非线性光学晶体的高压拉曼散射研究

 报道了高压下非线性光学晶体KNbO₃（KN）,KIO₃（KI）和KTiOAsO₄（KTA）的Raman散射研究结果,压力引起的Raman光谱非常丰富,在所有的样品中都观察到了压致相变。另外,在KN晶体中发现了非常强的压致振动耦合现象及高压非晶相。对于KTA,建立了Raman光谱变化与其倍频效率随压力提高之间的可能联系。在22 GPa以上,KI晶体的基本组成集团可能由IO₃变为IO₆。     

MnF2的高压Raman光谱研究

 本文首次报道了在0~3.21 GPa压力范围内MnF₂的高压Raman光谱，结果表明压力在1.32 GPa附近，MnF₂发生了一次结构相变，晶胞中氟原子构成的八面体没有解体。在3.21 GPa下，Raman谱带消失，表明又有一次结构相变发生。     

压致硼酸盐晶态物质的非晶化现象研究

 本文用X射线衍射、Eu²⁺的发射谱与激发谱、拉曼谱以及扫描电镜（SEM）颗粒形貌，研究了常压下合成的具有正交结构的SrB₂O₄:Eu²⁺晶体在3.0~7.0 GPa压力下的晶态非晶化现象。分析结果表明，压力导致晶粒细化和晶态非晶化。晶粒尺寸由常压下的微米量级细化为几十个纳米量级，随压力的变化为：2 μm（0.1 MPa），49.4 nm（3.0 GPa），29.7 nm（5.0 GPa），25.1 nm（7.0 GPa）。晶态与非晶态体积比随压力增加而减小，分别为：70/30（3.0 GPa），63/37（5.0 GPa），57/43（7.0 GPa）。在压力下Eu²⁺是处在晶态与非晶态两种不同的低对称的环境中。纳米级晶粒是以亚晶粒形式存在于微米级大晶粒中的，压致非晶态可能组成了纳米亚晶粒的界面区。     

低温高压下的Na5Eu(WO4)4的发光和晶体场参数

用低温金刚石对顶砧高压显微光谱系统在20—300K低温和0—10GPa高压范围内研究了白钨矿型化学计量的基质发光晶体四钨酸铕钠Na₅Eu(WO₄)₄中Eu³⁺的发光.确定了Eu³⁺荧光谱线和能级在低温下的压力移动率.它随温度变化,表明温度和压力对Eu³⁺谱线作用不是独立无关的.按晶体场理论简化方法推导了能级的晶体场参数表达式,并按实验数据拟合出在不同低温下晶体场参数随压力的移     

高温高压合成的SrSiO3:Eu3+Bi3+的结构及其对发光特性的影响

 本文首次报道在3.15 GPa、1 200 ℃高温高压条件下合成出了SrSiO₃:Eu³⁺Bi³⁺发光材料，并与常压合成产物相比较，研究了高温高压合成产物的结构以及合成压力、温度对发光特性的影响。结果表明，高压合成产物SrSiO₃:Eu³⁺Bi³⁺的结构为膺正交（单斜）结构，而常压合成的为六角结构，高压使发光强度下降，量子发光效率下降了88%，谱线红移达756 cm^-1，半值宽度也显著增加，发光性能的改变是由于压致结构的变化引起的。     

Cr4+:Ca2GeO4激光晶体生长及结构表征

采用助熔剂法,以CaCl₂为助熔剂,生长Cr⁴⁺ :Ca₂GeO₄新型近红外可调谐激光晶体.通过X射线衍射(XRD)、激光Raman光谱、X射线光电子能谱(XPS)等方法对晶体进行结构表征.结果表明,得到的晶体为单斜晶系镁橄榄石结构的低温γ-Cr⁴⁺ :Ca₂GeO₄单晶,晶格参数为a=5.3209 (1 =0.1 nm)     

