microstructure and electrical conductivity properties of novel synthesized cesium doped...

Elkady et al. Int. J. Res. Chem. Environ. Vol.4 Issue 2 April 2014(184-194)

[184]

International Journal of Research in Chemistry and Environment Vol. 4 Issue 2 April 2014(184-194)

ISSN 2248-9649

Research Paper

Microstructure and Electrical Conductivity Properties of Novel Synthesized

Cesium doped Nano-Zirconium Vanadate

*Elkady M.F.

1,2, Feteha M.Y.

3, El Essawy N.A

2, 3

1Chemical and Petrochemical Engineering Department, Egypt-Japan University of Science and Technology,

New Borg El-Arab City, Alexandria, EGYPT

2Advanced Technology and New Materials and Research Institute (ATNMRI), City of Scientific Research and

Technological Applications, Alexandria, EGYPT 3Institute of Graduate Studies and Research, Department of Materials Science, University of Alexandria, Alexandria,

EGYPT

(Received 13th

February 2014, Accepted 23rd

March 2014)

Available online at: www.ijrce.org

Abstract: Cesium-doped zirconium vanadate with doping ratio (Cs/Zr) equivalent to 0.1 were

fabricated using two different techniques of sol gel and hydrothermal. Thermal modification

treatment of this innovativenano-material was assigned using microwave technology at various

treatment conditions. The modified thermally treated cesium doped zirconium vanadate materials

were characterized for their phase and morphology using X-ray diffraction and scan electron

microscopy. The X-ray diffraction results investigated that all synthesized and thermally treated

specimens have cubic phase structural without any extra phase. However, the scan electron

microscopy examination indicates that the synthesized materials have nano-structure morphology

that was converted into micro-structure with thermal treatment. The electrical properties of this

material was determined by alternative current (ac.) impedance measurements. Finally, as

comparable study between cesium doped zirconium vanadate and its parentzirconium vanadate the

influence of preparation technique variation, the presence of doping element and the thermal

treatment on their properties have been considered.

Keywords: doping, impedance, ionic conductivity, microwave sintering.

Introduction

The existence of zirconium pyrovanadate

(ZrV2O7) was first reported by Peyronel [1]

in 1942. It

belongs to the AX2O7 (A = Zr, Hf and X = P, As, V)

families of compounds and has a framework structure

with space group symmetry Pa3, Z = 4. It displays two

first order structural phase transitions at 77ºC and

102ºC [2, 3]

. ZrV2O7 belongs to a 3x3x3 superstructure

at room temperature which vanishes above 102ºC, and

a strong isotropic negative thermal expansion behavior

is reported for the temperature up to 800 ºC. The

superstructure for this compound was established from

single crystal synchrotron data, high-resolution

neutron powder diffraction data, and electron

diffraction studies [4-6]

.

There are many synthetic processes currently

being used to produce Zirconium vanadateas sol–gel

technique, homogeneous precipitation, solid state

reaction and hydrothermal technique. The sol–gel

method, in particular, is one of the most useful and

attractive techniques for the synthesis of nano-sized

materials. This is regarded to its advantages such as

good stoichiometric control and the production of

ultrafine particles within narrow size distribution at a

relatively short processing time at very low

temperature[7]

.

While the hydrothermal method that

represents a soft-chemical method, resulting in the

formation of homogenized high purity products with

reduced particle sizes and larger surface area[8]

. This

synthesized technique has already been applied to

synthesize nano-sized ZrV2O7 with polycrystalline

http://www.ijrce.org/


[185]

phase and small crystallite size[9]

.

The previously stated research literatures

illustrated that there were many scientists were

considered with the behavior of zirconium vanadate

under different conditions. Some researchers stated

that ZrV2O7 undergoes a reversible phase transition

upon application of pressure at 1.38-1.58 GPa, where

it converted from cubic (α phase) to pseudo-tetragonal

(β phase). This converted phase displayed an

orthorhombic 2x3x3 super cell [10]

.Other researchers

were explored that the room temperature Raman and

infrared spectra of ZrV2O7 have been collected at 12

and 5.7 GPa and support the phase transition behavior

established by high pressure X-ray diffraction [11]

.

