No abstract

Andalusite, as a refractory material, transforms to mullite and a silica rich liquid phase at 1100-1600uC. The glassy phase constitutes about 20 wt-% of the reaction products, which is undesirable in refractories. In this research, alumina and zirconia were added to andalusite in order to reduce the amount of the glassy phase. Alumina was introduced by dry and solution mixing, while zirconia was added only by dry mixing method. The effects of MgO on andalusitemullite and andalusite-zirconia mixes were also studied. MgO was introduced by solution (precipitation) method on andalusite surface. The samples were fired at 1400, 1500 and 1600uC. X-ray diffraction and SEM results showed that alumina reduces the liquid phase at all of the temperatures, but zirconia was effective only at 1400 and 1500uC. MgO seemed to be capable of reducing in andalusite transformation by 100uC and had positive effect on reaction between alumina and liquid phase; it was not effective on reaction between zirconia and liquid phase.

No abstract

This paper reports an investigation of (Ba 0.85 Ca 0.15 )(Zr 0.1 Ti 0.9 )O 3 (50BCZT) piezoelectric ceramics doped with Bi 0.5 (Na 0.82 K 0.18 ) 0.5 TiO 3 (18BNKT). For compositions between 1-5 wt% 18BNKT, a perovskite phase was observed in the sintered ceramics, with d 33 values of approximately 370 pC/N measured at room temperature, which is about 80 % of that of pure 50BCZT. Also, the doped materials exhibit a remanent polarization of 2-5 ȝC/cm 2 at temperatures above the Curie temperature (> 90 °C) of the pure 50BCZT composition. This research shows a promising route to improve the working temperature range whilst maintain good piezoelectric properties of the 50BCZT ceramics. Keywords-piezoelectric, BCZT, BNKT, Curie temperature268 978-1-4799-9974-3/15/$31.00 ©2015 IEEE