Abstract
Low-temperature heat capacity of potassium germanate glasses (xK2O?(100-x)GeO2; x=0.0, 10.1, 19.0, 28.2, 39.0) (x indicates K2O mol% content) has been measured in the temperature range from 2 to 50 K with K2O content. From a result of the heat capacity Cp, it has been found that an excess heat capacity is not caused by a regular thermal motion but an interaction. In addition, it has also been found that a relationship between a maximum of reduced excess heat capacity CpT -3max and elastic modulus is dual. Moreover, a ‘hole’ model of liquid theory was applied to explain the formation of resonant mechanism. This model leads us to an idea that the excess heat capacity is described by degree of freedom of reallocated-and-isolated-structural units. Consequently, we conclude that the excess heat capacity is caused by the reallocated-main-network structure containing holes resonant with the reallocated-and-isolated-microstructural units.
Highlights
1.1 Purpose of ReseachThe purpose of reseach is to measure the heat capacities Cp of potassium germanate glasses in the range of temperature from 2 to 50 K with K2O content and to clarify an origin of the excess heat capacity compared with the Debye model from a viewpoint of the microstructure.1.2 Germanate AnomalyThe glass has been used in a human life from an ancient time after ceramics and studied invariably applied to a wide variety of fields for new products
Germanate glasses we study are used as a core part of optical fiber and an infrared emitting window
Germanate anomaly means when alkali-oxide such as Li2O, Na2O or K2O is added to germania (GeO2), a physical property of the resulting glass exhibits a maximum or a minimum at some addition of alkali-oxide content, for instance, a density of potassium germanate glass shows a maximum at about 10 mol% K2O content
Summary
1.1 Purpose of ReseachThe purpose of reseach is to measure the heat capacities Cp of potassium germanate glasses in the range of temperature from 2 to 50 K with K2O content and to clarify an origin of the excess heat capacity compared with the Debye model from a viewpoint of the microstructure.1.2 Germanate AnomalyThe glass has been used in a human life from an ancient time after ceramics and studied invariably applied to a wide variety of fields for new products. Germanate anomaly means when alkali-oxide such as Li2O, Na2O or K2O is added to germania (GeO2), a physical property of the resulting glass exhibits a maximum or a minimum at some addition of alkali-oxide content, for instance, a density of potassium germanate glass shows a maximum at about 10 mol% K2O content. On the other hand, when alkali-oxide is added to silica (SiO2), a physical property of the resulting glass shows neither a maximum nor a minimum. This anomaly is showed in many physical properties e.g. density, refractive index, glass transition temperature, viscosity, micro-hardness, internal friction, acoustic velocity and elastic moduli. The germanate anomaly has been extensively researched (Henderson, 2007; Yiannopoulos, Kamitsos, & Jain, 1997; Kamitsos, Yiannopoulos, Karakassides, Chryssikos, & Jain, 1996; Yiannopoulos, Varsamis, & Kamitsos, 2001; Yiannopoulos, Varsamis, & Kamitsos, 2002; Henderson & Fleet, 1991; Wang & Henderson, 2004; Soltay & Henderson, 2005; Hannon, Martino, Santos, & Almeida, 2007; Kiczenski, Hammarsten, Wilkerson, Affatigato, & Feller, 2000), especially a lot of studies by Kamitsos et al (Yiannopoulos et al, 1997; Kamitsos et al.,1996; Yiannopoulos et al, 2001; Yiannopoulos et al, 2002) and Henderson et al (Henderson, 2007; Henderson & Fleet, 1991; Wang & Henderson, 2004; Soltay & Henderson, 2005)
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