(Ba,Ca)TiO3 PTCR ceramics with LaNiO3 thin-film electrodes: Preparation and characterization of the interface

Conductive LaNiO3 thin film electrodes were deposited by chemical solution deposition (CSD) from nitrate solutions onto polycrystalline Al2O3 and (Ba, Ca)TiO3 PTCR ceramic substrates. The electrical properties of the LaNiO3 th in film on Al2O3 and of the interface consisting of LaNiO3 and the semicond uctive oxide ceramic were investigated. The deposited LaNiO3 films were abo ut 250 nm thick and consisted of nanosized particles. The resistivity of th e LaNiO3 film was about 3 x 10(-3) Ohm cm at 20 degrees C. The PTCR ceramic consisted of mu m sized particles and exhibited an electronic resistivity of about 10 Ohm cm at 20 degrees C and a steep increase of the resistivity of a few orders of magnitude above the Curie point at about 120 degrees C. The electrical properties of the LaNiO3/PTCR interface were dominated by th e properties of a barrier layer between the PTCR ceramic and the LaNiO3 ele ctrode. The potential dependence of the impedance indicated that the barrie r layer consisted of a depletion layer within the PTCR ceramic, when the fl at band potential of LaNiO3 on the PTCR ceramic at about -250 mV was exceed ed. Additionally the formation of an insulating layer at the LaNiO3 electro de has to be taken into account.