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Yongjie Zhao,Rongxia Huang,Rongzheng Liu,Heping Zhou,Wei Zhao 한국물리학회 2013 Current Applied Physics Vol.13 No.9
In the present work, lead-free K0.48Na0.52NbO3 (KNN) ceramics were synthesized by conventional ceramicsprocesses. The excess 3.3 mol% Na2CO3 and 1.1 mol% K2CO3 were added to decrease the sinteringtemperature to 990 ℃ and effectively promote the densification of KNN ceramics. X-ray diffraction resultsindicated that the excess Na2CO3 and K2CO3 would induce the formation of the A-site riched secondaryphase with the sintering temperature. Compositional segregation phenomenon enhanced bydifferent sintering temperature, spurs the formation of secondary phase in KNN-AEe ceramics. Inaddition, the difference between ferroelectric domain structure of the poled and as-sintered KNN-AEesamples for 990 ℃ was investigated. Via XRD analysis and SEM observation, it was found that the domainorientation was urged during the poling process.
Rongxia Huang,Yuzhen Zhao,Yongjie Zhao,Rongzheng Liu,Heping Zhou 한국물리학회 2011 Current Applied Physics Vol.11 No.5
Lead-free (K_0.462Na_0.48Li_0.058)_(1+x)NbO_3(0 ≤ x ≤ 0.03) ceramics with excessive alkaline elements were synthesized by conventional ceramics processes as functions of sintering temperatures and quantities of excess alkaline elements. X-ray diffraction results reveal a transformation from tetragonal phase to orthorhombic phase with increasing the contents of excessive alkaline elements. The grain size and the piezoelectric properties were enhanced when a certain amount of excessive alkaline elements were added. Further elevation in the amount of alkaline elements added resulted in excessive liquid phase in the ceramics and deteriorated the piezoelectric properties. With x = 0.01, the ceramics sintered at 1050 ℃ show better properties of planar electromechanical coupling factor k_p = 43.4%, piezoelectric constant d_33 = 204 pC/N, dielectric constant ε^T_33/ε_0 = 704.4, and loss tangent tan δ = 2.8%.