Cold sintering and co-firing of a multilayer device with thermoelectric materials

Cold-sintered ZnO and Ca₃Co₄O₉ polycrystalline materials were shown to have thermoelectric properties comparable to those of conventionally sintered ceramics. Extending these processing conditions into a cold sintering co-fired ceramic (CSCC) technology, we integrated n-type and p-type thermoelectric oxides and a separating insulating layer to demonstrate functional multilayer thermoelectric generator devices. A co-fired structure with an insulating 8 mol% yttria-stabilized zirconia (8YSZ) layer enabled multilayer thermoelectric generators (TEG) to be fabricated with a 5 n-p junction device (20 layers). A transmission electron microscopy analysis of the interfaces between the various materials under the co-firing cold sintering showed some interdiffusion of chemical constitutes in a 2.0 μm interface region between the respective ceramic phases. The co-firing of multilayer ceramic and polymer structures were also shown to be possible using insulation layers of polytetrafluoroethylene (PTFE) thermoplastic layers. This demonstrated the feasibility of a single-step process for new structures with both ceramics and polymers, opening up new directions for many new device designs.