Journal of Advanced Ceramics
2015, 4(1): 39–45
DOI: 10.1007/s40145-015-0129-1
ISSN 2226-4108
CN 10-1154/TQ
Research Article
Novel environmentally friendly inorganic red pigments based on
calcium bismuth oxides
WENDUSU, Tetsuro YOSHIDA, Toshiyuki MASUI, Nobuhito IMANAKA*
Department of Applied Chemistry, Faculty of Engineering, Osaka University, 2-1 Yamadaoka,
Suita, Osaka 565-0871, Japan
Received: July 24, 2014; Revised: September 18, 2014; Accepted: September 22, 2014
© The Author(s) 2015. This article is published with open access at Springerlink.com
Abstract: Novel environmentally friendly inorganic red pigments based on calcium bismuth oxide,
Ca3(Bi1−xREx)8O15 (0 ≤ x ≤ 0.09; RE = Sc3+, Er3+, Y3+, Ho3+ and Dy3+), were successfully synthesized
and the color properties were characterized. The color of these pigments depended on the composition
and the synthesis condition, and the most vivid red color was obtained for the Ca3(Bi0.93Y0.07)8O15
sample calcined thrice at 800 ℃ for 2 h. The L* and a* values corresponding to brightness and red
chromaticity for this pigment were 45.6 and +30.6, respectively, which were greater than those of a
commercially available Fe2O3 pigment (L* = 38.4, a* = +29.5). Since the present pigment is composed
of nontoxic and safe elements, it should be an attractive alternative to the conventional Fe2O3
pigment.
Keywords: calcium bismuth oxide; environmentally friendly; red pigment; solid solution; cation
complexation method
1 Introduction
Inorganic pigments are applied in a wide range of
products such as paints, ceramics, porcelains, plastics,
enamels and glasses, due to their high thermal and
ultraviolet stability compared to organic pigments [1].
In particular, inorganic red pigments are in demand
because of their wide applicability. For decades,
several inorganic red pigments such as red lead (Pb3O4
or 2PbO·PbO2), cadmium red (CdSe·CdS) and red
mercury sulfide (HgS) were popularly used in many
products. However, the use of these compounds has
been restricted because they contain the hazardous
elements (Pb, Cd, Se and Hg), which are harmful not
only to human health but also to the environment.

* Corresponding author.
E-mail: [email protected]
On the other hand, red iron oxide (Fe2O3) has
been widely known as an environmentally friendly
inorganic red pigment for many uses, but its color
performance is unsatisfactory in comparison to those
of the conventional toxic pigments. Several studies
have been carried out on new environmentally friendly
inorganic red pigments [2–10], but these pigments
cannot exceed the color of the nontoxic red iron oxide
(Fe2O3). Although perovskite-type oxynitrides
Ca1−xLaxTaO2−xN1+x have also been reported as
nontoxic inorganic red pigments, toxic and flammable
ammonia gas is required for the synthesis of these
pigments [11]. Furthermore, these oxynitride
compounds are decomposed to oxides at 420 ℃ and
higher temperatures [11], accompanying with
generation of toxic nitrogen oxides.
Because of this situation, we focused on calcium
bismuth oxide (Ca3Bi8O15), as a base material for novel
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J Adv Ceram 2015, 4(1): 39–45
40
environmentally friendly inorganic red pigment, where
bismuth is often mistaken for a toxic element, but it is
nontoxic. In fact, inorganic salts and oxides of bismuth
have been confirmed to be virtually nontoxic in some
medical references [12–14]. The coloring mechanism
of trivalent bismuth ion-based semiconductors like
Ca3Bi8O15 is based on a charge-transfer transition from
the valence band of a hybrid orbital of the Bi6s and O2p
orbitals to the conduction band of Bi6p orbital [15–17].
It is expected that the color of Ca3Bi8O15 can be tuned
by introducing other elements into the Ca3Bi8O15
lattice to control the lattice size, because the extent of
the Bi6s–O2p orbital hybridization in the valence band
should depend on the interionic distance between the
Bi3+ and O2− ions.
In this study, therefore, we synthesized
Ca3(Bi1−xREx)8O15 (0 ≤ x ≤ 0.09; RE = Sc3+, Er3+, Y3+,
Ho3+ and Dy3+) samples in an attempt to find a novel
environmentally friendly inorganic red pigment.
