A. Namiranian , M. Kalantar,
Volume 8, Issue 3 (september 2011 2011)
Abstract
The process of mullitization of kyanite concentrate was studied at different conditions of heat treatment (1400
– 1600 °C and 0.5 – 3.5 hours) and particle size of raw materials (38-300 ?m). Kyanite concentrate was obtained from
ore-dressing of kyanite deposits of Mishidowan-Bafgh region at 100 km northeastern part of Yazd. The results of
microstructure (shape, distribution and size of the grains) and phase evolution studies by SEM and XRD showed that
total transformation of kyanite to mullite takes place by heat treatment between 1500 –1550 °C during 2.5 hours.. At
temperatures below 1500 °C need-like mullite grains are always produced. At higher temperatures the mullite grains
reveal rounded and platelet morphology. At 1550 °C, the rate of mullitization and densification were improved by
increasing soaking time from 1h to 3h and decreasing particle size of materials from 300 to 38 m
M. Khaleghian, M. Kalantar, S. S. Ghasemi,
Volume 12, Issue 2 (June 2015)
Abstract
Lead zirconate titanate (PZT) as a piezoelectric ceramic has been used widely in the fields of electronics,
biomedical engineering, mechatronics and thermoelectric. Although, the electrical properties of PZT ceramics is a
major considerable, but the mechanical properties such as fracture strength and toughness should be improved for
many applications. In this study, lead monoxide, zirconium dioxide and titanium dioxide were used to synthesize PZT
compound with chemical formula Pb(Zr
0.52
,Ti
0.48
)O
3
by calcination heat treatment. Planetary mill with zirconia balls
were used for homogenization of materials. Two-stage calcination was performed at temperatures of 600˚C and 850˚C
for holding time of 2h. In order to improve the mechanical properties of PZT, various amount of ZnO and/or Al
2
O
3
particles were added to calcined materials and so PZT/ZnO, PZT/Al
2
O
3
and PZT/ZnO+Al
2
O
3
composites were
fabricated. Composites samples were sintered at 1100˚C for 2 h in the normal atmosphere. Microstructural component
and phase composition were analyzed by XRD and SEM. The density, fracture strength, toughness and hardness were
measured by Archimedes method, three-point bending, direct measurement length crack and Vickers method,
respectively. Dielectric and piezoelectric properties of the samples were also measured by LCR meter and d33metet
tester, respectively. The results showed that by addition of ZnO and Al
2
O
3
to composite materials, the relative density
of PZT based composites was increased in conjunction with a signification improvement of mechanical properties such
as flexural strength, toughness and hardness. Moreover, the dielectric and piezoelectric properties of PZT such as
dielectric constant, piezoelectric coefficient and coupling factor were decreased while the loss tangent was also
increased.
