Velocity of Sound and Elastic Properties of Alkali Metal Germanate Glasses

[目的]碱硼酸盐玻璃和碱锗酸盐玻璃表现出特殊的性质，分别称为硼酸盐异常和锗酸盐异常。本研究的目的是阐明碱硼酸盐玻璃和碱锗酸盐玻璃在声速和弹性性能上的异同。[实验]测定了M = Li, Na， K， Rb和Cs的二元碱金属锗酸盐玻璃xM_2O(1 - x)GeO_2的密度和声速。(1)以碱金属氢氧化物和石英型二氧化锗为原料，化学合成粉末，在1100 ~ 1450‰的温度下，在铂坩埚中熔融2 h，然后倒入石墨模具中，形成圆柱形块状玻璃。(2)用电位滴定法测定碱金属和二氧化锗的含量。(3)用差示扫描量热计测定了玻璃化转变温度和玻璃化转变时的热容变化。(4)采用静压称量法测定密度。(5)采用脉冲回波重叠法测量频率为10 MHz的超声声速。[结果与讨论]在x = 0.15 ~ 0.20时，碱锗酸盐玻璃的声速和弹性常数达到最大。这种行为与碱硼酸玻璃的不同之处在于：(1)硼酸锂玻璃中的速度随氧化锂含量的增加而单调增加；(2)硼酸钠和硼酸钾玻璃中的速度呈现单一最大值；(3)硼酸铷和硼酸铯玻璃中的速度依次呈现最大值、最小值和另一个最大值。由于锗酸盐玻璃的论文正在制备中，硼酸盐玻璃的论文在参考文献中给出。

[Objective] Alkali borate glasses and alkali germanate glasses exhibit peculiar properties termed borate anomalies and germanate anomalies, respectively. The purpose of the present research is to elucidate similarities and differences between alkali borate glasses and alkali germanate glasses from the velocity of soud and elastic properties of these glasses.[Experimental] For the binary alkali metal germanate glasses xM_2O(1 - x)GeO_2 where M = Li, Na, K, Rb and Cs, the density and the velocity of sound were determined. (1) A powder synthesized chemically from alkali metal hydroxide and quartz-type germanium dioxide was fused in a platinum crucible at temperatures from 1100 to 1450ﾟC for 2 h and then the liquid was poured into a graphite mold to form a cylindrical bulk glass. (2) The contents of alkali metal and germanium dioxide were determined by a potentiometric titrimetry. (3) The glass transition temperature and the change in heat capacity at the glass transition were determined by a differential scanning calorimeter. (4) The density was measuredby a hydrostatic weighing method. (5) The ultrasonic velocity was measured at a frequency of 10 MHz by means of the pulse-echo overlap method.[Results and Discussion] The velocity of sound and the elastic constants of alkali germanate glasses wed single maxima at the composition of x = 0.15-0.20. This behavior is different from the behavior of alkali borate glasses : (1) the velocity in lithium borate glasses increases monotonically with an increase in the content of lithium oxide, (2) the velocity in sodium and potassium borate glasses shows a single maximum, (3) the velocity in rubidium and caesium borate glasses exhibits a maximum, a minimum and another maximum in succession. Since the papers for germanate glasses are in preparation, the papers for borate glasses are given in References.