Phase evolution and enhanced room temperature piezoelectric properties response of lead-free Ru-doped BaTiO₃ ceramic

Recent years have witnessed considerable work on the development of lead-free piezoelectric ceramic materials and their structure-property correlations. The development of piezo response is a strong function of phase evolution in these materials. In this work, we report the effect of Ru doping and consequent phase evolution on the maximization of piezoelectric response of polycrystalline lead-free bariumtitanate, depicted as Ba(RuxTi1-x)O-3 (BRT). The samples were prepared in a narrow compositional range of 0 <= x <= 0.03 using the conventional solid-state reaction method. Ru doping increases the leakage current of BaTiO3 samples attributed to increased oxygen vacancy concentration due to substitution of Ti4+ by Ru3+. Detailed structural analysis reveals that samples exhibiting coexistence of tetragonal (space group: P4mm) and orthorhombic (space group: Amm2) structured phases near roomtemperature reveal relatively enhanced piezoelectric properties. The BRT sample with Ru content of 2 mol% yields a maximum longitudinal piezoelectric coefficient, d33 of similar to 269 pC/N, a high strain value of 0.16% with a large remnant polarization of similar to 19 mu C/cm(2) and a coercive field of 5.8 kV/cm. We propose that the '4d' orbital of Ruthenium plays a crucial role in improving the functional properties and in decreasing the ferroelectric Curie temperature. Our work provides clues into tailoring the phase evolution for designing lead-free piezoelectric materials with enhanced piezoelectric properties.