Correlation between the microstructure and electrical properties of Sb-doped BaSnO3 ceramics

Abstract

The non-magnetic, non-inductive electroconductive materials with linear current-voltage characteristic and low and almost constant electrical resistivity in the wide temperature range could be used in conditions unfavorable for metals and alloys. Particular emphasis is placed on the performance and endurance of these materials in conditions at constant high voltage, current, and energy, as well as operating in acidic and humid environmental conditions. The aim of this work was to investigate the influence of antimony concentration and sintering parameters on the structure, microstructure, and electrical properties of antimony-doped barium stannate, BaSn1-xSbxO3 (BSSO, x = 0,00; 0,04; 0,06; 0,08 and 0,10) to obtain conductive electroceramic samples with linear current-voltage (I- U) characteristics and low electrical resistivity. For this purpose three different sintering techniques were used: conventional, spark plasma and cold sintering. According to the X-ray diffraction (XRD) analysis, single-phase ceramic mater- ials with cubic BaSnO3 structure were obtained by conventional sintering at 1600 °C for 3 h and spark plasma sintering at 1100 °C for 5 min. Raising the spark plasma sintering temperature to 1200 °C induced the formation of Ba-rich secondary phase, Ba2SnO4. XRD analysis confirmed the presence of unreacted SnO2 and BaCO3 in cold sintered BaSn0.92Sb0.08O3 sample (310 °C for 5 min, 20 wt.% 1 M acetic acid). Scanning electron microscopy (SEM) indicates a significant decrease in grain size upon doping, regardless of the sintering technique. High-resolution transmission electron microscopy (HRTEM) revealed the presence of low angle grain boundaries (LAGBs) in conventionally and spark plasma sintered (1200 °C for 5 min) samples with x = 0.08. The results of electrical measurements confirmed the semiconducting properties of all BSSO, except the spark plasma sintered BaSn0.92Sb0.08O3 (1200 °C for 5 min) sample. This sample showed linear current-voltage characteristic, the lowest and almost constant electrical resistivity in the temperature range of 25–150 °C resulting from the loss of potential barriers at grain boundaries due to the large fraction of LAGBs present in BaSn0.92Sb0.08O3 ceramic sample