高压下正戊烷的稳定性研究

 利用Raman散射光谱在碳硅石压腔下研究了常温下的正戊烷从0.07~4.77 GPa的稳定性。结果表明：正戊烷的 CH₃、CH₂对称和反对称伸缩振动2 877 cm^-1、2 964 cm^-1和2 856 cm^-1、2 935 cm^-1以及－(CH₂)_n －同步扭曲振动1 303 cm^-1均随压力增大而基本呈线性向高频方向移动,并在2.47 GPa附近发生过压凝固,这是一种平衡稳定态之外的亚稳态现象。另外推测正戊烷在高压下可能发生固－固相变,最后通过平衡的固液共存相确定了正戊烷的平衡凝固压力为(1.90±0.05) GPa。     

非平衡磁控溅射制备类石墨碳膜及性能研究

利用中频非平衡磁控溅射技术在单晶硅基底上沉积了类石墨碳膜, 采用Raman光谱、高分辨透射电子显微镜、原子力显微镜分析了薄膜微观结构和表面形貌; 采用纳米压痕仪和CSM摩擦磨损试验机测试了碳膜力学性能和摩擦学性能. 结果表明: 利用中频非平衡磁控溅射技术沉积的碳膜是一种以sp²键合碳为主、结构非晶、硬度适中、应力较低、表面粗糙度较大、摩擦性能优异的薄膜. 脉冲占空比对薄膜微观结构和性能有显著影响, 随着脉冲占空比的增大, Raman光谱D峰和G峰的强度比I_D/I_G先减小后增大, 而硬度随脉冲占空比的增大却呈现出相反的变化趋势, 即先增大后减小; 大气氛围中的摩擦性能测试表明, 本实验制备的薄膜具有优异的抗磨性能(～10^-11 cm³/N^-1. m^-1)和承载能力(～2.5 GPa). 随脉冲占空比的增大, 薄膜摩擦系数变化甚微而磨损率却呈现先显著减小后轻微增大的变化趋势. 类石墨碳膜优异的摩擦学性能主要归因于其独特的结构、较低的内应力及良好的结构稳定性.     

气固化学反应体系产生单重态氧的初步实验研究

 介绍了一种新的产生单重态氧（O₂（¹△g）的气固化学反应体系，即在固定床式反应器中采用固体过氧化钠粉末与氯气（Na₂O₂/Cl₂）进行反应的气固化学反应体系。实验分别通过用对近红外敏感的光谱仪和锗探头监测了反应产生的（O₂（¹△g）的发射光谱和1 270 nm的光信号，同时通过数据采集系统监测了反应池固体反应层和测试池中气体的温度的变化曲线。实验测得了（O₂（¹△g）在1 270 nm附近的特征发射光谱，此光谱表明该体系是一个很好的产生（O₂（¹△g）的体系，同时，实验现象表明该反应是强放热反应。     

中心波长2.33 μm附近CO和CH4分子的同时探测

 采用分布反馈式半导体激光器作为探测光源,结合程长为100 m的离散型多通吸收池,采用直接吸收光谱技术,对室温下中心波长2.33 μm附近各种低体积分数的CO及混合气体（CO,CHCH₄和N₂）的直接吸收光谱进行了测量。选择CO在4 288.289 8 cm^-1位置的吸收谱线和CH₄在4 287.650 15 cm^-1处的吸收谱线进行痕量探测,在40 698 Pa的总压力下,实验测得CO的探测极限为8.15×10^-6(信噪比约为216）,CH4的探测极限为18.48×10^-6(信噪比约为147）。     

A high pressure Raman study of TeO2 to 30 GPa and pressure-induced phase changes

The effect of pressure on the Raman modes in TeO₂ (paratellurite) has been investigated to 30GPa, using the diamond cell and argon as pressure medium. The pressure dependence of the Raman modes indicates four pressure-induced phase transitions near 1 GPa, 4.5 GPa, 11 GPa and 22 GPa. Of these the first is the well studied second-order transition fromD ₄ ⁴ symmetry toD ₂ ⁴ symmetry, driven by a soft acoustic shear mode instability. The remarkable similarity in the Raman spectra of phases I to IV suggest that only subtle changes in the structure are involved in these phase transitions. The totally different Raman spectral features of phase V indicate major structural changes at the 22GPa transition. It is suggested that this high pressure-phase is similar to PbCl₂-type, from high pressure crystal chemical considerations. The need for a high pressure X-ray diffraction study on TeO₂ is emphasized, to unravel the structure of the various high pressure phases in the system.     

