scholarly journals Magnetotransport Behaviour of Nanocrystalline Pr1-xSrxMnO3 (0.40≤x≤0.60)

2013 ◽  
Vol 2013 ◽  
pp. 1-8
Author(s):  
Neelam Maikhuri ◽  
Anurag Gaur ◽  
Vasudha Aggarwal ◽  
Umesh Gaur ◽  
H. K. Singh
Keyword(s):  
Grain Boundaries ◽  
Single Crystals ◽  
Magnetic Structure ◽  
Sol Gel ◽  
Mixed Phase ◽  
Large Contribution ◽  
Metallic Component ◽  
Temperature Range ◽  
Wet Chemical ◽  
Successive Reduction

The nanocrystalline samples of Pr1-xSrxMnO3 (PSMO) (x=0.40, 0.50, 0.55, and 0.60) were synthesized by wet-chemical sol-gel route. Structural, magnetic, and magnetotransport properties have been studied systematically. It is found that Pr1-xSrxMnO3 samples with Sr content x=0.40 and 0.50 show paramagnetic to ferromagnetic (PM-FM) transition at TC~308 K with no trace of FM-AFM transition within the temperature range of 77–350 K. However, interestingly a second transition is observed at T~ 273 and 255 K, respectively, for samples x=0.55 and 0.60 correspond to an A-AFM magnetic structure. This indicates that samples x=0.40 and 0.50 are ferromagnetic below TC, while other samples (x=0.55 and 0.60) have a mixed phase consisting of FM and A-type AFM phases. Resistivity versus temperature (ρ-T) curve shows that the resistivity of all the samples is much larger than the single crystals of corresponding compositions due to large contribution of grain boundaries in the present nanocrystalline samples. Moreover, the decrease in metallic component at higher Sr concentration is also evidenced by the successive reduction in magnetoresistance (MR) with increasing Sr content from x=0.40 to 0.60.

Hydrogen Diffusion in Chalcopyrite Solar Cell Materials

1998 ◽  
Vol 513 ◽  
Author(s):  
A. Weidinger ◽  
J. Krauser ◽  
Th. Riedle ◽  
R. Klenk ◽  
M. Ch. Lux-Steiner ◽  
...  
Keyword(s):  
Thin Films ◽  
Solar Cell ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Diffusion Coefficients ◽  
Transport Process ◽  
Hydrogen Diffusion ◽  
Intrinsic Diffusion ◽  
Ion Energy ◽  
Temperature Range

ABSTRACTHydrogen diffusion in CuInSe 2 single crystals and CuInS2 thin films was studied by measuring the spreading of implantation profiles upon annealing. Deep implantation with an ion energy of 10 keV and sub-surface implantation with 300 eV were applied. The diffusion coefficients in both materials were found to be in the order of 10-14 to 10-13 cm2/s in the temperature range between 400 and 520 K.These fairly low diffusivities are typical for a trap and release transport process rather than intrinsic diffusion of interstitial hydrogen. In the polycrystalline CuInS2 films, hydrogen leaves the sample through the grain boundaries.

The observation of defects on (100) CdTe surfaces by chemical etching

1992 ◽  
Vol 50 (2) ◽  
pp. 1424-1425
Author(s):  
M.E. Lee
Keyword(s):  
Single Crystal ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Chemical Etching ◽  
Crystalline Perfection ◽  
Crystalline Defects ◽  
High Incidence ◽  
Crystallographic Defects ◽  
Cdznte Substrates ◽  
Device Technology

The crystalline perfection of bulk CdTe substrates plays an important role in their use in infrared device technology. The application of chemical etchants to determine crystal polarity or the density and distribution of crystallographic defects in (100) CdTe is not well understood. The lack of data on (100) CdTe surfaces is a result of the apparent difficulty in growing (100) CdTe single crystal substrates which is caused by a high incidence of twinning. Many etchants have been reported to predict polarity on one or both (111) CdTe planes but are considered to be unsuitable as defect etchants. An etchant reported recently has been considered to be a true defect etchant for CdTe, MCT and CdZnTe substrates. This etchant has been reported to reveal crystalline defects such as dislocations, grain boundaries and inclusions in (110) and (111) CdTe. In this study the effect of this new etchant on (100) CdTe surfaces is investigated.The single crystals used in this study were (100) CdTe as-cut slices (1mm thickness) from Bridgman-grown ingots.

