Tham khảo tài liệu 'ferroelectrics material aspects part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 340 Ferroelectrics - Material Aspects Fig. 6. Evolution concentration of ZrO2 and PZT as a function of thermal treatment after a milling time of 4 h for mixture powders with A PbO B PbO2 and Pb3O4 as source of Pb. i. T 350 C no reaction is present. ii. PbO TiO2 PbTiO3 from 350 to approx. 630 C formation of PT. iii. PbTiO3 PbO ZrO2 Pb O3 from 650 to approx. 950 C reaction of ZrO2 and formation of PZT. iv. Pb ZrxTi1-x O3 PbTiO3 Pb ZrxTi1-x O3 among 700 and 950 C complete reaction of PZT. The synthesis of Pb Zrx Ti1-x O3 by solid state reaction has been reported to be mainly attributed to Pb2 ion diffusion which is necessarily enhanced by the starting powders ranging from submicrometric to nanometric sizes. The mechanism of reaction starts with the formation of tetragonal PbTiO3 which reaches a maximum at temperatures close to 680 C with a subsequent reaction of the remaining ZrO2 and TiO2 leading to the complete solid state reaction of mixtures of PbTiO3 and PZT at temperatures above 800 C. In the case of oxide mixtures with mechanical activation the reactions that occur with the milling and heat treatments can be summarized into four stages following the scheme of Babushkin Lindbach . The first stage is developed during the milling process and the rest of the reactions of the stage are shown in Figure 5 and 6. The effect of the high energy milling is to lower the temperatures of the reaction in the formation of PZT. The reaction regions observed are the following 341 Synthesis of PZT Ceramics by Sol-Gel Method and Mixed Oxides with Mechanical Activation Using Different Oxides as a Source of Pb i. Mechanical activation by high energy milling which leads to phase transformations in the oxide precursors and the formation of PT and PZT with concentrations between 7 and 12 30 C . ii. Increased concentration of PT 17 to 33 and PZT 16 to 42 with the reduction of ZrO2 48 to 35 in a temperature range from 300 to 500 C. iii. PbTiO3 PbO ZrO2 Pb ZrxTi1-x O3 increase of
