scholarly journals Magnon and Phonon Excitations in Nanosized NiO

2019 ◽  
Vol 56 (2) ◽  
pp. 61-72 ◽  
Author(s):  
N. Mironova-Ulmane ◽  
A. Kuzmin ◽  
I. Sildos ◽  
L. Puust ◽  
J. Grabis
Keyword(s):  
Raman Spectroscopy ◽  
Single Crystal ◽  
Single Crystals ◽  
Room Temperature ◽  
Raman Band ◽  
Antiferromagnetic Phase ◽  
Magnetic Origin ◽  
Zone Centre ◽  
The One ◽  
Magnon Excitation

Abstract Single-crystal, microcrystalline and nanocrystalline nickel oxides (NiO) have been studied by Raman spectroscopy. A new band at ~200 cm−1 and TO-LO splitting of the band at 350–650 cm−1 have been found in the spectra of single-crystals NiO(100), NiO(110) and NiO(111). The Raman spectra of microcrystalline (1500 nm) and nanocrystalline (13–100 nm) NiO resemble those of the single crystals. They all contain the two-magnon band at 1500 cm−1, indicating that the oxides remain at room temperature in the antiferromagnetic phase. Besides, a new sharp Raman band has been observed at 500 cm−1 in nanocrystalline NiO. Its temperature dependence suggests the magnetic origin of the band, possibly associated with the one-phonon–one-magnon excitation at the Brillouin zone centre.

The Characteristic of the La3Ga5SiO14 Single Crystal Grown by Vertical Bridgman Method in Ar Atmosphere

2006 ◽  
Vol 510-511 ◽  
pp. 842-845 ◽  
Author(s):  
Noriko Bamba ◽  
Kentaro Kato ◽  
Toshinori Taishi ◽  
Takayuki Hayashi ◽  
Keigo Hoshikawa ◽  
...  
Keyword(s):  
Melting Point ◽  
Single Crystal ◽  
Single Crystals ◽  
Room Temperature ◽  
Color Change ◽  
Piezoelectric Materials ◽  
Lead Free ◽  
Piezoelectric Constant ◽  
Interstitial Oxygen ◽  
Vertical Bridgman

Langasite (La3Ga5SiO14: denoted by LGS) single crystal is one of the lead free piezoelectric materials with high piezoelectricity that is maintained up to its melting point (1470°C). Although LGS single crystals have usually been grown by Czochralski (CZ) method in oxygen contained atmosphere to prevent evaporation of Ga, they were grown by the vertical Bridgman (VB) method in Ar atmosphere without oxygen, and their properties were evaluated in this work. Transparent and colorless LGS single crystals were successfully obtained without Ga evaporation by the VB method in Ar atmosphere, and their resistivity at room temperature was much higher than that grown by conventional CZ method. Piezoelectric constant d11 of the crystal grown by the VB method was 6 x 10-12 C/N, which was close to that of the crystal grown by CZ method. The colorless transparent LGS single crystal turned to orange and its resistivity decreased by annealing in air. Since an orange-colored transparent LGS single crystal has been grown by conventional CZ method, this indicates that color change and the resistivity decrease of LGS crystal is caused by extra interstitial oxygen atoms in the crystal.

Refinement of the layered titanosilicate AM-1 from single-crystal X-ray diffraction data

2007 ◽  
Vol 63 (11) ◽  
pp. i186-i186 ◽  
Author(s):  
Stanislav Ferdov ◽  
Uwe Kolitsch ◽  
Christian Lengauer ◽  
Ekkehart Tillmanns ◽  
Zhi Lin ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Hydrogen Bonding ◽  
Single Crystal ◽  
Single Crystals ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
First Time ◽  
Ir And Raman ◽  
Bonding Scheme

The structure of the layered noncentrosymmetric titanosilicate AM-1 (also known as JDF-L1, disodium titanium tetrasilicate dihydrate), Na4Ti2Si8O22·4H2O, grown as small single crystals without the use of organics, has been refined from single-crystal X-ray diffraction data. The H atom has been located for the first time, and the hydrogen-bonding scheme is also characterized by IR and Raman spectroscopy. All atoms are in general positions except for the Na, the Ti, one Ti-bound O, one Si-bound O and the water O atoms (site symmetries 2, 4, 4, 2 and 2, respectively).

