| PLZT powders, one of ferroelectric ceramics, were prepared from the following raw materials of Pb(NO₃)₂, La(NO₃)₃·6H₂O, ZrOCl₂·8H₂O, and TiCl₄. Each one of the 1st three components were dissolved in deionized water and the last one was dissolved in ethyl alcohol. In order to avoid the fromation of PbCl₂, a two-stage coprecipitation method was used : coprecipitating the complex hydroxide of lanthanum, zirconium, and titanium with ammonia solution; adding lead nitrate solution to the dispersed LZT solution and coprecipitating PLZT hydroxide again with ammonia solution. The precipitates were washed and dried by the three different methods, and then calcined at temperatures ranging from 300℃ to 1100℃. Tests for the X-ray diffraction and the particle size distribution were carried out and the morphologies were observed by scanning electron microscopy. Perovskite crystal structure were found on the samples calcined for 2hours at temperatures higher than 650℃. The most fine-grained size distribution was. observed in the powders of freeze-dried precipitate. The sizes of the primary particles, which mutually agglomerate to form distinct secondary particles, were between 0.1-0.6μ and the morphologies were nearly spherical. |
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