本文實驗採用交叉式偏光顯微鏡附屬石膏版,觀察出K■Na(SeO■)■晶體
之鐵彈區域於溫度333K時,晶體鐵彈區域有所變化晶體鐵彈區域邊界逐漸
變成模糊,但仍能明顯看出晶體未變成全部消光,呈緩慢性變化,至約343K
左右,整個晶體才變成完全消光。室溫時K■Na(SeO■)■晶體由鐵彈相晶
軸[100]方向外加壓縮力,觀察鐵彈區域之區界及光影圈的變化情形,在足
夠應力下,能使整個晶體變為單一鐵彈區域D■,且此區域之二重軸垂直於
應力方向。當應力為晶軸[010]方向之壓縮力時,會發現K■Na(SeO■)■晶
體在足夠應 鐵彈區域(D■,D■)共存的現象,且以x=0,y=0之區界存在。利
用已測得之291K鐵彈相及390K初始相的結構參數,來計算K■Na(SeO■)■
之自發應變張量分量值為2.83×10■,其值僅約一般鐵彈物質之千分之一,
此結果符合鐵彈相變時存在偶合現象之理論。同時我們亦討論此鐵彈物
質 K■Na(SeO■)■相變過程和受力時晶體中原子之轉變過程,其結果與實
驗現象符合。

In the thesis we report the observation of the evolution of the
domain structure in K■Na(SeO■)■ with temperature using a
cros- sed polariser with accessory Gypsum plate.The domain
walls become ambiguous,but they are still distinguishable at
333K.The wholes of crystal become extinct about 343K.The change
of domain struct- ure in optical observation is not sharp.When
mechanical stress of compression X■ is applied on K■Na(SeO■)
■ at room temperature ,in monoclinic consideration it
cooresponds to [100],then the switching process occurs in such
a way that D■ and D■ domain disappear and D■ occupies more
and more volume of the crystal.If we keep increasing X■,then
the monodomain is attained and its 2- fold axis(b-axis) is
perpendicular to the orientation of stress. When mechanical
stress of compression X■ is applied, in monocli- nic
consideration it cooresponds to [010],then the switching pro-
cess occurs in such a way that D■ domain disappears, and D■
and D■ occupy equal volumes of the crystal and by formation of
doma- ins walls W■(y=0),W■(x=0),which divide neighboring
orientation- al states D■ and D■.Calculating the components
of spontaneous strain tensor,we obtain the result that the
magnitude of e■,2.83×10■,is only about 1/10■of general
ferroelastic crystals,which agrees with the theory of coupling
in ferroelastic phase transi- tion.The deformation patterns of
the structure phase transition and external mechanical stress
in K■Na(SeO■)■ are also discus- sed in the thesis,the
results are agreement with the phenomena of experiments.
In the thesis we report the observation of the evolution of the