Powder processing for the fabrication of electric-field textured electroceramics

Electroceramic materials are a key component to many modern technologies. The controlled development of crystallographic texture in electroceramics is one way for effectively improving their properties. The preferred orientation governs various structural and mechanical properties of these materials. Several methods have been demonstrated to texture electroceramic materials, including: 1) templated grain growth (TGG) and 2) the magnetic orientation. This thesis explores experimental techniques for processing of textured electroceramics using electric field particle orientation. It is proposed that the polarization anisotropy of a material may be used to align particles under an external electric field when the particle is free to rotate in a suspension medium. There are several technical difficulties to overcome to achieve such electrical orientation of particles and thus the project description can be described by four major components: 1) calculation of particle poling and reorientation fields, 2) particle preparation, 3) individual particle poling and reorientation, 4) preparation of final textured ceramics. Within this thesis both the calculations of required processing conditions and the production of suitable powders was achieved.BaTiO3 was chosen as a model system as it is one of the most extensively studied ferroelectric materials and can be generated in ceramic form with variable grain size. The use of BaTiO3 for piezoelectric applications is, however, limited due to the small piezoelectric coefficient and temperature instability of response. The texturing method explored however, should be applicable to a wide range of materials and may be of use for the development of future lead-free piezoelectric ceramics.BaTiO3 ceramics with optimum grain sizes of 25µm were processed by adjusting the sintering temperature used. These particles were then separated into particle size distributions with a narrow size width such that each particle has the minimum number of grains within it. When used with a suspension medium with a dielectric constant approximately 21 and a packing density of BT particles of 63%vol. it was found that an external field of 20.54kv/mm was required to first pole the individual particles and then reorient them.Further work is proposed to achieve the final goal of producing a textured electroceramic using the methods outlined in this thesis