Domain coarsening by grain boundary migration in ordered Ni4Mo

1986 ◽  
Vol 44 ◽  
pp. 560-561
Author(s):  
K. Vasudevan ◽  
H. P. Kao ◽  
C. R. Brooks ◽  
E. E. Stansbury
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Short Range ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Rapid Cooling ◽  
Temperature Range ◽  
Fee Structure ◽  
Domain Coarsening ◽  
Boundary Reaction

The Ni4Mo alloy has a short-range ordered fee structure (α) above 868°C, but transforms below this temperature to an ordered bet structure (β) by rearrangement of atoms on the fee lattice. The disordered α, retained by rapid cooling, can be ordered by appropriate aging below 868°C. Initially, very fine β domains in six different but crystallographically related variants form and grow in size on further aging. However, in the temperature range 600-775°C, a coarsening reaction begins at the former α grain boundaries and the alloy also coarsens by this mechanism. The purpose of this paper is to report on TEM observations showing the characteristics of this grain boundary reaction.

scholarly journals Internal melt figures in ice by rapid adiabatic compression

1994 ◽  
Vol 40 (134) ◽  
pp. 132-134
Author(s):  
R.E. Gagnon ◽  
C. Tulk ◽  
H. Kiefte
Keyword(s):  
Phase Transformations ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Adiabatic Compression ◽  
Air Bubbles ◽  
Water Ice ◽  
Deep Focus ◽  
And Behavior ◽  
First Time

AbstractSingle crystals and bicrystals of water ice have been adiabatically pressurized to produce, and clearly illustrate, two types of internal melt figures: (1) dendritic figures that grow from nucleation imperfections on the specimen’s surface, or from air bubbles at grain boundaries, into the ice as pressure is elevated; and (2) compression melt fractures, flat liquid-filled disks, that nucleate at imperfections in the crystal and grow with the application of pressure eventually to sprout dendritic fingers at the periphery. The transparency of the ice permitted visualization of the growth and behavior of the figures, and this could be an important tool in understanding the role of phase transformations in deep-focus earthquakes. Correlation between figure size and pressure is noted for the first time.

Thermodynamical Calculations and Experimental Confirmation about the Mg-Al-Spinel Reaction Path in the Sol-Gel-Process

2006 ◽  
Vol 317-318 ◽  
pp. 135-138 ◽  
Author(s):  
Wilfried Wunderlich ◽  
Krupathi Vishista ◽  
Francis D. Gnanam ◽  
Daniel Doni Jayaseelan
Keyword(s):  
Thermal Analysis ◽  
Reaction Path ◽  
Sol Gel ◽  
Chemical Processing ◽  
Aluminium Isopropoxide ◽  
Spinel Formation ◽  
Sol Gel Process ◽  
Wet Chemical ◽  
Enthalpy Data ◽  
Good Agreement

The aim of this research is, to clarify which route the sol-gel-process is taking in the case of a Al-Mg-spinel slurry, in particular, whether the hydrolysis reaction or the spinel formation is faster and which of the intermediate hydroxide phases Al(OH)3, and Mg(OH)2, or MgO and Al2O3 or MgAl2O4H2O are formed during the spinel formation. The spinel-alloy was produced using the polymeric route during wet chemical processing. Aluminium-isopropoxide was hydrolyzed in order to form the boehmite-sol and then the same amount of magnesia was added and mixed. This sol precipitated as boehmite (AlOOH) and brucite (Mg(OH)2) after ageing for 12h as confirmed by differential thermal analysis (DTA), and differential thermal gravity (DTG) measurements. After that, the powders were subsequently annealed at 900oC for 3h in air and observed by TEM. Calculations using thermodynamic enthalpy data are in good agreement with the experiments and can be used to predict reaction paths in other system as well.

