High-Pressure Raman Spectroscopic Study of Spinel (ZnCr2O4)

✍ Scribed by Zhongwu Wang; Peter Lazor; S.K. Saxena; Gilberto Artioli

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 214 KB
• Volume: 165
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2002.9527

✦ Synopsis

An in situ Raman spectroscopic study was conducted to investigate the pressure-induced phase transformation in the synthetic ZnCr 2 O 4 spinel up to pressures of 70 GPa at room temperature. Results indicate that ZnCr 2 O 4 spinel starts to transform to the CaFe 2 O 4 (or CaTi 2 O 4 ) structure at 17.5 GPa, and such a phase transformation is complete at 35 GPa. The coexistence of two phases over a wide range of pressure implies a sluggish mechanism upon phase transformation. No experimental evidence was observed to support the theoretical simulation with the dissociation of ZnCr 2 O 4 to ZnO and Cr 2 O 3 at 34 GPa. Moreover, enhancement of the intensity of the Raman peak at 642 cm\ \ 1 at either elevated pressures or temperatures is most likely caused by an enhanced order}disorder e4ect. Upon release of pressure, the recovered phase may exhibit an inverse spinel structure, which di4ers from the initial normal spinel structure.