Densification and mechanical properties of hot-pressed ZrN ceramics doped with Zr or Ti

The densification of hot-pressed ZrN ceramics doped with Zr or Ti have been investigated at 1500-1700 degrees C. It is shown that either Zr or Ti additive can facilitate the densification process. ZrN with 20 mol% Zr or Ti (named ZNZ and ZNT) sintered at 1700 degrees C can achieve above 98% relative densities whereas densification temperature up to 2000 degrees C is necessary for pure ZrN. The densification improvements are attributed to solid solution of Zr or Ti into ZrN to form non-stoichiometric ZrN1-x or (Zr, Ti)N1-x. The microstructures and mechanical properties of ZNZ and ZNT samples have been examined. Large grain size and flat fracture surface existed in ZNT sample sintered at 1700 degrees C, which lead to poor toughness as low as 2.3 MPa m(1/2). On the contrary, the fracture toughness of ZNZ sample sintered at 1700 degrees C was up to 5.9 MPa m(1/2), attributed to fine and uniform grain size distribution. (C) 2013 Elsevier Ltd. All rights reserved.