Pressure-induced phase transitions in gypsum

Abstract

We report high-pressure Raman scattering spectroscopy and energy dispersive X-ray diffraction investigations on gypsum, CaSO₄ · 2H₂O, at room temperature in a diamond cell. With increasing pressure, measurements indicate that CaSO₄ · 2H₂O undergoes two stages of crystalline-state phase transitions at 5 and 9 GPa, and then converts to a disordered phase above 11 GPa. The structures of the three high-pressure phases of gypsum have not been determined yet. These phases are tentatively named as “post-gypsum-I” (PG-I), “post-gypsum-II” (PG-II) and “disordered” according to the sequence of their appearance with pressure.

Gypsum shows anisotropic compressibility along three crystallographic axes with b > c > a below 5 GPa. The difference in the behavior of the two OH stretching modes in gypsum is attributed to the different reduction rate in the hydrogen bonding distances by the anisotropic axial compressibility.     

Effect of pressure on the Raman spectra of synthetic diamonds with boron impurity

The raman scattering technique is used for studying diamonds with a 0.04–0.1 at % boron impurity under a pressure up to 3 GPa in a chamber with sapphire anvils. The Raman frequency increases linearly with pressure for all samples with pressure coefficients of 2.947 cm^?1/GPa for pure diamond and 3.01 cm^?1/GPa for boron-doped samples. The Raman linewidths remain unchanged for pure diamond and for diamond with a boron concentration of about 0.04 at % and decrease linearly upon an increase in pressure for samples with a boron concentration of about 0.1 at %. The Raman spectra with a line profile corresponding to the Fano resonance do not change qualitatively up to a pressure of 3 GPa. In diamond samples with a boron impurity exceeding 0.1 at %, the boron concentration in the surface layer can be substantially higher than at the center of the sample.     

Raman spectra of aragonite at the pressure of 0.1-2 GPa and ambient temperature

Raman spectra of aragonite were studied at ambient temperature and pressure of 0.1 - 2 GPa in a moissanite anvil cell using Raman spectrum technique. The relations between the Raman shifts of aragonite and the system pressure are given as follows: v153 (cm(-1)) = 0.003 5p (MPa) +154.0, v206 = 0.006 0p + 206.3, v704 = 0.002 1p + 704.2, v1085 = 0.003 5p + 1 085.3. No phase transition occurred in aragonite within the range of experimental pressure. Similar to other carbonate minerals (magnesite, dolomite), the measured relative pressure-shift of the Raman line of the symmetric stretching vibration of aragonite is greater at 0.1-2 GPa than at ultrahigh pressure, which indicates that the C-O bond compressibility of the CO3 groups is related to the pressure, and it is more compressible at 0.1 - 2 GPa than at higher pressure.     

