$\\end{document} cations that can be detected by synchrotron x-ray diffraction. Our results reveal that at ambient pressure and room temperature the NBT-xMPB\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$x_\\mathrm{{MPB}}$$\\end{document}BT structure possesses anti-phase BO6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_6$$\\end{document} tilts with a relatively large correlation length and the same type of polar distortions as those present in pure NBT, but with strongly violated correlation length due to Ba2+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{2+}$$\\end{document}-induced local elastic-stress fields. For xMPB\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$x_{\ ext {MPB}}$$\\end{document} the effect of Ba on the mesoscopic-scale structure is compensated by a mild external pressure of only 0.7 GPa, resulting in structural features resembling those of pure NBT at ambient conditions.

Observation of the multiple magnetic phases in double perovskite Pr1.8La0.2CoFeO6

The structural and magnetic properties of the double perovskite Pr1.8La0.2CoFeO6 have been investigated. The X-ray diffraction study shows that the system acquires room-temperature orthorhombic phase with the Pnma space group. The X-ray photoemission spectroscopy (XPS) measurement confirmed that the B-site ions are present in mixed valence states i.e. Co has been found in Co2+ and Co3+ valance states whereas Fe has been found in Fe3+/Fe4+. Magnetic measurements of the system confirm the existence of several fascinating magnetic behaviors, such as long-range canted antiferromagnetism withTN ∼ 271 K, giant exchange bias, and re-entrant cluster glass phase (TG ∼ 33 K). Field-dependent magnetization shows a large spontaneous exchange bias; HSEB∼ 1.8 kOe and giant conventional exchange bias, HCEB∼ 2.4 kOe at 5 K. Antiferromagnetic materials with large exchange bias can be utilized in high-density spintronic devices. Temperature-dependent Raman study demonstrates that the observed phonon mode exhibits anomalous behavior close to the magnetic transition temperature. Analysis of anomalous softening of phonon mode below TN, clarifies the presence of significant spin-phonon coupling while the magnetostriction effect does not play any significant role in the observed phonon anomaly.

Crystal structures, phase transition, and Hirshfeld surface analyses of the bromide and chloride congeners of aqua[2,4,6-tris(pyridin-4-yl)-1,3,5-triazine]zinc(II) halide.

During the course of exploring crystallization conditions in generating metal-organic frameworks (MOFs) for use in the crystalline sponge method, two discrete metal-organic complexes, namely, aqua[2,4,6-tris(pyridin-4-yl)-1,3,5-triazine]zinc(II) bromide, [Zn(C18H12N6)(H2O)]Br2, and aqua[2,4,6-tris(pyridin-4-yl)-1,3,5-triazine]zinc(II) chloride, [Zn(C18H12N6)(H2O)]Cl2, were encountered. Structures in the orthorhombic space group Pnma (No. 62) for the bromide congener at 299 K and the chloride congener at 100 K were obtained. A phase transition for the bromide congener occurred upon cooling from 299 to 100 K, yielding a crystal polymorph with four domains that exhibits monoclinic P21/m space-group symmetry (No. 11), which arises from conformational changes. The main intramolecular contacts that contribute to the crystal packing in all observed structures are H...H, Halide...H/H...Halide, C...H/H...C, and N...H/H...N. Intramolecular hydrogen bonding between the Zn-bound water and non-Zn-bound pyridyl N atoms is a prominent feature within the three-dimensional networks. Aromatic π-stacking between the non-Zn-bound pyridine rings and contacts involving the halide ligands further stabilize the crystal packing.

