EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Functional ceramics with the perovskite structure are broadly used in electronic components as, for instance, high permittivity capacitors, piezoelectric components, and so on. Among them, BaTiO₃-based materials find their main application in multilayer ceramics capacitors (MLCCs), with an annual production of 11 thousand tons. In the development of new devices based on these materials, the contact characteristics between the ceramics and the liquid metals used to create internal and termination electrodes are of great importance. In this work, these issues are undertaken for BaTi_1-xZr_xO₃ (x = 0, 0.1, 0.2, 0.4) ferroelectric perovskites in contact to liquid pure Ag and Ag-Cu 3 at.% alloy.
Wetting in terms of contact angles and the work of adhesion was determined by the sessile drop method at 1000 °C in air atmosphere and the obtained metal/ceramic interfaces were characterised by SEM and EDS. Working in air, rather than under a protective atmosphere, presents several advantages such as the process simplicity, improved wetting due to the presence of oxygen, and avoids reduction of BaTiO₃, which leads to an undesired semiconducting behaviour of the ceramic.
Compared to Ag, the Ag-Cu 3 at.% alloy exhibited increased wetting due to the formation of interfacial CuO; no further interfacial phenomena or mutual interdiffusion of elements at the interfaces were detected. For both liquid Ag and Ag-Cu, the contact angle increased with increasing zirconium content in the ceramic substrate, due to the increased band-gap energy.