Synthesis Gas Sensor from CuFe2O3: Cu Films by Spin Coating
1,2Radiology Techniques Department, College of Medical Technology, The Islamic University, Najaf,
IRAQ
3Department of Physics, College of Science, University of Babylon, Iraq
IRAQ
Abstract: - Thin films from CuFe2O3: Cu were prepared with different weights and then the membranes were
prepared using a spin coating method with the rotation speed are (2000,3000,4000,5000) rpm respectively and
the rotation time is 7s.. The films were examined as gas sensor against NH3gas at operating temperatures (200)
oC, also sensitivity of films for gases increases with decreases temperature. The variation of the operating
temperature of the films have led to a significant change in the sensitivity of the sensor. The gas sensor at the
operating temperature increasing in recovery time and decreasing in response.
Key-Words: - Thin film, CuFe2O3: Cu, Operation Temperature, sensitivity, relatively, response, gas sensor,
Spin coating.
Received: May 21, 2021. Revised: April 22, 2022. Accepted: May 23, 2022. Published: July 19, 2022.
1. Introduction
Technological advancements have increased the
demand for soft magnetic materials in devices.
Among soft magnetic materials, polycrystalline
ferrites have attracted special attention due to their
good magnetic properties and high resistivity over
a wide frequency range from hundreds of hertz to
several gigahertz.[1]. Most of the materials of
electronic device produced today contain some
ferromagnetic spinel ferrite materials. Speaker,
motors, electromagnetic interference suppressors,
inductors, antenna rods, proximity sensors,
broadband transformers, memory devices,
recording heads, humidity sensors, filters, radar
absorbers, etc. are frequently based on ferrites [2].
Such a seeing helps us to explain why ferrites have
been used and studied for several years. The
properties of ferrites are being improved because of
the increasing way in ferrites technology. It is
believed that there is a shiny future for ferrite
technology [3]. Ferrites show dielectric properties,
that dielectric property means that even though
electromagnetic waves can pass during ferrites,
they do not easily conduct electricity [4]. This
gives them an advantage over iron, nickel and other
transition metals that are magnetic in many
applications because these metals conduct
electricity. Another important factor that is quite
important in ferrites and completely irrelevant in
metals is porosity [5]. Such a seeing helps us to
explain why ferrites have been used and studied for
several years. The properties of ferrites are being
improved because of the increasing way in ferrites
technology. It is believed that there is a shiny future
for ferrite technology [6].
2. Experimental
The thin film of CuFe2O3:Cu was prepared by
using spin coating, the rotation speed is
(2000,3000,4000,5000,) rpm respectively and the
rotation time is 7s.(0.1) gm of, CuFe2O3 solve in 5
ml of Dimethyl sulfoxide (DMSO). then applied on
a glass slide at room temperature. All substrates
were washed thoroughly using Distilled water, and
then left to Dry out. Interdigitated electrodes
1ALI J. KHALAF, 2ABEER S. ALFAYHAN, 3MOHAMMED A. AL-SHAREAFI
WSEAS TRANSACTIONS on APPLIED and THEORETICAL MECHANICS
DOI: 10.37394/232011.2022.17.13
Ali J. Khalaf, Abeer S. Alfayhan,
Mohammed A. AL-Shareafi
E-ISSN: 2224-3429
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(IDEs) substrate to study Gas Sensor
Measurements are carried out by measuring the
variation in resistivity resulting from exposing the
thin film surface to the gas (NO2).The temperature
is recorded by a k-type thermocouple (XB 9208B).
The bias voltage was supplied by (FARNELL
E350) power supply. The resistivity is recorded by
(Fluke Digital Mustimeter 8845A / 8846 A). In this
study, un-doped and Cu-doped CuFe2O3 thin films
were coated on glass substrates using low cost and
simple spin coating technique
to studying the variation of the sensitivity with
operating temperature of the films
3. Results and discussion
3.1. Determination of Operation
Temperature of the Sensor
Resistive sensors have been used to measure a
wide range of physical and chemical properties and
can be considered the most familiar and low-cost
sensors. The temperature at which the sensitivity of
the sensor reaches a constant value is called the
operating temperature. The change in resistance is
only affected by the presence of certain gases of
interest. Changes in resistance are only affected by
the presence of certain gases of interest. The
changing of resistance is just only influenced by the
presence of amount of some gases of interest.
Figure (1) Figure(2) shows that sensitivity as a
function of operating temperature in the range
(150-300)°C fo CuFe2O3:Cu thin films, which are
deposited on FTO substrates at an air mixing ratio
the bias voltage of (5) Volt are applied on all the
samples[7]., Figure (1) is obvious that the
sensitivity of all films increases with increasing of
the operating temperature until (200 ) oC. This is
attributed to increase in the rate of surface reaction
of the target gas. The optimal temperature that has
maximum values of temperature is (200) oC for all
films. At this temperature the activation energy
may be enough to complete the chemical reaction.
Also we observed that increases and decrease in the
sensitivity indicate the absorption and desorption
phenomenon of the gases. These results are in a
good agreement with studies conducted by [3].
For NO2,H2S gas, the sensitivity is observed to
increase at operating temperature (200) °C. After
(200)°C temperature, the surface would be unable
to oxidize the gas so intensively and the NO2
,H2Sgas may burn before reaching the surface of
the film at higher temperature. Thus, the gas
sensitivity decreases with increasing temperature
[34], also the increase of the of CuFe2O3: Cu causes
decreasing in the sensitivity of thin film [8]. The
sensitivity of all films is shown Table (1) and Table
(2).
