XRD of calcined MPB composition PZT powder showed pure perovskite phase but that of sintered pellet of the same composition at the same temperature showed some extra phase, possibly the extra pick is due to unreacted PbO. why the reaction is different in the pellet and powder form of the same composition?
HI.... PZT is very interesting material and we should prepare very carefully, because of lead. It shows high dielectric constant and ferroelectric properties. It need exact sintering temperature to get high quality product. Otherwise it might have some extra phases and impurities in the composition.
How did you prepared PZT in your work. While calcination or sintering have you used any atmosphere powder to arrest the lead from the composition. If there is any impurities, some times it showed pyrochlore phase in the XRD. pellets are compacted one and they were presintered before final sinter. So alsmot 100% chemical reaction will take place with compare to the powder.
My advise is while preparing PZT, you should take care in all the steps.
The scientific community is avoiding PZT now a days. Please take care while doing PZT. Wish you good luck.
Dear Temesgen TADEYOS Zate
I am working on projects related to the high-temperature behaviour of chromites. Based on this I can confirm that oxide powders do behave differently from pellets, for the same feed material composition.
You mentioned that you used the same composition, at the same temperature. I assume that you also used the same time. I suspect that the reason for the difference in behaviour is kinetics, both transport kinetics and subsequent phase transformation kinetics.
By pressing the material into a pellet, you are improving contact between particles, improving thermal conductivity, and reducing mass transfer distances. This will help the sample to approach equilibrium quicker than loosely packed powder.
My hypothesis is that the pelletised sample is closer to equilibrium than the powdered one, and that with more time the powdered one may also show the presence of the extra phase after a longer period.
All the best
Johan
The reaction of the components depends greatly on the contact surface between them. It is necessary to have an idea of the mechanisms that are activated during sintering to better anticipate possible reactions.
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