Thick films of BaLa4Ti4O15 (BLT) are potential candidates for applications in telecommunications devices, operating at microwave frequencies, in which miniaturization is required. The production of thick films usually involves the powder deposition on top of a dense substrate, followed by the constrained sintering of the powder layer. Constrained sintering of functional complex oxides as BLT has not been addressed. In this work we demonstrated that in opposition to isotropic constrained sintering model predictions, BLT films with density equivalent to freely sintered bulk samples were obtained after 180 min at 1500 ºC. Another unexpected observation is that films showed a larger grain size than the bulk sample sintered under the same conditions. A high degree of anisotropy was detected in grain's shape, with high aspect ratio, and in film's orientation, with grains oriented parallel to the substrate. In comparison, in freely sintered bulk sample, lower aspect ratio and lower grain orientation are observed. Stress assisted grain growth is shown to be responsible for the increased grain growth and high texturization observed in the films. Dielectric characterization was also performed in films and bulk and the electrical response correlated with the microstructural features. Both showed near-zero temperature coefficients of permittivity, revealing a dielectric response with great temperature stability, interesting for microelectronic applications.
Microstructure and Thermoelectric Properties of (Bi0.48Sb1.52)Te3 Thick Films Prepared with Tape Casting Method
