共查询到7条相似文献,搜索用时 15 毫秒
1.
本文利用溶剂热方法合成出具有锥形结构的四方白钨矿相PbWO4微晶,并结合金刚石对顶砧压机,利用Raman光谱手段研究了其在22GPa压力下的结构变化。结果发现,在大约4.2GPa,发生了向单斜结构PbWO4-Ш相的局部转变。随着压力继续增大至7GPa,又发现了向亚稳单斜结构的褐钇铌矿相的转变。大约13.2GPa后,亚稳相褐钇铌矿结构也转变为更为致密的PbWO4-Ш相。该相变过程为可逆相变,卸压后恢复为白钨矿结构。 相似文献
2.
Zuo Liang Zhang Yu-dong Zhao Xiang He Chang-shu Claude Esling 《Frontiers of Physics in China》2006,1(1):85-91
This paper summarizes our recent work on the application of high static magnetic fields to the austenite-to-ferrite transformation
and the tempering processes in hot-rolled 42CrMo steel. The thermodynamic and kinetic effects of the high magnetic fields
on austenite decomposition and the influences of the high magnetic field on carbide precipitation and the matrix recovery
during high- and low-temperature tempering are briefly outlined. Insight into these aspects may provide better understanding
of the effects of high magnetic fields on diffusional phase transformations and is of both theoretical significance and technical
interest. 相似文献
3.
紫外拉曼光谱研究钇掺杂的氧化锆体系表面相变 总被引:4,自引:1,他引:3
本文用紫外拉曼 ,近可见拉曼光谱和XRD检测了不同焙烧温度下Y2 O3-ZrO2 的相变过程。紫外拉曼光谱对样品表面相变极其灵敏 ,而近可见拉曼光谱和XRD提供的主要是体相和表面的混合信息。在紫外拉曼谱图中 ,只观察到单斜相的谱峰 ,没有明显的四方晶相的信号 ,这表明样品的表面主要是单斜晶相。然而 ,XRD和近可见拉曼光谱的结果显示Y2 O3-ZrO2 体相是四方晶相。焙烧温度超过 40 0°时 ,紫外拉曼 ,近可见拉曼和XRD晶之间明显不同的结果表明Y2 O3-ZrO2 在表面区四方相很易转变为单斜相 ,体相中的四方相由于钇的添加而稳定存在。根据紫外拉曼和XRD结果 ,当升高温度时 ,在样品的表面形成一单斜相层 ,体相钇稳定的四方相 ,且由于Y2 O3的存在抑制了单斜相进一步向体相发展。 相似文献
4.
Irena Jankowska-Sumara Min-Seok Jeong Jae-Hyeon Ko Andrzej Majchrowski Józef Żmija 《Phase Transitions》2016,89(7-8):768-776
ABSTRACTRaman light scattering measurements in the temperature range from 80 to 830 K were performed on a PbZr0.72Sn0.28O3 single crystal. The frequencies of the Raman lines were analyzed and discussed in terms of the sequence of structural phase transitions. It was found that Raman spectrum displays important changes near 440, 480 and 493 K. The incorporation of more than 25 mol% of Sn4+ ions into the structure of PbZrO3 enhances polar fluctuations above TC as compared to the less Sn-doped crystals. These fluctuations lead to appearance of a ferroelastic intermediate phase below TC. It is demonstrated that the structural phase transformation in PbZr0.72Sn0.28O3 can be considered as the result of softening of a number of modes. 相似文献
5.
为研究PbCO3在高压下的稳定性,利用金刚石对顶砧技术,采用NaCl固体、甲醇-乙醇-水混合液体(16∶3∶1)和甲醇-乙醇混合液体(4∶1)做传压介质,开展了PbCO3的高压拉曼实验,最高压强分别达到24.5、25.0和67.0 GPa。研究发现,PbCO3在10、15和30 GPa左右发生相变,在静水压强条件下CO2-3基团的ν2-外弯曲振动模出现了软化现象。通过对比得到不同传压介质中PbCO3的Grüneisen参数γ,发现相变机制略有不同,并且压强对晶格振动的影响CO2-3基团的影响大,这是由Pb2+―O键的键长较大造成的。在所研究的压强范围内,PbCO3没有发生分解或非晶化,30.0 GPa以上出现的PbCO3-Ⅳ相直至67.0 GPa都很稳定。 相似文献
6.
Fe72−x
Al28Cr
x
(x = 0,2,4,6) are made by arc melting a mixture of constituent elements in stoichiometric proportion, in argon atmosphere. The
ingots so obtained are filed to make powder samples thereby giving them substantial mechanical deformation. It is observed
that as-powdered samples show hyperfine field distribution typical of α-phase, where the atoms are randomly distributed on
the available sites. Annealing at 900°C for 60 h leads to preferential occupation of lattice sites by the atoms and this results
in better defined groups of hyperfine magnetic field (HMF) which can be associated with specific configuration in the neighbourhood
of probe iron atoms. The average HMF is found to decrease sharply with increasing Cr concentration even though the net chromium
concentration remains low (≤6 at%). The results show that cold working on samples is very important in changing the atomic
ordering and must be taken into account if properties of equilibrium phases are probed. 相似文献
7.
E. A. Oliveira E. N. Silva A. R. Paschoal S. M. Dantas I. Guedes J. Mendes‐Filho G. Polla A. P. Ayala 《Journal of Raman spectroscopy : JRS》2011,42(7):1567-1573
Raman spectroscopy, polarized microscopy and thermal measurements were used to investigate the sequence of phase transition in the lead oxide salts Pb8O5(XO4)2 (where X = As and V). For Pb8O5(AsO4)2, a second‐order phase transition is observed at 500 K. For Pb8O5(VO4)2, a second‐order and a first‐order structural phase transitions are observed at 425 and 525 K, respectively. The ferroelastic character of Pb8O5(VO4)2 is also discussed. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献