Transport properties and the structure of vanadium phosphate glasses

The adiabatic hopping model for the electrical conductivity of the vanadium phosphate glasses, V1+xP1−xO5−c/2, is examined in terms of their structures as derived from recent X-ray studies. These indicate that the relevant concentration variable for rationalizing the Seebeck coefficient data is c, the fraction of non-tetrahedral vanadium ion sites which are polarons. The polarons interlayer coordination number is 3. The average hopping distance varies by only 5% for 0 ≤ x ≤ 1. The experimental conductivities compared with[Formula: see text]suggest that n is near 3 and that the jump frequency v0 varies by nearly a factor of 3 over the composition range.

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Thermoelectric Performance of Glass Microsphere Dispersed Bi-Sb Composites at Low Temperature

Materials Science Forum ◽

10.4028/www.scientific.net/msf.743-744.120 ◽

2013 ◽

Vol 743-744 ◽

pp. 120-125

Author(s):

Zhen Chen ◽

Ye Mao Han ◽

Min Zhou ◽

Rong Jin Huang ◽

Yuan Zhou ◽

...

Keyword(s):

Thermal Conductivity ◽

Electrical Conductivity ◽

Seebeck Coefficient ◽

Thermoelectric Materials ◽

Sem Analysis ◽

Glass Microsphere ◽

Thermoelectric Performance ◽

X Ray Diffraction ◽

X Ray ◽

Measurement Results

In the present study, the glass microsphere dispersed Bi-Sb thermoelectric materials have been fabricated through mechanical alloying followed by pressureless sintering. The phase composition and the microstructure were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. Electrical conductivity, Seebeck coefficient and thermal conductivity were measured in the temperature range of 77~300 K. The ZT values were calculated according to the measurement results. The results showed that the electrical conductivity, Seebeck coefficient and thermal conductivity decreased by adding glass microsphere into Bi-Sb thermoelectric materials. However, the optimum ZT value of 0.24 was obtained at 260 K, which was increased 10% than that of the Bi-Sb matrix. So it is confirmed that the thermoelectric performance of Bi-Sb-based materials can be improved by adding moderate glass microspheres.

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Thermoelectric properties of polycrystalline Bi2Se3−x by powder compaction sintering

Modern Physics Letters B ◽

10.1142/s0217984920502061 ◽

2020 ◽

Vol 34 (18) ◽

pp. 2050206

Author(s):

Ying Zhou ◽

Zhenhua Ge ◽

Jun Guo ◽

Jing Feng

Keyword(s):

Electrical Conductivity ◽

Seebeck Coefficient ◽

Carrier Concentration ◽

Thermoelectric Properties ◽

Thermoelectric Materials ◽

Electrical Transport ◽

Bulk Material ◽

Powder Compaction ◽

Electrical Transport Properties ◽

X Ray

[Formula: see text] is a [Formula: see text] compound (where Pn = Bi and Sb, Ch = Te, Se, and S), which has attracted increasing attention as a candidate for use in thermoelectric applications. Previous studies demonstrated the advantage of [Formula: see text] thermoelectric materials, despite an inferior thermoelectric performance. Herein, a series of [Formula: see text] ([Formula: see text], 0.10, 0.15, 0.20, and 0.25) thermoelectric materials were prepared by powder compaction sintering. The effects of phase structures and microstructure of the [Formula: see text] bulk material were analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The thermoelectric properties, including Seebeck coefficient, electrical conductivity, and thermal conductivity, were measured systematically. The results show that carrier concentration increased with decreasing Se content, which in turn affected the electrical transport properties. Low Se contents gave larger power factor (PF) values than the pristine [Formula: see text] sample, the maximum PF value being [Formula: see text] at 320 K for [Formula: see text]. The variation in PF was attributed to the variations in electrical conductivity [Formula: see text] and Seebeck coefficient [Formula: see text] upon optimizing Se content. The [Formula: see text] samples showed an enhanced thermoelectric figure of merit (ZT) with increasing measurement temperature, due to the increased [Formula: see text] value, [Formula: see text], and decreased [Formula: see text]. The [Formula: see text] sample exhibited the highest ZT (0.28) at 575 K, while [Formula: see text] exhibited the lowest ZT (0.14) at 325 K. This indicated that tuning Se content was an effective way to enhance carrier concentration.