Pressure induced structural and electronic band transition in CsPbBr3

Cesium lead bromide (CsPbBr3) is a prominent halide perovskite with extensive optoelectronic applications. In this study, we report the pressure modulation of CsPbBr3’s crystal structure and electronic properties at room temperature up to 5 GPa. We have observed a crystal structure transition from the orthorhombic Pnma space group to a new monoclinic phase in the space group P21/c at 2.08 GPa. The structure is associated with ~8% of density jump across the transition boundary. DFT calculations have suggested that the structure transition leads to a change in the electronic band structure, and there is an emergent indirect bandgap at the Pnma-P21/c phase transition boundary at 2.08 GPa. Across the transition boundary, the electronic band gap of CsPbBr3 increased from 2.07 eV to 2.38 eV, which explains its pressure-induced color change. Our study demonstrates the importance of using in-situ crystal structure in the electronic band structure calculations in halide perovskites.

Impact of Nickel doping on microstructure and impedance spectroscopy of multiferroic YCrO3

In this work, we study the effect of Ni-doping on the structural and impedance spectroscopy properties of the polycrystalline YCrO3 ceramic sample. The structural analysis shows all the samples crystallize in an orthorhombic structure with the Pnma space group. The depressed and asymmetric semicircle of complex impedance spectra indicates that the relaxation of charge carriers is of non-Debye type, where the thermally activated charge carriers control it. The temperature dependence of relaxation time and electrical conductivity exhibit an anomaly in the vicinity of diffuse-like relaxor transition temperature (TC ∼ 460 K). The analysis of conductivity data shows hopping-type charge conduction. The analysis further indicates that while the dc conductivity increases continuously, the activation energy shows a non-monotonous variation with Ni concentration.

Effect of the glycerol dispersant on the structure, electrical transport and magnetoresistive properties of La0.67Ca0.33MnO3 ceramics prepared by the sol-gel routine

In this paper, the sol-gel technique is employed to synthesize polycrystalline La0.67Ca0.33MnO3 (LCMO) ceramics, where methanol is chosen as the solvent. The crystal structure, morphology, as well as electrical and magnetoresistive properties were examined. Moreover, the effect of amount of the dispersant glycerol on the properties of LCMO ceramics is studied. X-ray diffraction (XRD) results showed that all samples crystallized in single phases with orthogonal perovskite structure (pnma space group), without any detectable impurity phases. Results reveal that the grain size of LCMO ceramics exhibits an initial increase followed by a decrease, accompanied by a similar behavior in the temperature coefficient of resistance (TCR) and magnetoresistance (MR). When the volume ratio of glycerol and methanol reached 2 %, the grain size is determined to be 7.30 μm, with TCR value of 25.02 % K−1 at T= 263.2 K, and MR value recorded at 55.40 %. The study elucidates the influence of glycerol on LCMO polycrystalline ceramics and optimize the fabrication process, thereby improve the electric transport property and magnetoresistance.

Golden ratio of the r+/r- for the structure-selectivity in the thermoelectric BaZn2-xCdxSb2 system

A total of five Zintl phase compounds in the solid-solution BaZn2-xCdxSb2 (0.10(2) ≤ x ≤ 2) system have been successfully synthesized by the molten Pb-flux method. Both powder X-ray and single-crystal X-ray diffraction analyses proved that the title compounds displayed the phase transition between the BaCu2S2-type phase (space group Pnma, Z = 4) and the CaAl2Si2-type phase (space group P3¯m1, Z = 1) depending on the Zn/Cd mixed ratio. Furthermore, this kind of structure selectivity was dictated by the radius ratio criterion between the cationic and the anionic elements (r+/r–): three Zn-rich compounds with the r+/r– > 1 (BaZn1.90(1)Cd0.10Sb2, BaZn1.75(2)Cd0.25Sb2, and BaZn1.62(2)Cd0.38Sb2) preferred to adopt the BaCu2S2-type phase, while two Cd-rich compounds with the r+/r– ≤ 1 (BaZn0.16(2)Cd1.84Sb2 and BaCd2Sb2) preferred to crystallize in the trigonal CaAl2Si2-type phase. A series of TB-LMTO calculations using the two hypothetical models: BaZn1.5Cd0.5Sb2 and BaZn0.5Cd1.5Sb2, proved that a resonance peak in the density of states of BaZn1.5Cd0.5Sb2 implied the enhanced Seebeck coefficient of the three Zn-rich compounds, and the reduction of band gap observed in a band structure of BaZn0.5Cd1.5Sb2 influenced the electrical conductivity of the Cd-rich BaZn0.16(2)Cd1.84Sb2. Temperature-dependent thermoelectric property measurements showed the maximum ZT of 0.54 for the quaternary BaZn1.62(2)Cd0.38Sb2, which should mainly be attributed to the reduced κtot due to the Zn and Cd disordering in the anionic frameworks.

