Effect Of Systheis Conditions And Ph On Stabilization Of Matastable Tetragonal Zirconia

The present work deals with the effect of different synthesis conditions, pH and concentration of sodium borohydride $(NaBH_4)$ on the stabilization of tetragonal Zirconia nanopowders through reduction technique. Nanocrystalline $t-ZrO_2$ has technologically significant material that finds extensive use as catalyst, oxygen sensor and structural components. In this work $ZrO_2 $nanoparticles are synthesized using reduction technique at two different concentration of reducing agent .These technique are also promote the stabilization of t-phase of $ZrO_2$ at nano level at moderate temperature which is one of the primary objective of this work. For reduction technique, the Zr-salt reduced by addition of strong reducing agent $(NaBH_4)$. This reduction process includes three different synthesis process occurred at different pH. Here the main objective is to stabilize the t-ZrO2 through gelation (low pH), precipitation (High pH) and reduction at constant pH by using NaBH4. From XRD results, stabilization of metastable $t-ZrO_2$ was observed upto 600 °C for both gelation and precipitation but in case of reduction at constant pH it is purely amorphous at both the concentration of NaBH4 (0.5M, 5M). However with increase in temperature both tetragonal and monoclinic phase observed in case of both gelation and precipitation where as in case of reduction at constant pH pure $t-ZrO_2$ observed at 8000C. So it has been concluded that at low concentration with increase in pH the crystallite size decreases but at high concentration it decreases. Reduction technique controls the crystallite size and slowly converts to the $m-ZrO_2$ as calcination temperature increases.