Pressure-Induced Structural Phase Transitions in Ln2−xNdxCuO4 for Ln=La (0.6≤x≤2) and Ln=Pr (x=0)

✍ Scribed by H. Wilhelm; C. Cros; E. Reny; G. Demazeau; M. Hanfland

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 253 KB
• Volume: 151
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2000.8645

✦ Synopsis

We have investigated the structural properties of LaNdCuO 4 and Pr 2 CuO 4 under hydrostatic pressure up to 37 GPa at ambient temperature by high-resolution angle-dispersive X-ray powder di4raction. Upon increasing pressure a structural transformation into the T-structure (I4/mmm, K 2 NiF 4 -type) was observed at P T ‫؍‬ 11.4 GPa and P T ‫؍‬ 15.1 GPa, respectively. Full-pro5le re5nements of the di4raction data give evidence for a gradual distortion of the T-structure into the orthorhombic O-phase (Cmca, distorted K 2 NiF 4 -type) during pressure release in a certain pressure interval. At low pressures the initial Tstructure (I4/mmm, Nd 2 CuO 4 -type) is eventually recovered again. The axis and volume compressibilities are well described by a simple model that considers the linear compressibilities of di4erent polyhedra building the unit-cell. The occurrence of the O-phase can be understood within the tolerance factor t versus P T phase diagram.