Syntheses, optical properties and electronic structures of copper(I) tantalates: Cu{sub 5}Ta{sub 11}O{sub 30} and Cu{sub 3}Ta{sub 7}O{sub 19}

Journal Article · Thu Apr 15 00:00:00 EDT 2010 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2010.01.030· OSTI ID:21372558

Palasyuk, Olena; Palasyuk, Andriy ^[1]

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1. Department of Chemistry, 2620 Yarbrough Drive, North Carolina State University, Raleigh, NC 27695-8204 (United States)

Two copper tantalates, Cu{sub 5}Ta{sub 11}O{sub 30} (1) and Cu{sub 3}Ta{sub 7}O{sub 19} (2), were synthesized by solid-state and flux synthetic methods, respectively. A synthetic route yielding 2 in high purity was found using a CuCl flux at 800deg. C and its structure was characterized using powder X-ray diffraction (XRD) data (P6{sub 3}/m (no. 176), Z=2, a=6.2278(1) A, and c=20.1467(3) A). The solid-state synthesis of 1 was performed using excess Cu{sub 2}O that helped to facilitate the growth of single crystals and their characterization by XRD (P6-bar2c (no. 190), Z=2, a=6.2252(1) A, and c=32.516(1) A). The atomic structures of both copper tantalates consist of alternating single and double layers of TaO{sub 7} pentagonal bipyramids that are bridged by a single layer of isolated TaO{sub 6} octahedra and linearly-coordinated Cu{sup +}. Measured optical bandgap sizes of {approx}2.59 and {approx}2.47 eV for 1 and 2 were located well within visible-light energies and were consistent with their orange-yellow colours. Each also exhibits optical absorption coefficients at the band edge of {approx}700 and {approx}275 cm{sup -1}, respectively, and which were significantly smaller than that for NaTaO{sub 3} of {approx}1450 cm{sup -1}. Results of LMTO calculations indicate that their visible-light absorption is attributable mainly to indirect bandgap transitions between Cu 3d{sup 10} and Ta 5d{sup 0} orbitals within the TaO{sub 7} pentagonal bipyramids. - Graphical abstract: The copper(I) tantalates, Cu{sub 5}Ta{sub 11}O{sub 30} and Cu{sub 3}Ta{sub 7}O{sub 19}, were synthesized by high-temperature solid-state reactions and by a new CuCl flux method, respectively. Their structures consist of single and double layers of TaO{sub 7} pentagonal bipyramids separated by isolated TaO{sub 6} octahedra and Cu atoms. UV-vis spectra show visible-light bandgap sizes of {approx}2.5-2.6 eV, which LMTO calculations show arise primarily from indirect transitions between the filled Cu 3d{sup 10} and the empty Ta 5d{sup 0} orbitals in the TaO{sub 7} pentagonal bipyramids.

• OSTI ID: 21372558
• Journal Information: Journal of Solid State Chemistry, Vol. 183, Issue 4; Other Information: DOI: 10.1016/j.jssc.2010.01.030; PII: S0022-4596(10)00045-9; Copyright (c) 2010 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ABSORPTION
COPPER CHLORIDES
COPPER IONS
COPPER OXIDES
CRYSTAL GROWTH
ELECTRONIC STRUCTURE
EV RANGE 01-10
FLUX SYNTHESIS
HEXAGONAL LATTICES
LAYERS
MONOCRYSTALS
OPTICAL PROPERTIES
SYNTHESIS
TANTALATES
ULTRAVIOLET SPECTRA
VISIBLE RADIATION
VISIBLE SPECTRA
X-RAY DIFFRACTION
CHALCOGENIDES
CHARGED PARTICLES
CHLORIDES
CHLORINE COMPOUNDS
COHERENT SCATTERING
COPPER COMPOUNDS
COPPER HALIDES
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALS
DIFFRACTION
ELECTROMAGNETIC RADIATION
ENERGY RANGE
EV RANGE
HALIDES
HALOGEN COMPOUNDS
IONS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RADIATIONS
REFRACTORY METAL COMPOUNDS
SCATTERING
SORPTION
SPECTRA
TANTALUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS