synthesis of fe-doped titanite and quasi-titanite...

*Corresponding author: [email protected]

available online @ www.pccc.icrc.ac.ir

Prog. Color Colorants Coat. 11 (2018), 221-231

Synthesis of Fe-Doped Titanite and Quasi-Titanite Structures and Studying

the Effect of Doping on Physical and Optical Properties

S. Y. Vaselnia1, M. Khajeh Aminian

*1, R. Dehghan Banadaki

2

1. Nano Pigments and Coatings Laboratory, Department of Physics, Yazd University, P.O. Box: 89195-741, Yazd, Iran. 2. Color and Paint Laboratory, Eefa Ceram Company, P. O. Box: 89551-65833, Yazd, Iran.

ARTICLE INFO

Article history:

Received: 3 Sept 2018

Final Revised: 22 Oct 2018

Accepted: 24 Oct 2018

Available online: 11 Nov 2018

Keywords:

Fe-CaTiSiO5

Titanite

Iron

Beige

Pigments

e-doped titanite (TiCaSiO5) and quasi-titanite (Ti0.5CaSi1.5O5)

compositions were synthesized by the ceramic method. For each

structure, two samples with 0.1 mol% and 0.2 mol% Fe were used. The

synthesized samples were homogenized using a planetary ball mill in 2-

ethylhexyl stearate solvent and then printed on the ceramic with screen printing

system. The samples were characterized by scanning electron microscopy

(SEM), X-ray diffraction (XRD), dynamic light scattering (DLS), UV-Vis

spectroscopy and CIE L*a*b*colorimetry methods. XRD results showed that more

iron has entered to the titanite structure relative to the quasi-titanite structure

with different crystal parameters. The SEM images of the powder and the printed

ceramic as well as DLS results showed that the particle size of the quasi-titanite

structure is smaller than that of titanite structure. The results of colorimetry and

reflection spectra showed that the color of the synthesized quasi-titanite

structure was beige and yellowish beige while that of titanite structure was beige

and brown beige, according to the RAL color system. Prog. Color Colorants

Coat. 11 (2018), 221-231© Institute for Color Science and Technology.

1. Introduction

Inorganic pigments are used for the coloration of

glazes and ceramic bodies. Ceramic pigments benefit

from their high-temperature resistance and chemical

stability and have been widely used in the industry [1-

3]. Titanium is the ninth most abundant element in the

earth’s crust which is found in rocks and sediments.

The only silicate mineral with titanium component is

titanite, formerly called sphene [4]. Titanite (Sphene)

with general chemical formula of TiCaSiO5 has been

used for immobilization of radioactive waste from

nuclear power reactors or in luminescent materials [5-

7]. Malayaite with general chemical formula of

SnCaSiO5 has the same structure as titanite except that

titanite has more complicated composition. Titanite is

monoclinic and its crystal structure consists of corner-

sharing TiO6 octahedra that are connected via SiO4

tetrahedra to form a TiSiO5. Calcium ions make the

CaO7 polyhedra structure [3-10]. Titanite and

malayaite are colorless but becomes colored when

doped with transition metal cations. The reason is that

after doping with these cations, energy gap shifted and

middle levels are created and as a result, different

colors are created. So far, two brown and pink

pigments have been synthesized from Cr-doped titanite

and malayaite, respectively [3, 5, 10-12].

F

S. Y. Vaselnia et al.

222 Prog. Color Colorants Coat. 11 (2018), 221-231

One of the common ways for synthesis of ceramic

pigments is the ceramic method that involves the main

following steps: milling of reagents, mixing of

reagents, calcination under specific temperature and

time. To make ink used from solvents such as

naphthalenes, paraffin oils, fatty acids esters. The

particle size of the pigments for producing nano-inks is

important. For example, the particle size in inkjet

printers is about 100 nm. Two general methods are

used to reduce the size of pigments. In the first method,

pigments are synthesized via chemical methods, such

as sol-gel and hydrothermal, and the size of the

pigments in this method is in the range of nanometer.

