Nature of the High-Temperature Dielectric Anomaly in TlH_2PO_4

概要

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The dielectric constant of T1H2P04 along the b axis, e'7, was measured as a function of tem-perature between 290 and 443 K. The e'. displayed a new high-temperature anomaly at about425 K (Tp) on heating above the ferroelastic-paraelastic transition at 356 K (T?), while it showeda quasi-irreversibility on subsequent cooling to room temperature. After prolonged heat treat-ment at and above Tp, tnicroscopic spots, which grew into multigrains, were observed, indicatingan additional tendency towards the incipient partial decomposition at temperatures above Tp.The appearance of spots and the persistence of the high-temperatvtre state on cooling back toroom temperattrre suggest that the high-ternperattrre anomaly near Tp is topochemical in natture and that polymerization due to dehydration can take place on tempering near Tp. Thequasi-irreversibility of' e'j, seems to result from the nonstoichiornetry at the surface.
社団法人日本物理学会の論文
1997-05-15