Properties of compositionally graded Ba(1−x)SrxTiO3 self-standing thick films

Compositionally graded self-standing thick films (0.4 mm) have been fabricated using the airflow deposition method. Films were made of five layers with different composition Ba(1−x)SrxTiO3 (BST, x = 0, 0.1, 0.2, 0.3 and 0.4). The layers of different thicknesses, ranging from 80 to 30 μm, presented similar Vickers microhardness of about 0.25 GPa. The average particle size of deposited layers was finer than 500 nm and the density of as-deposited films was about 80% of theoretical. After sintering at 1350 °C samples presented increased-density (>90%) and maintained a compositional gradient. When compared to single-composition BST ceramics, permittivity of graded films was much less dependent on temperature over a wide range, from −50 to 250 °C. In addition, the films displayed polarization offset when driven by an alternating field and heated above 50 °C.