On the other hand, ZrV2O7 electrical

conductivity has also been investigated for the

prepared and hot pressed samples, where they were

showed good electrical conductivity suggesting

semiconductor n-type behavior, which ranges from 10-

5 to 10

-6 Ω

-1 cm

-1[12]. Moreover, zirconium vanadate

has been successfully utilized by numerous researches

as inorganic ion exchanger for the separation of 134

Cs

and 152

Eu from a synthetic mixture [12,13]

. Finally, many

zirconium vanadate solid solutions have been

established and there thermal expansion behaviors

have been considered. Where, various solid solutions

were developed from ZrV2O7-ZrP2O7 (0≤x ≤2.0) and

Zr1-xHfxV2O7 (x = 0-1) series, and their isotropic

thermal behaviors have been examined [3,14]

.

Generally, doping is the practice of adding

impurities to the material in order to alter its

properties. Xianran Xing and Zhenqi Zhu were

prepared zirconium vanadate doped with zirconia and

vanadium (V) oxide by solid state reaction and sol –

gel methods. They found that, the doping doesn’t

effect on the crystal structure neither nor its thermal

properties [13]

. While, other researchers were found that

the photo-catalytic activity of synthesized

molybdenum doped zirconium vanadate produced

from the solution combustion method was enhanced

toward the degradation of non-azoic dyes compared

with its parent zirconium vanadate [12]

.

However, till now there is no investigations

deal with the doping effect of mano-valent cations

(such as cesium ions) on the crystal, morphology and

electrical properties of zirconium vanadate.

Accordingly, cesium doped zirconium vanadate will

be synthesized in this investigation using two different

preparation techniques of sol-gel and hydrothermal,

where the sol-gel method represents the simplest

preparation techniques for powdered materials

production. Moreover, the hydrothermal doping

method was hoped to create a rational dopant alkali

metal distribution in ZrV2O7 with avoiding the

formation of heterogeneous metal oxides phases.

These synthesized materials will be thermally

modified using microwave advanced heating

technology.

Microwave processing of materials is the

technology that can provide new, powerful, and

significantly different tool for materials processes or to

improve the performance characteristics of existing

materials. In many cases, materials processing using

microwave technology have numerous advantages in

their properties compared to that using the traditional

materials processing techniques [15-18]

. Respecting to

this concept, microwave technology will be utilized as

a sintering process tool for thermal modification the

synthesized zirconium vanadate and its cesium

dopants.

As an innovative study the effect of both the

alkali metal (cesium) doping and the microwave

sintering processing onto zirconium vanadate crystal,

morphology and electrical properties will be explored.

This research activity will be highlighted through

studying: (i) the preparation possibility of cesium-

doped zirconium vanadate using two different

preparation techniques of sol gel and hydrothermal, (ii)

discuss the effect of cesium doping on the ionic

conductivity of prepared zirconium vanadate , in

which the ionic conductivity in zirconium vanadate is

closely related to oxygen-vacancy formation and

migration properties (iii) examine the sintering effect

on the prepared samples using microwave technology,

(iv) establishment the effect of both cesium doping and

thermal treatment onto the crystalline nature,

morphological structure and electrical properties of

prepared zirconium vanadate and their cesium-dopant

produced from each technique.

