| Summary: | 碩士 === 義守大學 === 材料科學與工程學系碩士班 === 97 === Sodium and potassium niobate 〈(Na,K)NbO3〉 is currently believed to be one of piezoelectric materials for replacing the lead-containing Pb(Zr,Ti)O3 from environmental concerns. However, there are so many problems for manufacturing (Na,K)NbO3-containing piezoelectric materials. For example, how to improve its sinterability to further increase its densification is one major task for improving the property of (Na,K)NbO3. Therefore, this research is concentrated on the process improvement of fabricating (Na,K)NbO3 ceramics.
There are five different process for sintering (Na,K)NbO3 materials through various initial materials; the first process is obtained from the combinations of Nb2O5 and carbonate salts; the second, Nb2O5 and nitrate solution; the third, Nb2O5 and hydroxide solution; the fourth, nitrate and chloride solutions; the last one, additions of BaTiO3. It is expected that the key points in densification problem of (Na,K)NbO3 can be further solved.
From experimental results, it is found: the optimal calcinations temperature in the carbonate system is 950℃; 500℃ in the nitrate system; 500℃ in the hydroxide system; and 350℃ in the nitrate and chloride aqueous solution. Optimal sintering temperature is found to be 1100℃ in the carbonate system; 1050℃ in the nitrate system; 800℃ in the hydroxide system; 1050℃ in the nitrate and chloride aqueous solution; 1050℃ for 0.05% BaTiO3 alloying systems, but 1150℃ for ≧0.10% BaTiO3 alloying systems.
As to the densification, the best bulk density of sintering (Na,K)NbO3 ceramics is 3.536g/cm3 in the carbonate system; 3.613g/cm3 in the nitrate system; 2.475g/cm3 in the hydroxide system; but only 3.120g/cm3 in the nitrate and chloride aqueous solution. Overall, from the densification, the nitrate system is found to be the best process for fabricating (Na,K)NbO3 ceramics in this research.
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