Influence of the zirconia nanopowders structure modification by the silica addition on the diffusion mechanisms during sintering.
M.V. Lakusta, I.A. Danilenko, G.K. Volkova, T.E. Konstantinova
Donetsk Institute for Physics and Engineering named after O.O. Galkin of NAS of Ukraine, Nauky av., 46, Kiev, 03680, Ukraine. E-mail: marharyta.lakusta@outlook.com
The development of science and technology requires the creation of ceramic functional materials with new specific properties. Zirconia based ceramics materials remains irreplaceable in various fields of technology and medicine due to their excellent physical and mechanical properties.
The modification of ceramic structures by different additives significantly effect on the sintering kinetics and the diffusion process during nanopowders consolidation. It plays an important role in the obtaining of ceramic materials with unique specific properties. It is known that silica additive leads to the change in zirconia nanopowders characteristics and diffusion mechanism changing from grain boundary (GBD) to the volume diffusion (VD) mechanism that accelerates the sintering process [1, 2]. 
In the present study were investigated the silica influence on the zirconia nanopowders (3Y-TZP) structure and diffusion mechanisms during initial sintering stage in depends on the different additive amount and the nanopowder’ production process.  The sintering behavior of 3Y-TZP with a different amount of SiO2 (0.2-10 wt%) obtained by different methods (co-precipitation and mixing methods) was investigated using the dilatometric data and CRH method applicable for non-isothermal data  [3].
 It was found that the silica leaded to the sintering mechanism changing from VD to the GBD in case of co-precipitated 3Y-TZP powders with concentration of 0.2-3 wt%. With additive amount increasing (5-10 wt%) sintering mechanism changed from GBD  via VD to viscous flow (VF) and it accompanied by a decrease in the activation energy of sintering. The completely opposite behavior of sintering kinetics was observed in nanopowders prepared by mixing method. The diffusion mechanism was not change with different silica amount (0.2-10 wt%) addition in PMM-3Y-TZP powders obtained by mixing. Predominant sintering mechanism was VD and this accompanied by a decrease in the activation energy of sintering that accelerate diffusion.
1. K Matsui. J. Am. Ceram. Soc., 91, 2534–2539, 2008.
2. K. Matsui, J. Hojo. J Mater Sci.,  43, 852–859, 2008.
3. M. Lakusta, I. Danilenko, T. Konstantinova. Nanoscale Research Letters, 11, 238, 2016.