PHYSICAL PROPERTIES AND STRUCTURE OF OXYFLUORIDE MELTS

本文研究了MO-MF_2（M=Ca,Sr,Ba）熔体的氧分压（OPP）与电导率的关系，并讨论了由萤石状结构的液体晶格引起的新现象。MO- mf_2熔体（MO<17mass%）在氩气和氧气气氛下的电导率随OPP功率的四分之一而变化。OPP对电导率kappa的依赖关系可表示为kappa^0_<离子>exp(-E/RT)+kappa^0_pP_<0^21/4>exp(-E'/RT)，其中kappa^0_<离子>exp（-E/RT）和kappa^0_pP_<0^21/4>exp（-E'/RT）为离子和正空穴的部分电导率。用热电偶法直接观察了加入OPP后熔体透明度的可逆变化。CaF_2、SrF_2、BaF_2等萤石的晶体结构具有较高的马德隆常数，因此即使在液态也能保持相对的长程有序。我们称这种状态为“液体晶格”。当氧化物MO加入时，氧化物MO被纳入液体晶格中。MO的离子M^<2+>和O^<2->分别位于MF_2形成的液体晶格中的M^<2+>-位和F^——位。O^<2->和F^-的不等电荷导致熔体中的阴离子空位。气态氧被电离并溶解到大气中高于临界OPP的熔体中，氧与阴离子空位反应并形成正空穴。正孔通过吸收光使熔体不透明，并有助于传导。

The dependence of oxygen partial pressure(OPP)on electrical conductivity have been studied for MO-MF_2(M=Ca,Sr,Ba) melts and discussed the newly observed phenomena caused by the liquid lattice of fluorite-like structure.Electrical conductivities of MO-MF_2 melts (MO<17mass%) varied with the one-quarter power of OPP in argon and oxygen atmosphere.The dependence of OPP on electrical conductivity kappa can be expressed as kappa^0_<ion>exp(-E/RT)+kappa^0_pP_<0^21/4>exp(-E'/RT), where kappa^0_<ion>exp(-E/RT) and kappa^0_pP_<O^21/4>exp(-E'/RT) are partial conductivity for ions and positive holes.The reversible change in transparency of these melts with OPP was directly observed by the hot-thermocouple method. The crystal structure of fluorite such as CaF_2,SrF_2,and BaF_2 has a high Madelung constant,therefore,the relative long range order is maintained even in liquid state. We call this state "liquid lattice". When oxide MO is added,oxide MO is incorporated into the liquid lattice.The ions M^<2+> and O^<2-> of MO are located on the M^<2+>-site and F^--site,respectively,in the liquid lattice formed by MF_2.The unequal charges of O^<2-> and F^- causes the anion vacancy in the melts. The gaseous oxygen is ionized and dissolved into the melts above a critical OPP in the atmosphere and the oxygen reacted with the anion vacancy and results in the formation of positive holes.The positive holes make the melts to be opaque by the absorption of light and contribute to the conduction.