Processing, characterization and development of rare earth doped lead magnesium niobate ferroelectric ceramic capacitors by sol-gel technique

The present thesis demonstrates synthesis, characterization and electrical properties of relaxor ferroelectric pure Lead Magnesium Niobate (PMN) and Rare Earths (RE) (Er, Eu, Dy, Sm and Tb) doped nano scale powders and PMN thin films on n-type Si substrates using sol-gel technique for capacitor applications. With this respect, transparent solutions were prepared from Pb, Mg and Nb based precursors, methyl alcohol and glacial acetic acid (GAA). The obtained solutions were dried at 80 degree celcius for 60 minutes in air to form gel structure of PMN mixture and heat treated at 530 degree celcius for 3 hours and consequently annealed at 950 degree celcius for 2 hours in air. After the sintering, the PMN powders were milled for 12 hours at room temperature to obtain PMN based nano scale powders. Finally, the powders were dispersed in alcohol and the obtained suspensions were deposited on n-type Si substrates using drop and spin coating systems and then annealed at 730 degree celcius for 1 hour in air. Thermal, structural, microstructural, optical, mechanical and electrical properties of the powder and the coatings were characterized through differential thermal analysis-thermogravimetry (DTA-TG), Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), atomic force microscopy (AFM), dynamic ultra hardness tester (DUH), scratch tester, refractometer, spectrophotometer, high resolution dielectric analyzer machines and Keithley 2400 for current-voltage characterization. The results showed that it was possible to produce the perovskite phase PMN based thin films at 730 degree celcius using sol-gel derived powder precursor suspension method. The optimum capacitor films were successfully applied to a light emitting diode (LED) flash device for camera for very low filling and draining time (17 ms).