Characteristic Investigations of Stoichiometric LiNbO3 Single Crystal Fiber Co-Doped with Tb and Mn

2004 ◽  
Vol 449-452 ◽  
pp. 985-988
Author(s):  
S.M. Lee ◽  
J.W. Shur ◽  
T.I. Shin ◽  
W.S. Yang ◽  
G.Y. Kim ◽  
...  
Keyword(s):  
Absorption Band ◽  
Single Crystal ◽  
Optical Microscopy ◽  
Single Crystals ◽  
Absorption Spectra ◽  
Room Temperature ◽  
Crystal Fiber ◽  
Ft Ir ◽  
Homogeneous Distributions ◽  
Co Doped

[MnO2(1.0mol%) : Tb4O7(0.5mo%)] doped stoichiometric LiNbO3 (Mn:Tb:SLN) single crystals of 0.5~1.0 mm in diameter and 30~35 mm in length were grown by micro pulling down(µ-PD) method. We investigated the photoluminescence (PL) properties of Mn:Tb:SLN single crystal. The OH- absorption band of the single crystals observed infrared the absorption spectra by using an FT-IR spectrophotometer at room temperature. Homogeneous distributions of Mn and Tb concentration were confirmed by the EPMA and observed defects by optical microscopy.

Electrical Transport Properties of the Pentatelluride Materials Hfte5 and Zrte5

1997 ◽  
Vol 478 ◽  
Author(s):  
T. M. Tritt ◽  
M. L. Wilson ◽  
R. L. Littleton ◽  
C. Feger ◽  
J. Kolis ◽  
...  
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Electrical Transport ◽  
Entire Range ◽  
Room Temperature ◽  
Polycrystalline Material ◽  
Polycrystalline Materials ◽  
Electrical Transport Properties ◽  
Low Dimensional ◽  
P Type

AbstractWe have measured the resistivity and thermopower of single crystals as well as polycrystalline pressed powders of the low-dimensional pentatelluride materials: HfTe5 and ZrTe5. We have performed these measurements as a function of temperature between 5K and 320K. In the single crystals there is a peak in the resistivity for both materials at a peak temperature, Tp where Tp ≈ 80K for HfTe5 and Tp ≈ 145K for ZrTe5. Both materials exhibit a large p-type thermopower around room temperature which undergoes a change to n-type below the peak. This data is similar to behavior observed previously in these materials. We have also synthesized pressed powders of polycrystalline pentatelluride materials, HfTe5 and ZrTe5. We have measured the resistivity and thermopower of these polycrystalline materials as a function of temperature between 5K and 320K. For the polycrystalline material, the room temperature thermopower for each of these materials is relatively high, +95 μV/K and +65 μV/K for HfTe5 and ZrTe5 respectively. These values compare closely to thermopower values for single crystals of these materials. At 77 K, the thermopower is +55 μV/K for HfTe5 and +35 μV/K for ZrTe5. In fact, the thermopower for the polycrystals decreases monotonically with temperature to T ≈ 5K, thus exhibiting p-type behavior over the entire range of temperature. As expected, the resistivity for the polycrystals is higher than the single crystal material, with values of 430 mΩ-cm and 24 mΩ-cm for Hfre5 and ZrTe5 respectively, compared to single crystal values of 0.35 mΩ-cm (HfTe5) and 1.0 mΩ-cm (ZrTe5). We have found that the peak in the resistivity evident in both single crystal materials is absent in these polycrystalline materials. We will discuss these materials in relation to their potential as candidates for thermoelectric applications.

Ion Induced Damage and their Annealing in LiTaO3 Single Crystal

1995 ◽  
Vol 396 ◽  
Author(s):  
Z Zhang ◽  
I.A. Rusakova ◽  
W.K. Chu
Keyword(s):  
Curie Temperature ◽  
Single Crystal ◽  
Single Crystals ◽  
Thermal Annealing ◽  
Crystalline Structure ◽  
Room Temperature ◽  
Complete Recovery ◽  
Oxygen Ions ◽  
Annealing Temperatures ◽  
Crystal Interface

AbstractLiTaO3 single crystals have been implanted with 100 keV oxygen ions at room temperature with doses of 1×1014 /cm2,6xl014/cm2,1.2x1015/cm2, 6xl015/cm2, and 2xl016/cm2. Annealing temperatures ranged from 550 °C to 1075 °C. RBS-channeling and TEM were used for characterization. For partially damaged samples, complete recovery of the crystalline structure was achieved after annealing at 550 °C, which is below the Curie temperature. For totally amorphized samples, thermal annealing induced multidomain growth. These domains extend beyond the original amorphous/crystal interface deep into bulk (1 – 1.5 μm ).

