Institute of Physica. Academy of Sciences of the h e r b . SSR, Baku
Investigation of Structural Transionnations in CuSe
Structural transformations in Cu,Se have been studied by the method of hightemperature roentgenography.
From a diffraction record of reflection angles and from a Debye-powder pattern the unit-cell parameters of a rhombic a-modification have been calculated at temperatures of 25, 50, 100, and 132 "C. Using the diffraction line (027) disappearing under the a + /? transformation and appearing again in the course of the inverse /? + a transformation it has been found that the equilibrium temperature between the a-and /?-modifications is To = 134 f 0.5 "C. The unit cell parameter of a hightemperature face-centered cubic /?-modification a t temperatures of 150, 200, 250, and 300 "C also has been determined.
I n the course of mutual transformations a rigid orientational linkage has been found to exist between the a-and /?-modifications.
It has been discovered that when the multiplicity of a + /? and B + a transformations n reaches a value of approximately 30, a /?-Cu,Se -+ Cuz-%Se transformation (where x = 0.20) takes place which is not followed by an inverse transformation.
Strukturelle Umwandlungen in Cu& wurden rontgenographisch bei hoheren Temperaturen untersucht. Aus Pulveraufnahmen werden die Gitterparameter einer rhombischen a-Modifikation bei 25, 50, 100 und 132 "C berechnet. Die Gleichgewichtstemperatur zwischen der a-und j?-Modifikation wird boi 134 f 0.5 "C gefunden. Gitterparameter einer Kfz-Hochtemperatur /?-Modifikation werden ebenfalls bestimmt. Bei mehrfachen Umwandlungen a + /?, /? + a bildete sich Cur-,Se mit x = 0,2;das nicht invers umgewandelt wird.