Diffuse phase transition and relaxor properties of nanocrystalline lead calcium titanate

Recently the question arised, how the physical properties of a ferroelectri c change when the grain size is reduced to the nanometer range. We have pro duced amorphous Lead Calcium Titanate (PTC) films by rf-sputtering onto Pt/ Ti/Si substrates. We then prepared different grain sizes by two different t ypes of annealing processes. To investigate the dielectric properties the t emperature and frequency dependence of the dielectric constant was recorded and temperature dependent Raman spectroscopy was used to look for phase tr ansitions and symmetries. Independent of the annealing method all nanocryst alline samples showed a significant diffusivity of the phase transition. Th e dielectric properties also changed from classical ferroelectric to relaxe r behaviour with a large frequency dependence of the dielectric constant.