Drastic improvement of Curie temperature by chemical pressure in N-type diluted magnetic semiconductor Ba(Zn,Co)$$_{2}$$As$$_{2}$$

We report the effect of chemical pressure on the ferromagnetic ordering of the recently reported n-type diluted magnetic semiconductor Ba(Zn$$_{1-x}$$ 1 - x Co$$_{x}$$ x )$$_{2}$$ 2 As$$_{2}$$ 2 which has a maximum $$T_C$$ T C $$\sim$$ ∼ 45 K. Doping Sb into As-site and Sr into Ba-site induces negative and positive chemical pressure, respectively. While conserving the tetragonal crystal structure and n-type carriers, the unit cell volume shrink by $$\sim$$ ∼ 0.3$$\%$$ % with 15$$\%$$ % Sr doping, but drastically increase the ferromagnetic transition temperature by 18$$\%$$ % to 53 K. Our experiment unequivocally demonstrate that the parameters of Zn(Co)As$$_{4}$$ 4 tetrahedra play a vital role in the formation of ferromagnetic ordering in the Ba(Zn,Co)$$_{2}$$ 2 As$$_{2}$$ 2 DMS.

Two-Dimensional Buckled Tetragonal cadmium chalcogenides, including CdS, CdSe, and CdTe Monolayers as Photo-catalysts for Water Splitting

Pure hydrogen production via water splitting is an ideal strategy for producing clean and sustainable energy. The two-dimensional (2D) cadmium chalcogenides single-layers with a tetragonal crystal structure, namely Tetra-CdX (X=S,...

Structural and optical characterization of Er-doped CaMoO4 down-converting phosphors

xEr2O3–(1−x)CaMoO4 (x = 1, 3, 5, 7 and 10 mol%) nanoparticles were synthesized by solid-state sintering at 800°C. X-ray diffraction studies confirmed the tetragonal crystal structure of CaMoO4, while the doped samples show the co-existence of cubic Er2O3 and tetragonal CaMoO4 and rule out the replacement of Ca2+ by Er3+ in the structure. The crystal unit-cell dimensions, phase concentration and atomic position coordinates were determined by Rietveld refinement. The short-range structure of CaMoO4 consists of tetrahedral MoO4 and snub disphenoid deltahedral CaO8 units, while the unit cell of Er2O3 consists of two types of ErO6 octahedral units. All MoO4 units contain Mo—O bonds of equal lengths, whereas two types of slightly different Ca—O bond lengths exist in CaO8. Raman spectra of the doped samples show only Mo—O vibrational modes and the Raman peaks of Er2O3 are masked by Mo—O bond vibrations. CaMoO4 shows bluish-green emission at 500 nm, while Er-doped samples show strong green emission under UV excitation. UV irradiation (380 nm) induces down-conversion green emission at 531 nm and 552 nm and good color purity in 1 mol% Er2O3–CaMoO4 sample which makes it a potential candidate for applications in optical devices.

High temperature tetragonal crystal structure of UPt2Si2

High temperature crystal structure of UPt2Si2 determined using single-crystal neutron diffraction at 400 K is reported. It is found that the crystal structure remains of the primitive tetragonal CaBe2Ge2 type with the space group P4/nmm. Anisotropic displacement factors of the Pt atoms at the 2a (3/4 1/4 0) and Si atoms at the 2c (1/4 1/4 z) Wyckoff sites are found to be anomalously large.

Effect of CeO2 Nanoparticle on the Structural and Electrical Properties of BSCCO-2223 High Temperature Superconductor

A study of the effects of Cerium oxide nanoparticle doped with BSCCO-2223 on the microstructure and superconducting properties was carried out. All samples were synthesized using solid state reaction method. Ce concentration is varied from x = 0.0 up to 0.1 in a general stoichiometry of Bi1.6Pb0.4Sr2Ca1-xCexCu3Oy. The samples were characterized structurally and electrically by X-Ray Diffraction (XRD) and four-point probe method respectively. XRD analysis shows that both (Bi,Pb)-2212 and (Bi,Pb)-2223 phases coexist in the samples having tetragonal crystal structure but changed to orthorhombic when x=0.10. The values of critical transition temperature, TC and critical current density, JC of the samples decreased with the increase in Ce concentration. The possible reasons for the observed degradation in superconducting and structural properties of Bi-2223 due to Ce nanoparticles addition were discussed.

