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The defects, the behavior of 3d electrons and the hyperfine interactions in binary Fe-Al alloys with different Al contents have been studied by measurements of positron lifetime spectra, coincidence Doppler broadening spectra of positron annihilation radiation and Mössbauer spectra. The results show that on increasing the Al content in Fe-Al alloys, the mean positron lifetime of the alloys increase, while the mean electron density of the alloys decrease. The increase of Al content in binary Fe-Al alloys will decrease the amount of unpaired 3d electrons; as a consequence the probability of positron annihilation with 3d electrons and the hyperfine field decrease rapidly. Mössbauer spectra of binary Fe-Al alloys with Al content less than 25 at.% show discrete sextets and these alloys make a ferromagnetic contribution at room temperature. The Mössbauer spectrum of Fe70Al30 shows a broad singlet. As Al content higher than 40 at.%, the Mössbauer spectra of these alloys are singlet, that is, the alloys are paramagnetic. The behavior of a 3d electron and its effect on the hyperfine field of the binary Fe-Al alloy has been discussed. 相似文献
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以Zn O为烧结助剂,采用固相合成法制备了(K0.5Na0.5)Nb O3(缩写为KNN)压电陶瓷,研究了烧结温度对Zn O掺杂KNN陶瓷致密性、微结构以及压电性能的影响。结果表明:随着烧结温度的升高,KNN陶瓷的压电常数d33、密度?和机电耦合系数Kp均先升高后降低,在1100oC时达到最大值;而试样的介电常数则随烧结温度的升高而增大。烧结温度过高(达到1120oC),将会引起Na、K的大量挥发和晶粒异常生长,使得其结构变疏松。当Zn O含量为0.5wt%、烧结温度为1100oC时,KNN陶瓷的密度达到了4.43g/cm3;其压电学性能达到最优:d33=113p C/N,tan?(1k Hz)=5.31%,Kp=0.35。 相似文献
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