3.2. Response Time and Recovery Time
It is the time interval over which the resistance of
the sensor material attains a fixed percentage
(usually 90 %) of final value when the sensor is
exposed to the full-scale concentration of the gas.
A small value of the response time is highly
desirable in application such as detection of
flammable or combustible gases to prevent fire
[10].Recovery Time It is the time interval above
which sensor resistance reduced to (10 %) of the
saturation rate when the target gas is switched off
and the sensor sited in artificial (or reference) air a
sensor should have a small recovery time so that it
can be ready for the next detection [10].Figures
(3a) (3b) (4 a)(4b) show the relation between the
response time and the recovery time with the
operating temperature of the Sb2O3 ,
Sb2O3:In2O3thin films for H2S and NO2 gas and
bias voltage 5V. From Table (3) note that the
increasing Vol.% of Cu is due to increasing in
response time and decreasing in recovery time at
optimal temperature (200) oC The large recovery
time would be due to lower operating temperature.
At lower temperature O2species is more
prominently adsorbed on the surface and thus it is
less reactive as compared to other species of
oxygen, O- and O- .
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Fig (1): The variation of sensitivity with the operating temperature of the 1- pure CuFe2O3 2- CuFe2O38%,Cu2 2%
wt 3- CuFe2O3 6% wt , Cu 4% wt 4 CuFe2O3 4% wt , Cu2 6% wt
Fig (2): The variation of sensitivity with the operating temperature of the 1- pure CuFe2O3 2 CuFe2O3 3-
CuFe2O3 6% wt , Cu 4% wt 4 CuFe2O3 4% wt , Cu26% wt
0
10
20
30
40
50
60
050 100 150 200 250 300 350
Sensitivity (%)
Operation temperature (oC)
NO2
1 2
3 4
0
10
20
30
40
50
60
050 100 150 200 250 300 350
Sensitivity (%)
Operation temperature (oC)
H2S gas
1 2
3 4
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Table (1): Sensitivity of the CuFe2O3:Cu thin films with H2Sgas.
Sample
pure CuFe2O3
CuFe2O38%,Cu2 2% wt
CuFe2O3 6% wt , Cu 4% wt
CuFe2O3 4% wt , Cu26% wt
Table (2): Sensitivity of the CuFe2O3:Cu thin films with NO2gas
Sample
Sensitivity% at the optimal temperature (200) oC
pure CuFe2O3
29.21523
CuFe2O38%,Cu2 2% wt
53.70748
CuFe2O3 6% wt , Cu 4% wt
32.28261
CuFe2O3 4% wt , Cu26% wt
49.83607
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Fig (3a): The variation of response time with operating1- Pure 2- the 1- pure CuFe2O3 2 CuFe2O3 3- CuFe2O3
6% wt , Cu 4% wt 4 CuFe2O3 4% wt , Cu26% wt NH3gas
Fig (3b): The variation of response time with operating1- Pure 1- pure CuFe2O3 2 CuFe2O3 3- CuFe2O3 6% wt ,
Cu 4% wt 4 CuFe2O3 4% wt , Cu26% wt H2Sgas
0
5
10
15
20
25
30
35
40
45
050 100 150 200 250
Response Time (s)
Operation temperature (oC)
NH3 gas
1 2
3 4
5
0
5
10
15
20
25
30
35
40
050 100 150 200 250 300 350
Response Time (s)
Operation temperature (oC)
H2S gas
1 2
3 4
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Fig (4a): The variation of Response time with operating1- Pure 1- pure CuFe2O3 2 CuFe2O3 3- CuFe2O3 6% wt ,
Cu 4% wt 4 CuFe2O3 4% wt , Cu26% with NO2gas
Fig (4b): The variation of response time with operating 1- pure CuFe2O3 2- CuFe2O3 3- CuFe2O3 6% wt , Cu 4% wt
4 CuFe2O3 4% wt , Cu26% with NO2gas
0
5
10
15
20
25
30
050 100 150 200 250 300 350
Response Time (s)
Operation temperature (oC)
NO2 gas
1 2
3 4
0
10
20
30
40
50
60
70
80
90
100
050 100 150 200 250 300 350
Recovery Time (s)
Operation temperature (oC)
NO2 gas
1 2
3 4
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Table (3): The response time and the recovery time with the Temp.(⁰C) temperature of CuFe2O3:Cu thin films
for H2S and NO2 gas
Sample
Response Tim(s)
at (200) oC with
H2Sgas
Recovery Time (s)
at (200) oC with
H2Sgas
Response Tim(s)
at (200) oC
NO2gas
Recovery Time
(s)
at (2) oC NO2gas
pure Sb2O3
19.8
94.5
25.2
90
pure CuFe2O3
36.9
77.4
24.3
65.7
CuFe2O38%,Cu2 2% wt
22.5
61.2
15.3
64.8
CuFe2O3 6% wt , Cu 4%
wt
27
83.7
18
54.9
4. Conclusions
The samples is tested for gas NO2 , H2S at a
temperature range of 150–300 °C. Sensitivity,
response time, recovery time and selectivity of
samples are studied. The results showed that the
CuFe2O3:Cu thin films produced are a good
candidate to be used as a sensor. The sensing
measurements show that the films have high
sensitivity to these gases and vapors. The best
result recorded for sensitivity at 2% Cu Sensitivity
reactions of films decrease with increasing of cu %.
Increased recovery response time and decreased
response time of gas sensor at operating
temperature.
Acknowledgments
First of all, praise is thanks to Allah, the
almighty God, the most gracious and the most
merciful, who provided me with the capability
to complete this research work. would like to
express my gratitude and appreciation for the
staff in the Radiology Techniques Department,
College of Medical Technology, The Islamic
University.
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