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STRUCTURE AND ELECTRICAL PROPERTIES OF SrO-BOROVANADATE (V2O5)z(SrO)0.2(B2O3)0.8-z GLASSES

International Journal of Modern Physics B ◽

10.1142/s0217979210053033 ◽

2010 ◽

Vol 24 (11) ◽

pp. 1471-1488

Author(s):

A. MEKKI ◽

G. D. KHATTAK ◽

M. N. SIDDIQUI

Keyword(s):

Electrical Conductivity ◽

Temperature Dependence ◽

Inductively Coupled Plasma ◽

Glass Structure ◽

Model Parameters ◽

Nominal Composition ◽

Polaron Hopping ◽

X Ray ◽

Dc Electrical Conductivity ◽

Hopping Model

SrO -borovanadate glasses with the nominal composition (V 2 O 5 ) z( SrO )0.2 ( B2 O 3 ) 0.8-z, 0.4≤z ≤0.8 were studied by direct current (DC) electrical conductivity, inductively coupled plasma (ICP) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and X-ray-powder-diffraction (XRD). These glasses were prepared by a normal quench technique and the actual compositions of the glasses were determined by ICP spectroscopy. XRD patterns confirm the amorphous nature of the present glasses. The temperature dependence of DC electrical conductivity of these glasses has been studied in terms of different hopping models. The IR results agree with previous investigations on similar glasses and it has been concluded that similar to SrO -vanadate glasses, metavandate chainlike structures of SrV 2 O 6 and individual VO 4 units also occur in these SrO -borovanadate glasses. The SrV 2 O 6 and VO n polyhedra predominate in the low B 2 O 3 containing SrO -borovanadate glasses as the B substitutes into the V sites of the various VO n polyhedra and only when the B 2 O 3 concentration exceeds the SrO content do BO n structures appear. This qualitative picture of three distinct structural groupings for the Sr -vanadate and Sr -borovanadate glasses is consistent with the proposed glass structure on previous IR and extended X-ray absorption fine structure (EXAFS) studies on these types of glasses. The conductivity results were analyzed with reference to theoretical models existing in the literature and the analysis shows that the conductivity data are consistent with Mott's nearest neighbor hopping model. However, both Mott VRH and Greaves models are suitable to explain the data. Schnakenberg's generalized polaron hopping model is also consistent with the temperature dependence of the activation energy, but the various model parameters such as density of states, hopping energy obtained from the best fits were found to be not in accordance with the prediction of the Mott model.

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X-ray photoelectron spectroscopy (XPS) and magnetic susceptibility studies of copper–vanadium phosphate glasses

Journal of Non-Crystalline Solids ◽

10.1016/s0022-3093(99)00700-0 ◽

2000 ◽

Vol 262 (1-3) ◽

pp. 66-79 ◽

Cited By ~ 34

Author(s):

G.D. Khattak ◽

M.A. Salim ◽

L.E. Wenger ◽

A.H. Gilani

Keyword(s):

Magnetic Susceptibility ◽

Photoelectron Spectroscopy ◽

Phosphate Glasses ◽

Vanadium Phosphate ◽

X Ray

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X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy and electrical conductivity studies of copper phosphate glasses

Journal of Non-Crystalline Solids ◽

10.1016/0022-3093(94)00683-0 ◽

1995 ◽

Vol 185 (1-2) ◽

pp. 101-108 ◽

Cited By ~ 44

Author(s):

M.A. Salim ◽

G.D. Khattak ◽

M.Sakhawat Hussain

Keyword(s):

Electrical Conductivity ◽

Fourier Transform ◽

Infrared Spectroscopy ◽

Fourier Transform Infrared Spectroscopy ◽

Photoelectron Spectroscopy ◽

Fourier Transform Infrared ◽

Phosphate Glasses ◽

X Ray ◽

Copper Phosphate

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Combinatorial Synthesis and Evaluation of Vanadium Oxide Films

Advanced Engineering Forum ◽

10.4028/www.scientific.net/aef.2-3.1071 ◽

2011 ◽

Vol 2-3 ◽

pp. 1071-1076

Author(s):

Qun Jiao Wang

Keyword(s):

Vanadium Oxide ◽

Composition Range ◽

Growth Conditions ◽

Oxide System ◽

Combinatorial Synthesis ◽

X Ray ◽

Lattice Constants ◽

Good Crystallinity ◽

New Material ◽

Vanadium Ion

Combinatorial technology is a powerful tool for new material exploration. La1-xCaxVO3composition-spread films were fabricated by combinatorial pulsed laser deposition and their thermoelectric properties were evaluated paralelly by the multi-channel thermoelectric measurement system. Concurrent X-ray analysis verified the formation of solid soluted films in the full composition range (0≤x≤1) as judged from the linear variation of the lattice constants. Growth conditions of LaVO3films were optimized. Good crystallinity of LaVO3film was obtained at 800°C, and the power factor of 0.6 µW/cm K2was achieved. The effects of oxygen content and the substitutions of Ca and Ce ions on TE properties of were also analysed respectively. Large TE properties in vanadium oxide system can be expected with the change of vanadium ion valence from 3+ to 2+. In La1-xCexVO3(0≤x≤1) system, Ce ion takes 3+ although Ce4+is stable in theory.

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