Atomic and Electronic Structure of Zinc and Copper Pyrovanadates with Negative Thermal Expansion

Zinc and copper pyrovanadates are promising materials for micro- and optoelectronics due to their negative coefficient of volume thermal expansion (NTE). Besides, solid solutions on the base of these compounds can be used to obtain grade materials with variable thermal coefficients. Thermal deformation of both Zn2V2O7 and Cu2V2O7 structures was studied. According to the structural data, NTE of these substances is provided by the zigzag shape of zinc (copper) chains alongside with stable distances between layers. The structural and electronic characteristics depending on temperature were studied for α-Zn2V2O7 and α-Cu2V2O7 by using the first principle method. Our results demonstrate that the lowest total energies corresponds to the structural parameters at 400° C and 200° C for α-Zn2V2O7 and α-Cu2V2O7, respectively. We predict that α- Zn2V2O7 is a semiconductor with the band gap of 1,5 эВ and the bottom of conduction band is determined by the vanadium 3d states with small addition of antibonding oxygen 2р-states. For α- Cu2V2O7, the lowest interband transitions correspond to energy of 1,6 eV and involve also the O2p and V 3d states.

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Size and crystal symmetry breaking effects on negative thermal expansion in ScF3 nanostructures

Physical Chemistry Chemical Physics ◽

10.1039/d1cp02809j ◽

2021 ◽

Author(s):

Chunyan Wang ◽

Dahu Chang ◽

Junfei Wang ◽

Qilong Gao ◽

Yinuo Zhang ◽

...

Keyword(s):

Thermal Expansion ◽

Symmetry Breaking ◽

Coefficient Of Thermal Expansion ◽

Negative Thermal Expansion ◽

Crystal Symmetry ◽

Negative Coefficient ◽

Membrane Vibration

New membrane vibration and surface symmetry breaking effects determine the negative coefficient of thermal expansion at the nanoscale.

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Structure and thermal expansion of liquid bismuth

Materials Science-Poland ◽

10.1515/msp-2015-0100 ◽

2015 ◽

Vol 33 (4) ◽

pp. 767-773 ◽

Cited By ~ 3

Author(s):

S. Mudry ◽

I. Shtablavyi ◽

U. Liudkevych ◽

S. Winczewski

Keyword(s):

Thermal Expansion ◽

Thermal Expansion Coefficient ◽

Expansion Coefficient ◽

Negative Thermal Expansion ◽

Structural Data ◽

Structure Parameters ◽

Main Structure ◽

Liquid Bismuth ◽

Structure Changes ◽

Temperature Ranges

AbstractExperimental structural data for liquid Bi were used for estimation of the main structure parameters as well as the thermal expansion coefficient both in supercooled and superheated temperature ranges. It was shown that the equilibrium melt had a positive thermal expansion coefficient within a temperature range upon melting and a negative one at higher temperatures. The former was related to structure changes upon melting, whereas the latter with topologic disordering upon further heating. It was found that the superheated melt had a negative thermal expansion coefficient. The results obtained from structural data were compared with the thermal expansion coefficient calculated from the data of density for liquid Bi.

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Quartz: structural and thermodynamic analyses across the α ↔ β transition with origin of negative thermal expansion (NTE) in β quartz and calcite

Acta Crystallographica Section B Structural Science Crystal Engineering and Materials ◽

10.1107/s205252061600233x ◽

2016 ◽

Vol 72 (2) ◽

pp. 249-262 ◽

Cited By ~ 4

Author(s):

Sytle M. Antao

Keyword(s):

Thermal Expansion ◽

Order Parameter ◽

Polymorphic Transformation ◽

Landau Theory ◽

Structural Parameters ◽

Negative Thermal Expansion ◽

Framework Structure ◽

X Ray Diffraction ◽

X Ray ◽

First Order

The temperature variation,T, of the crystal structure of quartz, SiO2, from 298 to 1235 K was obtained with synchrotron powder X-ray diffraction data and Rietveld structure refinements. The polymorphic transformation fromP3221 (low-T, α quartz) toP6222 (high-T, β quartz) occurs at a transition temperature,Ttr= 847 K. TheTvariations of spontaneous strains and several structural parameters are fitted to an order parameter,Q, using Landau theory. The change in Si atom coordinate, Six, givesTtr−Tc= 0.49 K, which indicates an α ↔ β transition that is weakly first order and nearly tricritical in character (Q4∝T). Strains give higherTtr−Tcvalues (≃ 7 K). Other fitted parameters are the oxygen Ozcoordinate, Si—Si distance, Si—O—Si and φ angles, and intensity of the (111) reflection,I111. In α quartz, the Si—Si distance increases withTbecause of cation repulsion, so the Si—O—Si angle increases (and φ decreases) and causes the thermal expansion of the framework structure that consists of corner-sharing distorted rigid SiO4tetrahedra. The Si—Si distances contract withTand cause negative thermal expansion (NTE) in β quartz because of increasing thermal librations of the O atom in the Si—O—Si linkage that occur nearly perpendicular to the Si—Si contraction. In calcite, CaCO3, the short Ca—Ca distance expands withT, but the next-nearest Ca—Ca distance, which is of equal length to theaaxis, contracts withTand causes NTE along theaaxis. The thermal librations of the atoms in the rigid CO3group increase withTalong thecaxis.