Material and Methods Materials and equipment: The main reagents used

for synthesis Zirconium vanadate and its cesium

dopant was Zirconium oxy chloride (AVONCHEM,

United Kingdom), Sodium vanadate (ACROS, USA),

Cesium chloride (APPLICHEM, Germany), and

Hydrochloric acid (ALDRICH, USA.). All chemicals

were of analytical grade. The main instruments used in

the preparation and heat treatment modification are

analytical balance with shield chamber 4 digits

(Sartorius, Model CP225D, Germany), Magnetic hot

plate with stirrer (Stuart, Model SB 162, United

Kingdum), Autoclave (Systec, Model 3850-EL),

Drying oven ( Nabertherm, Model TR60, Germany),

Vacuum pump (Barnant, Model 400-3912, USA), and

Microwave Assisted Technology (MAT) furnace

(CARBOLITE , Model MRF 16/22 ,UK).

Preparation techniques of nano-cesium doped

zirconium vanadate: Zirconium vanadate

nanopowder and different samples of zirconium

vanadate doped with cesium were prepared by two


[186]

different techniques namely sol–gel precipitation and

hydrothermal synthesis using zirconium oxy chloride

and sodium vanadate in presence of hydrochloric acid

as shown in figure 1 and 2.

Figure 1: Preparation scheme for zirconium vanadate nano-powder doped with cesium as a dopant element

using sol gel technique.

Figure 2: Preparation scheme for zirconium vanadate nano-powder doped with cesium as a dopant element

using hydrothermal technique.

Thermal modification for the prepared samples using microwave technology: The different

synthesized samples either that doped or un-doped

have been sintered using Microwave Assisted

Technology (MAT). The prepared powdered samples

were exposed to two different types of heating

techniques that include conventional heating only and

conventional associated with microwave heating. For

conventional heating, the influence of heating

temperature (500,600ºC) variation on the materials

properties was elucidated at constant exposure time

interval (30min). However, the prepared powdered

Aqueous solution NaVO3

+ 0.1M HCl

Mixing with magnetic

stirring on cold

Yellow precursors formed, interred into autoclave

for 60min at 120oC.

The precipitate was washed thoroughly and dried by

gentle heating at 40oC .Then the product was

grounded

The reaction mixture was diluted in 1 L of ultra pure

water and allowed to settle for 24 h.

Cl-

free precipitate

Filtering and washing

Aqueous solution ZrOCl.8H2O

+ CsCl

Aqueous solution ZrOCl.8H2O + CsCl

Aqueous solution NaVO3 +

0.1M HCl

Mixing with magnetic stirring

Yellow gel precursors formed, The reaction mixture was diluted to 1 l and allowed to settle for 24 h.

added dropwise

The precipitate was washed thoroughly and dried by gentle

heating at 40oC , then the product is grounded

Cl-

free precipitate

Filtering and washing


[187]

materials was heated gradually at specific heating

temperature (either 500 or 600) using conventional

heating then exposed to microwave radiation for

another 30min. The properties of all thermally treated

materials were examined using the different

characterization techniques.

Characterization of the synthesized nano-cesium

doped zirconium vanadate : The influence of both

cesium doping and microwave heat treatment on the

crystal, morphology and electrical properties of nano-

zirconium vanadate samples were monitored through

the different characterization tools of XRD

(Schimadzu-7000, U.S.A.) with CuKα radiation beam

(λ=0.154060 nm), SEM (JEOL JSM 6360LA, Japan)

and impedance measurement procedure using a

computer controlled Gamry Instruments a

Potentiostats/ Galvanostat (Model: Zr, G750) at a

frequency range 10-300000 Hz.

Results and Discussion Crystalline structure detection of prepared

materials using X-ray diffraction (XRD): X- ray

diffraction patterns of prepared zirconium vanadate

showed that samples prepared using sol gel have

amorphous nature, while those produced from

hydrothermal technique have some degree of

crystallinity. Accordingly, the hydrothermally

prepared materials can be considered as polycrystalline [9]

. In order to elucidate the cesium doping effect on

the crystalline nature of prepared zirconium vanadate,

the XRD patterns of cesium doped ZrV2O7 samples

which prepared by sol gel technique have amorphous

structure without any preferred orientation, similar to

the un-doped samples (figure 3), so, the cesium dopant

element has no effect on the amorphous structure of

zirconium vanadate prepared using sol gel technique

possibly demonstrating that, the quantity of the dopant

element was small.

