Abstract
Ba0.5CaxSr0.5-xTiO3 (BCST) ceramics, where x = 0, 0.1, 0.2, 0.3 and 0.4, were prepared by the conventional solid state reaction technique. X-ray diffraction (XRD) analysis confirmed the formation of BST perovskite phase structure besides some calcium oxide peaks for samples with high Ca content, x. Scanning electron microscopy (SEM) results confirmed the XRD results, i.e., as x increased, the average grain size decreased. Energy dispersive X-ray (EDX) analysis verified the increase of the amount of Ca element with increasing of its content. Mechanical properties such as ultrasonic attenuation, longitudinal wave velocity, and longitudinal elastic modulus were studied by an ultrasonic pulse echo technique at 2 MHz frequency. Investigations of ceramic microstructures and mechanical properties showed their dependence on composition. Increasing of Ca content resulted in a decrease in bulk density and ultrasonic attenuation and an increase in porosity, velocity, and modulus. High temperature ultrasonic studies showed, in addition to Curie phase transition, three or more relaxation peaks and its origin was investigated.
Highlights
BaTiO3 and SrTiO3 are representatives for ABO3-type perovskite materials
X-ray diffraction (XRD) data confirmed the formation of the perovskite phase structure in addition to peaks observed for some tested ceramics which have been related
Scanning electron microscopy (SEM) images and Energy dispersive X-ray (EDX) analysis confirmed the appearance of the major perovskite phase and an increase of Ca ions upon increasing its content
Summary
BaTiO3 and SrTiO3 are representatives for ABO3-type perovskite materials. BaTiO3 is usually a ferroelectric material with Curie temperature of 120 ̊C. Ba1−xSrxTiO3 (BST) has the simultaneous advantage of high dielectric constant of BaTiO3 and the structural stability of SrTiO3 [1,2] These ferroelectric materials have attracted considerable attention owing to their unique properties such as chemical stability, high permittivity, high tunability, and low dielectric losses. BST has shown a great promise in applications, such as phase shifting elements in phased array antennas and as tuning elements in devices operating at microwave frequencies [1,3,4,5,6,7,8,9] In view of their merits, the investigation on BST solid solution is significantly important [1,2,9,10]. The Curie temperature of BST can be controlled by adjusting the Ba/Sr ratio and/or doping ions to substitute for A or B sites in the ABO3 perovskite systems [11,12]
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