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Synthesis and Investigation of Properties of (K,Na)NbO3-Based Piezoelectrics

Rahimpour, Milad | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53560 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Nemati, Ali; Faghihi Sani, Mohammad Ali
  7. Abstract:
  8. The fabrication of potassium sodium niobate piezoceramic with oriented microstructure and study of its piezoelectric properties is one of the main objectives of the present study. For this purpose, first the raw materials were synthesized. solid state reaction and topochemical reaction were used for the synthesis of potassium sodium niobate and sodium niobate respectively. The X-ray diffraction results determined that the powder synthesized by the solid state method in the binary system KNbO3-NaNbO3 is closer to the morphotropic phase boundary compared to the powder synthesized in the ternary system Na2CO3-K2CO3-Nb2O5. Particles morphology also includes coarse cubic shape and small equiaxed particles. topochemical synthesized sodium niobiate also has a plate-like morphology, and according to the X-ray diffraction pattern, it can be said that the topochemical reaction is not complete and some residual bismuth is present in the system. Subsequently, potassium sodium niobate synthesized in the binary system and plate-like sodium niobiate were used with a certain ratio to prepare the green sample by tape casting. After binder burnout, conventional sintering of the samples was performed under the furnace atmosphere. For comparison, conventional sintering in atmospheric powder was also performed.Finally, the sintered samples were turned into piezoceramic during the poling process. In the study of the properties of sintered samples, low densities were often measured. For the sintered samples in the atmospheric powder, a higher piezoelectric charge coefficient was obtained compared to the sintered samples in the air atmosphere. morphotropic phase boundary compositions, absence of non-perovskite secondary phases and residual bismuth in the NN plates is effective in increasing the piezoelectric charge coefficient. However, reaching a piezoelectric charge coefficient of about 150 pC/N can only be due to the presence of bismuth as a doping agent. Also, only at 1180°C/10h some microstructural orientation has been observed, but due to the presence of the secondary phase, the piezoelectric charge coefficient was low and about 86 pC/N
  9. Keywords:
  10. Morphotropic Phase Boundary ; Second Phase Particles ; Potassium Sodium Niobate ; Oriented Microstructure ; Piezoceramic ; Piezoelectric Peoperties

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