Effect of liquid phase chemistry and processing conditions on the structural reliability of cold sintered ZnO
JABR A. 1, JONES H. 2, ARGÜELLES A. 3,4, TROLIER-MCKINSTRY S. 2,4, RANDALL C. 2,4, BERMEJO R. 1,2
1 Department of Materials Science, Montanuniversitaet Leoben, Leoben, Austria; 2 Materials Science and Engineering Department, The Pennsylvania State University, University Park, United States; 3 Department of Engineering Science and Mechanics, Penn State University, University Park, United States; 4 Materials Research Institute, Millennium Science Complex , University Park, United States
Among the different alternative low temperature sintering techniques, the cold sintering process (CSP) enables densification of ceramics at temperatures below 300°C. The process is driven by a chemo-mechanical effect activated by a compatible transient liquid phase and high pressure. This study aims at optimizing the processing conditions in CSP, taking into consideration the effect of liquid phase chemistry, heating rate and homogeneity of applied pressure on the density and structural integrity of cold sintered parts. A combination of non-destructive testing followed by biaxial bending and fractographic analyses were employed to identify macroscopic strength-limiting flaws. It was found that the strength of cold sintered samples can be remarkably compromised by improper processing conditions associated with temperature and/or pressure gradients related to insufficient tooling quality, resulting in delamination effects. The prevention of such defects is demonstrated by appropriate selection of the processing parameters in CSP, resulting in structurally reliable cold sintered ZnO samples with strengths exceeding 100 MPa.