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INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)
ISSN No. 2321-2705 | DOI: 10.51244/IJRSI |Volume XII Issue IX September 2025
Thermal Decomposition of Co-Fe-Cr-Citrate Complex Via Structural
and Spectral Study.
Umesh Sankpal
1*
1
Department of Chemistry, R. P. Gogate College of Art’s & Science and R. V. Jogalekar
College of Commerce (Autonomous), Ratnagiri, Maharashtra, India 415 612.
*Corresponding Author
DOI: https://dx.doi.org/10.51244/IJRSI.2025.120800278
Received: 22 September 2025; Accepted: 28 September 2025; Published: 04 October 2025
ABSTRACT
A Citrate gel precursor method was employed to prepare CoFeCrO
4
. The citrate complex of cobalt-iron-
chromium was investigated with the help of thermoanalytical technique. Its thermal decomposition study in air
by subsequent analysis by FT-IR and XRD were studied to predict the stepwise reaction mechanism at various
temperature ranges to get single phase pure spinel compound.
Keywords: Citrate precursor; TG-DTA; FT-IR; Single phase; XRD
INTRODUCTION
Homogenous and fined sized ferrospinels have huge numbers of scientific and technological applications [1-3]
due to their physical, chemical and thermal stability. The ferrospinel oxides have general formula AB
2
O
4
, where
A and B are cations with oxidation state 2+ and 3+ respectively. They have been proved as significant materials
due to their interesting structural, electrical and magnetic properties [4-6]. These materials can be synthesized
by various physical, chemical as well as biological methods [7-10]. Amongst them, simple and economic
chemical method, citrate-gel precursor method is mostly employed by various researches to achieve
stoichiometry and homogenous particle size in the mixed-metal oxides [11]. This method has great latent in the
preparation of fine and uniform sized oxides having potential application as magnetic recording media,
microwave devices, catalysis, gas sensors, pigments [12-14] and many more. Thermal decomposition of oxalate
solid-solution precursor form fine sized oxides through the formation of various intermenidtae were reported by
Schuele et.al. as well as Ravindranathan et.al. [15-16]. Gajbhiye et. al.[17] has been reported the thermal
decomposition study of zinc-iron-citrate precursor while Gabal [18] work on oxalate-iron (II) oxalate mixture
and Verenkar et.al. worked on thermal decomposition of hydrazinated cobalt zinc ferrous succinate as well as
cobalt substituted nickel zinc ferrites from hydrazinated mixed metal fumarates [19-20]. The study on citrate
solid-solution precursor and its thermal decomposition/combustion of these metal-precursors, like hydrazinium,
metal –hydrazine carboxylate hydrates gives fine-particle sized mixed-metal oxides with versatile physico-
chemical properties [21]. It leads to the formation of ultrafine nanoparticles. Hence an attempt had been made
to study a systematic thermal decomposition of citrate precursor of Co-Fe-Cr spinel with the possible formation
of intermediates which results ultrafine ferrospinel.
Experimental
Simple and economic citrate-gel auto combustion method has been employed to synthesize Cr substituted cobalt
ferrite nanoparticles [07]. It offers a significant saving of time and energy consumption over traditional methods
and requires less sintering temperature. Physico-chemical investigation of the dry citrate complex of CoFeCr
was carried out by formation of spinel structural and thermal analysis. Structural study was followed by XRD
while thermal study of in the temperature range of room temperature - 1000°C in static air at the heating rate of
10°C/min. using TG-DTA. FT-IR spectrums were recorded in the range of 400-4000 cm
-1
.
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INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)
ISSN No. 2321-2705 | DOI: 10.51244/IJRSI |Volume XII Issue IX September 2025
Result and Discussion
The TG-DTA curve of citrate-precursor heated in air atmosphere is shown in Fig. 1. The above graphs reveal
that the reaction steps are in the order of dehydration, decomposition of citrates and carbonates then final
formation of Co-Fe-Cr oxide. An endothermic peak corresponds to the dehydration of citrate precursor. The two
close endothermic peaks result the thermal decomposition of citrate to carbonate to then formation of CoFeCrO
4
by solid-state diffusion process to get (2CoO + Fe
2
O
3
+ Cr
2
O
3
) i.e. 2CoFeCrO
4.
The observed results in the loss
in masses with respect to their temperature ranges are represented in Table 1. In the I
st
step, the water content
numbers absorbed by the metal-citrate-precursor could be varied with respect to atmospheric humidity. The extra
water molecules can be removed by heating at about 100℃. An endothermic peak at 80 - 110℃ reveals the
removal of co-ordinated water molecules of 10.31 % which corresponds to the loss of water molecules
exclusively. On the basis of molar mass, the loss of 18 coordinated water molecules were predictable.
Nextly, in the temperature range of citrate decomposition were takes place in the temperature range 275 - 375°C
with loss of 38.10 % and two endotherms at 295°C and 330°C respectively. In these two stages, decomposition
is a complex reaction which involves dissociation of aconitate along with decarboxylation with the evolution of
CO, H
2
O, CO
2
as well as oxidation of CO to CO
2.
The methylene proton could be oxidizing to water vapors.
