Dielectric and leakage current properties of Li doped (Ba,Sr)TiO 3 thick film interdigital capacitors on the alumina substrates

Abstract

Li doped (Ba,Sr)TiO 3 thick films were fabricated by employing the screen printing method on the alumina (Al 2O 3) substrates. Interdigital capacitor patterns with seven fingers of 200 μm gap, 250 μm length were designed and screen printed on the alumina substrates. Ba 0.5Sr 0.5TiO 3 materials, paraelectric state at the room temperature, have been chosen for the microwave devices due to high dielectric permittivity and low loss tangent, however, the sintering temperature of (Ba,Sr)TiO 3 is over 1350 °C. In order to lower the sintering temperature, Li (3 wt%) was added to the (Ba,Sr)TiO 3 materials. Li doped (Ba,Sr)TiO 3 thick films screen printed on the alumina (Al 2O 3) substrates were sintered at 900 °C for 1.5 h. The structural feature was analyzed with X-ray diffraction method. Temperature dependent dielectric properties were characterized from 303 to 403 K at 1 MHz. Within the ±100 V of bias voltage, current–voltage characteristics of Li doped (Ba,Sr)TiO 3 films were investigated from 303 to 403 K. Through the current–voltage characteristics, the resistivity of Li doped (Ba,Sr)TiO 3 films were calculated. In this paper, the significant negative temperature coefficient of resistance (NTCR) of Li doped (Ba,Sr)TiO 3 films will be presented through the activation energy fitting. Measured activation energy is approximately 0.366 eV.