Introduction of smaller rare earth ions (ionic radii: Sc3+
0.0885 nm [18], Er3+ 0.103 nm [18], Y3+ 0.104 nm [18],
Ho3+ 0.1041 nm [18] and Dy3+ 0.1052 nm [18]) into
the Bi3+ (0.117 nm) [18] sites of Ca3Bi8O15 generates
lattice shrinking, which reduces the bandgap energy by
modifying the band width of Bi6s–O2p hybrid orbital.
The color properties were characterized and the
composition and the calcination condition of them
were optimized to obtain the most vivid red hue.
2 Experimental
CaCO3 (Wako Pure Chemical Industries Ltd., 99.95%),
Bi2O3 (Kishida Chemical Co. Ltd., 99.9%), Sc2O3
(Kojundo Chemical Laboratory Co. Ltd., 99.9%),
Er2O3 (Shin-Etsu Chemical Co. Ltd., 99.9%), Y2O3
(Shin-Etsu Chemical Co. Ltd., 99.99%), Ho2O3
(Shin-Etsu Chemical Co. Ltd., 99.9%), Dy2O3
(Shin-Etsu Chemical Co. Ltd., 99.9%), citric acid
(Wako Pure Chemical Industries Ltd., 98.0%) and
nitric acid (Kishida Chemical Co. Ltd., specific gravity
1.38, density 60%) were used for the sample
preparation as received without further purification.
The Ca3(Bi1−xREx)8O15 (0 ≤ x ≤ 0.09; RE = Sc3+,
Er3+, Y3+, Ho3+ and Dy3+) pigments were synthesized
by a cation complexation method using citric acid. An
aqueous solution of 1 mol·dm−3 of citric acid was
added into a stoichiometric mixture of 0.1 mol·dm−3
Ca(NO3)2, 0.5 mol·dm−3 Bi(NO3)3 and 0.1 mol·dm−3
RE(NO3)3 (RE = Sc3+, Er3+, Y3+, Ho3+ and Dy3+)
aqueous solutions. The molar ratio of citric acid to the
total amount of the metal cations was adjusted to 3:2.
After stirring at 80 ℃ for 12 h, the mixed solution was
heated at 190 ℃ until the solvent was vaporized. The
resulting solid was calcined at 800 ℃ for 2 h to afford
the product. All samples were gently ground in an
agate mortar before characterization.
The samples were characterized by X-ray powder
diffraction (XRD, Rigaku, SmartLab) with Cu Kα
radiation (40 kV and 30 mA) to identify their crystal
structures. The lattice volumes of the samples were
calculated from the XRD peak angles, which were
refined using α-Al2O3 as a standard. The sample
compositions were determined by X-ray fluorescence
spectroscopy (XRF, Rigaku ZSX-100e). The optical
reflectance was measured using an ultraviolet–visible
(UV–Vis) spectrometer with an integrating sphere
attachment (Shimadzu, UV-2600 and ISR-2600) using
barium sulfate as a reference, where the illuminants
were a deuterium arc lamp (D2 lamp) and a halogen
lamp (tungsten-iodine lamp), and the angles of the
incident lights were 0° for the sample beam and 8° for
the reference beam. The bandgap energies of the
samples were estimated from the absorption edge of
the absorbance spectra represented by the Kubelka–
Munk function, f(R) = (1 − R)2/(2R), where R is the
reflectance [19,20]. The color properties of the samples
were evaluated in terms of the CIE L*a*b* system using
a chromometer (Konika-Minolta, CR-400) using the
standard illuminant C, which represented average day
light with a correlated color temperature of 6774 K.
This apparatus employs a diffused illumination and
vertical light receiving system, which is designed to
illuminate a specimen from all directions with almost
equal brightness, and the detector receives the light
vertically reflected from the specimen. Before the
measurements, the apparatus was calibrated using a
white calibration plate. The samples were pressed into
green pellets without any additives. The color
coordinate data were measured for 5 times and the
average values were calculated. The standard deviation
was 0.07, indicating that the experimental error can be
ignored. The L* parameter represents the brightness or
darkness of a color relative to a neutral grey scale, and
the a* (the red–green axis) and b* (the yellow–blue axis)
parameters express the hue of a color qualitatively.
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J Adv Ceram 2015, 4(1): 39–45
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2 (°)
Fig. 1 XRD patterns of the Ca3(Bi0.93RE0.07)8O15
(RE = Sc3+, Er3+, Y3+, Ho3+ and Dy3+) samples.
