Thermal Evolution of Single Phase Lanthanum Zirconate |
| Journal |
Key Engineering Materials (Volumes 317 - 318) |
| Volume |
The Science of Engineering Ceramics III |
| Edited by |
T. Ohji, T. Sekino and K. Niihara |
| Pages |
31-36 |
| DOI |
10.4028/www.scientific.net/KEM.317-318.31 |
| Online since |
August, 2006 |
| Authors |
Maria Ophelia D. Jarligo,
Y.S. Kang,
Akira Kawasaki
|
| Keywords |
Crystallization, Lanthanum Zirconate, Mechanochemical Activation, Sintering |
| Abstract |
Lanthania (La2O3) and zirconia (ZrO2) powders in ethanol based suspension were
mechanochemically treated in a planetary ball mill for 12 hours at 200 rpm, dried and sintered at
various temperatures from 400 to 1500. Particles in nanometer sizes are produced after milling.
X-ray diffractometry results show the formation of single phase lanthanum zirconate on subsequent
heat treatment for 1h at 1500. Phase evolution based on the intensities of the XRD plots and BET
surface area analysis indicates three stages of crystallization: below 800, between 800 and
~1100, and above 1100 where reflections of La2Zr2O7 with pyrochlore structure are increased
with further heating. Only endothermic energy peaks are observed in the differential thermal analysis
(DTA) curve of the milled powders, which could be attributed to the reactions involving
dehydroxylation, decarboxylation and complete disintegration of ethanol. This indicates that probably,
lanthanum zirconate has grown on sintering at high temperatures from the very fine particles
produced by mechanochemical activation during milling. Thermogravimetric analysis has recorded a
total weight loss of ~9% from the original weight of the milled powder on sintering at 1500. The
values of the surface area of the powders are found to decrease while the crystallite size of La2Zr2O7
are increased with increasing temperature. |
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