JOURNAL OF MATERIALS SCIENCE 39 (2 0 0 4 ) 1233 – 1239 Dielectric and thermal properties of xPbTiO 3 -(1 - x)SrTiO 3 Polycrystals E. MART ´ INEZ CICESE, Physics of Materials Graduate Program, Km. 107 Carr. Tijuana—Ensenada, C.P. 22800, BC. M´ exico S. GARC ´ IA, E. MARIN, O. VASALLO Facultad de F´ısica-IMRE, Universidad de la Habana, Vedado, La Habana 10400, Cuba G. PE ˜ NA-RODR ´ IGUEZ, A. CALDER ´ ON CICATA-IPN, Legaria 694, 11500 M´ exico D.F. J. M. SIQUEIROS Centro de Ciencias de la Materia Condensada, UNAM C.P. 2681, B.C., M´ exico E-mail: jesus@ccmc.unam.mx SrTiO 3 and PbTiO 3 perovskites are combined to form the x PbTiO 3 -(1 − x )SrTiO 3 (PST) solid solution. In this work, a study of its dielectric and thermal properties is reported as a function of PbTiO 3 content. The dielectric properties of the x PbTiO 3 -(1 − x )SrTiO 3 solid solution are determined through a thermoelectric analysis technique and hysteresis measurements. Such measurements made at room temperature for all compositions show the influence of one component upon the other resulting in a response to the electric field that involves a strained lattice behavior. A limiting case of antiferroelectric-like behavior is observed for x = 0.5. The thermal properties such as the specific heat capacity (c) and thermal diffusivity (α) were determined using a photoacoustic technique (PA) and the temperature relaxation method (TRM). The thermal conductivity was calculated from the results obtained for c and α. C  2004 Kluwer Academic Publishers 1. Introduction Nowadays, there is considerable interest in crystalline and polycrystalline ferroelectric materials due to their many known and potential applications [1]. In the de- sign of devices based in ferroelectrics, it is very impor- tant to take into account the thermal properties of the involved materials, because the rate at which the gen- erated heat inside the device dissipates, may determine its performance and lifetime [2]. As an example, to en- hance the operating parameters of integrated pyroelec- tric IR-sensors the thermal properties must be improved for the optimal functioning. A low thermal conductivity is essential for materials used as pyroelectric detectors [3]. It is well known that thermal properties of dielectric ceramics, especially the ferroelectric ones, are directly related to their microstructure where phonon propaga- tion accounts for the transport of thermal energy. There- fore, the understanding of the correlation between mi- crostructural aspects and thermal properties is of great importance [2]. That is, since the dielectric behavior is temperature dependent, their response to heat ex- change phenomena will be of relevance, whether they are used as pyroelectric detectors, memory elements or high permittivity capacitors. Heat capacity and thermal conductivity are fundamental in fixing the resistance to thermal stresses and also determine operating temper- atures and temperature gradients [2]. Solid solutions such as (Pb x Sr 1−x )TiO 3 have received some attention when looking for a material with intermediate proper- ties (dielectric properties) between those of the extreme compositions (PbTiO 3 and SrTiO 3 ) [4–6], however, the knowledge of the thermal properties for mixtures of PbTiO 3 and SrTiO 3 perovskites has not been reported before. In this work we investigate the dielectric and ther- mal properties of a system that consist of a mix- ture of PbTiO 3 and SrTiO 3 perovskites that we call x PbTiO 3 -(1 − x )SrTiO 3 . Among the thermal proper- ties studied are the specific heat capacity (c), the ther- mal diffusivity (α) and the thermal conductivity (k ) for x PbTiO 3 -(1 − x )SrTiO 3 (x = 0.1, 0.3, 0.5, 0.7, 0.9) ce- ramic samples using a photoacoustic (PA) technique [7, 8] and the temperature relaxation method (TRM) [9]. 2. Experimental procedure High purity (>99.9%) PbTiO 3 and SrTiO 3 powders were used for the preparation, via the conventional ce- ramic technique, of the nominal composition x PbTiO 3 - (1 − x )SrTiO 3 , where x is 0.1, 0.3, 0.5, 0.7 and 0.9. The powders were mixed in an agate mortar with ethyl alcohol for 2 h and heated at 1300 ◦ C for 2 h. The resulting powders were uniaxially die-pressed at 0022–2461 C  2004 Kluwer Academic Publishers 1233