Low energy excitation and low tempereture heat capacity of superionic conductors

超离子导体的低能激发和低温热容

基本信息

批准号：
05453075
负责人：
ATAKE Tooru
金额：
$ 5.31万
依托单位：
Tokyo Iistitute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05453075/
关键词：
Superionic conductors Low temperature heat capacity Low energy-excitation Adiabatic calorimeter Solid state ionics Lattice dynamics 位励起モード

项目摘要

Thermodynamic studies have been made on superionic conductors which have long been attracting much attention because of its high potentiality in a variety of applications such as fuel cells, gas sensors and so on. However, the mechanism of high ionic conductivity in the solids is still an open question.At first, the structural and thermodynamic properies have been studied on AgCrS_2, CuCrS_2, NaCrS_2.Rb_4Cu_<16>I_7Cl_<13>, Ag_8GeTe_6, Cu_8GeTe_6, Cu_3BiS_3, and PbSnF_4 on which the experiments and measurements have been made by X-ray diffractometry, impedance measurements, neutron diffractometry and precise heat capacity measurements. For the low temperature calorimetry down to 0.5 k, a small size calorimeter was newly designed and constructed using ^3He-evaporation type refrigerator.Fine powders of Y_2O_3-ZrO_2 containing different amounts of Y_2O_3 were prepared by a hydrolysis techniques using ZrOCl_2・8H_2O and YCl_3. The elemental analysis gave the values of x=0,0.0200,0.0396,0.0776,0.0970 for the five samples represented as (ZrO_2) _<1-x> (Y_2O_3) _x. The samples were characterized by SEM,ICP analysis, X-ray diffractometry and Raman scattering, and then precise heat capacity measurements were made on the fine powder and sintered specimens. Yttria doping softens the crystal lattice and causes increasing of the heat capacity value, and thus the heat capacity of the sample of x=0.0970 is larger than that of x=0.0776 at high temperature region where almost all the lattice vibrations are fully excited and the number of vacancies corresponds to the heat capacity. In the lowest temperature region, however, the distribution of the vacancies plays an important role as well as the number of vacancies over the crystal lattice sites, because only low-frequency vibrations are excited in the low temperature region and such low-energy modes are strongly influenced by the distributin of the vacancies.

热力学研究已经对超级离子导体进行了长期引起了很多关注，因为它在燃料电池，燃气传感器等各种应用中具有很高的潜力。但是，固体中高离子电导率的机制仍然是一个空旷的问题。首先，结构和热力学特性已在AGCRS_2，CUCRS_2，NACRS_2.RB_4CU_ <16> I_7CL_ <13>上研究通过X射线衍射测量，阻抗测量，中子衍射法和精确的热容量测量进行了测量。对于低温量热量至0.5 k，使用 ^3he蒸发类型式冰箱新设计和构建的小尺寸量热计。Y_2O_3-Zro_2的粉末粉含有不同量的Y_2O_3的粉末，该粉末是通过使用Zrocl_2・8H__2o和Ycl__3的水解技术制备的。元素分析给出了x = 0,0.0200,0.0396,0.0776,0.0970的值，表示为（zro_2）_ <1-x>（y_2o_3）_x。样品的特征是通过SEM，ICP分析，X射线衍射法和拉曼散射，然后在细粉末和烧结的标本上进行精确的热容量测量。 Yttria掺杂晶状晶格并导致热容量值的增加，因此在高温区域，X = 0.0970的样品的热容量大于X = 0.0776的热容量，几乎所有晶格振动都完全激发了，空位的数量与热容量相对应。然而，在最低温度区域中，空缺的分布起着重要作用，并且在晶格晶格位点的空缺数量以及空缺数量，因为只有低温振动在低温区域受到激发，并且这种低能模式受到空缺分布素的强烈影响。