Densification of nanostructured zIrconia : a change of Paradigm through LOw-teMperATure approaches – DIPLOMAT

Yttria-stabilized zirconia (YSZ) is one of today’s most important ceramic materials because of its unique combination of properties: high strength and fracture toughness at room temperature, hardness, wear resistance, high temperature stability and low thermal conductivity, potential ionic conductivity for high yttria content, etc. It is thus one key material in technical fields such as in thermal barrier coatings, bearings, fuel cell membranes, oxygen sensors, optical ferrules, and, more recently, biomedical devices and the watchmaking industry. Although YSZ ceramics have attractive features, they have also some drawbacks (e.g. aging in presence of water) and there is anyway always a balance between mechanical properties (strength), long-term stability (aging) and optical properties (translucency), which limit some applications. Commonly used YSZ, sintered at conventional temperature of 1400°C or above, are in the range 0.3-1 micron and there is a lack of study looking at the three main functional properties cited above in relation to nanoscale features. Thus, for particular properties and applications, there an opportunity for zirconia ceramics with much smaller grain (and pore) sizes than what is commonly commercially available today. What would be the properties of dense nanostructured ceramics with controlled structure, porosity, phase composition and nature of grain boundaries? This is the ambitious objective of DIPLOMAT to answer this question by associating unconventional emerging low-temperature sintering methods (CSP, HSS and reactive HP-SPS) and modeling (esp. of optical properties). This project therefore targets several novelties, including: processing of nano-structured zirconia under novel low-temperature sintering, revealing mechanisms by which they can exhibit an outstanding balance between apparently competing properties and understanding how to tune these properties as required for specific applications.
DIPLOMAT gathers three academic partners (CIRIMAT, ICMCB, MATEIS). The unique combination of techniques and expertise within the consortium covers all aspects of the project and is a major asset in meeting the ambitious challenges targeted.