BaTiO3 formation by thermal decomposition of a (BaTi)-citrate polyester resin in air

Barium titanate nanosized powders were prepared by a slightly modified Pech ini method. The obtained polymerized resin was used as the precursor for Ba TiO3 powder production. DTA TG thermal analysis indicated that thermal deco mposition of the precursors proceeds through four major step processes: (i) dehydration reaction; (ii) combustion reactions; (iii) intermediate phases formation; (iv) decarbonation of the intermediate to give BaTiO3. X-ray di ffractometry (XRD) and Raman spectroscopy results indicated that, depending on the heating rate, the BaTiO3 formation took place via a predominant sol id-state reaction between nanosized BaCO3 and amorphous TiO2 (TiO2-x) when crystallized by a low-heating rate (1.5 degreesC/min), although a small amo unt of a quasi-amorphous intermediate phase was also present. BaTiO3 crysta llization by rapid heating rate (5 degreesC/min) took place through a quasi -amorphous intermediate phase formation as the main rate-controlling factor for the crystallization process. The fact that the low heating rate minimi zes the intermediate phase content indicates the strong influence of the th ermal heating on the kinetics of the involved transformation or in the mech anism. Although XRD results seem to indicate the formation of pseudocubic B aTiO3 as the final reaction product, the Raman spectra indicated as more pr obable the formation of a mixture of an oxygen-deficient hexagonal and tetr agonal BaTiO3 phases below 700 degreesC. Above that temperature the tetrago nal BaTiO3 was the only phase present. As-prepared BaTiO3 strongly agglomer ated powders were relatively sinter active, leading to dense ceramic bodies (greater than or equal to 95% of the theoretical value). Microstructural. (grain size approximately 1 mum) and room-temperature dielectric properties (epsilon (tau) approximate to 2000 and tan delta less than or equal to 2%) at 10 kHz indicated that the obtained powders have to be optimized.