Structural peculiarities of 0.67 Pb(Mg1/3Nb2/3)O3–0.33 PbTiO3 thin films grown directly on SrTiO3 substrates

Growth of Pb(Mg 1/3 Nb 2/3 )O 3 –33PbTiO 3 thin films by pulsed-laser deposition directly on non-conductive SrTiO 3 substrates for d 33 -mode energy harvesters (EHs) was studied, as they offer a higher figure-of-merit than d 31 -mode EHs. It was found that a high defect density, present in the film grown at 0.13 mbar, is manifested in the form of splitting of the (00 l ) peaks in X-ray diffraction, which was avoided by raising the process pressure to 0.27 mbar. Nevertheless, both films grow in a combined 2D and 3D manner, and form out-of-phase boundaries (OPBs) with a PbO rock-salt structure between the as-grown islands. It was found that the overall composition of the sample with optimized structural and functional properties was Pb 1.07 Mg 0.19 Nb 0.44 Ti 0.32 O 3 , which is close to stoichiometric. The surplus of Pb is compensated by the formation of OPBs and Mg deficit maintains macroscopic electroneutrality. In-plane and out-of-plane relative permittivities of 1900 and 980, respectively, imply macroscopic out-of-plane polarization.