scholarly journals [HMIM][Br9]: a Room-temperature Ionic Liquid Based on a Polybromide Anion

2013 ◽  
Vol 68 (10) ◽  
pp. 1103-1107 ◽  
Author(s):  
Heike Haller ◽  
Michael Hog ◽  
Franziska Scholz ◽  
Harald Scherer ◽  
Ingo Krossing ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Raman Spectroscopy ◽  
Ionic Liquid ◽  
Nmr Spectroscopy ◽  
Single Crystal ◽  
Room Temperature ◽  
High Electrical Conductivity ◽  
Conductivity Measurements ◽  
X Ray Diffraction ◽  
X Ray

[HMIM][Br9] ([HMIM]=1-hexyl-3-methylimidazolium) has been investigated by Raman spectroscopy, single-crystal X-ray diffraction and NMR spectroscopy. Conductivity measurements show a high electrical conductivity like other polybromides.

Infrared Transmission and Reflectivity Measurements of 4H- and 6H-SiC Single Crystals

2015 ◽  
Vol 821-823 ◽  
pp. 265-268 ◽  
Author(s):  
Ying Xin Cui ◽  
Xiao Bo Hu ◽  
Xian Gang Xu
Keyword(s):  
Raman Spectroscopy ◽  
Fourier Transform ◽  
Single Crystals ◽  
High Purity ◽  
Room Temperature ◽  
Boron Concentration ◽  
Nitrogen Concentration ◽  
Infrared Transmission ◽  
Infrared Transmittance ◽  
P Type

Room temperature infrared transmittance and reflectance spectra of 4H and 6H-SiC single crystals were measured by a NEXUS 670 Fourier Transform Infrared-Raman spectrometer. The transmittance and reflectance of non-doped, V-doped semi-insulating (SI), high purity semi-insulating, n-type and p-type SiC wafers have been compared and assessed. The effect of nitrogen and boron concentration on the transmittance is discussed. In addition, the carrier concentrations in 4H-SiC wafers were measured by Raman spectroscopy at room temperature. The influence of nitrogen concentration on the transmittance is also discussed.

The crystal structure of a simple enol formed in a single-crystal-to-single-crystal enolene rearrangement

2004 ◽  
Vol 82 (2) ◽  
pp. 301-305 ◽  
Author(s):  
Kenneth CW Chong ◽  
Brian O Patrick ◽  
John R Scheffer
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Single Crystals ◽  
Diffraction Data ◽  
Room Temperature ◽  
Thermal Reaction ◽  
Thermal Rearrangement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Phenyl Ketone

When crystals of 9-tricyclo[4.4.1.0]undecalyl-4-(carbomethoxy)phenyl ketone (1) were allowed to stand in the dark for extended periods of time at room temperature, the compound underwent a thermal reaction — the enolene rearrangement — to afford enol 2. The crystals remained transparent and appeared unchanged in shape as the reaction proceeded. X-ray diffraction data were collected on single crystals containing 17%, 25%, 66%, and 100% of the enol. The crystal structure of a simple enol was obtained via this novel single-crystal-to-single-crystal enolene rearrangement.Key words: single crystal, thermal, rearrangement, enol, enolene.

scholarly journals Transport properties in nanostructured thermoelectric materials and single crystal perovskites

2021 ◽  
Author(s):  
◽  
Michael Ng
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Single Crystal ◽  
Single Crystals ◽  
Thermoelectric Properties ◽  
Thermoelectric Materials ◽  
Ligand Exchange ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Surface Degradation