The ink is made by adding the ink solvent to the

pigment. In the second method, the pigments have

micrometer size and the particle size is reduced by

using high-energy ball mills. Then, the ink solvent is

added to the pigments to produce the desired ink. The

particle size in the first method is smaller than that

obtained from the second method [10, 11, 13-16].

In this article, we have used new quasi-titanite

structure in addition to the titanite structure. We study

the effect of Fe-doped titanite and quasi-titanite by the

ceramic method and we synthesize novel pigments

from them and compare their color and physical

properties. Two base structures, i.e. Ti0.5CaSi1.5O5

(quasi-titanite) and TiCaSiO5 (titanite), are used and

iron chloride 6-hydrate has been used as iron source.

2. Experimental

2.1. Materials

In this article, we have supplied silicon oxide (SiO2)

and calcium carbonate (CaCO3) from Samchun

company, iron chloride 6-hydrate (FeCl3.6H2O, 99%)

and stearic acid (CH3(CH2)16COOH) from Merck

company, titanium dioxide (TiO2, 99%) from Kimix

and shows that the particle size of S2 sample is smaller

smaller than that of S4 sample. If we compare the particl

company.

2.2. Powder preparation

The samples are named S1, S2, S3 and S4 based on the

amount of iron used and the formula as shown in

Table 1. Synthesis process was initiated by adding the

precursors, such as SiO2, TiO2, CaCO3, FeCl3.6H2O,

and 2 wt% H3BO3 as well as distilled water as a solvent

to a beaker under magnetic stirrer. Then the solution

was placed on a heater. After drying, the samples were

placed in the furnace at 1000 °C for two hours.

2.3. Ink preparation and ceramic printing

After synthesis of pigments, the ink was fabricated by

using 2-ethylhexyl stearate as solvent. In the next step,

2-ethylhexyl stearate was homogenized with pigment

in a planetary ball mill at 450 rpm for 2 hours. The

prepared ink was applied via screen printing method to

the ceramic and has been heated at 1140 oC under

industrial production conditions.

2.4. Characterization

The crystal structure was investigated via X’Pert Pro

(40kV-30mA) instrument with radiation of CuKα

(λ=1.54Ao). The microstructure of the samples was

investigated via Scanning electron microscope (SEM,

VEGA3 TESCAN). Particles size distribution was

measured by Image J software. The optical properties

of the suspensions were measured by Dynamic Light

Scattering (DLS, SZ-100z). The colorimetric and

reflection spectrum investigations have been done via

Xrite Sp-64.

Table 1: Description of the synthesized samples.

Structure name Quasi-Titanite Titanite

Structure Ti0.5CaSi1.5Fe0.1O5 Ti0.5CaSi1.5Fe0.2O5 Ti0.9CaSiFe0.1O5 Ti0.8CaSiFe0.2O5

Sample S1 S2 S3 S4

FeCl3 0.1 mol 0.2 mol 0.1 mol 0.2 mol

Synthesis of Fe-Doped Titanite and Quasi-Titanite Structures

Prog. Color Colorants Coat. 11 (2018), 221-231 223

3. Results and discussion

3.1. The results of powder samples

Images of pigments S1, S2, S3, S4 that synthesized by

ceramic method at 1000 oC are shown in Figure 1. The

general reaction to form the titanite structure during the

heating process is given as below [5, 8]:

TiO2(s)+CaCO3(s)+SiO2(s) → TiCaSiO5(s)+CO2(g)

(1)

This reaction involves two steps:

TiO2(s)+CaCO3(s) → CaTiO3(s)+CO2(g) (2)

CaTiO3(s)+SiO2(s) → CaTiSiO5(s) (3)

SEM images of powder samples S2 and S4 at 1 µm

and 10 µm magnifications are shown in Figures 2 and

3. The particle size distribution graphs which are

obtained from SEM images at 1 µm magnification for

S2 and S4 are shown in Figure 4-a and Figure 4-b. The

average size of the particles for S2 is about 110 nm and

for S4 is about 130 nm.

