Temperature-induced phase transitions in TlReO4: A Raman spectroscopic and x-ray diffraction study

Jayaraman, A; Kourouklis, GA; Fleming, RM; Van Uitert, LG

dc.contributor.author	Jayaraman, A	en
dc.contributor.author	Kourouklis, GA	en
dc.contributor.author	Fleming, RM	en
dc.contributor.author	Van Uitert, LG	en
dc.date.accessioned	2014-03-01T01:39:25Z
dc.date.available	2014-03-01T01:39:25Z
dc.date.issued	1988	en
dc.identifier.issn	01631829	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/22785
dc.title	Temperature-induced phase transitions in TlReO4: A Raman spectroscopic and x-ray diffraction study	en
heal.type	journalArticle	en
heal.identifier.primary	10.1103/PhysRevB.37.664	en
heal.identifier.secondary	http://dx.doi.org/10.1103/PhysRevB.37.664	en
heal.publicationDate	1988	en
heal.abstract	Temperature-induced phase transitions in TlReO4 have been investigated by Raman spectroscopy and by x-ray powder diffraction. The data reveal the occurrence of a hitherto unreported phase transition from orthorhombic to the tetragonal scheelite-type structure near 200 K and this is a first-order transition. At temperatures above 400 K the orthorhombic phase is known to transform to the scheelite-type structure. These phase changes present a unique situation. The lattice parameters of the low-temperature (LT) scheelite phase are a0=5.798 and c0=12.920 at 70 K and for the tetragonal high-temperature (HT) scheelite phase are a0=5.761, and c0=13.33 at 400 K. The corresponding unit-cell volumes are 434 3 and 442 3. For the orthorhombic phase a0=5.623, b0=5.791, c0=13.295, and V=432 3 at 293 K. The orthorhombic-LT-scheelite and the orthorhombic-HT-scheelite phase boundaries drawn on the basis of the V's at the transition point intersect at negative pressures in a P-T diagram. This intersection appears to satisfy the criteria required for the occurrence of an ""isolated point"" in the P-T plane; namely a point at which two first-order phase boundaries intersect to become a continuous transition. This is probably the first experimental indication for such a possibility. © 1988 The American Physical Society.	en
heal.journalName	Physical Review B	en
dc.identifier.doi	10.1103/PhysRevB.37.664	en
dc.identifier.volume	37	en
dc.identifier.issue	1	en
dc.identifier.spage	664	en
dc.identifier.epage	667	en