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Electrical breakdown phenomena of barium titanate ceramic were studied. Sintered ceramic samples made from high purity BaTiO 3 powders with varying particle sizes were obtained by heat treatment in the range of 1280∼1400 • C. The resulting average grain size value changed from 1.3 µm to over 40 µm. After applying gold electrodes, electrical breakdown test was performed at two different temperatures, i.e. room temperature and 150 • C, for samples immersed in silicone oil bath using 60 kV dc power supply with voltage rate of 500 V/s. As a consequence, both intrinsic and extrinsic failure mechanisms were identified and commonly occurred in these materials. Effects of sample thickness and grain size on breakdown strength are discussed in some details. Crystalline state, i.e. either ferroelectric tetragonal phase or paraelectric cubic phase, showed great influence on intrinsic breakdown mode. A qualitative model for intergranular and transgranular mechanisms is proposed.

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Optical properties of La2Ti2O7 thin films were investigated by spectroscopie ellipsometry and compared to those of bulk sintered ceramics. Thin films were prepared by pulsed laser deposition (PLD) from bulk targets. To separate the effects of thickness, porosity, and index of refraction on observed Ψ and δspectra in thin films, a Cauchy model for n vs. λ was developed from sintered samples, with known porosity. Assuming the effective bulk index of refraction followed the rule of mixtures, corrected models for La2Ti2O7 without porosity were used to determine thickness and porosity of thin films as a function of fabrication parameters such as laser energy, substrate material and temperature. Ellipsometry models were tested and refined through XRD, EDX, ESCA, and SEM.

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