Physico-chemical nanomaterials science

Study of the effects of MgO additive and sintering temperature on mechanical behavior of fine-grained ZrO2–MgO ceramics
Kulyk V.V.1, Duriagina Z.A.1,2, Vasyliv B.D.3, Vavrukh V.I.1, Lyutyy P.Ya.1, Kovbasiuk T.M.1, Vira V.V.4
1 Department of Materials Science and Engineering, Lviv Polytechnic National University, 12 S.Bandera str., Lviv 79000, Ukraine.
E-mail: kulykvolodymyrvolodymyrovych@gmail.com
2 Department of Materials Engineering, The John Paul II Catholic University of Lublin, 14 Racławickie Al., Lublin 20-950, Poland.
3 Department of Hydrogen Technologies and Alternative Energy Materials, Karpenko Physico-Mechanical Institute of the NAS of Ukraine, 5 Naukova str., Lviv 79060, Ukraine.
4 Department of Strength of Materials and Structural Mechanics, Lviv Polytechnic National University, 12 S.Bandera str., Lviv 79000, Ukraine.

Zirconia ceramics partially stabilized with various amounts of MgO have been studied. The aim of this work was to investigate changes in mechanical behavior of the ceramics depending on the sintering temperature and percentage of MgO additive. Conventional sintering of series of ceramic specimens in a temperature range of 1510 °C to 1850 °C with and without annealing was performed. A set of mechanical tests were carried out: (i) strength test of beam specimens under three-point bending; (ii) Vickers microhardness test; (iii) fracture toughness test by Vickers indentation (VI method); (iv) single-edge notch beam test under three-point bending (SENB method).
Among the materials studied, ZrO2–2.5 mol% MgO ceramics sintered at 1850 °C showed the best crack growth resistance behavior for both VI and SENB methods. In contrast to other ceramic variants containing about 12–15 wt% c-ZrO2 and 85–88 wt% m-ZrO2, this material contained 58 wt% c-ZrO2 and 42 wt% m-ZrO2. Such a comparatively high percentage of c-ZrO2 in this material variant caused a distinct difference in its mechanical behavior. Based on the obtained results of mechanical tests and the analysis of fracture surface morphology it was concluded that the fracture toughness of optimally fabricated ZrO2–MgO ceramics is attributed to particle-crack interactions, which result in a transformation zone around the crack tip. An increase in crack growth resistance of this material variant was accompanied by a slight increase in its strength and microhardness.