ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 54, (3) 253 - 257 (2010)

Lidjici Hamza 1, Rguiti Mohamed 3, Hobar Farida 2, Courtois Christian 3, Leriche Anne 3
1 Laboratoire d’étude et de développement des matériaux diélectriques et semiconducteurs, Université de Laghouat, Route de Ghardaia B.P.37G. Laghouat, Algérie
2 Laboratoire des microsystemes et instrumentation, Département d’électronique, Université Mentouri de Constantine, Route Ain El bey, Constantine, Algérie
3 Laboratoire des Matériaux et Procédés, Université de Valenciennes et du Hainaut-Cambrésis, Z.I. du Champ de l’Abbesse 59600 Maubeuge, France

Keywords: Lead-free ceramics, Sintering temperature, Dielectric and piezoelectric properties

The effects of sintering temperature on structure, microstructure, dielectric and piezoelectric properties of 0.935(Bi0.5Na0.5)TiO₃ -0.065BaTiO₃ (BNT6.5BT) lead free ceramics prepared by solid sintering technique at 1150-1200°C were investigated. The X-ray diffraction patterns showed that all of the BNT6.5BT ceramics exhibited a single perovskite structure with the co-existence of the rhombohedral and tetragonal phase. A fine and homogeneous grains were observed for samples sintered at 1150 and 1160°C and the increase of the sintering temperature up to 1180-1200°C induces significant grain growth with the appearance of coarse grains. The dielectric constant- temperature curves of the compositions exhibited strong dispersion with the increasing temperature, and the dielectric loss increased dramatically while the temperature over 230°C. The lowest value of depolarization temperature (Td) was found at samples sintered at 1160°C. The values of remnant polarization Pr obtained at room temperature are 31 and 29 µC/cm² for specimens sintered at 1160°C and 1200°C respectively. At room temperature, BNT6.5BT ceramics sintered at 1180°C exhibited good performances: dielectric constant was 833 at 1 KHz, thick coupling factor kt was 0.52 and the kt/kp ratio was 2.08. Therefore, the ceramics can be suitable for ultrasonic transducers in commercial applications.

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