PREPARATION OF SOME NANO SIZE COLOSSAL MAGNETO RESISTANCE MATERIALS BY THE SOL-GEL ROUTE

2003 ◽  
Vol 17 (01) ◽  
pp. 19-24 ◽  
Author(s):  
K. PADMAVATHI ◽  
V. RAJAKUMARI ◽  
M. VITHAL ◽  
V. PRASD ◽  
S. V. SUBRAMANYAM ◽  
...  
Keyword(s):  
Single Phase ◽  
Sol Gel ◽  
Solid State Reaction Method ◽  
X Ray Diffraction ◽  
Resistivity Measurements ◽  
Temperature Range ◽  
Ionic Size ◽  
Colossal Magneto Resistance ◽  
Magneto Resistance ◽  
Nano Size

A series of colossal magneto resistance materials having compositional formula Re 0.67 Sr 0.33 MnO 3 (Re = Nd, Gd, … etc.) were prepared by the sol-gel method, using Ethylene glycol as a gelating reagent. The materials were characterized by the powder X-ray diffraction technique and are found to be single phase with orthorhombic structure. The particle size of all the materials were calculated using the well known Shearer formula and are found to be in the range of 20–45 nm. In order to determine the transition temperature (T c ), the DC electrical resistivity measurements were also carried out over a temperature range 80–300 K using the four probe method and it has been observed that the T c values are found to increase with increasing ionic size. Finally the magneto resistance measurements were also undertaken in the temperature range 80–300 K and it has been found that the MR values of these materials are better when compared with those prepared by the solid state reaction method.

scholarly journals PSEUDO-GAP FEATURES OF INTRINSIC TUNNELING IN (HgBr2)-Bi2212 SINGLE CRYSTALS

1999 ◽  
Vol 13 (29n31) ◽  
pp. 3758-3763 ◽  
Author(s):  
AUGUST YURGENS ◽  
DAG WINKLER ◽  
TORD CLAESON ◽  
SEONG-JU HWANG ◽  
JIN-HO CHOY
Keyword(s):  
Temperature Dependence ◽  
Single Crystals ◽  
Room Temperature ◽  
Unit Cell ◽  
Superconducting Gap ◽  
Axis Direction ◽  
Temperature Range ◽  
Dynamic Conductance

The c-axis tunneling properties of both pristine Bi2212 and its HgBr 2 intercalate have been measured in the temperature range 4.2-250 K. Lithographically patterned 7-10 unit-cell heigh mesa structures on the surfaces of these single crystals were investigated. Clear SIS-like tunneling curves for current applied in the c-axis direction have been observed. The dynamic conductance d I/ d V(V) shows both sharp peaks corresponding to a superconducting gap edge and a dip feature beyond the gap, followed by a wide maximum, which persists up to a room temperature. Shape of the temperature dependence of the c-axis resistance does not change after the intercalation suggesting that a coupling between CuO 2-bilayers has little effect on the pseudogap.

Structural-phase transition in (Cu2Te)2−x(ZnTe)x at high temperature

2021 ◽  
pp. 2150113
Author(s):  
H. B. Gasimov ◽  
R. M. Rzayev
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
High Temperature ◽  
Single Crystals ◽  
Structural Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Range ◽  
Xrd Study ◽  
Xrd Method

Cu2Te single crystal was grown by the Bridgman method. X-ray diffraction (XRD) study of Cu2Te single crystals in the temperature range of 293–893 K was performed and possible phase transitions in the mentioned range of temperature have been investigated. (Cu2Te)[Formula: see text](ZnTe)[Formula: see text] single crystals also were grown with [Formula: see text], 0.05, 0.10 concentrations and structural properties of the obtained single crystals were investigated by the XRD method in the temperature range 293–893 K. Lattice parameters and possible phase transitions in the mention temperature range were determined for (Cu2Te)[Formula: see text](ZnTe)[Formula: see text] single crystals for [Formula: see text], 0.05, 0.10 concentrations.

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