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Negative Thermal Expansion Behaviour in The NZP Phase NbTi(PO4)3

MRS Proceedings ◽

10.1557/proc-547-191 ◽

1998 ◽

Vol 547 ◽

Cited By ~ 5

Author(s):

D. A. Woodcock ◽

P. Lightfoot ◽

R. I. Smith

Keyword(s):

Thermal Expansion ◽

Neutron Diffraction ◽

Volume Expansion ◽

Negative Thermal Expansion ◽

Structural Data ◽

Thermal Expansion Behaviour ◽

Powder Neutron Diffraction ◽

Positive Volume ◽

The Difference ◽

Expansion Behaviour

AbstractWe present new detailed structural data versus temperature on the Nasicon structured material NbTi(PO4)3 obtained from powder neutron diffraction studies. This material shows a significant volume contraction over the range 20°C < T < 700°C. αa varies between –4.34 and -0.11 × 10-6°C-1 and αc between 0.08 and 3.07 × 10-6°C-1 over this range. This behaviour contrasts with the case of NaTi2(PO4)3 (NaTP) which shows a positive volume expansion. The difference in this behaviour can be explained by the presence of filled MI sites in NaTP which are vacant in the case of NbTP.

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Structural investigation of the negative-thermal-expansion material ZrW2O8

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768198016966 ◽

1999 ◽

Vol 55 (3) ◽

pp. 333-340 ◽

Cited By ~ 130

Author(s):

John S. O. Evans ◽

W. I. F. David ◽

A. W. Sleight

Keyword(s):

Phase Transition ◽

Thermal Expansion ◽

Structural Investigation ◽

Cell Parameter ◽

Coefficient Of Thermal Expansion ◽

Structural Parameters ◽

Negative Thermal Expansion ◽

Three Dimensional ◽

Simple Cubic ◽

Increasing Temperature

High-resolution powder diffraction data have been recorded on cubic ZrW2O8 [a = 9.18000 (3) Å at 2 K] at 260 temperatures from 2 to 520 K in 2 K steps. These data have confirmed that α-ZrW2O8 has a negative coefficient of thermal expansion, α = −9.07 × 10−6 K−1 (2–350 K). A `parametric' approach to Rietveld refinement is adopted and it is demonstrated that a full anisotropic refinement can be performed at each temperature, despite using a data collection time of only 5 min. Examination of the resulting structural parameters suggests that the origin of the contraction with increasing temperature can be traced straightforwardly to the rigid-body transverse librations of bridging O atoms. α-ZrW2O8 undergoes a phase transition from P213 to Pa3¯ at 448 K that is associated with the onset of considerable oxygen mobility. The phase transition can be described in terms of a simple cubic three-dimensional Ising model. Unusual kinetics are associated with this phase transition. Hysteresis in the cell parameter through the phase transition is the opposite of that normally observed.

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Investigation of the Dilation of Epoxy with Negative Thermal Expansion Fillers

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.44-47.2950 ◽

2010 ◽

Vol 44-47 ◽

pp. 2950-2953

Author(s):

Sheng Yi Chang ◽

Hsi Hsun Tsai ◽

Sheng Ching Wang

Keyword(s):

Thermal Expansion ◽

Coefficient Of Thermal Expansion ◽

Ceramic Powder ◽

Negative Thermal Expansion ◽

Negative Coefficient ◽

Silica Powder ◽

Silica Filler ◽

The One ◽

Silicon Based ◽

Electronic Elements

The bonding glue is well used in packaging of the opto-electronic elements. The light paths of the elements are aligned accurately before bonding, the coefficient of thermal expansion of bonding glue is much more large than the one of silicon based optoelectronic elements, the light paths of the elements are thus misalignment after the bonding. The silica filler is usually mixed into the bonding glue for lowering the coefficient of thermal expansion. In this paper, the ceramic powder of the ZrW2O8 with negative coefficient of thermal expansion is thus mixed the commercial bonding glue for deriving of the extra low dilation adhesion. The thermal expansion of the composite bonding glue with negative coefficient of thermal expansion fillers is measured accurately to compare with the filler of silica powder. The results show that a composite glue with the very low coefficient of thermal expansion is therefore acquired for packaging of optoelectronic elements.

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