Dimethylamine Copper(I) Halide Single Crystals: Structure, Physical Properties, and Scintillation Performance.

Hybrid copper(I) halides have garnered a significant amount of attention as potential substitutes in luminescence and scintillation applications. Herein, we report the discovery and crystal growth of new zero-dimensional compounds, (C2H8N)3Cu2I5 and (C2H8N)4Cu2Br6. The bromide and iodide have a triclinic structure with space group P1̅ and an orthorhombic structure with space group Pnma, respectively. (C2H8N)3Cu2I5 exhibits cyan emission peaking at 504 nm with a photoluminescence quantum yield (PLQY) of 34.79%, while (C2H8N)4Cu2Br6 shows yellowish-green emission peaking at 537 nm with a PLQY of 38.45%. The temperature-dependent photoluminescence data of both compounds were fitted to theoretical models, revealing that nonradiative intermediate states significantly affect thermal quenching and antiquenching. Electron-phonon interactions, the origin of emission line width broadening and peak shifting, were also investigated via fittings. The scintillation properties of (C2H8N)3Cu2I5 were evaluated, and an X-ray imaging device was successfully fabricated using (C2H8N)3Cu2I5. This work demonstrates the potentiality of copper halides in lighting and X-ray imaging applications.

Magnetic properties of the solid solutions CePt1−x Au x Al (x = 0.1–0.9)

Abstract Members of the solid solutions CePt1–x Au x Al have been synthesized from the elements and pure samples could be obtained for the whole range of x from 0.1–0.9. Powder X-ray diffraction patterns indicated the TiNiSi-type structure (orthorhombic, space group Pnma) for the whole series, consistent with the end members CePtAl and CeAuAl. The lattice parameters and therefore also the unit cell volumes evolve in a linear fashion when going from CePtAl to CeAuAl. Magnetic susceptibility and magnetization investigations were performed for the compounds with x = 0.1, 0.2, 0.3, 0.5, 0.7 and 0.9. The results show that the ferromagnetic ground state of CePtAl gets destabilized for small degrees of substitution (x = 0.1) resulting in a lower Curie temperature. For larger values of x, changes towards an antiferromagnetic ground state are observed, in line with pure CeAuAl.

Role of Bi/Te co-dopants on the thermoelectric properties of SnSe polycrystals: an experimental and theoretical investigation

A sustainable solution to the energy crisis may be found in thermoelectric materials and generators, capable of transforming thermal energy into electrical energy or vice versa. SnSe is one of the emerging thermoelectric materials with distinctive properties. The main advantages of this compound are earth-abundant, inexpensive, non-toxic and it is also known for its high thermoelectric performance. Here we prepared Bi/Te co-doped SnSe polycrystals; whereas, Bi and Te are added with different compositions such as (x = 0.0,0.02,0.04,0.06 and y = 0.03) in (Sn1-xBixSe1-YTeY) matrix by using the solid-state reaction method. XRD data confirms the samples belong to the orthorhombic crystal system with the Pnma space group. DFT calculations were used to see structural stability and electronic properties for pure and doped SnSe samples. Temperature-dependent semiconducting behavior of the samples has been demonstrated by electrical resistivity. The Seebeck coefficient, correlated with carrier concentration and mobility, validates the p-type behavior for the pristine samples and the n-type behavior for co-doped samples. The dominant behavior of phonon scattering has been demonstrated by thermal conductivity analysis. After co-doping there is decrement in total thermal conductivity was observed which 1.3 times lower than SnSe. A theoretical calculation was used to validate experimental results to estimate electrical properties, Seebeck coefficient, specific heat capacity, thermal conductivity, and power factor using Quantum espresso code with Boltzmann transport Equation. 4% Bi-doped sample displayed a significant increment in electrical conductivity and an enhanced Seebeck coefficient, which led to the power factor enhancement of approximately 2.0 times in contrast to the pristine sample and enhanced ZT of about 0.055 which is 3.43 times higher than the pristine SnSe.Graphical abstract

