KSr_2Nb_5O_<15>固溶体のキュリー温度に及ぼす粒子配向の影響

概要

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Grain-oriented KSr_2Nb_5O_<15> solutions were prepared by hot-pressing. The compositions examined were 0.333 KNbO_3-0.667 SrNb_2O_6(stoichiometric KSr_2Nb_5O_<15>abbreviated as KSN 33/67)and 0.420 KNbO_3-0.580 SrNb_2O_6(abbreviated as KSN 42/58). The maximum degree of orientation for KSN 33/67 was 0.21 as measured by the Lotgering method, whereas that for KSN 42/58 was 0.86. KSN 42/58 formas a liquid phase at the hot-pressing temperatures. The liquid phase promoted grain boundary sliding and the formation of rod-like grains with large aspect ratios during hotpressing, resulting in the large degree of orientation. The Curie temperature was dependent on the degree of orientation. Samples with larger degree of orientations had the lower Curie temperatures for KSN 33/67, for which the larger grain size was responsible. For KSN 42/58, on the other hand, samples with larger degree of orientation had higher Curie temperatures. The shift of the Curie temperature is caused by internal stress generated at the ferroelectric to paraelectric phase transition. The neighboring grains with similar orientation reduce the magnitude of the internal stress.
社団法人日本セラミックス協会の論文
1995-02-01