Optimized Pyroelectric Vidicon Thermal Imager. Volume II. Improper Ferroelectric Materials.

摘要

A comprehensive survey of improper ferroelectrics was carried out to identify materials with potential to enhance the performance of the pyroelectric vidicon. Representatives of four families of improper ferroelectrics were selected for detailed experimental and theoretical analysis: rare-earth molybdates, the sulfate family, propionates, and boracites. A thorough experimental and theoretical characterization of the rare-earth molybdates confirmed the expectation that the dielectric anomaly could be nearly absent in improper ferroelectrics and thus lead to a high value of the figure-of-merit p/epsilon c. Experimental confirmation of the theoretical models allows one to obtain an optimized figure-of-merit of 10,000 sq cm/C for materials of this family as compared to 3,000 sq cm/C for TGS at 40 C). From the sulfate family, lithium ammonium sulfate and its deuterated analog exhibited a room-temperature value of the figure-of-merit about equal to that of TGS at 40 C. The other analog sulfates examined exhibited a characteristically different behavior and smaller values for the figure-of-merit.