Table 1
Reflectance (%)
Intensity (a.u.)
The compositions of all samples were determined by
the XRF measurement, and they were in good
agreement with the charge ratio of the starting
mixtures. Figure 1 shows the XRD patterns of the
Ca3(Bi0.93RE0.07)8O15 (RE = Sc3+, Er3+, Y3+, Ho3+ and
Dy3+) samples. A single Ca3Bi8O15 phase is observed
for the Ca3(Bi0.93RE0.07)8O15 (RE = Sc3+, Er3+ and Y3+)
samples, and there are no extra lines due to other
compounds or impurity phases. In contrast, for the
Ca3(Bi0.93RE0.07)8O15 (RE = Ho3+ and Dy3+) samples, a
Bi1.6Ca0.4O2.8 phase is observed as an impurity in
addition to the Ca3Bi8O15 phase. Table 1 lists
lattice volumes of the Ca3Bi8O15 phase in the
Ca3(Bi0.93RE0.07)8O15 (RE = Sc3+, Er3+, Y3+, Ho3+ and
Dy3+) samples calculated from the diffraction angles in
the XRD patterns. The lattice volume of Ca3Bi8O15 is
decreased by substituting Sc3+, Er3+, Y3+, Ho3+ and
Dy3+ ions for Bi3+, because the ionic radii of these rare
earth ions (Sc3+ 0.0885 nm [18], Er3+ 0.103 nm [18],
Y3+ 0.104 nm [18], Ho3+ 0.1041 nm [18] and Dy3+
0.1052 nm [18]) are smaller than that of Bi3+
(0.117 nm) [18]. These results indicate that solid
solutions with the Ca3Bi8O15 structure are successfully
obtained in a single-phase form for the
Ca3(Bi0.93RE0.07)8O15 (RE = Sc3+, Er3+ and Y3+) samples.
In contrast, the Bi1.6Ca0.4O2.8 impurity is observed for
the Ca3(Bi0.93RE0.07)8O15 (RE = Ho3+ and Dy3+)
samples, although the lattice volumes for these
samples are smaller than that of Ca3Bi8O15 indicating
the formation of solid solutions.
Figure 2 depicts the UV–Vis diffuse reflectance
spectra for the Ca3(Bi0.93RE0.07)8O15 (RE = Sc3+, Er3+,
Y3+, Ho3+ and Dy3+) samples. Strong optical absorption
behavior was observed for all samples at wavelengths
shorter than 560 nm, including the green light region
(490–560 nm). As a result, these samples are red,
because green is a complementary color to red.
Furthermore, the absorption intensity is dependent on
the sample compositions. Among these pigments,
Ca3(Bi0.93Y0.07)8O15 absorbs the green light most
efficiently compared with the others.
The L*a*b* color coordinate data of the
Ca3(Bi0.93RE0.07)8O15 (RE = Sc3+, Er3+, Y3+, Ho3+ and
Dy3+) samples are tabulated in Table 2. The color
parameters L*, a* and b* are affected by introducing
the rare earth ions into the Bi3+ site in the Ca3Bi8O15
lattice. In particular, the a* value which corresponds to
the red chromaticity in the positive direction for these
samples becomes greater than that of the non-doped
Ca3Bi8O15 sample (a* = +23.2). Among them,
Ca3(Bi0.93Y0.07)8O15 pigment exhibits the most brilliant
red hue, of which the a* value is +28.2. These results
clarify that the partial substitution of the Bi3+ ions in
the Ca3Bi8O15 lattice with the smaller rare earth ions
Reflectance (%)
3 Results and discussion
Wavelength (nm)
Lattice volume of the samples
Sample
Ca3Bi8O15
Ca3(Bi0.93Sc0.07)8O15
Ca3(Bi0.93Er0.07)8O15
Ca3(Bi0.93Y0.07)8O15
Ca3(Bi0.93Ho0.07)8O15
Ca3(Bi0.93Dy0.07)8O15
Lattice volume (nm3)
34.243
33.700
33.899
33.958
33.986
34.073
Wavelength (nm)
Fig. 2 UV–Vis diffuse reflectance spectra of the
Ca3(Bi0.93RE0.07)8O15 (RE = Sc3+, Er3+, Y3+, Ho3+ and
Dy3+) samples.
