INFLUENCE OF BI3-BATIO3 CERAMICS( IONS IN ENHANCING THE MAGNITUDE OF POSITIVE TEMPERATURE COEFFICIENTS OF RESISTANCE IN N)

Bi3+ ions substituting at Ba-sites in a limited concentration range wi th another donor dopant occupying the Ti-sites in polycrystalline BaTi O3 enhanced the positive temperature coefficient of resistance (PTCR) by over seven orders of magnitude. These ceramics did not require norm al post sinter annealing or a change to an oxygen atmosphere during an nealing. These ceramics had low porosities coupled with better stabili ties to large applied electric fields and chemically reducing atmosphe res. Bi3+ ions limited the grain growth to less than 8 mum in size, th ey enhanced the concentration of acceptor-type trap centres at the gra in-boundary-layer regions and maintained complete tetragonality at low grain sizes in BaTiO3 ceramics.