These results are correlated and are agree well with DTA curve. The sharp peak at 350°C indicates the possibility
of decomposition of whole citrate-complex form Co-O with evolution of CO
2 &
H
2
O [17]. In the same
temperature range the (FeO
.
OH) and (CrO
.
OH) get decompose to form their oxides as Fe
2
O
3 &
Cr
2
O
3
respectively
.
The notable peak at 520°C gives the formation of CoFeCrO
4
phase initiated by solid-state diffusion process,
2CoO + Fe
2
O
3
+
Cr
2
O
3
2CoFeCrO
4.
The IR bands for precursor, metal-precursors and various products of thermal decomposition of citrate precursor
are represented in Table 2 & 3. The broad peak in the region of 3000-3600 cm
-1
& 1600 cm
-1
could be due to the
presence of water which goes to be decrease in the intensity with the heating process. Similar behavior is obtained
at 1718, 1559, 1443, & 1255 cm
-1
which is due to the loss of coordinated water molecules. The band appear at
1254 cm
-1
is due to formation of metal-hydroxo complex {(δ MOH)
bending mode
} which is weak and disappear at
420°C. It could be the formation of aconitate-metal complex [18]. Further it goes on decomposition which
reveals by the absence of band in the range of 2950 – 2850 cm
-1
while the formation (δ H-OH) at 1609 cm
-1
by
the formation of
FeO
.
OH & CrO
.
OH at 280 - 350°C. Over here citrate group is oxidize totally i.e. disappearance
of ν(CH), ν
asym.
(C=O), ν (CO
3
) / ν
asym.
(CO
3
). Some bands at 1511, 1106 and 870 cm
-1
gives the formation of
hrdrocobaltite and carbonates which were not observed after 400°C, result the almost complete decomposition
of carbonates to form oxides. A weak band at about 2350 cm
-1
is due to the free CO
2
after
400°C. X-ray diffraction
pattern of sintered sample (500℃) which is decided after thermal study reveals the formation of single phase
cubic spinel structure as shown in Fig. 2.
CONCLUSION
The citric acid could be a desired precursor to get ultrafine sized mixed-metal oxide. The decomposition
mechanism of the citrate-precursor in air is predicted in various thermal stages. Many of the thermal parameters
like decomposition rate, decomposition temperature and heat dissipation with respect to evolution of various
gases / vapors to form CoFeCrO
4.
The
FT-IR study is quite well agreeing with thermal decomposition study to
decide sintering temperature and get single phase spinel compound.
REFERENCES
1. Maria Arshad, Muhammad Khalid, Muhammad Younas, Zaheer Uddin, Wahab Ullah, Imed Boukhris,
M.G.B. Ashiq, Farhan Aziz, Materials Characterization, Volume 215, September 2024, 11421.
2. Chetna C. Chauhan, Tanuj M. Gupta, Reshma A. Nandotaria, Abhishek A. Gor, Charanjeet Singh
Sandhu, Kanti R. Jotania, Rajshree B. Jotania, Ceramics International, Volume 47, Issue 19, 1 October
2021, Pages 27441-27452.
3. Swarupamayee Nayak, Pratiksha Agnihotri, Jagadis Prasad Nayak, Charul Joshi, Radheshyam Rai,
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INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)
ISSN No. 2321-2705 | DOI: 10.51244/IJRSI |Volume XII Issue IX September 2025
Current Applied Physics, Volume 73, May 2025, Pages 49-76
4. G. Blasse, Philips Res. Rep. Suppl. 3 (1964) 96.
5. M. A. Gabal, J. Materials Research and Technology, 15, (2021), 5841.
6. J. B. Goodenough, Prog. Solid State Chem. 5 (1971) 145.
7. P. P. Hankare, U. B. Sankpal, R. P. Patil, I. S. Mulla, R. Sasikala, A. K. Tripathi, K. M. Garadkar, J.
Alloys Compounds 496, (2010) 256.
8. P. P. Hankare, U. B. Sankpal, R. P. Patil, K.M. Garadkar, A. V. Jadhav, B.K. Chougule, J. Magn. Magn.
Mater.323, (2011) 389.
A. Chatarjee, D. Das, S. K. Pradhan, D. Chakravorty, J. Magn. Magn. Mater. 127 (1993) 443.
9. J. P. Wang, Mater. Sci. Eng. B 127 (2006) 81.
10. P. P. Hankare, U.B. Sankpal, R.P. Patil, P.D. Lokhande, R. Sasikala, Mater. Sci. Eng. B: Solid-State
Mater. Adv. Tech., 176, (2011) 103.
11. B. L. Shinde, U. M. Mandle, A. M. Pachpinde, K. S. Lohar, J. Thermal Analysis & Calorimetry 147, 4
(2022), 2947
12. C. V. Gopal Reddy, S. V. Manorama, V. J. Rao, J. Mater. Sci. Lett. 19 (2000) 775.
13. P. Y. Lee, K. Ishizaka, H. Suemastu, W. Jiang, K. Yatsui, J. Nanaoparticles Res. 8 (2006) 29.
14. W. J. Schuele and V. D. Dectscreek, Fine Particle Ferrites, in W. E. Kuhn, H. Lamprey and C. Sheer
(Eds.), Ultrafine Particles, Wiley, New York, 1963, 218.
