Solid State Growth of Piezoelectric Single Crystals

The aim is to grow single crystals of piezoelectric materials employing a solid-state process rather than the conventional melt-growth (Bridgman) route. The latter has inherent disadvantage of composition gradients resulting from partitioning of elements between the melt and the solid. The solid state route in which a seed crystal is propagated through a polycrystalline body by elimination of grain boundaries at high temperature. Solid state crystal growth (SSCG) precludes such partitioning gradients and also avoids the high cost associated with the use of platinum crucibles.

The project will focus on crystals of the Pb(Mg1/3Nb2/3)O3 - PbTiO3 - PbZrO3 perovskite and will explore the use of hot-pressing to prepare fine-grained, pore-free, polycrystalline precursors. This also has the advantage of containing the loss of any volatile cations. Selection of annealing conditions for the crystal growth step will be based on investigations of the diffusion processes in the material that result in preferential grain growth at a seed interface.

The resulting crystals will be characterized for chemical and physical uniformity using electron microscopy and X-ray diffraction. Piezoelectric and dielectric properties will be compared with similar compositions grown by the Bridgman route.