On the other side, comparing the X- ray

diffraction patterns of both cesium- doped and

undoped zirconium vanadate samples produced from

the hydrothermal technique (figure 3). Similarity was

induced between pure nano powder zirconium

vanadate and its cesium dopant, where no additional

peaks that may represent cesium impurities were

observed, which indicates the high purity of the

obtained Cs co-doped materials [19]

.

Regarding to there is no observation in the X-

ray spectrum of cesium doped zirconium vanadate

structure for any diffraction peaks arising from the

possible impurity phase’s formation inside its structure

such as Cs2O, this is demonstrating that Cs ions were

dispersed uniformly onto ZrV2O7 nanoparticles. These

results confirmed that there is no other compounding

was produce beside the prepared cesium doped

zirconium vanadate.

So, the cesium element was completely doped

inside zirconium vanadate structure and there is no

other cesium compounding production as impurities.

In addition, there is little shifting for all characteristics

peaks toward lower diffraction angle, which is

corresponding to the increase of the interlayer distance

due to the partial replacement of Zr atoms in ZrV2O7

by Cs atoms that has larger ionic radius compared with

Zr atoms.

10 20 30 40 50 60 70 800

200400600800

10001200140016001800

10 20 30 40 50 60 70 80

0

100

200

30010 20 30 40 50 60 70 80

0400800

12001600200024002800

10 20 30 40 50 60 70 80600700800900

1000110012001300

(d)

Inte

nsity

(Arb

itra

ry u

nit)

(a)

(b)

(c)

2 (degree) Figure 3: XRD patterns of (a) ZrV2O7 particles

prepared by sol gel, (b) ZrV2O7 particles prepared

by hydrothermal, (c) Cs doped ZrV2O7 particles

prepared by sol gel, (d) Cs-doped ZrV2O7 particles

prepared by hydrothermal.

Effect of microwave sintering on crystalline nature of nano-cesium doped zirconium vanadate: As the

different prepared cesium doped zirconium vanadate

samples were thermally treaded using microwave

sintering, so, their crystallinity degree will be

improved as expected. Increasing heat treatment

temperature and microwave radiation exposure

improves the characteristics peak intensities for all

prepared materials that by its role convert their

amorphous structures into polycrystalline structures as

illustrated from figure 4. All the characteristics

material peaks were indexed based on the cubic unit

cell through comparing their spectrums patterns with

zirconium vanadate reference cards (01-088-0583, 01-

088-0584, 01-088-0585, 01-088-0586 & 01-016-

0422).

Morphological structure detection of prepared

materials using Scanning electron microscopy

(SEM)


[188]

300

600

900

10 20 30 40 50 60 70 80

300

600

900

300

600

900

10 20 30 40 50 60 70 80

300

600

900

(c)

Inte

nsity

(Arb

itrar

y un

it)

2 (d e g r e e)

(b)

(a)

c(22

0)c(21

1)

c(21

0)

c(20

0)

c(11

1)

c(31

1)

(d)

Figure 4 : Effect of microwave sintering on XRD

pattern of undoped and Cs-doped ZrV2O7 samples

prepared by hydrothermal , (a) ZrV2O7 sintered

sample using conventional heating at 500°C

followed by microwave radiation for 30min., (b)

ZrV2O7 sintered sample using conventional heating

at 600°C followed by microwave radiation for

30min., (c) Cs-doped ZrV2O7 sintered sample using

conventional heating at 500°C followed by

microwave radiation for 30min.,(d) Cs-doped

ZrV2O7 sintered sample using conventional heating


30min.

(a)

(b)

(c)

(d)

Figure 5: SEM micrograph of prepared samples

using two different techniques (a) ZrV2O7prepared

by sol-gel method (b) ZrV2O7 prepared by

hydrothermal method, (c) Cs- doped ZrV2O7

prepared by sol-gel method, (d) Cs doped ZrV2O7

prepared by hydrothermal method.

