PbZn(1/3)Nb(2/3)O3 at 4.2 and 295 K.

The structure of the relaxor ferroelectric lead zinc niobium trioxide, Pb(Zn(1/3)Nb(2/3))O3, known as PZN, was determined at 4.2 and 295 K from very high resolution neutron powder diffraction data. The material is known for its extraordinary piezoelectric properties which are closely linked to the structure. Pseudo-cubic lattice parameters have led to considerable controversy over the symmetry of the structure, which was found to be rhombohedral in the space group R3m at both temperatures. Atomic coordinates have been determined for the first time. They show that, whereas the deviation of the rhombohedral angle from 90 degrees approaches zero at 295 K, the atomic coordinates do not approach typical cubic positions and hence the polarization remains high.