Structural investigation of the negative-thermal-expansion material ZrW2O8

1999 ◽  
Vol 55 (3) ◽  
pp. 333-340 ◽  
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.

Role of Out-of-Plane Coefficient of Thermal Expansion in Electronic Packaging Modeling

1999 ◽  
Vol 122 (2) ◽  
pp. 121-127 ◽  
Author(s):  
Manjula N. Variyam ◽  
Weidong Xie ◽  
Suresh K. Sitaraman
Keyword(s):  
Thermal Expansion ◽  
Electronic Packaging ◽  
Thermal Loading ◽  
Coefficient Of Thermal Expansion ◽  
Plane Deformation ◽  
Three Dimensional ◽  
Dissimilar Materials ◽  
3D Models ◽  
Material Behavior ◽  
Element Analysis

Components in electronic packaging structures are of different dimensions and are made of dissimilar materials that typically have time, temperature, and direction-dependent thermo-mechanical properties. Due to the complexity in geometry, material behavior, and thermal loading patterns, finite-element analysis (FEA) is often used to study the thermo-mechanical behavior of electronic packaging structures. For computational reasons, researchers often use two-dimensional (2D) models instead of three-dimensional (3D) models. Although 2D models are computationally efficient, they could provide misleading results, particularly under thermal loading. The focus of this paper is to compare the results from various 2D, 3D, and generalized plane-deformation strip models and recommend a suitable modeling procedure. Particular emphasis is placed to understand how the third-direction coefficient of thermal expansion (CTE) influences the warpage and the stress results predicted by 2D models under thermal loading. It is seen that the generalized plane-deformation strip models are the best compromise between the 2D and 3D models. Suitable analytical formulations have also been developed to corroborate the findings from the study. [S1043-7398(00)01402-X]

Synthesis of ZrW2O8 Ceramics and Composites from Aqueous Sol-Gel Precursors

2006 ◽  
Vol 45 ◽  
pp. 218-222
Author(s):  
Klaartje de Buysser ◽  
Serge Hoste ◽  
Isabel Van Driessche
Keyword(s):  
Phase Transition ◽  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Sol Gel ◽  
Negative Thermal Expansion ◽  
Oxide Mixture ◽  
Stability Range ◽  
Cubic Symmetry ◽  
Geometrical Effect

The thermal expansion of a ceramic material in general leads to a positive thermal expansion coefficient (α). In the last decennium, several families of materials which exhibit negative thermal expansion, arising from a specific geometrical effect in their so-called open framework structures, have been discovered. Usually, this negative thermal expansion coefficient is small, anisotropic and the phenomena occur in a very small temperature interval. ZrW2O8 is an exception because of its large and isotropic negative thermal expansion coefficient (NTE) in a temperature range from 0.5K to 1050K. A cubic symmetry is found over the entire stability range with a phase transition from α-ZrW2O8 to β-ZrW2O8 near 430K. This phase transition is noticed by a change in α. The aqueous citrate-gel method is a suitable synthesis route for negative thermal expansion ceramics and will give a fine, pure and homogenous oxide mixture, well suitable for the preparation of ZrW2O8. The expansion coefficient of α–ZrW2O8 is -11 μm/m K whereas for the β- ZrW2O8 a value of -3 is obtained.

scholarly journals Structural investigation of the negative thermal expansion in yttrium and rare earth molybdates

2011 ◽  
Vol 23 (32) ◽  
pp. 325402 ◽  
Author(s):  
Candelaria Guzmán-Afonso ◽  
Cristina González-Silgo ◽  
Javier González-Platas ◽  
Manuel Eulalio Torres ◽  
Antonio Diego Lozano-Gorrín ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Rare Earth ◽  
Structural Investigation ◽  
Negative Thermal Expansion ◽  
Rare Earth Molybdates

Phase transition temperature and negative thermal expansion of Sc-substituted In2(MoO4)3 ceramics

2020 ◽  
Vol 55 (14) ◽  
pp. 5730-5740
Author(s):  
Zhiping Zhang ◽  
Yuenan Wang ◽  
Weikang Sun ◽  
Xiuyun Zhang ◽  
Hongfei Liu ◽  
...  
Keyword(s):  
Phase Transition ◽  
Thermal Expansion ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Negative Thermal Expansion

scholarly journals A Proposal for a Composite with Temperature-Independent Thermophysical Properties: HfV2–HfV2O7

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5021
Author(s):  
Philipp Keuter ◽  
Anna L. Ravensburg ◽  
Marcus Hans ◽  
Soheil Karimi Aghda ◽  
Damian M. Holzapfel ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Temperature Coefficient ◽  
Thermophysical Properties ◽  
Coefficient Of Thermal Expansion ◽  
Negative Thermal Expansion ◽  
Phase Fraction ◽  
Formation Temperature ◽  
Oxygen Mobility ◽  
Zero Temperature ◽  
Coefficient Of Elasticity

The HfV2–HfV2O7 composite is proposed as a material with potentially temperature-independent thermophysical properties due to the combination of anomalously increasing thermoelastic constants of HfV2 with the negative thermal expansion of HfV2O7. Based on literature data, the coexistence of both a near-zero temperature coefficient of elasticity and a coefficient of thermal expansion is suggested for a composite with a phase fraction of approximately 30 vol.% HfV2 and 70 vol.% HfV2O7. To produce HfV2–HfV2O7 composites, two synthesis pathways were investigated: (1) annealing of sputtered HfV2 films in air to form HfV2O7 oxide on the surface and (2) sputtering of HfV2O7/HfV2 bilayers. The high oxygen mobility in HfV2 is suggested to inhibit the formation of crystalline HfV2–HfV2O7 composites by annealing HfV2 in air due to oxygen-incorporation-induced amorphization of HfV2. Reducing the formation temperature of crystalline HfV2O7 from 550 °C, as obtained upon annealing, to 300 °C using reactive sputtering enables the synthesis of crystalline bilayered HfV2–HfV2O7.

ChemInform Abstract: Phase Transition and Negative Thermal Expansion in Orthorhombic Dy2W3O12.

ChemInform ◽  
2016 ◽  
Vol 47 (52) ◽  
Author(s):  
Weigang Cao ◽  
Qiang Li ◽  
Kun Lin ◽  
Zhanning Liu ◽  
Jinxia Deng ◽  
...  
Keyword(s):  
Phase Transition ◽  
Thermal Expansion ◽  
Negative Thermal Expansion
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