Comparable study on the morphological

structure of both cesium doped and un-doped nano-

zirconium vanadate samples was investigated to

demonstrate the influence of microwave radiation and

conventional heat treatment techniques. Typical SEM

micrographs of undoped and cesium doped ZrV2O7

nano-specimens were investigated at figure 5, a non

uniform distribution of particles for all prepared

samples was explored. However, the average particle

sizes of materials produced from hydrothermal

technique were comparatively smaller than that

produced from sol-gel technique.

As these synthesized nano-materials thermally

treated, changes in the particle shapes and sizes were

induced by thermal treatments especially for undoped

ZrV2O7 produced from sol gel technique. It can be

elucidated from figure 6 that the morphological

structure of samples produced from two techniques

then heated conventionally only at 500°C consisted of

multifaceted particles, as the heating temperature

incremented up to 600°C the majority of particles tend

to agglomerate without a well-defined particle shape.

However, utilizing the conventional heating at 600°C

followed by microwave radiation for 30min (figure 7-

a) the particle surfaces became smooth and well-

defined.

(a)


[189]

(b)

Figure 6: Effect of convention sintering

temperature on SEM morphology for prepared

samples (a) at 500°C, (b) at 600°C.

(a)

(b)

(c)

(d)

Figure 7: SEM image for different samples sintered

using conventional heating at 600°C followed by

microwave radiation for 30min., (a) ZrV2O7

particles prepared by sol gel technique, (b) ZrV2O7

particles prepared by hydrothermal technique (c)

Cs doped ZrV2O7 particles prepared by sol gel

technique,(d) Cs doped ZrV2O7 particles prepared

by hydrothermal technique.

The average size of the well-defined

agglomerated particles ranged between 1 μm to 0.5

μm. Accordingly, it is notable that the microwave

sintering process increases the densification behavior

of ZrV2O7 and enhances the grain-growth rate of the

materials. While considering the undoped ZrV2O7

material produced from the hydrothermal technique

figure (7-b), its particle surfaces became smooth and

well-defined compared with that produced from sol gel

technique. In order to assign the microwave influence

in the sintering process compared with conventional

heating, figure 8 investigated that the grain growth rate

of the microwave treated samples is markedly larger

than that of the conventional only treated samples.

Where, a progressive increase in grain size

due to the heat treatments was observed that by its role

reduces the surface areas of the heat-treated samples.

Concerning the cesium doping effect on the sintering

process, the material morphological structure was

transformed from homogeneous agglomerated

particles for the undoped sample (figure 7-b) into two

distinct morphological structures of the rod-like shapes

beside the agglomerated particles at doped sample

(figure 7-d). The average aspect ratio of produce

micro-rods was equal to 8, the formation of these

micro-rods may be related to the intrinsic tension

inside the material particles that have tendency to

release their stress and decrease their total energy

through plates splitting into rods, which results in the

micro-rods formation as shown in figure (7-d).


[190]

(a)

(b)

Figure 8: Effect of sintering technique on SEM

imaging of Cs- doped ZrV2O7 samples prepared by

hydrothermal technique (a) sintered using

conventional heating only at 600°C for 30min.,(b)

sintered using conventional heating at 600°C

followed by microwave radiation for 30min.

Impedance measurements of prepared materials:

Respecting to the distinguish cubic structure of

zirconium vanadate, the unshared terminal oxygen ion

of the VO4 tetrahedron may hop between two

equivalent sites accompanied by breaking and

rebuilding of the bond between vanadium and the

terminal oxygen [20, 21]

. This process seems to be

similar to the oxygen migration responsible for the

ionic conductance observed in Ln2O3 stabilized ZrO2

and CeO2 solid electrolytes [20-23]

.