高压下L-丝氨酸的拉曼光谱研究

压力可以引起蛋白折叠与变性。作为蛋白质的基本构成单位,氨基酸在高压下的变化近来年备受关注。在常见的20种氨基酸中,学者们利用高压拉曼技术已研究了多种氨基酸在高压下的变化,研究的最高压力达到30 GPa。为了探究L-丝氨酸(C₃H₇NO₃)在极高压力下的结构变化情况,采用原位高压拉曼技术在常温下对L-丝氨酸晶体进行研究,最高压力达到22.6 GPa。研究发现,当压力达到2.7 GPa时,在102 cm-1处出现新峰,在1 123 cm-1(NH₃反对称摇摆振动)处的特征峰出现劈裂;当压力达到5.4 GPa时,L-丝氨酸晶体在574 cm-1处出现新峰,同时原来164 cm-1处峰消失;当压力达到6.0 GPa时,位于226,456,770和2 968 cm-1(CH₂伸缩振动)等处出现新峰,877 cm-1处的CC伸缩振动峰发生劈裂,产生894 cm-1新峰;当压力达到7.9 GPa时,在145,151和2 946 cm-1等出现新峰,同时原在CO₂摇摆振动峰的肩峰531 cm-1消失;当压力达到11.0 GPa时,位于249 cm-1处的振动峰开始劈叉,在241 cm-1处形成新峰,位于2 956 cm-1(CH₂伸缩振动)同时原位于391和431 cm-1处的峰消失;当压力达到17.5 GPa时,在200 cm-1处出现新峰。通过进一步分析L-丝氨酸的拉曼波数随压力的变化,发现很多拉曼峰在1.37,2.2,5.3,7.46和11.0 GPa以及15.5 GPa等压力点处都出现了拐点。其结果表明：L-丝氨酸在0.1～22.6 GPa之间共发生7处结构相变,分别位于压力区间0.1~1.37,2.2~2.7,5.3,6.0,7.46~7.9,10.1~11.0和15.5~17.5 GPa之间。而且,在6.0 GPa新的相变点在之前文献中未论述过。由于L-丝氨酸晶体在6.0 GPa时CC伸缩振动峰发生劈裂,这现象可能是由于压力引起L-丝氨酸晶体分子发生重排导致的,同时L-丝氨酸晶体分子重排导致氢键发生重排,使得L-丝氨酸晶体出现新的CH₂伸缩振动峰。L-丝氨酸晶体在10.1~11.0 GPa之间的拉曼光谱变化主要集中在低波数段,该波数段的拉曼振动模式主要与晶体晶格振动等低能量振动有关。同时在高波数段出现新的CH₂峰,由此可推测在10.1~11.0 GPa之间,L-丝氨酸晶体的晶格振动发生变化,产生了新的氢键,从而导致了L-丝氨酸晶体结构的改变。L-丝氨酸晶体在15.5~17.5 GPa之间,由于没有发现直接证据证明其发生结构相变,只是在拉曼波数随压力变化中,发现其在17.5 GPa时出现拐点,因此推测L-丝氨酸晶体在15.5~17.5 GPa之间可能发生结构相变。     

斜锆石（ZrO2）高温高压相变的Raman光谱研究

 以Ar作压力介质，在0~23 GPa压力范围内，利用金刚石压腔装置（DAC）和激光加温技术，采用显微拉曼光谱进行原位测试，对处于准静水压力条件下的斜锆石开展高温高压相变研究。研究结果表明：室温下斜锆石ZrO₂于3.4 GPa时开始发生相变，到10.4 GPa时其明显转变成一个空间群为Pbca的斜方相。此新相随着压力升高，直到15.3 GPa，仍稳定存在。通过研究，首次获得了Pbca相的拉曼谱图。随后在15.3 GPa压力下进行了激光加温后淬火，结果发现，加热前的Pbca相又转变成了空间群为Pnam的PbCl₂结构类型的高压相，该相直到实验最高压力23 GPa仍稳定存在。     

Raman spectroscopy of natural cordierite at high water pressure up to 5 GPa

The high‐pressure behaviour of cordierite, a widespread ring aluminosilicate with channels incorporating fluid compounds (H₂O, CO₂), is characterized by the absence of phase transitions up to 2.5 GPa. However, the distortion of the ring tetrahedra observed previously at 2.3 GPa is supposed to introduce a phase transition at higher pressure, which has not been checked so far. This work presents a high‐pressure Raman spectroscopic study of natural cordierite compressed in water medium up to 4.7 GPa in a diamond anvil cell. At P > 4 GPa, a disordering of both the framework and intrachannel H₂O subsystem is apparent from significant broadening of Raman peaks and the evolution of short‐range order parameters. This is followed by abrupt shifts of the framework and O–H stretching modes at about 4.5 GPa, indicating a first‐order phase transition. Its reversibility is seen from the recovery of the initial spectrum at P < 3 GPa. The shift amplitudes of different framework modes indicate the predominance of distortion over contraction of the framework polyhedra upon this transition. The disordering of the H₂O subsystem in the high‐pressure phase is likely a consequence of distortion of the channel‐forming framework elements, which is supposed to be a driving force of this transition. Copyright © 2011 John Wiley & Sons, Ltd.     

