# Cryogenic sensors from semiconducting barium titanate ceramics with strong negative temperature coefficient of resistance

Padmini, P and Hari, NS and Kutty, TRN (1995) Cryogenic sensors from semiconducting barium titanate ceramics with strong negative temperature coefficient of resistance. In: Sensors and Actuators A, 50 (1-2). pp. 39-44.

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## Abstract

Stable sensors for low-temperature applications are realized from donor-doped $BaTiO_3$ polycrystalline ceramics having a strong negative temperature coefficient of resistivity (NTCR) below the orthorhombic-rhombohedral phase-transition point, from $10^2-10^3 \hspace{2mm}\Omega$ cm at 190 K to $10^{10}-10^{13}\hspace{2mm} \Omega$ cm at $\approx$ 50 K, and a thermal coefficient of resistance, $\alpha =20-23\%\hspace{2mm} K^{-1}$. The temperature region of the NTCR can be modified by substituting isovalent ions in the lattice. Highly non- linear current-voltage (I-V) curves are observed at low temperatures, with a voltage maximum followed by the negative differential resistance. The I-V curves are sensitive to dissipation, so that cryogenic sensors can be fabricated for liquid-level control, flow-rate monitoring, radiation detection or in-rush voltage limiting. The observed NTCR of $n-BaTi0_3$ ceramics at low temperatures is made use of in evaluating the composition of aliphatic hydrocarbon (petrol)-alcohol mixtures through the determination of freezing points, since these liquid mixtures are used as an alternative fuel in internal combustion engines.

Item Type: Journal Article Copyright of this article belongs to Elsevier. Barium titanate;Cryogenic sensors;Semiconducting ceramics Division of Chemical Sciences > Materials Research Centre 18 May 2007 19 Sep 2010 04:38 http://eprints.iisc.ernet.in/id/eprint/11011