It is well known that more oxygen vacancies

can be produced in selected solid solutions containing

substituted low-valent ions [20-21, 24]

. Thus, it would be

expected that low-valent ions introduce in the crystal

lattice of ZrV2O7 may modify its conductivity.

According to this consideration, the influence of

cesium ions as mono-valentcations on the material

conductivity has been conducted.

Impedance measurements without thermal modifications: Figure 9 shows complex impedance

spectrum (Nyquist plots, i.e., Z' versus Z'') at room

temperature for undoped and doped zirconium

vanadate that were produced from the two different

preparation techniques. The impedance spectra are

composed of one arc or two,the intercepts of the

semicircular arc at high frequency with the real axis

(Z) give prediction about the material grain resistance [25-27]

.As previously recorded from XRD & SEM

results, all prepared materials are free from second

phases and intergranular films and they may be

representing polycrystalline ceramics.

Thus, their oxygen ion conductivity comprises

grain and grain boundary contributions [21, 28-30]

inside

the material structure. Figure 9 (a, b) shows a single

semicircle obtained at high frequency that attributed to

the superposition of grain and grain boundary effects

for nano-polycrystalline ZrV2O7 produced from the

two different preparation techniques. The bulk

conductivities, as terminated from the high frequency

intercepts on the real axis for polycrystalline ZrV2O7

showed no dependence on grain size, which may be

due to nanometer material size, where, the distinction

between grain and grain boundary regions tends to

vanish as the grain size reduced [31]

.

0.0 500.0k 1.0M 1.5M 2.0M

0.0

200.0k

400.0k

600.0k

0.0 100.0k 200.0k 300.0k 400.0k

Z im

ag (

ohm

)

Z real (ohm )

(a)

0.0 5.0k 10.0k 15.0k 20.0k 25.0k 30.0k 35.0k 40.0k 45.0k 50.0k

0.0

2.0k

4.0k

6.0k

8.0k

Z im

ag (o

hm )

Z real (ohm )

(b)

0.0 20.0k 40.0k 60.0k 80.0k 100.0k 120.0k 140.0k

0

10k

20k

30k

40k

Z im

ag (o

hm )

Z real (ohm )

(c)


[191]

0.0 50.0k 100.0k 150.0k 200.0k 250.0k 300.0k 350.0k 400.0k 450.0k

0

100k

200k

300kZ

imag

(ohm

)

Z real (ohm ) (d)

Figure 9: Impedance spectroscopy measurements

at room temperature for a) ZrV2O7 (sol-gel),b)

ZrV2O7(hydrothermal), c) Cs-doped ZrV2O7 (sol-

gel),d) Cs-doped ZrV2O7 (hydrothermal).

While Nyquist plots for cesium doped ZrV2O7

produced from the two different techniques have been

observed as two overlapping semicircular arcs as

investigated in figure 9 (c, d). These results are

compatible with the previous researchers results on

other ionic conductor materials [26, 29, 32-34]

, where, the

grain properties are associated with the semi-circular

arc at higher frequencies, whereas the grain boundary

properties are associated with the semi-circular arc at

lower frequencies [26, 29]

.

Effect of microwave sintering on impedance

measurements: The electrical measurements were

carried out on both undoped and cesium doped ZrV2O7

samplessintered at 500ºC and 600 ºC with and without

microwave radiation. From their impedance

measurements, the bulk conductivities of the different

samples are tabulated in table 1. It was elucidated from

this table that the ionic conductivity of the materials

varies strongly with the sintering conditions [35]

.

Comparing the conductivity values of the different

prepared and sintered materials that stated at table 1

and figure 10, the following observations were

noticed:

The samples prepared by hydrothermal technique

has more conductivity than those prepared using

sol gel technique, this is probably due to the

hydrothermally prepared samples have more

densification structure (less porosity) than the

comparable sol gel produced samples. This

reduction in conductivity may be attributed to

more porosity of sol gel materials that can be

considered as oxygen ion transportation trap [35, 36]

.