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Table 2
L*a*b* color coordinate data of the samples
Table 3
*
Sample
Ca3Bi8O15
Ca3(Bi0.99Y0.01)8O15
Ca3(Bi0.97Y0.03)8O15
Ca3(Bi0.95Y0.05)8O15
Ca3(Bi0.93Y0.07)8O15
Ca3(Bi0.92Y0.08)8O15
Ca3(Bi0.91Y0.09)8O15
Sample
Ca3Bi8O15
Ca3(Bi0.93Sc0.07)8O15
Ca3(Bi0.93Er0.07)8O15
Ca3(Bi0.93Y0.07)8O15
Ca3(Bi0.93Ho0.07)8O15
Ca3(Bi0.93Dy0.07)8O15
L
52.1
41.9
47.9
43.5
44.3
45.8
*
a
+23.2
+27.3
+27.4
+28.2
+26.3
+26.4
*
b
+34.2
+29.4
+36.6
+32.3
+31.6
+32.5
(Sc3+, Er3+, Y3+, Ho3+ and Dy3+) is effective to enhance
the red hue of Ca3Bi8O15, and the most vivid red color
is obtained for Ca3(Bi0.93Y0.07)8O15 (a* = +28.2), which
is obtained in a single Ca3Bi8O15 phase without any
impurity.
Subsequently, the amount of Y3+ ions introducing
into the Bi3+ site of Ca3Bi8O15 is optimized to give the
most vivid reddish hue. Figure 3 depicts the XRD
patterns of the Ca3(Bi1−xYx)8O15 (0 ≤ x ≤ 0.09) samples.
The Ca3Bi8O15 structure is obtained in a single-phase
form for the samples in which Y3+ content is 7 mol%
or less, and no diffraction peaks of impurities or other
compounds are evident in the patterns. On the other
hand, Bi1.8Y0.2O3 is observed as a secondary phase for
the samples in which Y3+ content is more than 7 mol%.
The lattice volumes for the Ca3Bi8O15 phase in
Ca3(Bi1−xYx)8O15 (0 ≤ x ≤ 0.09) are summarized in
Table 3. The lattice volume decreases linearly with
increasing the amount of Y3+ ions in the single-phase
region (0 ≤ x ≤ 0.07), but it becomes approximately
constant in the multi-phase region (0.08 ≤ x ≤ 0.09).
These results suggest that solid solutions are
successfully formed for the samples with compositions
of Ca3(Bi1−xYx)8O15 (0.01 ≤ x ≤ 0.07), and the
solubility limit of Y3+ is 7 mol% for this system.
Lattice volume (nm3)
34.243
34.175
34.116
34.042
33.958
33.949
33.944
Figure 4 illustrates the UV–Vis diffuse reflectance
spectra for the Ca3(Bi1−xYx)8O15 (0 ≤ x ≤ 0.09)
samples. Strong optical absorption is observed for all
samples at wavelengths between 490 nm and 560 nm
(i.e., in the green light region), and therefore, these
samples are also red, as the reason mentioned above.
Furthermore, the absorption intensity in the green light
(490–560 nm) increases with increasing the amount of
Y3+ ions in the single-phase region (0 ≤ x ≤ 0.07),
while it decreases in the two-phase region (0.08 ≤ x ≤
0.09). Among these pigments, the Ca3(Bi0.93Y0.07)8O15
sample absorbs the green light most efficiently.
The L*a*b* color coordinate data and optical
bandgap energies (Eg) for Ca3(Bi1−xYx)8O15 (0 ≤ x ≤
0.09) are listed in Table 4. The a* values corresponding
to the red chromaticity of these pigments are
dependent on the composition, and the highest a* value
is obtained for Ca3(Bi0.93Y0.07)8O15 (a* = +28.2). The
optical bandgap energies of the Ca3(Bi1−xYx)8O15
(0.01 ≤ x ≤ 0.09) samples decrease with increasing
the Y3+ concentration in the single-phase region
(0.01 ≤ x ≤ 0.07), and the bandgap energy of
Ca3(Bi0.93Y0.07)8O15 (2.25 eV) is the lowest. This is
caused by the enhancement in the hybridization effect
of Bi6s–O2p orbital by introducing Y3+ ions into the
Reflectance (%)
Intensity (a.u.)
Reflectance (%)
:Bi1.8Y0.2O3
Lattice volume of the samples
2 (°)
Wavelength (nm)
Wavelength (nm)
Fig. 3 XRD patterns of the Ca3(Bi1−xYx)8O15
(0 ≤ x ≤ 0.09) samples.