<p>Energy consumption worldwide is constantly increasing, bringing with it the demand for low cost, environmentally friendly and efficient energy technologies. One of these promising technologies is thermoelectrics in which electric power is harvested from waste heat energy. The efficiency of a thermoelectric device is determined by the dimensionless figure of merit ZT = σS²T/k where σ is the electrical conductivity, S is the thermopower, k is the thermal conductivity, and T is the average temperature. In this thesis we investigate the use of nanostructuring, which has been known to lead to significant reduction in the lattice thermal conductivity to maximise the figure of merit.  One of the most successful bulk thermoelectric materials is Bi₂Te₃, with a ZT of unity at room temperature. Here we investigate the effects of nanostructuring on the thermoelectric properties of Bi₂Te₃. Sub-100 nm ₂Te₃ nanoparticles were successfully synthesized and the figure of merit was found to be ZT ~ 5X10⁻⁵ at room temperature. The effect of a ligand exchange treatment to replace the long chain organic ligand on the as-synthesized nanoparticles with a short chain alkyl ligand was explored. After ligand exchange treatment with hydrazine the figure of merit of sub-100 nm Bi₂Te₃ was found to increase by two fold to ZT ~ 1X10⁻⁴ at room temperature. Overall the figure of merit is low compared to other nanostructured Bi₂Te₃, this was attributed to the extremely low electrical conductivity. The thermopower and thermal conductivity were found to be ~96 μVK⁻¹ and ~0.38 Wm⁻¹ K⁻¹ at 300 K respectively, which show improvements over other nanostructured Bi₂Te₃.  Further optimisation of the figure of merit was also investigated by incorporating Cu, Ni and Co dopants. The most successful of these attempts was Co in which 14.5% Co relative to Bi was successfully incorporated into sub-100 nm Bi₂Te₃. The figure of merit of nanostructured Bi₁.₇₁Co₀.₂₉Te₁.₇₁ alloy was found to increase by 40% to a ZT ~ 1.4X10⁻⁴ at room temperature. Although overall the figure of merit is low, the effect of Co alloying and hydrazine treatment shows potential as a route to optimise the figure of merit.  A potential novel material for thermoelectrics applications is inorganicorganic perovskite single crystals. Here we report a synthetic strategy to successfully grow large millimetre scale single crystals of MAPbBr₃₋xClx, FAPbBr₃₋xClx, and MAPb₁-xSnxBr₃ (MA = methylammonium and FA = formamidinium) using inverse temperature crystallisation (ITC) in a matter of days. This is the first reported case of mixed Br/Cl single crystals with a FA cation and mixed Pb/Sn based perovskites grown using ITC. The bandgap of these single crystals was successfully tuned by altering the halide and metal site composition. It was found that single crystals of FAPbBr₃₋xClx were prone to surface degradation with increased synthesis time. This surface degradation was observed to be reversible by placing the single crystals in an antisolvent such as chloroform.  A tentative model was proposed to analyse the IV characteristics of the single crystal perovskites in order to extract mobilities and diffusion lengths. The MAPbBr₃ and MAPbBr₂.₅Cl₀.₅ single crystal mobilities were found to be between 30-390 cm² V⁻¹ s⁻¹ and 10-100 cm² V⁻¹ s⁻¹ respectively, the diffusion lengths were found to be between 2-8 μm and 1-4 μm respectively. This is an improvement over polycrystalline thin film perovskites and comparable to other single crystal perovskites. The conductance of MAPb₁-xSnxBr₃ based perovskites was found to increase by 2 orders of magnitude even with just 1% of Sn incorporated. The thermal conductivity of MAPbBr₃ single crystals was found to be ~1.12 Wm⁻¹ K⁻¹ at room temperature which is reasonable low for single crystals, however no other thermoelectric properties could be measured due to the self cleaving nature of the single crystals with decreasing temperature and the high resistivity of the material.</p>

Lewis-Base Adducts of Group 11 Metal(I) Compounds. LXXIV Synthesis and Structure of the 1 : 1 Adduct of Silver(I) Nitrate with Triphenylstibine

1997 ◽  
Vol 50 (6) ◽  
pp. 671 ◽  
Author(s):  
Effendy ◽  
John D. Kildea ◽  
Allan H. White
Keyword(s):  
Single Crystal ◽  
Structure Determination ◽  
Related Species ◽  
Room Temperature ◽  
Structural Data ◽  
Lewis Base ◽  
One Dimensional ◽  
X Ray ◽  
The One

The synthesis and room-temperature single-crystal X-ray structure determination of the 1 : 1 adduct of silver(I) nitrate with triphenylstibine, AgNO3/SbPh3 (1 : 1), is recorded, being monoclinic, Cc,a 12·824(2), b 15·794(4),c 9·796(2) Å, β 117·50(1)°, Z= 4; conventional R on F was 0·030 for 2881 independent ‘observed’ (I > 3σ(I)) reflections. The complex is a one-dimensional polymer with bridging nitrate groups, resembling in this respect its phosphine and arsine analogues. The completion of this study, along with related species recorded in accompanying papers, means that full structural data are now available for the complete array AgNO3/EPh3 (1 : n), E = P, As, Sb, n = 1–4, with the one exception of E = Sb, n = 2.

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