Effects of MgO stoichiometry on the dielectric and mechanical response of Pb(Mg1/3Nb2/3)O3

Careful control of the magnesia stoichiometry and hydration level overcomes the problem of pyrochlore formation in the synthesis of Pb(Mg1/3Nb2/3)O-3 (PMN). Careful removal of volatiles from MgO showed that excess MgO is not required to form pyrochlore-free PMN using the columbite method; this clarifies the previously reported need of excess MgO. The stoichiometric PMN shows a peak dielectric constant of similar to 15 000 for 1 kHz. In addition, the presence of volatiles in the MgO has been linked with a change in fracture mode. The relation between the MgO stoichiometry and the microstructural and dielectric properties is presented in an integrated study using X-ray diffraction at various temperatures, dielectric response, and microscopy,