Crystal Structure of Zirconium Tungstate

The arrangement of the groups in the structure of cubic ZrW2O8 is analogous to the simple NaCl structure, with ZrO6 octahedral at the Na sites, and W2O8 groups at the Cl sites. The unit cell consists of 44 atoms aligned in a primitive cubic Bravais lattice, with unit cell length 9.15462 Angstroms.

The ZrO6 octahedral are only slightly distorted from a regular conformation, and all oxygen sites in a given octahedron are related by symmetry. The W2O8 unit is made up of two crystallographic ally distinct WO4 tetrahedral, which are not formally bonded to each other. These two types of tetrahedral differ with respect to the W-O bond lengths and angles. The WO4 tetrahedral are distorted from a regular shape since one oxygen is unconstrained (an atom that is bonded only to the central tungsten (W) atom), and the three other oxygen’s are each bonded to a zirconium atom (i.e. the corner-sharing of polyhedral).

The structure has P213 space group symmetry at low temperatures. At higher temperatures, a centre of inversion is introduced by the disordering of the orientation of tungstate groups, and the space group above the phase transition temperature (~180C) is Pa .

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Zirconium Tungstate Definition by Wiki

At high pressure, zirconium tungstate undergoes a series of phase transitions, first to an amorphous phase, and then to a U3O8-type phase, in which the zirconium and tungsten atoms are disordered.

Zirconium tungstate (Zr(WO4)2) is a metal oxide with unusual properties. The phase formed at ambient pressure by reaction of ZrO2and WO3 is a metastable cubic phase, which has negative thermal expansion characteristics, namely it shrinks over a wide range of temperatures when heated. In contrast to most other ceramics exhibiting negative CTE (coefficient of thermal expansion), the CTE of ZrW2O8 is isotropic and has a large negative magnitude (average CTE of -7.2x10−6K−1) over a wide range of temperature (-273 °C to 777 °C). A number of other phases are formed at high pressures.

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Zirconium Tungstate

Zirconium tungstate (Zr(WO4)2) is a metal oxide with unusual properties. The phase formed at ambient pressure by reaction of ZrO2 and WO3 is a metastable cubic phase, which has negative thermal expansion characteristics, namely it shrinks over a wide range of temperatures when heated.[1] In contrast to most other ceramics exhibiting negative CTE (coefficient of thermal expansion), the CTE of ZrW2O8 is isotropic and has a large negative magnitude (average CTE of -7.2x10−6K−1) over a wide range of temperature (-273 °C to 777 °C).[2] A number of other phases are formed at high pressures.

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