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Title: Exploring the high-pressure behavior of the three known polymorphs of BiPO{sub 4}: Discovery of a new polymorph

We have studied the structural behavior of bismuth phosphate under compression. We performed x-ray powder diffraction measurements up to 31.5 GPa and ab initio calculations. Experiments were carried out on different polymorphs: trigonal (phase I) and monoclinic (phases II and III). Phases I and III, at low pressure (P < 0.2–0.8 GPa), transform into phase II, which has a monazite-type structure. At room temperature, this polymorph is stable up to 31.5 GPa. Calculations support these findings and predict the occurrence of an additional transition from the monoclinic monazite-type to a tetragonal scheelite-type structure (phase IV). This transition was experimentally found after the simultaneous application of pressure (28 GPa) and temperature (1500 K), suggesting that at room temperature the transition might by hindered by kinetic barriers. Calculations also predict an additional phase transition at 52 GPa, which exceeds the maximum pressure achieved in the experiments. This transition is from phase IV to an orthorhombic barite-type structure (phase V). We also studied the axial and bulk compressibility of BiPO{sub 4}. Room-temperature pressure-volume equations of state are reported. BiPO{sub 4} was found to be more compressible than isomorphic rare-earth phosphates. The discovered phase IV was determined to be the less compressible polymorph of BiPO{sub 4}. On the other hand, themore » theoretically predicted phase V has a bulk modulus comparable with that of monazite-type BiPO{sub 4}. Finally, the isothermal compressibility tensor for the monazite-type structure is reported at 2.4 GPa showing that the direction of maximum compressibility is in the (0 1 0) plane at approximately 15° (21°) to the a axis for the case of our experimental (theoretical) study.« less
Authors:
;  [1] ;  [2] ;  [1] ;  [3] ; ;  [4] ; ;  [5] ;  [6]
  1. Departamento de Física Aplicada-ICMUV, MALTA Consolider Team, Universidad de Valencia, Edificio de Investigación, C/Dr. Moliner 50, Burjassot, 46100 Valencia (Spain)
  2. Centro de Tecnologías Físicas, MALTA Consolider Team, Universitat Politècnica de Valencia, 46022 Valencia (Spain)
  3. (United Kingdom)
  4. Departamento de Física, Instituto de Materiales y Nanotecnología, MALTA Consolider Team, Universidad de La Laguna, La Laguna 38205, Tenerife (Spain)
  5. Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)
  6. CELLS-ALBA Synchrotron Light Facility, Cerdanyola, 08290 Barcelona (Spain)
Publication Date:
OSTI Identifier:
22399281
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 10; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; APPROXIMATIONS; BARITE; BISMUTH PHOSPHATES; COMPARATIVE EVALUATIONS; COMPRESSIBILITY; EQUATIONS OF STATE; MONAZITES; MONOCLINIC LATTICES; ORTHORHOMBIC LATTICES; PHASE TRANSFORMATIONS; PRESSURE DEPENDENCE; TEMPERATURE DEPENDENCE; TEMPERATURE RANGE 0273-0400 K; X-RAY DIFFRACTION