Fig. 4 UV–Vis diffuse reflectance spectra of the
Ca3(Bi1−xYx)8O15 (0 ≤ x ≤ 0.09) samples.
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Table 4 L*a*b* color coordinate data and bandgap
energy (Eg) of the samples
Sample
Ca3Bi8O15
Ca3(Bi0.99Y0.01)8O15
Ca3(Bi0.97Y0.03)8O15
Ca3(Bi0.95Y0.05)8O15
Ca3(Bi0.93Y0.07)8O15
Ca3(Bi0.92Y0.08)8O15
Ca3(Bi0.91Y0.09)8O15
L*
52.1
43.0
43.6
42.8
43.5
46.8
50.5
a*
+23.2
+25.2
+26.0
+26.8
+28.2
+26.9
+26.8
b*
+34.2
+27.4
+30.2
+30.1
+32.3
+35.2
+40.3
Eg (eV)
2.30
2.26
2.25
2.25
2.25
2.29
2.37
Table 5 Lattice volume of the Ca3(Bi0.93Y0.07)8O15
calcined 1–4 times at 800 ℃ for 2 h
Sample (number of calcination times)
Ca3(Bi0.93Y0.07)8O15 (1)
Ca3(Bi0.93Y0.07)8O15 (2)
Ca3(Bi0.93Y0.07)8O15 (3)
Ca3(Bi0.93Y0.07)8O15 (4)
Lattice volum (nm3)
33.958
33.848
33.733
33.733
Intensity (a.u.)
Reflectance (%)
Reflectance (%)
Ca3Bi8O15 lattice, where the lattice volume is shrunk
(Table 3) to decrease the bandgap due to broadening of
the conduction band. As a result, the green light
absorption increases with the increasing amount of Y3+
ions in Ca3(Bi1−xYx)8O15 (0 ≤ x ≤ 0.07), as already
shown in Fig. 4. On the other hand, the bandgap
energies increase in the two-phase region
(0.08 ≤ x ≤ 0.09) where the Bi1.8Y0.2O3 impurity is
observed. From these results, it is considered that the
Bi6s–O2p hybridization effect in Bi1.8Y0.2O3 is
significantly less than that of Ca3Bi8O15, and therefore,
the apparent bandbap energies for the multi-phase
samples are larger than those for the single-phase
samples. Accordingly, generation of the Bi1.8Y0.2O3
phase is inadequate to improve the redness of
Ca3Bi8O15.
Furthermore, calcination condition is another
important factor which affects the color properties of
ceramic pigments. Especially, repetitive calcination is
an effective way to obtain homogenous solid solutions
for ceramic compounds. In order to further increase the
red hue of Ca3(Bi0.93Y0.07)8O15, dependence of the
number of calcination in the synthesis process on the
pigment color is also discussed. Figure 5 shows the
XRD patterns of Ca3(Bi0.93Y0.07)8O15 calcined 1–4
times at 800 ℃ for 2 h. A single phase of the Ca3Bi8O15
structure is observed for all samples, and no peaks of
other impurities are evident, even if the calcination
(800 ℃ for 2 h) is repeated 4 times. As listed in Table
5, the lattice volume of Ca3(Bi0.93Y0.07)8O15 decreases
with repeating the calcination number up to 3, but
it becomes constant after the 4th calcination.
These results indicate that solid solution of
Ca3(Bi0.93Y0.07)8O15 is formed homogenously, when it
is calcined thrice or more at 800 ℃ for 2 h.
UV–Vis
diffuse
reflectance
spectra
of
Ca3(Bi0.93Y0.07)8O15 calcined 1–4 times at 800 ℃ for 2
h, and for comparison, that of the commercial Fe2O3
pigment (MR-320A, Morishita Bengara Kogyo
Co. Ltd.) are illustrated in Fig. 6. Among the
Ca3(Bi0.93Y0.07)8O15 samples synthesized with the
different repeat number of calcination, the strongest
optical absorption in the green light region at
wavelengths between 490 nm and 560 nm is observed
for the sample calcined thrice at 800 ℃ for 2 h and the
Bi6s–O2p orbital hybridization becomes the greatest in
this sample. Consequently, this pigment exhibits the
most brilliant red hue (a* = +30.6), and this value is
almost constant after the 4th calcination as listed in
Table 6.
In comparison with the commercial Fe2O3 pigment,
Wavelength (nm)
Wavelength (nm)
Wavelength
2 (°) (nm)
Fig. 5 XRD patterns of Ca3(Bi0.93Y0.07)8O15 calcined 1–4
times at 800 ℃ for 2 h.
