Vs. Tiwari et D. Pandey, STRUCTURE AND PROPERTIES OF (BA,CA)TIO3 CERAMICS PREPARED USING (BA,CA)CO3 PRECURSORS .2. DIFFUSE PHASE-TRANSITION BEHAVIOR, Journal of the American Ceramic Society, 77(7), 1994, pp. 1819-1824
Ferroelectric phase transition in (Ba,Ca)TiO3 ceramics has been invest
igated using dielectric measurements. It is shown that samples prepare
d using (Ba,Ca)CO3 precursors exhibit diffuse phase transition (DPT) w
hile those prepared by the conventional route show BaTiO3-type sharp t
ransition. The diffuseness of the phase transition is found to increas
e with increasing calcium content. The critical exponent for the diele
ctric stiffness (1/epsilon') departs significantly from the mean field
value of unity and is shown to increase from 1.21 to t.86 with increa
sing calcium content. Arguments are advanced to show that the DPT beha
vior in these ceramics is inexplicable in terms of either the internal
stress model due to the absence of 90-degrees domains in fine-grain c
eramics or the compositional inhomogeneity model. It is proposed that
DPT behavior is intrinsic to the system and is intimately linked with
the appearance of polar phase in the critical regime whose width is sh
own to increase with increasing Ca content.