Upconversion, downshifting, quantum cutting and back energy trasfer from Yb3+ to Er3+ in Er3+/Yb3+ co-doped CaTiO3 phosphor, intense NIR generation for communication

The perovskite based phosphor materials are widely used to increase the efficiency of solar cells. In this work, Er3+ doped and Er3+/Yb3+ co-doped CaTiO3 perovskite phosphor samples have been synthesized by solid state reaction technique at 1473 K. The phosphor samples show orthorhombic phase with Pnma (62) space group. The average crystallites and particles size of CaTiO3 are increased in presence of Er3+ and Yb3+ ions. Er3+ doped CaTiO3 phosphor samples give downshifting emission under 379 nm excitation. Though upconversion emission is seen in Er3+ under 980 nm excitation without Yb3+ ions in this host. The emission intensity of Er3+ ion is enhanced by 46 and 16 times for green and red emissions, respectively in presence of Yb3+. An intense quantum cutting (QC) emission is observed at 980 nm in presence of Yb3+ in CaTiO3:0.5Er3+ phosphor under 379 nm excitation. The QC efficiency has been found to be 119 % for CaTiO3:0.5Er3+/5 Yb3+ phosphor. Further an interesting phenomenon of back energy transfer (BEnT) from Yb3+ to Er3+ giving an intense NIR emission from Er3+ at 1002 and 1550 nm have been observed. The phosphor sample also shows an intrinsic optical bistablity (IOB) by upconversion. Thus, the prepared phosphor samples may be useful to increase the efficiency of c-Si solar cell, NIR emission for communication, bistable material and green light emitting source.

Optimized TCR and MR of La0.67Ca0.33-xSrxMnO3: Ag0.15 ceramics by Sr doping

Herein, in order to successfully create high-density La0.67Ca0.33-xSrxMnO3: Ag0.15 (LCSMO: Ag) ceramics (0 ≤ x ≤ 0.05), this research combines sol-gel and solid-phase processes. LCSMO: Ag ceramics electrical transport and magnetic properties were thoroughly investigated. XRD verified that the high-purity orthorhombic perovskite structure (space group Pnma) was produced. As Sr doping rises, the grain size grows, the single electron bandwidth increases, the metal-insulator transition temperature (TMI) continues to climb, and temperature coefficient of resistance (TCR) and magnetoresistance (MR) steadily drop. When x = 0.04, the TMI reaches 302.2 K. At this time, the TCR peak (TCRpeak) reaches 24.0 %·K−1 and the MRpeak reaches 49.2 %. These results demonstrate that Sr may effectively raise the TMI of LCMO: Ag ceramics to room temperature while maintaining high TCR and MR Values, which benefits the material's potential applications in devices such as uncooled infrared detectors.

