Synthesis, morphology and color tone properties of the lanthanum substituted hematite

Bhuiyan, Tarequl Islam; Nakanishi, Makoto; Kusano, Yoshihiro; Fujii, Toru; Takada, Jun; Ikeda, Yasunori

doi:10.1016/j.matlet.2006.12.032

Cited by 14 publications

(8 citation statements)

References 8 publications

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“…As to morphology, different habits may be assumed (hexagonal plate, rhombohedra, spindle, rod, ellipsoid, cube, disc, sphere, star, bipyramid, wire, hollow sphere) [7], as morphology depends, inter alia, on the presence in the synthesis medium of surfactants [10] and [11], cations [3], [12], [13], [14] and [15] and, especially, anions [16], [17], [18] and [19], which all may cause an anisotropic growth by driving it along certain crystallographic directions. For instance, chloride ions (Cl−) restrain the growth in the direction normal to the {0 1 2} faces, so yielding micro particles with a pseudo-cubic shape [18].…”

Section: Introductionmentioning

confidence: 99%

“…Guest cations may alter the particles shape, as occurs with Al cations which cause a peanut-like shape [15], or induce change in optical properties, as observed for La-substituted micro-hematite [14]. To this respect, rare-earth elements are an attractive class of dopant elements, as they give easily trivalent cations with peculiar magnetic and optical properties related to their f-electronic configuration.…”

Section: Introductionmentioning

confidence: 99%

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Eu-doped α-Fe2O3 nanoparticles with modified magnetic properties

Freyria

Barrera

Tiberto

et al. 2013

Journal of Solid State Chemistry

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Eu-doped α-Fe2O3 nanoparticles with modified magnetic properties

Freyria

Barrera

Tiberto

et al. 2013

Journal of Solid State Chemistry

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“…The hue values of hematite were also different from those proposed by Cornell and Schwertmann (1996) (5R to 2.5YR). Bhuiyan et al (2007) verified that hematite substituted by Nd³ + exhibited a brighter yellowish-red color compared to the pure phase.…”

Section: Colormentioning

confidence: 64%

Thermal Transformation and Characterization of Synthetic Al-Substituted Maghemites (γ-Fe2-xAlxO3)

Nonaka

Batista

Inoue

et al. 2016

Rev. Bras. Ciênc. Solo

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ABSTRACT:Burning is a common practice in tropical areas and related changes in mineralogy might affect the chemical and physical behavior of soils. Maghemite is a common iron oxide in soils formed from basic rocks in tropical regions. This mineral and hematite are the main pigments in these soils and exhibit high magnetization stemming from the precursor magnetite formed during the weathering process of primary minerals. The objective of the present study was to analyze changes in color, magnetic suceptibility values, Fourier transform infrared spectroscopy (FTIR) spectra, and available Fe and Al contents extracted with 1 mol L -1 KCl during the process of thermal transformation of synthetic Al-maghemites into Al-hematites. Synthetic substituted maghemites with different degrees of Al-substitution (0.0, 1.0, 2.0, 2.9, 3.8, 5.6, 6.7, 10.0, 12.0, and 17.1 mol% Al) were subjected to a temperature of 500 ± 10 °C for 0, 5, 10, 16, 64, 128, 192, 360, 720, 2160, 3600, 5040 and 6480 min. The color of the samples was analyzed by a Munsell system in a colorimeter. Mass-specific magnetic susceptibility (χ LF ) was measured at low-frequency. Available Fe and Al contents were estimated by a 1 mol L -1 KCl solution. Fourier transform infrared spectroscopy (FTIR) spectra were obtained through use of a Bruker Vertex 70X FTIR spectrophotometer at a spectral resolution of 4 cm -1 . Contents of Fe and Al extracted by 1 mol L -1 KCl in Al-hematites were not detected. All samples analyzed exhibited YR hue. Hue proportion decreased with increased heating time, and color changed from brown to red. The increase in isomorphic substitution (IS) led to increased hue values from maghemite to hematite, and the latter then became yellower. The χ LF values decreased with an increase in heating time, indicating transformation from a ferrimagnetic phase (maghemite) to an antiferrimagnetic phase (hematite). With increasing IS, the maghemite χ LF values decreased. Bands of the initial members (time 0) in the FTIR spectra were indexed as maghemites. The end members after completion of the heat treatment were identified as hematites. The IS of Fe by Al in maghemite influenced the thermal transformation to hematite, as well as the color and χ LF of the minerals. The χ LF proved to be very efficient in detecting maghemites remaining after thermal processing. Fe and/or Al were not ejected from the hematite crystalline structure after heat treatment.

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“…Various forms of hematite crystals and polycristals have been synthesized and used in optical applications [3,11,26,32,33]. Synthesis techniques of hematite nanoparticles offer a wide range of dispersion [19] and particle shapes [12,13].…”

Section: Introductionmentioning

confidence: 99%

“…(2) and FFT computations in Sec. (3). We compare measurements and modeling of the optical properties in Sec.…”

Section: Introductionmentioning

confidence: 99%

Optical Response of a Hematite Coating: Ellipsometry Data versus Fourier-Based Computations

Couka¹,

Willot²,

Callet³

et al. 2015

Adv Sci Engng Med

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The optical properties of a hematite-epoxy coating are predicted numerically and compared with ellipsometry measurements. The highly-heterogeneous dispersion of nanocubic hematite particles in the epoxy resin is simulated using a previously developed two-scales random model. The local anisotropic permittivity tensor of hematite particles, and that of the epoxy, are estimated by ellipsometry measurements carried out on a macroscopic hematite and epoxy samples. Fourier-based methods using a "discrete" Green operator are used to treat complex permittivities. They predict the effective and local electric displacement field in the quasi-static approximation. The former is close to two estimates based on the Hashin-Shtrikman bounds and a self-consistent approximation. Good agreement is found between experimental data and FFT computations in the whole range of the visible spectrum.

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Synthesis, morphology and color tone properties of the lanthanum substituted hematite

Cited by 14 publications

References 8 publications

Eu-doped α-Fe2O3 nanoparticles with modified magnetic properties

Eu-doped α-Fe2O3 nanoparticles with modified magnetic properties

Thermal Transformation and Characterization of Synthetic Al-Substituted Maghemites (γ-Fe2-xAlxO3)

Optical Response of a Hematite Coating: Ellipsometry Data versus Fourier-Based Computations

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