Positive temperature coefficient of electrical resistivity below 150 K in barium strontium titanate

The resistivity of Ba(1-y)(1-x)Sry(1-x)LaxTiO3 ceramics with x = 0.0025 and y = 0.25, 0.5, 0.75, and 0.9 was measured between 50 and 400 K. A resistivity anomaly corresponding to the positive temperature coefficient of electrical resistivity (PTCR) effect was observed for all compositions. The onset temperature decreased from 320 K (y = 0.25) to 70 K (y = 0.9). The extent of the PTCR effect was significantly enhanced for the strontium-rich composition and reached ~ 8 orders of magnitude for y = 0.9. These results strongly suggested the possibility to fabricate PTCR devices based on (Sr,Ba)TiO3 ceramics for application at cryogenic temperatures.