High-energy shift of Boson peak and its broadening in crystallization regime : A qualitative aspect
High-energy shift of Boson peak and its broadening in crystallization regime : A qualitative aspect
复制标题
玻色子峰的高能位移及其在结晶范围中的展宽：定性方面
DOI：
10.1143/jpsj.80.095003
复制
发表时间：
2011
影响因子：
1.7
通讯作者：
藤原巧
中科院分区：
文献类型：
--
作者：
高橋儀宏;長田実;井原梨恵;藤原巧
非弹性光散射（即布里渊和拉曼）可以提供化学键和配位态的信息，使其成为研究非晶态物质在过冷液体（SCL）和熔体状态下的有效技术。一些研究已经报道，在结晶过程中（发生在这些制度之间），二元系统玻璃表现出异常的弹性行为[即，同时发生声速（或弹性）的增加，这是由布里渊光谱估计的]和显著的阻尼。4,5)在从SCL到晶体（SCL -晶体转变）的低能振动模式（$1 THz）的拉曼散射（称为玻色子峰，BP）中也报道了这种行为。6,7)虽然这些异常似乎与结晶现象有关，但尚未进行深入分析。因此，在本研究中，为了获得有关结晶状态异常的额外信息，我们准备了合适的样品进行BP的原位观察，并研究了BP在非等温和等温加热条件下的行为。通过非弹性光散射观察结晶动力学时，表现出较强均匀成核倾向的玻璃样品是优选的，因为样品具有较大的界面，在此界面处发生scl晶体转变。7)由于BaSi2O5玻璃具有较高的成核能力(8)，而TiO2在硅酸盐玻璃体系中是一种有效的成核剂，我们采用熔融淬火技术（熔化条件：1773K， 1h）制备了二氧化钛取代SiO2的玻璃，即BaTixSi2¿xO5 （xº0{0:25）。在每个玻璃化转变温度（Tg）下对淬火后的样品进行退火。1 (b)]静置20 h，得到成核样品。这是因为对于具有均匀成核趋势的玻璃，最大成核速率明显的温度接近Tg。9)用差热分析（DTA）、透射电子显微镜（TEM）和原位非弹性光散射观察对样品进行了表征。这些分析的详细条件在其他地方描述。6,7)在低能区得到的光谱相对于玻色-爱因斯坦因子进行了约简，并使用BP和高斯函数的和进行了拟合。这是因为Ba-O键产生的振动带对光谱有贡献。10)用对数正态函数对观测到的BP进行分析，评价其最大值的位置！BP及其半最大全宽度（FWHM）。图1显示了研究样品的热分析结果。这里，xº0:125的样品代表了所有样品。在淬火态样品中，它们的Tg随x值的增加而增加。在每个Tg下退火样品的结晶峰温度（Tp）都倾向于低于淬火态样品[图5]。1 (a)和1 (b)]。特别是，淬火和退火样品之间的Tp差异（即：Tp）表明在xº0:125 （BaTi0: 125Si1: 875O5；±pº73 K）时最大值。该值远大于基材玻璃（BaSi2O5；±40k）。根据Marotta等人的研究，显示出均匀成核并经过热处理的氧化玻璃，由于内部核的过量演化，显示出Tp的温度比未处理的玻璃低。11)这些结果表明BaTi0: 125Si1: 875O5玻璃具有较高的成核能力。此外，退火后的样品没有组织发育，只有光晕。
Inelastic light scattering (ie, Brillouin and Raman) can provide information about chemical bonding and coordination states, making it an efficient technique for studying amorphous matter in supercooled liquid (SCL) and melt regimes. 1–3) Several studies have reported that, during crystallization (which occurs between these regimes), binary system glasses exhibit anomalous elastic behavior [ie, simultaneous occurrence of increases in sound velocity (or elasticity), which is estimated by Brillouin spectra] and significant damping. 4, 5) Such behavior has also been reported in the low-energy vibration mode ($1 THz) of Raman scattering (known as the Boson peak, BP) during transition from SCL to crystals (SCL–crystal transition). 6, 7) Although the anomalies appear to be related to the crystallization phenomenon, in-depth analysis has not been conducted yet. Therefore, in this study, in order to obtain additional information concerning the anomaly in the crystallization regime, we prepared an appropriate sample for the in situ observation of the BP and examined the behavior of the BP under nonisothermal and isothermal heating conditions. For observing crystallization dynamics through inelastic light scattering, glass samples that show a strong tendency of homogeneous nucleation are preferable because the samples have a large interface, at which the SCL–crystal transition occurs. 7) Since a BaSi2O5 glass possesses high nucleation ability 8) and TiO2 is known to be an effective nucleation reagent in a silicate glass system, we prepared the glasses in which SiO2 was substituted by TiO2, ie, BaTixSi2¿ xO5 (x º 0 {0: 25), using a melt-quenching technique (melting condition: 1773K for 1h). The as-quenched samples were annealed at each glass-transition temperature (Tg)[Fig. 1 (b)] for 20 h to obtain nucleated samples. This was done because for glass with a homogeneous nucleation trend, the temperature at which the maximum nucleation rate is evident is close to Tg. 9) The samples were characterized by differential thermal analysis (DTA), transmission electron microscopy (TEM), and in situ inelastic light scattering observation. Detailed conditions for these analyses are described elsewhere. 6, 7) The spectra that were obtained in the low-energy region were reduced with respect to the Bose–Einstein factor and were fitted using the sum of the BP and the Gaussian function. This was done because the vibrational band, which results from the Ba–O bond, contributes to the spectra. 10) The observed BP was analyzed using a log-normal function to evaluate the position of its maximum! BP and its full width at half maximum (FWHM). Figure 1 shows the results of thermal analysis in the studied samples. Here the samples with x º 0: 125 are representative of all the samples. In the as-quenched samples, their Tg increased with the value of x. The annealed samples at each Tg tended to show lower crystallization-peak temperatures (Tp) than the as-quenched samples [Figs. 1 (a) and 1 (b)]. In particular, the difference in Tp between the as-quenched and annealed samples (ie,¡ Tp) indicated the maximum value at x º 0: 125 (BaTi0: 125Si1: 875O5;¡ Tp º 73 K). This value was much larger than that of the base glass (BaSi2O5;¡ Tp º 40 K). According to Marotta et al., oxide glass showing homogeneous nucleation and subjected to thermal treatment reveals a shift of Tp to a temperature that is lower than that of the nontreated glass because of the evolution of an excess of internal nuclei. 11) These results suggest that the BaTi0: 125Si1: 875O5 glass possesses high nucleation ability. In addition, the annealed sample showed no structural development, and only the halo …