July 1998 Ž . Materials Letters 36 1998 95–101 ž / Thermal and electrical characterization of CdTe Te 1yx x composites: electron–phonon system M.E. Rodriguez a , J.J. Perez-Bueno b,c , O. Zelaya-Angel c, ),1 , J. Gonzalez-Hernandez b a Centro de InÕestigacion en Ciencia Aplicada y Tecnologıa AÕanzada del I.P.N, Queretaro, Qro., Mexico ´ ´ b Laboratorio de InÕestigacion en Materiales, CINVESTAV, Queretaro, Qro., Mexico ´ c Centro de InÕestigacion y de Estudios AÕanzados del I.P.N, P.O. Box 14-740, 07000 Mexico D.F., Mexico ´ ´ Received 14 November 1997; accepted 24 December 1997 Abstract Ž . Ž . Pressed discs of mixed powders of CdTe semiconductor and Te semimetal with different mass concentrations were Ž . thermally and electrically characterized. In this granular system: CdTe Te , studied in the entire range 0 Fx F1, where 1yx x x is the fractional weight of Te, it has been found to exist a percolation critical point, x s15.05%, for the electrical c Ž . Ž 8 2 . resistivity r , by showing an abrupt decreasing of six orders of magnitude r ;10 to r ;10 V cm . The fractional weight value of x s15.05% corresponds to a volumetric fraction of 15.4%, according within the error scattering with the c accepted theoretical value of 16.0%, for a volumetric fraction at the critical percolation in a three-dimensional system based in a mixture of conductive-insulator materials. The study of the theoretical properties of the composite were reduced to the Ž . analysis of the thermal diffusivity a , as this is a dynamical property responsible for the establishment of the thermal equilibrium in a given material. The experimental results show a complex dependence of a as a function of the parameter x, evidencing a thermal transport influenced by an electron–phonon interaction. q 1998 Elsevier Science B.V. All rights reserved. PACS: 44.30.qv; 63.20.Dj; 64.70.yp; 66.10.De; 81.40.yz Keywords: Heat conduction; Percolation; Composites; Electron–phonon interaction 1. Introduction Composite materials are widely used in industrial applications such as resistors, sensors, transducers, wx thermistors, piezoresistors, chemical sensor 1 , and packaging materials in electronic applications like ) Corresponding author. Tel.: q52-5-747-7000, XT 4230; fax: q52-5-747-7096; e-mail: ozelaya@fis.cinvestav.mx. 1 Also at CICATA-IPN. Mexico D.F. substrates. The investigation of heat and electrical transport phenomena in those materials is an impor- tant topic which is closely linked to their basic fundamental physical properties. The topic of heat transport in composite materials has received substantial attention in recent years because of their use in materials for electronic appli- cations. Two properties of composites are very im- portant in the design of electronic devices: thermal Ž . diffusivity a and the coefficient of thermal expan- 00167-577Xr98r$19.00 q 1998 Elsevier Science B.V. All rights reserved. Ž . PII: S0167-577X 98 00016-0