Monoclinic PZN-8%PT [Pb(Zn0.3066Nb0.6133Ti0.08)O3] at 4 K

The structure of the relaxor ferroelectric Pb(Zn0.3066Nb0.6133Ti0.08)O-3 (lead zinc niobium titanium trioxide), known as PZN-8% PT, was determined at 4 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. We find the structure to be monoclinic in the space group Cm (No. 8), with the Zn, Nb and Ti cations sharing the octahedrally coordinated B site (site symmetry m, special position 2a) and Pb occupying the 12-coordinate A site (site symmetry m, special position 2a). O atoms occupy a disorted octahedron around the B site (site symmetry m and special position 2a, and site symmetry 1 and general position 4b). Atomic coordinates have been determined for the first time, allowing the direction of spontaneous polarization to be visualized.