This paper presents 3D printed low temperature sintered (< 700 °C) ceramic materials for microwave applications. The advantages of using cold sintered ceramics include better material compatibility with conductive elements in future multi-material additive manufacturing for microwave devices. Molybdate based ceramics have been synthesized and prepared in slurry form that can be printed by using extrusion based additive manufacturing facilities. Dielectric measurement indicates that the sintered ceramic substrates offer relative permittivity up to 76 with low loss tangents less than 0.001.
Additive manufacturing (AM) of co-fired low temperature ceramics offers a unique route for fabrication of novel 3D radio frequency (RF) and microwave communication components, embedded electronics and sensors. This paper describes the first-ever direct 3D printing of low temperature co-fired ceramics/floating electrode 3D structures. Slurry-based AM and selective laser burnout (SLB) were used to fabricate bulk dielectric, Bi2Mo2O9 (BMO, sintering temperature = 620–650°C, εr = 38) with silver (Ag) internal floating electrodes. A printable BMO slurry was developed and the SLB optimised to improve edge definition and burn out the binder without damaging the ceramic. The SLB increased the green strength needed for shape retention, produced crack-free parts and prevented Ag leaching into the ceramic during co-firing. The green parts were sintered after SLB in a conventional furnace at 645°C for 4 h and achieved 94.5% density, compressive strength of 4097 MPa, a relative permittivity (εr) of 33.8 and a loss tangent (tan δ) of 0.0004 (8 GHz) for BMO. The feasibility of using SLB followed by a post-printing sintering step to create BMO/Ag 3D structures was thus demonstrated.
Metamaterials consist of a family of engineered materials whose properties do not exist in nature. They are novel electromagnetic materials (EM) whose effective properties are delivered by their structure rather than the bulk behavior of their materials they are composed of and their overall geometrical characteristics such as size, orientation and arrangement of their unit cells in space, is what grants them their desired electromagnetic properties (i.e. permittivity, permeability etc.). In the context of Radio-frequency (RF) communication, metamaterials are envisaged to be of use in planar antennae and various RF componentry, comprising of sub-wavelength highly ordered alternating arrays of conductive and dielectric materials with a characteristic structural length of one or more orders of magnitude smaller than the EM wavelengths of interest. The realization of such challenging composite materials, would require a fabrication process that can not only utilize a broad range of materials but also the ability to manufacture functional geometries of high geometrical complexity as given in the metamaterials scenario. Additive Manufacturing (also known as 3D Printing) possesses both the aptitude to process a wide range of engineering materials and the ability to deliver three-dimensional structures of high geometrical complexity as required for the realization of 3D metamaterials, with several benefits over traditional manufacturing methods used in the electronics manufacturing industry such as micro/nano-machining and lithography-based techniques. In this research project, we are investigating the application of combined metal/dielectric multi-material printing, to manufacture 3D metamaterial structures. The choice of both metallic and dielectric materials is discussed, together with their followed processing strategy and properties of resulting structures. The project is part the EPSRC Grand Challenge; SYMETA-SYnthesizing 3D METAmaterials for RF, microwave and THz applications (EP/N010493/1). Figure 1. Printing of a Metal/Ceramic Array of Split Ring Resonators (SRR).
This project aims to investigate the feasibility of fabricating novel metamaterial structures from microwave dielectric ceramics using additive manufacturing techniques for high-frequency applications.
This research project will assess the feasibility of introducing novel metamaterials through the real integration of advanced manufacturing technologies and material sciences to produce complex structures with characteristics that are not generally offered by existing materials. This could offer a radically new way of designing and manufacturing electronic components with tailored performance characteristics. To achieve this multidisciplinary project, electronic components or substrates comprising of selected ceramic and/or metal metaatoms of various sizes and shapes will be formulated, fabricated, processed, characterised, and their electronic properties measured at high frequencies.
This research project will asses the feasibility of introducing novel metamaterial structures (nano-micron-meso-macro scale) and the integration of an additive manufacturing process into electronic component design. This interdisciplinary research work will combine the use of materials synthesis, characterisation and novel field assisted processing methodologies to develop customized 3D printing and sintering techniques capable of fabricating hybrid ceramic/metal/polymer metamaterials structures for high-frequency applications in electronics, communication, defense etc.