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We synthesize LiTal-x FexO3-σ (LTFO) remain single phase up to x = 0.09 ceramics by the conventional solid-state reaction method. The samples The magnetic measurements show that the doping of Fe successfully realizes ferromagnetism of LTFO at room temperature. The dielectric measurements indicate that LTFO is ferroelectric, similarly to LiTaO3 (LTO), but its ferroelectric Curie temperature seems to decrease with the increasing Fe content. By means of doping Fe ions into LTO, the coexistence of spontaneous electric polarization and spontaneous magnetic moment is realized at room temperature. 相似文献
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In situ high pressure energy-dispersive x-ray synchrotron radiation diffraction and resistance experiments are carried out on CaCuMn6O12. Its crystal structure is stable in the measured pressure range. The equation of state of CaCuMn6O12 is obtained from the V/Vo - P relationship (V and Vo are the volumes at pressure P and at atmosphere). The bulk modulus Bo is calculated based on the Birch-Murnaghan equation. Low temperature x-ray diffraction shows no phase transition occurring down to 160K. 相似文献
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Ferroelectric behaviour of 30nm BaTiO3 ceramics prepared by high pressure assisted sintering 下载免费PDF全文
Dense nanocrystalline BaTiO3 ceramics with a homogeneous grain size of 30 nm was obtained by pressure assisted sintering. The ferroelectric behaviour of the ceramics was characterized by the dielectric peak at around 120 ℃, the P-E hysteresis loop and some ferroelectric domains. These experimental results indicate that the critical grain size for the disappearance of ferroelectricity in nanocrystalline BaTiO3 ceramics fabricated by pressure assisted sintering is below 30 nm. The ferroelectric property decreasing with decreasing grain size can be explained by the lowered tetragonality and the 'dilution' effect of grain boundaries. 相似文献
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为了抑制激光在线测厚时入射角波动引起的误差,根据几何光学分析了激光透射式和反射式测厚原理,发现激光在特定入射角附近波动时,两种方式的测厚误差一正一负,具有互补性,在此基础上提出基于透射和反射同时测量的互补式测厚方法,该方法可将误差限定在透射式和反射式测量误差之间,抑制在线测厚误差.对于有机玻璃平板,理论计算表明,当激光入射角在67.013°±4°波动时,相对误差绝对值在1%以内,误差抑制率均值大于90%;当入射角为61.536°时,误差抑制率为100%.利用线结构激光器和两个线阵CCD相机搭建互补式测厚实验系统,测量了标称厚度为1~5mm的有机玻璃平板,与透射式和反射式测厚结果进行对照,除厚度为1mm的玻璃外,互补式测厚误差被限制在透射式和反射式之间,最大误差抑制率达61%.实验结果表明,该互补式方法有效抑制了误差,提高了在线厚度测量准确度,解决了在线测量不可重复性导致的无法通过均值法减小误差的问题. 相似文献
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The “111” type Li x FeAs (x ranges from 0.8 to 1.2) with Cu2Sb type tetragonal structure was synthesized with T c 18 K. The isostructure NaFeAs was further studied, which shows superconductivity with T c up to 26 K. The effect of pressure on superconductivity was investigated. 相似文献
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A new oxide CaCr_(0.5)Fe_(0.5)O_3 was prepared under high pressure and temperature conditions. It crystallizes in a B-site disordered Pbnm perovskite structure. The charge combination is determined to be Cr~(5+)/Fe~(3+) with the presence of unusual Cr~(5+) state in octahedral coordination, although Cr~(4+) and Fe~(4+) occur in the related perovskites CaCrO_3 and CaFeO_3.The randomly distributed Cr~(5+) and Fe~(3+) spins lead to short-range ferromagnetic coupling, whereas an antiferromagnetic phase transition takes place near 50 K due to the Fe~(3+)–O–Fe~(3+) interaction. In spite of the B-site Cr~(5+)/Fe~(3+) disorder,the compound exhibits electrical insulating behavior. First-principles calculations further demonstrate the formation of CaCr_(0.5)~(5+)Fe_(0.5)~(3+)O_3 charge combination, and the electron correlation effect of Fe~(3+) plays an important role for the insulting ground state. CaCr_(0.5)Fe_(0.5)O_3 provides the first Cr~(5+) perovskite system with octahedral coordination, opening a new avenue to explore novel transition-metal oxides with exotic charge states. 相似文献
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为了同时同位测量石英管的外径和壁厚,建立了激光透射成像系统,对系统测量原理进行研究。基于几何光学和菲涅尔公式,分别导出平行光垂直照射石英管后的透射光线偏向角、相对光强与入射光线离轴距离之间的关系;通过数值计算,分析了偏向角、相对透射光强随入射光线离轴距离的变化特点;针对物方远心光路,分析了光阑对偏向角和相对光强的限制;基于CCD成像原理,通过引入标定系数和补偿因子,导出石英管外径与壁厚的计算公式。实验结果表明:外径绝对误差和相对误差的平均值分别为0.119mm和0.91%,壁厚绝对误差和相对误差的平均值分别为0.153mm和6%。 相似文献