Obtained large room-temperature TCR of La0.67Ca0.25Sr0.08MnO3 ceramics by optimizing sintering temperature

Over the past few decades, perovskite manganese oxide Lax(CaSr)1-xMnO3 has presented new opportunities for uncooled infrared bolometers due to its exceptional electrical transport performance. In this study, La0.67Ca0.25Sr0.08MnO3 (LCSMO) ceramics were prepared at different sintering temperatures (Ts, Ts = 1450, 1470, 1490, 1510, 1530 °C) by changing the previous sol-gel preparation process parameters. The research results indicated that the tolerance factor (τ) of the ceramics is τ = 0.935, and all ceramics exhibit a Pnma space group perovskite structure with excellent crystallinity. LCSMO ceramics exhibit good crystal quality and higher room-temperature TCR (14.58 % K−1) at Ts = 1510 °C. As Ts increases, the grain size, Mn–O bond length (dMn-O), Mn–O–Mn bond angle (θMn-O-Mn) and cell volume (V) of ceramics have a slight affected. The decrease of grain boundary scattering, electron-electron scattering, and strong coupling between electrons, so the peak resistivity value of all sintered samples firstly decreases and then increases with the increase in Ts, which effectively yields ceramics with high TCR. The peak TCR value (TCRmax) increased from 8.38 % K−1 (Ts = 1450 °C) at 296.91 K to 14.58 % K−1 (Ts = 1510 °C) at 298.18 K. On the same component, the TCRmax was increased by 42 % from 8.38 % K−1 to 14.58 % K−1 at Ts = 1450 °C–1510 °C. The high room-temperature TCR of LCSMO is expected to be used in advanced uncooled infrared bolometers, providing a basis for studying the influence of Ts on the electrical transport performance of ceramics.

Structural Refinement and Optoelectrical Properties of Nd2Ru2O7 and Gd2Ru2O7 Pyrochlore Oxides for Photovoltaic Applications.

High-performance photovoltaic devices require active photoanodes with superior optoelectric properties. In this study, we synthesized neodymium ruthenate, Nd2Ru2O7 (NRO), and gadolinium ruthenate pyrochlore oxides, Gd2Ru2O7 (GRO), via the solid-state reaction technique, showcasing their potential as promising candidates for photoanode absorbers to enhance the efficiency of dye-sensitized solar cells. A structural analysis revealed predominantly cubic symmetry phases for both materials within the Fd-3m space group, along with residual orthorhombic symmetry phases (Nd3RuO7 and Gd3RuO7, respectively) refined in the Pnma space group. Raman spectroscopy further confirmed these phases, identifying distinct active modes of vibration in the predominant pyrochlore oxides. Additionally, a scanning electron microscopy (SEM) analysis coupled with energy-dispersive X-ray spectroscopy (EDX) elucidated the morphology and chemical composition of the compounds. The average grain size was determined to be approximately 0.5 µm for GRO and 1 µm for NRO. Electrical characterization via I-V measurements revealed that these pyrochlore oxides exhibit n-type semiconductor behavior, with conductivity estimated at 1.5 (Ohm·cm)-1 for GRO and 4.5 (Ohm·cm)-1 for NRO. Collectively, these findings position these metallic oxides as promising absorber materials for solar panels.

The Solubility of Indium in Na2Ga7

AbstractThe ternary solid solution Na2Ga7−xInx (x≤0.25) was synthesized by annealing the elements at 300 °C in sealed Ta ampoules. Differential thermal analysis (DTA) indicated incongruent phase formation. The peritectic temperature ranges from 501(2) °C (x=0) to 474(2) °C (x=0.25). In addition, the unit cell parameters increase significantly with In content. At its maximum of x=0.25, the unit cell volume increases by 1 % compared to Na2Ga7. The In positions are deduced from single‐crystal X‐ray diffraction data obtained for the composition Na2Ga6.95In0.05 (space group Pnma; Z=8; a=14.876(3) Å, b=8.688(2) Å, c=11.605(4) Å). In the crystal structure of Na2Ga7, which consists of Ga12 icosahedra and 4‐bonded Ga atoms, the In atoms solely substitute the latter. The Na atoms are located in the channels and cavities of the framework. The phase is electron‐precise and can be considered a Zintl‐Wade compound with the formula unit [Na+]16[(12b)Ga122−]4[(4b)Ga−]7.6[(4b)In−]0.4.