Thermal expansion and conductivity of CuGa_x In_1−x Se₂ solid solution

Abstract

Thermal properties of a series of ternary compounds of the AIBIrlCgl -type and those of the C U I~S~, S~~(~ -x) solid solutions have been investigated by BODNAR, KOR-XIJN ; MAKOVETSKAYA, BODNAR e t al. ; MAKUVETSKAYA, BUNDAR e t al. (in press). No analogous literature on the CuGa,Inl -,Se, solid solutions is reported so far. The aim of this paper is to study thermal expansion and conductivity of the CuGa,Inl-,Se, solid solutions, where polymorphous transformations occur.The investigations were carried out on the samples obtained by one temperature synthesis with vibration (BODNAR, BOLOGA) or by the method described by BODNAR

Preparation, structure and thermal properties of CuGa5Se8

“…The investigations showed that thermograms have a single peak at 1339 K which corresponds to melting. The defined magnitude is close to the values of T m obtained by us for CuGa 3 Se 5 (1359 K) [8] and for CuGaSe 2 (1361 K) [10].…”

“…The [10]. From the Debye temperatures Θ D , the molar volumes v a , the thermal expansion coefficients α m , obtained at different temperatures, we evaluated in the Debye approximation some thermodynamic characteristics: the heat capacity c p , the vibrational parts of entropy S T , the difference enthalpy ∆H T = H T -H 0 , and the intrinsic energy (E T +E 0 ) with a view to zero-point energy E 0 =4.5RΘ D .The defined values (c V =24.08 J/K⋅mole, S T =37.8 J/K⋅mole, ∆H T =20.8 kJ/mole, E O =9.41 kJ/mole, E T =20.59 kJ/mole) are consistent with corresponding data derived in the same approximation for CuGa 3 Se 5 [8] and CuGaSe 2 [27].…”

“…where m a is the average atomic mass (in g), v a =0.03765a Besides, the Debye temperatures Θ D L were derived from our values of the mean linear thermal expansion coefficients α m according to formula [10,18,24,25,26,27] …”

X-ray study of CuGa x In1−x Se2 solid solutions

“…2 and it is evident from the figure that the size is minimum for the solid solution CuGao.sIno.sS% and increases on both sides, corresponding to ternary compounds CuGaSe2 and CulnSe2 respectively. A similar type of variation was observed by Bodnar, Bologa, Makovetskaya & Popelnyuk (1985) on specific thermal conductivity measurements of these solid solutions with composition x. SEM examination of these powders revealed that the average grain size varies from 2 to 5 i~m and is minimum for x = 0.5. The representative scanning electron micrographs for x = 1, 0-5 and 0 are shown in Fig.…”

“…The solid solutions, allowing one to vary the physical parameters of the crystals smoothly, are of considerable interest. The difference in the latticeconstant ratios A(c/a) of CuGaSe2 and CuInSe2 is only ---0-05 and, therefore, complete miscibility can be expected (Robbins, Phillips & Lambrecht, 1973)• Solid solutions of these compounds have been made by several researchers and some properties have been reported (Horig, Moiler, Neumann, Reccius & Kuhn, 1979; Paorici, Zanotti, Romeo, Sberveglieri & Tarricone, 1979;Bodnar, Bologa, Makovetskaya & Popelnyuk, 1985). An electron spin resonance study on CuGa,,Inl_xSe2 solid solutions suggested that the intrinsic charge carriers are mainly n type due to electrons released from Se vacancies for x --0.50 and away from x = 0.50 the p-type charge carriers resulting from Cu vacancy are present and have been reported by Rai, Gupta, Suri & Ali (1984).…”