The change of YSZ nanoparticles crystalline structure by powerful ultrasound activation

The changes of phase composition in polymorphous ZrO/sub 2/-5wt% Y/sub 2/O/sub 3/ (YSZ) nanopowder, size of crystallites and their microstrains induced by influence of powerful ultrasound activation (PUA) were studied by XRD techniques. It was shown that during the process of dry nanopowder sonication the part of tetragonal (t) phase transforms to cubic (c) one, its significant smaller part - to monoclinic (m) phase. With PUA power W increasing from O up to 3 kW the rise of apparent crystallite sizes (ACS) was observed for all the phases. Such increasing the ACS is unusual, as it would be expected decreasing the crystallite sizes because of the destroying action of PU-oscillations on crystalline substances. The analysis of ACS values versus phase composition showed that the smallest in size crystallites of t-phase (with the sizes about 10 nm) transfer to c-phase, therewith the average value of ACS of c-phase increases (but not ACS values themselves) at the expense of rise of crystallite amount with the sizes of /spl sim/10 nm. The larger crystallites of t-phase (sizes about 40 nm) martensitely transfer to m-phase increasing the average value of ACS for this phase. As a result the t-phase loses the most part of its crystallites with small and medium sizes (from 10 up to 40 nm), and the average size of the rest of t-phase crystallites (but not the sizes by themselves) rises at increase of W. The essential influence of PUA on the relative crystallite microstrains in c-phase (consisting of small crystallites /spl sim/10 nm) and slight influence on larger crystallites of m- and t-phases were observed.