Low temperature preparation of ferroelectric relaxor composite thick films

In this work, the fabrication and characterization of a composite films comprising classical ferroelectric (PbTiO3, PT) and relaxor (PbMg1/3Nb2/3O3, PMN) material is reported. Thick films consisting of ferroelectric and relaxor phases in the thickness range of 2-10 mu m are fabricated on Pt-coated Si substrates at a temperature of <= 550 degrees C via a modified sol-gel route. The phase purity of the composite films was determined by X-ray powder diffraction pattern. The morphology and composition homogeneity were analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and by X-ray mapping method, respectively. High dielectric permittivity (epsilon approximate to 1100) and low loss values (tan delta approximate to 0.03) at 1 kHz and room temperature were measured on 2-mu m-thick composite films for a particular composition of 83 mol% of a PT phase and 17 mol% of a PMN phase, with associated remanent polarization of P approximate to 31.6 mu C/cm(2) and coercive field of E-c congruent to 166 kV/cm. Piezo-response force microscopy analysis of the composite film showed that the film is piezoelectric and switchable. The temperature dependence of the effective dielectric permittivity and loss of the films at different frequencies was studied in the temperature range -50 degrees to 200 degrees C. In the temperature range used for applications (-50 degrees to +100 degrees C) the composite shows quite low temperature coefficient of capacitance (TCC=100%(C-T-C-50 degrees)/C-50 degrees C))=18%, much lower than both PMN thick film and PT film in the same temperature range. This composition is therefore promising for low TCC applications.