Nanofabrication, characterization and electrical properties of sol-gel derived ferroelectric PLZT 7/65/35 ceramic thin films and fibers

Thin films and fibers of ferroelectrics have potential applications as piezoelectric, pyroelectric, dielectric and electro-optic devices when integrated with the existing microelectronics and fiber-optics technologies. This study utilized polymeric sol-gel processing as a technique which enabled the fabrication of ceramic thin films and polycrystalline ceramic fibers of PLZT 7/65/35. The raw materials utilized were lead acetate trihydrate, lanthanum acetate hydrate, zirconium n-propoxide and titanium n-propoxide along with 2-methoxyethanol as the solvent and 0.1M HNO{dollar}sb3{dollar} as the catalyst. IR and Raman spectral techniques were utilized to characterize the precursor to sol to gel to crystals transformations and related to the structural evolution. The films were formed by spin-coating the partially hydrolyzed precursor sol on various substrates. The substrates used were conductors (Au, Al, Pt), single-crystal semiconductors (Si (100), Si (111)) and insulators (SiO{dollar}sb2{dollar}, Al{dollar}sb2{dollar}O{dollar}sb3{dollar}, MgO). Rapid thermal processing was utilized as an alternate firing technique. The one-coat film was about 80 nm to 110 nm while the 25-coat film was about 3 {dollar}mu{dollar}m to 5 {dollar}mu{dollar}m thick. The microstructure of the PLZT 7/65/35 films on Si (100) substrates showed the largest islands which had an average size of 90 {dollar}mu{dollar}m for one-coat and 50 {dollar}mu{dollar}m for 25-coat films with grain size of about 100 nm to 200 nm. The mechanism of crystallization of the films on Si (100), Si (100) and SiO{dollar}sb2{dollar} substrates was found different to be from that on the polycrystalline metal and ceramic substrates. The electrical characterization yielded lower dielectric constants due to the cracks and the presence of the interaction layers. The sol-gel derived ferroelectric fibers were about 35 {dollar}mu{dollar}m in diameter and had a grain size about 100 nm to 200 nm. The sintered fibers had a circular cross-section and were fragile.