Influence of high hydrostatic pressure on lattice parameters of a single crystal of La 3 Nb 0.5 Ga 5.5 O 14

✍ Scribed by Pavlovska, A.; Werner, S.; Boehler, R.

• Book ID: 118032846
• Publisher: Oldenbourg Wissenschaftsverlag
• Year: 2002
• Tongue: English
• Weight: 153 KB
• Volume: 217
• Category: Article
• ISSN: 2194-4946
• DOI: 10.1524/zkri.217.5.212.20637

✦ Synopsis

Abstract

Unit-cell parameters of La~3~Nb~0.5~Ga~5.5~O~14~ (langanite) have been determined at a number of pressures up to 23GPa in diamond anvil high pressure cells with single crystal X-ray diffraction techniques. The anisotropic behaviour of unit cell parameters of langanite is caused by differences of bonding strength in direction parallel to the a- and c-axis. Within the investigated pressure range, the c/a-ratio increases from 0.6232 to 0.6503. The volume compressibility of trigonal langanite (space group __P__321) is the 0.007 GPa^-1^, with calculated bulk modulus of 145(3)GPa (B'~0~=1.4(8)). At a pressure of 12.4(3)GPa a first-order phase transition was detected, characterised by a discontinuity in the pressure dependence of lattice parameter c. The high-pressure phase (presumably monoclinic, __A__2) with a volume compressibility of 0.011 GPa^-1^ (B~0~=93(2) GPa, B'~0~=1.9(9)) is more compressible as compared to the initial phase due to an abnormal pressure dependence of lattice parameter a.