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Synthesis and Properties of Porous PZT-PCN Piezoelectric Ceramics

AL-obaidi, Firas Fouad Abdullah | 2015

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  1. Type of Document: Ph.D. Dissertation
  2. Language: English
  3. Document No: 47617 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Nemati, Ali; Bagheri, Reza
  7. Abstract:
  8. Although studies have shown interesting piezoelectric and dielectric properties of PZT containing composite piezoelectric ceramics, there has been no systematic investigation on the PZT-PCN, especially on the porous one.In this study, the dense ceramics of 0.8Pb (Zr1/2Ti1/2)O3–0.2Pb(Co1/3Nb2/3)O3 abbreviated to (PZTCN) systems were successfully prepared by the columbitewolframite precursor method via the mixed oxide technique. Porous PZT-PCN ceramics were prepared by burnable plastic sphere process (BURPS) technique with three types of pore forming agents (PFAs), poly vinyl chloride (PVC), stearic acid (SA), and poly methyl methacrylate (PMMA) at different weight percentages(5, 10,and 15 %).The main objective of this study is to investigate the effects of processing parameters,PFA additions, and sintering temperature on the formation of phases, micro structural evolution, piezoelectric, and dielectric properties of the system.The challenges are PbO atmosphere control, pyrochlore phase formation, and determination of sintering procedure.Within the dense PCN ceramic preparation process, undesired pyrochlore phase was detected in XRD test for low milling time (6 h) between PbO and CoNb2O6 powder and disconnection between grains indicated by fracture surface. In comparison, for 24h milling time, the fracture surface of the produced powder was more spherical and indicated a high connection between the grains.The relative density of porous PZTCN with addition of 15 wt% of pore formers was decreased about 18.9% and 24.4% for (PVC) and (SA), respectively. When (PVC),(SA), and (PMMA) were added to ceramic powder, the XRD data after sintering showed no change in the perovskite crystal structure.EDAX analysis for both dense and porous PZTCN ceramics near the grain boundary indicate the excess Co and Nb content in powder composition as compared with the bulk grain.Both piezoelectric constant (d33) and Relative permittivity (Ɛr) of PZTCN ceramics decreased with increasing PFA ratio from 5 to 15 wt%. In addition, both the hydrostatic piezoelectric voltage coefficient (gh) and figure of merit (dhgh) of porous PZTCN ceramics increased with decreasing density. Therefore, the (dhgh) of porous PZTCN ceramics prepared using 15 wt% SA with porosity of 36% reached 2138 ×10−15 m2/N, which is approximately four times greater than that of dense ceramic at 1200℃. In comparison, the hydrostatic figure of merit (dhgh) of porous PZTCN ceramics, prepared using 10 wt% of PMMA , reached 5379 × 10−15 m2/N, that is approximately eleven times greater than that of dense ceramic at 1250℃. The porosity of PZTCN ceramics decreased and the grain size increased with an increase in the sintering temperature at a fixed PMMA addition
  9. Keywords:
  10. Piezoelectric Ceramic ; Merit Matherials Figure ; X Ray Diffraction ; PZT-PCN Ceramic ; Porous Ceramic ; Piezoelectric Peoperties ; Burnable Plastic Sphere (BURPs)

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