Phase Stability of Lanthanum Orthovanadate at High Pressure

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• 作者：Daniel Errandonea ; Julio Pellicer-Porres ; Domingo Martínez-García ; Javier Ruiz-Fuertes ; Alexandra Friedrich ; Wolfgang Morgenroth ; Catalin Popescu ; Placida Rodríguez-Hernández ; Alfonso Muñoz ; Marco Bettinelli
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：June 30, 2016
• 年：2016
• 卷：120
• 期：25
• 页码：13749-13762
• 全文大小：610K
• 年卷期：0
• ISSN：1932-7455

文摘

When monoclinic monazite-type LaVO₄ (space group P2₁/n) is squeezed up to ∼12 GPa at room temperature, a phase transition to another monoclinic phase has been found. The structure of the high-pressure phase of LaVO₄ is indexed with the same space group (P2₁/n) but with a larger unit cell in which the number of atoms is doubled. The transition leads to an 8% increase in the density of LaVO₄. The occurrence of such a transition has been determined by X-ray diffraction, Raman spectroscopy, and ab initio calculations. The combination of the three techniques allows us to also characterize accurately the pressure evolution of unit-cell parameters and the Raman (and IR)-active phonons of the low- and high-pressure phase. In particular, room-temperature equations of state have been determined. The changes driven by pressure in the crystal structure induce sharp modifications in the color of LaVO₄ crystals, suggesting that behind the monoclinic-to-monoclinic transition there might be important changes of the electronic properties of LaVO₄.