Sol-Gel Processing and Electrospinning of Barium Strontium Titanate for Energy Conversion Applications

Abstract

Barium strontium titanate (Ba\(_{1-x}\)Sr\(_{x}\)TiO\(_{3}\), or BST) is a highly versatile dielectric material because its properties can be changed and controlled via its stoichiometry, x. Because of this, BST is excellent for isolating and investigating numerous electrical effects such as piezoelectricity, pyroelectricity and flexoelectricity. This makes it a very useful material for developing thermoelectrical and electromechanical devices and for use in other energy conversion applications. While BST is quite commonly worked with in the form of thin-films or as nanoparticles for studying electrical phenomena, much less research has looked into using BST in the form of nanowires. Nanowires are particularly useful because they have high surface-area-to-volume ratios and often exhibit useful poling effects. Thus, studying the various electrical phenomena via BST-nanowires is interesting and worthwhile. In this thesis, BST-0.6 (Ba\(_{1-x}\)Sr\(_{x}\)TiO\(_{3}\) with x = 0.4) was successfully synthesized via the sol-gel process and converted into thin-films. Conditions and parameters for producing high quality thin-films were established. BST-0.6 nanowires were then successfully synthesized via electrospinning. Metal-insulator-metal (MIM) heterostructures with electrospun BST-0.6 nanowire-film as the insulating layer in a silver sandwich were created. Basic electrical measurements of MIM heterostructures provided a starting point for further discussion of applications of BST-nanowires such as in unique energy conversion mechanisms such as pyro-flexoelectricity. The proving of the novel energy conversion mechanism of ‘pyro-paraelectricity’ via sputtered BST-0.625 is explained in detail. The future outlook of BST thin-films and nanowires is discussed as well.