Title: THE EFFECT OF ISOVALENT SUBSTITUTIONS AND DOPANTS OF 3$D$-METALS ON THE PROPERTIES OF FERROELECTRICS- SEMICONDUCTORS
Author(s): O.I.V'yunov (E-mail: vyunov@ionc.kar.net), L.L.Kovalenko, A.G.Belous (V.I.Vernadskii Institute of General and Inorganic Chemistry 32/34 Palladina Ave., 03680 Kyiv-142, Ukraine)

Electrophysical properties and microstructure of PTCR ceramics of the system (Ba,Ca,Sr,Y)TiO$_{3}+y\%$Mn have been investigated. It has been shown that manganese ions increase the potential barrier at grain boundaries and form a high-resistance outer layer in (Ba,Ca,Sr,Y)TiO$_{3}$ ceramics. The resistance of grains, outer layers and grain boundaries, the values of temperature coefficient of resistance as well as the varistor effect as a function of manganese content of PTCR materials have been investigated.

Key words: PTCR, manganese dopant, varistor effect, microstructure, potential barrier, complex impedance
PACS:61.66.Fn, 77.80.Bh, 78.40.Fy