15. P. Ravindranathan and K. C. Patil, Am. Ceram. Soc. Bull. 66(4) (1987) 688.
16. N. S. Gajbhiye, U. Bhattacharya, V. S. Darshane, Thermochimica Acta. 264 (1995) 219-230.
17. M. A. Gabal, Journal of Materials Research and Technology, Volume 15, November–December 2021,
Pages 5841-5848.
18. Pratik A. Asogekar, V. M. S. Verenkar Ceramics International Volume 45, Issue 17, Part A, 1 December
2019, Pages 21793-21803.
19. S. G. Gawas, V. M. S. Verenkar, Thermochimica Acta Volume 605, 10 April 2015, Pages 16-21.
20. V. K. Sankaranarayana and N. S. Gajbhiye, Thermochimica Acta 153 (1989) 337-348.
Fig. 1 TGA and DTA curve for citrate precursor of CoFeCr
(before sintering)
60
70
80
90
100
0 200 400 600 800 1000
Temperature (
o
C)
Weight (%)
-0.5
-0.3
-0.1
0.1
0.3
0.5
0.7
0.9
1.1
1.3
1.5
1.7
1.9
Temperature Difference (
o
C/mg)
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INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)
ISSN No. 2321-2705 | DOI: 10.51244/IJRSI |Volume XII Issue IX September 2025
Fig. 2 XRD pattern of CoFeCrO
4
Table 1. Losses in mass in the thermal decomposition of Co-Fe-Cr-Citrate Complex.
Temperature
Range (°C)
Loss of mass
(%)
Molecular Formula
25 - 800
-
(CoFeCr)
3
(C
6
H
5
O
7
)
8
.18H
2
O
80 – 200
10.31
(CoFeCr)
3
(C
6
H
5
O
7
)
8
[M-aconitate]
220 – 300
6.58
Co
6
(CO
3
)
2
.6(OH)+6(CrO.OH)+ 6(FeO.OH)
300 – 400
31.50
Co
6
CO
2
+ (Cr
2
O
3
) CO
2
+ (Fe
2
O
3
) CO
2
450 – 500
0.86
(CoFeCrO
4
)
6
.CO
2
500 – 600
1.20
CoFeCrO
4
Table 2 FT-IR spectral frequency assignments of various compounds (cm
-1
)
Citric Acid
Precursor
Fe-Citrate
Assignment
3497
(vs)
3412
(s)
3412
(s)
ν (OH) hydroxyl
3291
(vs)
3236
(br)
3239
(br)
ν (OH) water
2910 - 2880
(br)
2951
(s)
2950-2850
(br)
ν (CH)
1744
(vs) ,
1705
(vs)
1718
(vs),
1611
(vs),
1561
(vs)
1718
(vs),
1611
(vs),
1561
(vs)
ν
asym.
(C=O)
δ(H-OH)
ν
asym
(COO) Carboxylate
1426
(s),
1309
(s)
1440
(s), 1390(s)
1440
(s),
1390
(s)
ν
asym
(COO)
1239 - 1140
(s)
1260-1195
(br)
1255
(m)
δ(M-OH)
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INTERNATIONAL JOURNAL OF RESEARCH AND SCIENTIFIC INNOVATION (IJRSI)
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1086 - 1065
(sh)
1081
(m)
1116
(m)
Citrate
942
(s)
987
(s)
978-956
(m)
775
(vs)
851
(vs),
804
(m)
804
(m)
640
(m)
652
(sh)
673
(sh)
597
(m)
609
(s)
565
(sh)
Table 3 FT-IR spectral assignments for metal-citrate complex and decomposition products (cm
-1
)
Assignment
85℃
295℃
330℃
430℃
510℃
ν (OH) hydroxyl
3412
(s)
3412
(s)
3412
(br)
3412
(br)
-
δ(H-OH) water
1609
(s)
1609
(s)
1609
(w)
1609
(w)
1609
(w)
ν
asym.
(C=O)
1718
(s)
1718
(w)
1718
(w)
-
-
ν
asym
(COO)
Carboxylate
1559
(s)
1559
(m)
1559
(m)
-
-
ν
asym
(COO)
1443
(m)
1443
(vw)
-
-
-
δ(M-OH)
1252
(m)
1252
(w)
1252
(vw)
-
-
ν
(CO
3
)
-
870
(m)
-
-
-
ν
(CO
2
)
-
-
-
2350
(w)
2350
(w)
ν (CH)
2950-2850
(br)
2950-2850
(w)
-
-
-
ν
asym.
(CO)
1718
(s)
1718
(s)
-
-
-
δ(M-OH)
1252
(m)
1252
(m)
-
-
-
ν (Fe-O) /
(Cr-O)
614
(m)
614
(m)
614
(m)
614
(m)
614
(m)
480
(m)
480
(m)
480
(m)
480
(m)
480
(m)
Abbreviations: s – strong, br-broad, m – medium, w – weak, vw – very weak, sh-shoulder