SURPRISING BEHAVIOR OF RESISTIVITY OF 2 MACROCRYSTALLINE SAMPLES OF ZR-DOPED SRTIO3 BETWEEN 170-K AND 100-MK

In two samples of SrTiO3 with 3% Ti replaced by Zr, resistance rises by several orders of magnitude as temperature is lowered between 90 K and 600 mK, and then falls between 600 mK and 100 mK by factors of 300 for one sample and 7 for another. The second sample also shows a rise in resistance as the temperature is lowered through 170 K, and a sudden fall by a factor of 2.5 between 103 and 93 K. The falls in resistance below 600 mK are argued to arise from transitions to a non-uniform state including superconducting and non-superconducting regions. Average charge carrier concentrations at 600 mK in the second, higher-resistance specimen are estimated to be ≲ 1021m−3 confirming previous inferences from results on ceramic specimens that superconductivity or superconducting-like phenomena can occur at these low carrier concentrations. © 1990, Elsevier Science Publishers B.V. (North-Holland). All rights reserved.