Fig. 6 UV–Vis diffuse reflectance spectra of the
Ca3(Bi0.93Y0.07)8O15 calcined 1–4 times at 800 ℃ for
2 h and the commercial Fe2O3 pigment.
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Table 6
L*a*b* color coordinate data of the
Ca3(Bi0.93Y0.07)8O15 calcined 1–4 times at 800 ℃ for 2 h,
Ca1−xLaxTaO2−xN1+x (x = 0.9) and the commercial Fe2O3
pigment
Sample (number of calcination times)
Ca3(Bi0.93Y0.07)8O15 (1)
Ca3(Bi0.93Y0.07)8O15 (2)
Ca3(Bi0.93Y0.07)8O15 (3)
Ca3(Bi0.93Y0.07)8O15 (4)
Commercial Fe2O3 pigment
Ca1−xLaxTaO2−xN1+x (x = 0.9) [11]
L*
43.5
45.0
45.6
45.1
38.4
31.6
a*
+28.2
+29.1
+30.6
+30.5
+29.5
+49.3
b*
+32.3
+33.7
+35.4
+35.1
+23.0
+39.3
the Ca3(Bi0.93Y0.07)8O15 pigment calcined thrice at
800 ℃ for 2 h reflects red light (605–750 nm) more
significantly (Fig. 6). As a result, both brightness and
redness for the Ca3(Bi0.93Y0.07)8O15 pigment (L* = 45.6,
a* = +30.6) are greater than those for the commercial
one (L* = 38.4, a* = +29.5) (Table 6). This is due to a
difference in the coloring mechanism of Fe2O3 with
that of the present Ca3(Bi0.93Y0.07)8O15 pigment. For the
Fe2O3 pigment, the bandgap transition and some d–d
transitions of Fe3+ ions occur simultaneously. As a
result, optical absorption is occurred in almost all the
visible part of the spectrum. In contrast, for the
Ca3(Bi0.93Y0.07)8O15 pigment, only the bandgap
transition occurs, as mentioned in the introduction.
Consequently, the Ca3(Bi0.93Y0.07)8O15 pigments reflect
red light more significantly, in spite of the fact that the
absorption in the green light region is less than that of
the commercial Fe2O3, as illustrated in Fig. 6. In
comparison with the Ca1−xLaxTaO2−xN1+x (x = 0.9) [11],
the redness value of the present Ca3(Bi0.93Y0.07)8O15
pigment (a* = +30.6) is much smaller than that of
Ca1−xLaxTaO2−xN1+x (x = 0.9, a* = +49.3). However,
the brightness of the present Ca3(Bi0.93Y0.07)8O15
pigment (L* = 45.6) is much larger than that of
Ca1−xLaxTaO2−xN1+x (x = 0.9, L* = 31.6) [11], probably
due to the difference of partial nitriding in the latter
compound.
4
Conclusions
The Ca3(Bi1−xREx)8O15 (0 ≤ x ≤ 0.09; RE = Sc3+,
Er3+, Y3+, Ho3+ and Dy3+) samples are successfully
synthesized as novel environmentally friendly
inorganic red pigments through a cation complexation
method using citric acid. The redness value of these
pigments is dependent on the ionic species of rare
earths introduced into the Bi3+ site of the Ca3Bi8O15
lattice and the number of calcination in the synthesis
process. Among these pigments, the most brilliant red
hue is obtained for Ca3(Bi0.93Y0.07)8O15 calcined thrice
at 800 ℃ for 2 h, and this pigment exhibits a brighter
red color than the commercial Fe2O3 pigment, as the
brightness and redness values for this pigment (L* =
45.6, a* = +30.6) are greater than those for the
commercial Fe2O3 (L* = 38.4, a* = +29.5). Since the
present pigment consists of nontoxic elements (Ca, Bi,
Y and O), it should be an effective alternative to the
conventional Fe2O3.
Acknowledgements
This work was supported by the Development of
Alternative Technology for Hazardous Chemical
Substances and Development of Novel Environmentand Human-friendly Inorganic Pigments for Three
Primary Colors (FY2010-2014) programs of the New
Energy and Industrial Technology Development
Organization (NEDO) and the Ministry of Economy,
Trade and Industry, Japan (METI).