Figure 1: Images of pigments: a-S1, b-S2, c-S3, d-S4 synthesized at 1000

oC.

Figure 2: SEM images of S2 powder sample.

Figure 3: SEM images of S4 powder sample.



Figure 4: a- particle size distribution for S2, b- particle size distribution for S4.

X-ray diffraction spectra of samples S2 and S4 are

shown in Figure 5-a and Figure 6-a. Diffraction pattern

related to diffraction spectrum of samples S2 and S4 are

shown in Figure 5-b and Figure 6-b.

For sample S4, peaks are shifted 0.1-0.3 degree

relative to the reference peak due to the presence of iron

as impurity which changes the lattice parameter and as a

result, the peaks are shifted. In this sample, it can be

seen the impurity peaks related to SiO2 (quartz) and

CaTiO3 and this indicates that SiO2 and CaTiO3 do not

enter the titanite structure and form a distinct structure.

The reason is related to the titanite synthesis

temperature. Reaction No. 3 completes at approximately

1200-1300 °C, but at lower temperatures, the reaction is

done partially [5, 11].

Figure 5: a- XRD spectrum of S2, b-XRD diffraction pattern of S2.



Figure 6: a- XRD spectrum of S4, b-XRD diffraction pattern of S4.

The S2 diffraction spectrum has more complex

structure than that of the S4 sample. In sample S2, peaks

are shifted 0.005-0.1 degree relative to the reference peak

which is less than that of S4 sample and shows that less

iron has entered into the structure of S2 sample relative to

S4 sample. This arises from the differences in the structure

of these two samples. The S4 sample has titanite-related

structure (TiCaSiO5) but in S2 sample, the structure is

slightly deviated from titanite structure (Ti0.5CaSi1.5O5).

The crystallite direction is also different in these

structures, so iron cannot occupy some locations. In S2

sample, like S4 sample, some of the peaks are related to

titanite and this indicates that reaction No. 3 has been

done completely. Here again, SiO2 (quartz) and CaTiO3

have not entered the titanite structure and have formed a

separate structure. By comparing the X-ray diffraction

spectrum of S2 and S4, it can be concluded that the number

of pure peaks in S4 sample is higher than those in S2

sample. The crystallographic parameters for the two

structures are shown in Table 2.

Table 2: The crystallographic parameters of the structures.

Structure name Quasi-Titanite Titanite

Sample S2 S4

Crystal system monoclinic monoclinic

Space group C 12/c 1 C 12/c 1

Space group number 15 15

a(Å) 6.4550 6.5640

b(Å) 8.6520 8.7190

c(Å) 6.9410 7.0570

α(o) 90.0000 90.0000

β(o) 113.3570 113.7900

γ(o) 90.0000 90.0000



The crystal system for S2 and S4 is monoclinic and

the space group is C 12/c 1, but the crystal parameters

are different for both samples. The list of pure peaks for

S2 and S4 is shown in Table 3 and Table 4. Comparing

the intensity of the peaks with the reference peaks shows

that in some directions, the intensity of the peaks

is increased and in other directions it is decreased.

The crystallite size obtained from Scherrer equation

for S2 and S4 samples is 17.2 nm and 35.7 nm,

respectively.

The colorimetry results of the samples in the CIE

L*a*b*system are shown in Table 5. In this system, L*

is the color lightness (L*=0: black, L*=100: white) and

+a* is red and -a* is green, and +b* is yellow and -b*

is blue [17, 18]. It can be seen that with increasing the

iron in samples S2 and S4, a* and b* increased and the

L* is reduced (compared to samples S1 and S3). The

positive values of a* and b* parameters show that the

samples have a combination of red and yellow colors.

