What we do

Our Core Business

The Laboratory for Materials Process Technology is primarily focused on ceramic materials, which, due to their outstanding physical and mechanical properties, are becoming increasingly important in modern microsystems. Ceramic materials are typically used in electrical engineering (e.g. as capacitors or substrates), in microsystem engineering (e.g. as sensors or actuators) and in microreaction and medical technology. Research activities at our lab are based on two columns. The first is the development of new or modified functional ceramics and polymer-composites. The second is the adaptation of already existing methods of processing ceramic and polymer materials for microsystems and electrical engineering. The Laboratory has close relations in both academic and personnel terms to the Karlsruhe Institute of Technology (KIT) in particular to the Institute of Materials Research . Moreover we have strong ties to the department of microwave engineering at the University of Darmstadt (Techische Universität Darmstadt, Fachbreich Mikrowellentechnik (MWT) and the Institute of Materials for Electrical and Electronic Engineering (IWE) at KIT. Such a collaboration creates valuable synergies, providing access to additional facilities and a stimulating and healthy exchange of ideas.

Tunable Ceramic Films
 
 

Cross-section of tunable coplanar waveguide on BST thick-film and alumina substrate

Oxide ceramics which exhibit the Perovskite-structure show a great variety of properties, which may be used in technical devices. The Lab for Materials Process Technology has a close collaboration with TU Darmstadt on the emerging field of tunable dielectric films, which once may be integrated in new, steerable devices. These devices show a high potential for applications in mobile and satelite communication as well as in RFID-sensors at microwave frequencies. We are able to deposit ceramic films from suspensions and true solutions. Mainly the systems BaTiO3, SrTiO3, Ba/SrTiO3 and Lead-Zirconate-Titanate (PZT) are of current interest. To deposit such films from powder-based suspensions we make use of screen-printing and electrophoretic deposition. To deposit such films from precursor solutions we use CSD-methods like spin-coating and ink-jet printing. To gain specifically doped powders we have developed tailored chemical routes..

      
Synthesis of ceramic oxide powders
 

Freeze-dried precursor-granules

To gain specifically doped powders for electrophoretic deposition we have developed a tailored sol-drying method for the systems BaTiO3, SrTiO3, Ba/SrTiO3 and Lead-Zirconate-Titanate (PZT). However, the well established mixed oxide method is used, too. The chemically produced powders are easy to deagglomerate and ready for further processing.
   
      
Ceramic Films derived from Suspensions

Cross-section of BST thick-film deposited on Pt-coated alumina (mounted in resin)

Ceramic thick-films may be deposited from suspensions of ceramic powders. The small-sized powders are deagglomerated by ball-milling, ultrasonic treatment or roller-milling. By adding additives as dispersing agents and polymeric binders the finely dispersed suspension is stabilized and reagglomeration of the nanoscaled particles is prevented. In addition the stability and adhesion of the green layer on the substrate is increased due to the additives. Thus ceramic films can be deposited from such suspensions by two different means. The first is electrophoretic deposition (EPD). Here surface-charged particles move along an electric field and coagulate on a conductive electrode. The second one is Ink-Jet-printing or Drop-on-Demand. This method ejects droplets of suspension from a piezo-actuated nozzle and allows for directly printing ceramic structures on a substrate. The green ceramic coatings are finally sintered to obtain a solid film.

      
Ceramic Films derived from Sols

true solution (left), sol with initiated particle growth (middle), sol with gel-particles in the final stage (right)

Ceramic thin-films may be deposited from suspended gel particles or true solutions. Small-sized particles are synthesized by means of a adjusted sol-gel process. By initiating a controlled particle growth very finely dispersed suspensions of nanoscaled gel-particles can be generated. From such sols and true solutions ceramic thin-films can be deposited by two different means. The first is electrophoretic deposition (EPD). Here surface-charged gel-particles move along an electric field and coagulate on a conductive electrode. The second one is Ink-Jet-printing or Drop-on-Demand. This method makes uses the ejection of droplets of true solutions through a piezo-actuated nozzle and allows for directly printing ceramic structures on a substrate. The green xerogel coatings are finally thermally converted to the oxide and sintered to obtain a ceramic film.
    
      
Composites - Ceramics work wonders
 
Many properties of synthetic materials can be improved by adding ceramic powder. The effects of light or heat can also be used to harden synthetic resins, with or without ceramic powder. Using a reaction casting process, it is therefore possible to produce microstructured prototypes with, for example, improved thermomechanical and optical properties.

 
Lithography - Working with light

Following crosslinking initiated either thermally or photochemically, polymers containing silicon can be transformed by subsequent pyrolysis (combustion) into ceramics with a silicon content. As in the production of electronic components, the original polymers can be microstructured using light of varying wavelengths (from visible light to x-rays). In this way, microstructured ceramic components with details in the µm range or smaller can be produced directly without any need for an interim moulding stage. To carry out such work, the Laboratory makes use of both IMTEK’s standard mask aligner for UV lithography and, for x-ray lithography, the new „ANKA“ synchrotron source at the Karlsruhe Research Centre.