STABILITY OF THE PEROVSKITE PHASE IN PMN-PZN-PT CERAMICS

The thermal stability of ceramics based on PMN, PZN and their solid so lutions PMN-PT, PZN-PT (PMN = PbMg1/3Nb2/3O3, PZN = PbZn1/3Nb2/3O3, PT = PbTiO3) during sintering is investigated. The present work confirms that the incorporation of a limited excess of MgO in the starting mat erials is actually quite beneficial for the synthesis of a pure PMN pe rovskite phase, and that it prevents the formation of a secondary pyro chlore-type phase, after PbO loss during firing. An excess of ZnO is m uch less efficient for the stabilization of the PZN compound. Examinat ion of the microstructural evolution as well as analysis of second pha ses in these materials and in their solid solutions formed with lead t itanate by wavelength dispersive spectroscopy and/or energy dispersive X-ray spectroscopy techniques, allows a mechanism to be proposed for the stabilization of the PMN-based perovskite phases by an excess of M gO.