B. Tunaboylu

Characterization of dielectric and electro-optic properties of PLZT 9/65/35 films on sapphire for electro-optic applications

Lead lanthanum zirconate titanate (PLZT) thin films were deposited on r-plane sapphire at low temperatures by RF triode magnetron sputtering using lead compensated hot-pressed targets. To obtain fully perovskite phase in the films, two types of post-deposition processing were investigated: rapid thermal annealing (RTA) and furnace annealing (FA). Dielectric and electro-optic properties of PLZT films were found to be strongly dependent on annealing conditions. The peak dielectric constant of the films were 1200 and 2800 with Curie temperatures of 110/spl deg/C and 190/spl deg/C after RTA and FA processing, respectively. The dielectric losses in the films were fairly low; tan deltas were less than 0.02 after RTA and less than 0.04 after FA processing. The films showed good optical transmission characteristics after annealing and an anomalously large effective quadratic electro-optic effect was observed in one furnace annealed film.

Microwave and conventional sintering of rapidly solidified Al2O3-ZrO2 powders

The Al2O3-ZrO2 eutectic composition was rapidly solidified, forming amorphous and crystalline structures. The as-quenched material was crushed and pressed into pellets which were sintered conventionally or with microwaves. Conventional and microwave sintering at temperatures up to 1600 °C resulted in a microstructure where 100–200 nm ZrO2 grains were present intergranularly in the α-Al2O3 grains. Larger ZrO2 grains (∼1 μm) were found intergranularly. The as-quenched lamellar structure spheroidized during sintering at high temperatures. Boron contamination of the powders resulted in more homogeneous and dense as-fired samples but promoted the ZrO2 tetragonal-to-monoclinic transformation, which was attributed to increased grain boundary diffusivity. Conventional sintering at low temperatures resulted in the formation of “rods” of an Al2O3-rich phase which grew from a low-melting B2O3-rich liquid.

Microstructure of magnetron sputtered PLZT thin films on sapphire

Abstract The microstructural development and crystal structures of sputtered PLZT 9/65/35 films on r-plane sapphire with respect to deposition/annealing conditions were studied. The films were deposited at substrate temperatures below 500°C and annealed in the range 700° to 730°C for 1 min to 20 min for complete perovskite formation either by rapid thermal annealing (RTA) or furnace annealing (FA). The optical transparency was excellent with smooth surfaces in the stoichiometric films but reduced in the Pb-deficient films. The grain sizes in the films varied from 0.1 μm to 0.8 μm and 0.2 μm to 1.2 μm after RTA and FA respectively.

Synthesis and properties of KTN films by sol-gel deposition and RF-magnetron sputtering

Abstract Homogeneous KTN (Potassium Tantalate Niobate) solutions were prepared using potassium acetate and metal alkoxides in 2-methoxyethanol by controlled hydrolysis with 1:2 (KTN/H2O) molar ratio. We report on the synthesis of sol-gel KTN for both the fabrication of homogeneous, dense and stoichiometrically correct ceramic discs by hot isostatic pressing and the deposition of spin-on as well as sputtered thin films. The spin-on KTN films on Pt/Si or r-sapphire were polycrystalline and stoichiometric, however, sputtered films on sapphire were fully (100) oriented and polycrystalline on Pt/SiO2/Si substrates with some potassium deficiency. The refractive indices of sputtered, dense KTN films on sapphire were between 2.00 and 2.05.

Ferroelectric PLZT thin films deposited by RF triode magnetron sputtering for spatial light modulators

Lead lanthanum zirconate tit an ate , PLZT (9/65/35) thin films were deposited on r-plane sapphire and PtISi by triode-magnetron sputtering at low temperature and transformed to t h e perovskite phase by rapid-thermal annealing. To form perovskite phase directly during depos i t ion requires high substrate temperatures which generally cause lead and/or titanium deficiency. A t relatively low deposition temperatures, t h e deposited films tend to consist of both pyrochlore and perovskite phases. A full transformation o f pyrochlore to perovskite phase is difficult. With low temperature deposition and rapid-thermal annealing, perovskite PLZT (9/65/35) films wi th strong (110) orientation were obtained. Their optical and dielectric properties are reported.

Compaction of Submicron and Nanocrystalline Al2O3-ZrO2 Ceramics

The eutectic in the Al2O3-ZrO2 system was rapidly solidified by heating with an O2-H2 torch and then quenching the melt with a twin roller device. The as-quenched material, which was amorphous or nanocrystalline, was milled with B4C or Al2O3 media and pressed into pellets which were sintered conventionally or with microwaves. Samples contaminated with boron carbide resulted in compacts with substantially reduced porosity and a lower fraction of tetragonal ZrO2. Conventional sintering at low temperatures resulted in the formation of ‘rods’ of an Al2O3 rich phase which grew from the presence of a low melting B2O3-rich liquid. Conventional and microwave sintering at temperatures up to 1600°C resulted in a microstructure where 100–200 nm ZrO2 grains were present intragranularly in the α—Al2O3 grains. Larger ZrO2 grains (~1 μm) were found intergranularly. As-quenched lamellar microstructures were preserved at low temperatures but spheroidized at sintering temperatures > 1600°C.