UTILIZATION OF INDONESIAN LOCAL STANNIC CHLORIDE (SnCl4) PRECURSOR IN THE PROCESS OF MAKING FLUORINE- DOPED TIN OXIDE (FTO) CONDUCTIVE GLASS

UTILIZATION OF INDONESIAN LOCAL STANNIC CHLORIDE (SnCl4) PRECURSOR IN THE PROCESS OF MAKING FLUORINE-DOPED TIN OXIDE (FTO) CONDUCTIVE GLASS. Thin layer of fluorine- doped tin oxide (FTO) conductive glass has been deposited on a glass substrate heated at a temperature of 350°C using the ultrasonic spray pyrolysis nebulizer method with variations in fluorine doping and substrate temperatures. This experiment uses the raw material of Indonesian local stannic chloride (SnCl4) (PT Timah Industri) as a precursor with a temperature variation of 250, 300, 350, 400°C. The structure and morphology of the optical and electrical properties of all the thin layers have been examined. XRD results show that all thin layers have a tetragonal crystal structure. In this experiment, there is a significant influence on the role of fluorine doping on resistivity and transmittance values. With the addition of 2% wt doping, the resistivity and transmittance values decrease. The optimum value is obtained by doping 2 wt%, substrate temperature of 350°C with a resistivity value of 9.28.10-5 Ω.cm and transmittance value of 88%.

Semicoherent growth of single-crystal β-In2S3 layers on InP(111) and InAs(111)

The (103) surface of β-In2S3 consists of a purely accidental hexagonal-like periodicity despite the tetragonal crystal structure of β-In2S3. β-In2S3 layers grow, as a consequence, semicoherently on the (111) surfaces of InP and InAs due to small lattice mismatches.

Thermoelectric properties of hot pressed CZTS micro spheres synthesized by microwave method

ABSTRACTMicrowave synthesis of Copper Zinc Tin Sulphide (CZTS) sphere like particles has been demonstrated. The structural and morphological properties of CZTS particles are characterized by XRD, SEM and Raman spectroscopy and subsequently thermoelectric properties are investigated. XRD results of prepared powder sample matches well with tetragonal crystal structure of CZTS bulk. No other impurity phase has been detected from the XRD analysis. Raman spectrum further confirms the formation of single phase CZTS with characteristics peak for CZTS at 334.1 cm-1. SEM studies reveal that the CZTS particles are spherical in shape with uniform sizes of ∼ 250-350 nm. Hot pressed CZTS system shows a power factor ∼21 µW/mK2 and ZT∼ 0.024 at 623 K. Significant enhancement in the Figure of merit for CZTS system is observed in comparison to reported nanostructures of the same system may be due to increased electrical conductivity.

Characterization of tin dioxide nanoparticles synthesized by oxidation

Tin dioxide (SnO2) is a promising material with great potential for applications such as gas sensors and catalysts. Nanostructures of this oxide exhibit greater activation efficiency given their larger effective surface. The present study presents results of the synthesis and characterization of tin dioxide under different conditions via oxidation of solid tin with nitric oxide. SnO2powder was characterized primarily by X-ray diffraction and scanning electron microscopy, as well as complementary techniques such as energy-dispersive X-ray spectroscopy, dynamic light scattering and Fourier transform infrared spectroscopy. The results indicated that the established synthesis conditions were suitable for obtaining rutile tin dioxide nanoparticles with a tetragonal crystal structure.

Studied on Structural Characterization of Lanthanum Doped Barium Titanium Ceramics

La-doped barium titanate (BaTiO3) was prepared using conventional solid state synthesis route. All peaks for sample x=0 are approaching the phase pure of BaTiO3 structure with tetragonal crystal structure (P4mm). Sintering of pressed powder are performed at 1300oC, 1400oC and 1450oC for overnight for pure BaTiO3 and 1350oC for 3 days for BaTiO3 doped lanthanum with intermittent grinding. Phase transition was studied by different x composition. The changes in the crystal structure of the composition x=0.1 and 0.2 were detected by using X-ray diffraction (XRD). The phase changes between tetragonal-cubic and cubic-tetragonal depending on the temperature. Rietveld Refinement analysis is carried out to determine the lattice parameter and unit cell for BaTiO3.