Open Access: This article is distributed under the
terms of the Creative Commons Attribution License
which permits any use, distribution, and reproduction
in any medium, provided the original author(s) and the
source are credited.
References
[1] Faulkner EB, Schwartz RJ. High Performance Pigments,
2nd edn. Weinheim: Wiley-VCH, 2009.
[2] Kumari LS, Rao PP, Koshy P. Red pigments based on
CeO2−MO2−Pr6O11 (M = Zr and Sn): Solid solutions for
the coloration of plastics. J Am Ceram Soc 2010, 93:
1402−1408.
[3] Candeia RA, Bernardi MIB, Longo E, et al. Synthesis and
characterization of spinel pigment CaFe2O4 obtained by the
polymeric precursor method. Mater Lett 2004, 58:
569−572.
[4] Šulcová P, Vitásková L, Trojan M. Thermal analysis of the
Ce1−xTbxO2 pigments. J Therm Anal Calorim 2010, 99:
409−413.
[5] Llusar M, Vitásková L, Šulcová P, et al. Red ceramic
pigments of terbium-doped ceria prepared through classical
and non-conventional coprecipitation routes. J Eur Ceram
Soc 2010, 30: 37−52.
[6] Aruna ST, Ghosh S, Patil KC. Combustion synthesis and
properties of Ce1−xPrxO2−δ red ceramic pigments. Int J
Inorg Mater 2001, 3: 387−392.
[7] George G, Vishnu VS, Reddy MLP. The synthesis,
characterization and optical properties of silicon
and praseodymium doped Y6MoO12 compounds:
www.springer.com/journal/40145
J Adv Ceram 2015, 4(1): 39–45
[8]
[9]
[10]
[11]
[12]
[13]
[14]
45
Environmentally benign inorganic pigments with high NIR
reflectance. Dyes Pigments 2011, 88: 109−115.
Vishnu VS, George G, Reddy MLP. Effect of molybdenum
and praseodymium dopants on the optical properties of
Sm2Ce2O7: Tuning of band gaps to realize various color
hues. Dyes Pigments 2010, 85: 117−123.
Vishnu VS, Reddy MLP. Near-infrared reflecting inorganic
pigments based on molybdenum and praseodymium doped
yttrium cerate: Synthesis, characterization and optical
properties. Sol Energy Mat Sol C 2011, 95: 2685−2692.
James V, Rao PP, Sameera S, et al. Multiferroic based
reddish brown pigments: Bi1−xMxFeO3 (M = Y and La) for
coloring applications. Ceram Int 2014, 40: 2229−2235.
Jansen M, Letschert HP. Inorganic yellow-red pigments
without toxic metals. Nature 2000, 404: 980−982.
Bradley B, Singleton M, Li Wan Po A. Bismuth
toxicity—A reassessment. J Clin Pharm Ther 1989, 14:
423−441.
Winship KA. Toxicity of bismuth salts. Adverse Drug
React Acute Poison Rev 1983, 2: 103−121.
Serfontein WJ, Mekel R. Bismuth toxicity in man II.
Review of bismuth blood and urine levels in patients after
[15]
[16]
[17]
[18]
[19]
[20]
administration of therapeutic bismuth formulations in
relation to the problem of bismuth toxicity in man. Res
Commun Chem Pathol Pharmacol 1979, 26: 391−411.
Kudo A, Omori K, Kato H. A novel aqueous process for
preparation of crystal form-controlled and highly
crystalline BiVO4 powder from layered vanadates at room
temperature and its photocatalytic and photophysical
properties. J Am Chem Soc 1999, 121: 11459−11467.
Tang J, Zou Z, Ye J. Efficient photocatalytic decomposition
of organic contaminants over CaBi2O4 under visible-light
irradiation. Angew Chem Int Edit 2004, 43: 4463−4466.
Wiegel M, Middel W, Blasse G. Influence of ns2 ions on
the luminescence of niobates and tantalates. J Mater Chem
1995, 5: 981−983.
Shannon RD. Revised effective ionic radii and systematic
studies of interatomic distances in halides and
chalcogenides. Acta Cryst 1976, A32: 751−767.
Eppler DR, Eppler RA. Analyzing the color of reddish
glazes. Ceram Eng Sci Proc 1996, 17: 77−87.
Kato M, Takahashi M. Synthesis of Cr-doped
NdAlO3−Al2O3 reddish pink pigment. J Mater Sci Lett
2001, 20: 413−414.
www.springer.com/journal/40145