Investigating the Trade-off between Optical and Mechanical Properties during Constrained Sintering of Mesomorphic Ceramic Films

摘要

Robust, transparent, and birefringent inorganic films are demanded forpolarization control of high-power lasers. While single crystals or filmsobtained via glancing angle deposition exhibit desirable optical properties andlaser damage resistance, these methods are limited by cost and scalability.Mesomorphic ceramics as inorganic solids with liquid crystallinesuperstructure offer appealing transparency and birefringence but lackmechanical robustness due to their high porosity. Here, the effect of sinteringon optical and mechanical properties of mesomorphic ceramics is evaluated.Films prepared by blade coating are sintered under varying conditions.Constrained sintering accomplished crystallite growth, densification, andmorphological changes including necking as well as cracking while preservingthe crystallographic orientation. The extent of sintering as a function ofthermal treatment is quantified by morphology, surface area loss, andcrystallite growth. Moreover, activation energies for surface diffusion andgrain growth are estimated by surface area analysis and X-ray diffraction peaknarrowing, respectively. After sintering, birefringence decreases while Young’smodulus and hardness improve as the film densifies. Upon partial sintering,mesomorphic ceramics retain transparency, high birefringence, and enhancedmodulus. Laser-induced damage threshold is measured as well. The reportedresults represent an important step toward the assembly and sintering ofrobust waveplates with high laser damage resistance.