High Resolution Laser Transient Spectroscopic Technology under Two-Stage Light Gas-Gun Loading Condition and Stability Study of Shocked BenzeneEI北大核心CSCD

The present paper reports the high resolution transient Raman laser testing technology under two-stage light gas-gun loading experiment, and its application to studying the Raman spectroscopy of shocked benzene. In the experiments, the frequency shift of C-C stretching vibration (992 cm(-1)) and C H stretching vibration peak (3 061 cm(-1)) in the low pressure section (less than 8 GPa) varies linearly with the pressure, and the results agree well with reported data in the literature. The structural changes in liquid benzene about 13 GPa were clarified firstly by the Raman spectral technique; the experimental results show that at a pressure of 9.7 GPa, the structural change of liquid benzene has taken place, not reported in the literature about 13 GPa. But the composition in the production is not clear. The measurement system provides an effective means to study the microstructure changes of transparent and translucent material under dynamic loading experiment.     

Raman and X-Ray Investigation of Pyrope Garnet （Mg0.76Fe0.14Ca0.10）3Al2Si3O12 under High Pressure

The compressional behavlour of natural pyrope garnet is investigated by using angle-dlspersive synchrotron radiation x-ray diffraction and Raman spectroscopy in a diamond anvil cell at room temperature. The pressureinduced phase transition does not occur under given pressure. The equation of state of pyrope garnet is determined under pressure up to 25.3 GPa. The bulk modulus KTO is 199 GPa, with its first pressure derivative K′TO fixed to 4. The Raman spectra of pyrope garnet are studied. A new Raman peak nearly at 743 cm^-1 is observed in a bending vibration of the SiO4 tetrahedra frequency range at pressure of about 28 GPa. We suggest that the new Raman peak results from the lattice distortion of the SiO4 tetrahedra. All the Raman frequencies continuously increase with the increasing pressure. The average pressure derivative of the high frequency modes （650-1000 cm^-1） is larger than that of the low frequency （smaller than 650 cm^-1）. Based on these data, the mode Grǖneisen parameters for pyrope are obtained.     

In situ study of calcite-III dimorphism using dynamic diamond anvil cell

The phase transitions among the high-pressure polymorphic forms of CaCO₃ (cc-I, cc-II, cc-III, and cc-IIIb) are investigated by dynamic diamond anvil cell (dDAC) and in situ Raman spectroscopy. Experiments are carried out at room temperature and high pressures up to 12.8 GPa with the pressurizing rate varying from 0.006 GPa/s to 0.056 GPa/s. In situ observation shows that with the increase of pressure, calcite transforms from cc-I to cc-II at ～ 1.5 GPa and from cc-II to cc-III at ～ 2.5 GPa, and transitions are independent of the pressurizing rate. Further, as the pressure continues to increase, the cc-IIIb begins to appear and coexists with cc-III within a pressure range that is inversely proportional to the pressurizing rate. At the pressurizing rates of 0.006, 0.012, 0.021, and 0.056 GPa/s, the coexistence pressure ranges of cc-III and cc-IIIb are 2.8 GPa-9.8 GPa, 3.1 GPa-6.9 GPa, 2.7 GPa-6.0 GPa, and 2.8 GPa-4.5 GPa, respectively. The dependence of the coexistence on the pressurizing rate may result from the influence of pressurizing rate on the activation process of transition by reducing the energy barrier. The higher the pressurizing rate, the lower the energy barrier is, and the easier it is to pull the system out of the coexistence state. The results of this in situ study provide new insights into the understanding of the phase transition of calcite.