In order to determine the color of the samples, they

were compared with the RAL color system. The RAL

is a color matching system used in Europe and is used

for varnishes and coatings. The RAL associates

numbers to individual colors [19].

Table 3: Peak list for sample S2.

Peak no 2θ(deg) [h k l] I [%] reference I [%] S2

1 27.9297 [-1 1 2] 100.0 28.53

2 30.3468 [2 0 0] 85.7 63.91

3 34.6099 [1 3 0] 98.4 42.98

4 41.7874 [0 4 0] 5.2 37.36

5 44.2256 [0 4 1] 8.2 44.12

6 56.1160 [3 3 0] 31.1 54.30

7 57.7315 [0 0 4] 7.3 41.29

8 62.2826 [-4 2 1] 0.8 50.72

9 72.6040 [3 5 0] 0.6 35.02

Table 4: Peak list for sample S4.

Peak no 2θ(deg) [h k l] I [%] reference I [%] S4

1 18.1929 [1 1 0] 22.7 6.92

2 27.7712 [0 0 2] 3.4 100.00

3 29.9889 [2 0 0] 75.7 89.21

4 31.7003 [-2 0 2] 6.2 5.80

5 34.4881 [1 3 0] 67.0 78.26

6 34.8004 [0 2 2] 46.6 49.09

7 38.1131 [1 1 2] 4.8 2.65

8 39.9906 [-1 1 3] 9.8 10.44

9 41.5749 [0 4 0] 2.3 4.83

10 43.0628 [-3 1 1] 9.8 21.96

11 43.5261 [2 2 1] 4.7 9.11

12 44.0424 [0 4 1] 10.4 37.69

13 46.7500 [3 1 0] 6.8 14.18

14 53.1366 [-3 3 2] 2.8 17.57

15 54.4959 [3 1 1] 0.1 6.80

16 55.9781 [3 3 0] 25.4 42.24

17 57.2102 [0 0 4] 4.0 7.11

18 64.9833 [3 1 2] 5.0 9.45

19 66.4485 [1 1 4] 0.1 10.32



Table 5: The colorimetry results of the samples and the color codes of the RAL system in the CIE L

*a*b*.

Sample L*

a* b

* color

S1 71.82 7.55 27.52 Beige

S2 65.74 9.7 29.4 Yellowish beige

S3 70.17 8.22 22.8 Beige

S4 56.82 14.62 26 Brown beige

RAL 1001 [23] 73.59 5.47 27 Beige

RAL 1024 [23] 62.26 8.45 41.52 Ochre yellow

RAL 1011 [23] 57.34 12.48 33.39 Brown beige

The values of L*a*b* for samples S1 and S3 are close

to RAL 1001 color code (Beige color). For sample S2,

the b* parameter increased more than the other samples

and the color of the sample S2 is in the region between

RAL 1001 (Beige color) and RAL 1024 (Ochre yellow

color) and closer to RAL 1001. For sample S4, a*

parameter increased more than the other samples and the

values of L*a*b* for this sample are close to RAL 1011

(Brown beige) color code [20-23]. With increasing the

iron in samples S2 and S4, b* and a* parameters are

increased and the effect of iron on these samples is

different according to the XRD results. The structures of

S2 and S4 samples are different and as a result, the

location of iron ions is different. The reflection spectrum of the pigments is shown in

Figure 7. There is no significant difference between the

reflection spectra of the samples. Samples S1, S2 and S3

have the most reflection in the 590-700 nm range. For

sample S4, the curve is shifted approximately 30 nm to

the right and has the most reflection in the 620-700 nm

range. But the curve shift for sample S2 is not

significant. The cause of this phenomenon is consistent

with the XRD results. XRD results showed that in

sample S4 more iron has entered into the structure than

sample S2 and as a result, the increase of a* parameter in

sample S4 is higher than b* parameter in sample S2 and

the curve has shifted to the higher wavelengths. The

region of 590-700 nm corresponds to the beige color

region [24].

