Thermal-decomposition chemistry of modified lead-titanate aquo-diol gels used for the preparation of thin films

Lead-titanate gels and thin films modified with calcium, lanthanum or samarium have been prepared by chemical solution deposition (CSD) methods. Lead acetate, titanium di-isopropoxide bis-acetylacetonate and 1,3-propanediol were used for the synthesis of Pb-Ti-sols. Calcium, lanthanum or samarium were added to these sols as acetates or nitrates dissolved in water. The solutions were dried to obtain the gels or spin-coated onto platinised silicon substrates to obtain the films. Thermal decomposition of the gels was followed by means of simultaneous thermogravimetric and differential-thermal analysis (TGA/DTA) coupled with evolved gas analysis (EGA). Infrared (IR) analysis of the gels helped to identify the compounds formed during the thermal decomposition. Crystal structure and microstructure of the films were observed by grazing incidence X-ray diffraction (GIXRD) and scanning electron microscopy (SEM). These analyses indicated that the structure and microstructure of the modified-lead-titanate thin films are related to the thermal decompositions of the corresponding gels. It was inferred from these studies that the decomposition sequence is linked to the type of modifier, Ca, La or Sm, and to the precursor salt (acetate or nitrate) used for the incorporation of the modifier into the Pb-Ti-sol.