Effect of mechanical constraint on the dielectric and piezoelectric behavior of epitaxial Pb„Mg1/3Nb2/3...O3„90%...– PbTiO3„10%... relaxor thin films

The effect of heteroepitaxy-induced constraint on the structure and piezoelectric properties of the relaxor ferroelectric lead magnesium niobate–lead titanate ~PMN–PT! were investigated. Relaxor PMN–PT epitaxial thin films with oxide electrodes were grown by pulsed-laser deposition on ~100! LaAlO3 substrates. We observe a systematic decrease in the phase transition temperature ~temperature at which a maximum in dielectric response occurs!, from around 250 to around 60 °C as the relaxor thickness is increased from 100 to 400 nm. This is accompanied by an increase in the relative dielectric constant (er), measured at room temperature and 10 kHz, from 300 to 2000. The piezoelectric coefficient d33 measured using a scanned probe microscope, increase by almost an order of magnitude with increasing film thickness. © 1999 American Institute of Physics. @S0003-6951~99!01952-X#