由於物質的超聲波的性質，可直接反應其空間的彈性係數。其彈性係數依
據Kul'bitskaya的凍結理論，可以合理解釋超聲波在矽氧玻璃之聲速變化
情形。在矽氧玻璃中我們加入鹼金屬氧化物，發現在180K至室溫間其聲速
變化對溫度呈線性關係；且溫度係數和鹼金屬氧化物莫耳百分比亦是線性
關係。在Li■O- nSiO■玻璃中，其聲速的溫度係數和Li■O 莫耳百分比
的關係，以25% 為界，呈現兩不同斜率的直線，此乃因Li■O 的分布情形
不同。本文對照前人以SEM 方法分析鋰原子團大小的研究結果，可推論鋰
玻璃25% Li■O 莫耳百分比以下者為二相玻璃，而在此之上者轉為單相玻
璃。根據玻璃凍結理論的分析，可推知當鹼金屬氧化物莫耳濃度甚低時，
玻璃聲速變化的溫度係數，主要取決於因矽氧鍵被破壞而形成單鍵氧的莫
耳濃度。比照鋰玻璃的相位分離情形，我們推測鹼金屬氧化物矽氧玻璃中
，Na■O-nSiO■ 及 K■O-nSiO■玻璃結構為單相；而 Cs■O -nSiO■則
為二相分離。

Ultrasonic measurments of a series of R■O-nSiO■ (R=Li ,Na,K,
Cs) glasses samples are presented. In term of the model of
frozen-in thermal fluctuations in glasses, the analysis of the
relationship of temperature coefficient of ultrasonic velocity
change versus Li■O molar frac- tion provides evidence of the
existence of two-phase separation phenomenon in lithium oxide
less than 0.25. It also provides some information about the
structural change of the glasses from a system of two phase
to a single phase. A comparison of the temperature coeffi-
cient of lithium glass with those of Na,K and Cs glass- es
reveals some interesting feature of structure. The structured
feature of Na or K glasses is single phase; The structured
feature of Cs glass is two phase separa- tion.
Ultrasonic measurments of a series of R■O-nSiO■ (R=Li ,Na,K,