3.2. The results of samples after printing on the

ceramic

Inks are printed on a ceramic by screen printing

system. The image of the samples printed on the

ceramic surface is shown in Figure 8.

Figure 7: The pigments reflection spectrum.



Figure 8: Image of printed ceramic surface.

The SEM images of the ceramic surface for S2 and

S4 samples at 1 µm and 10 µm magnifications are

shown in Figure 9 and Figure 10. The particle size

distribution graphs obtained from SEM images at 10

µm magnification for S2 and S4 samples are shown in

Figure 11-a and Figure 11-b. The average size of the

particles after printing on the ceramic for S2 sample is

about 240 nm and for S4 sample is about 370 nm. So

the particle size of S2 sample is smaller than that of S4

sample.

The particle size distribution graphs for the

suspensions of S2 and S4 samples measured by the

dynamic light scattering (DLS) method are shown in

Figure 12-a and Figure 12-b. The average size of the

particles for S2 sample is 183.5 nm and for S4 sample is

356 nm and shows that the particle size of S2 sample is

smaller than that of S4 sample. If we compare the

particle size of the suspensions with the particle size

after printing on the ceramic surface it is observed that

the particle size has become larger after printing on the

ceramic surface because some particles agglomerate

during heating the ceramic at high temperature.

Figure 9: SEM images from S2 sample after printing on the ceramic surface.

Figure 10: SEM images of S4 sample after printing on the ceramic surface.



Figure 11: a- particle size distribution for S2 sample

after printing on the ceramic surface, b- particle size

distribution for S4 sample after printing on the ceramic

surface.

Figure 12: a- particle size distribution for the

suspension of S2, b- particle size distribution for the

suspension of S4.

The colorimetric results of the samples printed on

the ceramic surface are shown in Table 6. By

comparing the L*a*b* values of samples printed on

ceramic and of powder samples it can be seen that a*

and b* parameters of the printed samples have

decreased, but the L* parameter has increased which

may be due to glaze on the surface. The purity of the

beige color for the printed samples has decreased

compared to the powder samples but the samples are

still in the beige colors region. The chromatic diagram

of powder samples and printed samples on ceramic in

the CIE XY color space is shown in Figure 13.

Table 6: The colorimetry results of the printed ceramic surface.

Sample L*

a*

b *

S1 89.27 -0.58 7.09

S2 86.91 -0.44 10.32

S3 85.94 -0.47 10.85

S4 77 -0.31 11.69



Figure 13: Chromatic diagram of powder samples and printed samples on ceramic in the CIE XY color space.

4. Conclusions

Fe-doped titanite and quasi-titanite were synthesized

by the ceramic method and their ink was prepared and

printed on ceramic via screen printing system. XRD

showed that the crystal structure of the samples is

monoclinic with a shift due to the iron doping, while

their crystal parameters are different. The crystallite

size and SEM images and DLS results for S2 and S4

showed that the particle size of S2 is smaller than S4.

The results of colorimetry and reflection spectra for

powder samples showed that according to the RAL

color system, the colors of the samples S1 and S2 are

Beige and Yellowish beige while for S3 and S4 are

Beige and Brown beige. For samples S2 and S4, b* and

a* parameters are more than those of S1 and S3. The

colorimetry results for ceramic surface showed that a*

and b* parameters are decreased but L* parameter is

increased after heating the ceramic.

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How to cite this article:

S. Y. Vaselnia, M. Khajeh Aminian, R. Dehghan Banadaki, Synthesis of Fe-Doped

Titanite and Quasi-Titanite Structures and Studying the Effect of Doping on Physical

and Optical Properties. Prog. Color Colorants Coat., 11 (2018), 221-231.

synthesis of fe-doped titanite and quasi-titanite...

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