Structure and Phase Transitions of SnP2O7

✍ Scribed by R.K.B Gover; N.D. Withers; S. Allen; R.L. Withers; J.S.O. Evans

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 402 KB
• Volume: 166
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2002.9554

✦ Synopsis

SnP 2 O 7 is a member of the ZrP 2 O 7 family of materials, several of which show unusual thermal expansion behavior over certain temperature ranges and which show a number of displacive phase transitions on cooling from high temperature. Here we describe the structural properties of SnP 2 O 7 from 100 to 1243 K as determined by X-ray and neutron powder di4raction. These studies reveal that SnP 2 O 7 shows two phase transitions in this temperature range. At room temperature the material has a pseudo-cubic 3؋3؋3 superstructure. Electron di4raction studies show that the symmetry of this structure is P2 1 3 or lower. On warming to &560 K it undergoes a phase transition to a structure in which the subcell re6ections show a triclinic distortion; above 830 K the subcell re6ections show a rhombohedral distortion. Signi5cant hysteresis in cell parameters is observed between heating and cooling. The structure of SnP 2 O 7 is discussed with references to other members of the AM 2 O 7 family of materials. ^2002 Elsevier Science (USA)