1 research outputs found
Insights into BaTi<sub>1–<i>y</i></sub>Zr<sub><i>y</i></sub>O<sub>3</sub> (0 ≤ <i>y</i> ≤ 1) Synthesis under Supercritical Fluid Conditions
The
production of BaTi<sub>1–<i>y</i></sub>Zr<sub><i>y</i></sub>O<sub>3</sub> (0 ≤ <i>y</i> ≤
1, BTZ) nanocrystals is known to be challenging due the
low reactivity of zirconium precursors. Here we have successfully
studied the impact of zirconium on the BTZ particle formation in sub-
and supercritical fluid conditions along the entire solid solution. <i>In situ</i> synchrotron wide angle X-ray scattering (WAXS) analyses
were conducted in batch at 150 and 400 °C to follow, in real
time, the BTZ crystallite synthesis. This approach revealed the complexity
behind the nucleation and growth mechanisms of ABO<sub>3</sub> nanocrystals,
especially toward high zirconium content (more than 50 atomic %).
This type of substitution induces, among other things, microstrain
within the structure. Moreover, for the cases of BaTi<sub>0.4</sub>Zr<sub>0.6</sub>O<sub>3</sub> and BaTi<sub>0.2</sub>Zr<sub>0.8</sub>O<sub>3</sub>, the experiments showed the apparition of two crystallite
size populations. In the BaTi<sub>0.4</sub>Zr<sub>0.6</sub>O<sub>3</sub> case, at 400 °C, these two size populations merged into a single
one after at least 8 min; in contrast to what was observed for the
case of BaTi<sub>0.2</sub>Zr<sub>0.8</sub>O<sub>3</sub>. This is a
manifestation of how with increasing the zirconium content the particles
become more refractory and in these cases the temperature is not high
enough to enable their ripening. It is important to note that this
behavior was not observed for particles produced at 400 °C using
a flow synthesis method, with a residence time of only 50 s. There,
the particles presented a single size population close to the one
obtained after 8 min in batch. This thus suggests that for batch syntheses
a longer time is required to achieve a similar product quality to
the one obtained with a flow process