Velocity of Sound and Elastic Properties of Alkali Metal Germanate Glasses

【目的】碱金属硼酸盐玻璃和碱金属锗酸盐玻璃分别具有硼酸盐异常和锗酸盐异常。本研究的目的是从玻璃的声速和弹性性质来阐明碱金属硼酸盐玻璃和碱金属锗酸盐玻璃的异同。[实验]测定了二元碱金属锗酸盐玻璃xM_2O（1 - x）GeO_2（M = Li，Na，K，Rb，Cs）的密度和声速。(1)将由碱金属氢氧化物和石英型二氧化锗化学合成的粉末在铂坩埚中在1100至1450 ℃的温度下熔融2小时，然后将液体倒入石墨模具中以形成圆柱形块体玻璃。(2)用电位滴定法测定了碱金属和二氧化锗的含量。(3)通过差示扫描量热计测定玻璃化转变温度和玻璃化转变时的热容变化。(4)密度的测定采用静液称重法。(5)超声波速度测量的频率为10 MHz的脉冲回波重叠法。[结果与讨论]碱金属锗酸盐玻璃的声速和弹性常数在x = 0.15 ~ 0.20之间有一个极大值。这种行为与碱金属硼酸盐玻璃的行为不同：（1）锂硼酸盐玻璃中的速度随着锂氧化物含量的增加而单调增加，（2）钠和钾硼酸盐玻璃中的速度显示出单一的最大值，（3）铷和铯硼酸盐玻璃中的速度连续出现最大值、最小值和另一个最大值。由于有关锗酸盐玻璃的论文正在准备中，有关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.