Local vibrations and negative thermal expansion in ZrW2O8.

Frustrated soft modes and negative thermal expansion in ZrW2O8.

Negative thermal expansion (NTE) in cubic ZrW2O8 has generated much interest due to its large, isotropic, and temperature independent behavior. Here, x-ray absorption fine structure data are presented for various atom pairs, providing evidence that the low-energy modes causing NTE correspond to the correlated vibrations of a WO4 tetrahedron and its three nearest ZrO6 octahedra. This involves tr...

Synthesis and thermal expansion properties of ZrO2/ZrW2O8 composites

In this work, a ceramic composite of ZrW2O8 and ZrO2 was synthesized, in order to investigate the possibility of compensating the positive thermal expansion of ZrO2 with the negative thermal expansion (NTE) compound ZrW2O8, tailoring the thermal expansion of these composites. The NTE material was mixed with varying amounts of ZrO2. The thermal expansion coefficients of this series of composites...

Unusual low-energy phonon dynamics in the negative thermal expansion compound ZrW2O8.

An infrared study of the phonon spectra of ZrW2O8 as a function of temperature which includes the low-energy (2-10 meV) region relevant to negative thermal expansion is reported and discussed in the context of specific heat and neutron density of state results. The prevalence of infrared active phonons at low energy and their observed temperature dependence are highly unusual and indicative of ...

The Route to Negative Thermal Expansion in ZrW2O8

Finite-element analysis of thermal expansion and thermal mismatch stresses in a Cu–60vol%ZrW2O8 composite

Thermal mismatch stresses in the ceramic particles of a Cu–ZrW2O8 composite were calculated using a finite-element model, and found to be high enough to trigger a pressure-induced phase transformation, in agreement with previous measurements by X-ray diffraction. The calculated thermal expansion/contraction curves also agree with previous experimental dilatometric results. 2004 Elsevier Ltd. Al...