The samples modified using microwave radiation

has more conductivity comparable to those

modified using conventional heating only at the

same temperature, this is probably regarded to the

microwave heating may improve the material

densification structure.

The conductivity of cesium doped zirconium

vanadate was decreased compared with the

undoped samples. This may be regarded to the

blocking effect of the Cs 1+

ions located at the

materials grain boundaries that hindering the

oxygen ion transportation which is the main

responsible for the ionic conductivity of material [35,37-38]

.

The sintering process has negative effect on the

ionic conductivity profiles of all sintered samples

except that attain the micro-rod structure. This

may be attributed to the samples before heat

treatment have unstable structures (amorphous for

sol gel preparation or polycrystalline for

hydrothermal preparation) which contain water

molecules and high density of atoms disorder that

by its role improve the ionic conductivity of the

materials [39-42]

. However, after materials thermal

treatment their structures go to their stability states

and the degree of ordered atoms increased that

reduce the materials conductivities.

Moreover, as the heat treatment temperature

or the heat energy absorbed by microwave

radiation incremented, the materials conductivities

were increased. This is may be regarded to the

reduction of grain boundaries and enlargement of

grain sizes, which improve the materials ionic

conductivity.

Regarding to the prepared material that attain

micro-rod structure for cesium doped zirconium

vanadate produced from hydrothermal technique,

its grain resistances are smaller than the grain

boundary resistances as illustrated from figure 10

(d). This behavior may be attributed to the

breakdown of the agglomerated grains into rod

structure [37]

.

0 1M 2M 3M 4M 5M

0.0

2.0M

4.0M

0.0 1.0M 2.0M 3.0M 4.0M 5.0M

Z im

ag (o

hm )

Z real (ohm )

(a)

10M

9M

8M

7M

6M

5M

4M

3M

2M

1M

0

0.0 1.0M 2.0M 3.0M 4.0M 5.0M 6.0M 7.0M 8.0M

Z im

ag (o

hm )

Z real (ohm ) (b)


[192]

0 100k 200k 300k 400k 500k

0

100k

200k

300kZ

imag

(ohm

)

Z real (ohm )

(c)

0.0 5.0M 10.0M 15.0M 20.0M

0.0

5.0M

10.0M

15.0M

20.0M

0.0 2.0M 4.0M 6.0M 8.0M

Z im

ag (o

hm )

Z real (ohm )

Figure 10: Impedance spectroscopy measurements

at room temperature for different sintered samples


30min. (a) ZrV2O7 (sol gel), (b) ZrV2O7

(hydrothermal), (c) Cs doped ZrV2O7 (sol gel), (d)

Cs-doped (hydrothermal).

Conclusion

The X-ray spectrums of zirconium vanadate

samples either that doped or undoped produced

from the sol–gel technique has an amorphous

structural, while those produced from the

hydrothermal synthesis technique have semi-

crystalline structural, and the plane orientation not

affected by dopants addition.

The SEM morphological structure of the prepared

samples confirms their nano-size structures. The

cesium dopant element has a great effect on the

innovative prepared cesium doped zirconium

vanadate.

Sintering conditions has considerable effect on the

crystalline, morphological and conductivity for

both undoped and cesium dopant zirconium

vanadate.

The micro-rods architecture of cesium doped

zirconium vanadate has been acquired through the

thermal treatment of hydrothermally produced

material at 600°C with microwave radiation for 30

min. This simple method for materials

architecturing expected to be of great importance

for the materials utilization at different industrial

applications such as catalysis,

adsorption/separation and in nano-devices.

Table 1

The bulk conductivities A.C. at room temperature for prepared samples

Sample ID σ A.C. X 10-6

ZrV2O7(sol gel), without heat treatment 0.6 Ω-1

cm-1

ZrV2O7(sol gel), sintered using conventional heating only at 500°C for 30min. 0.028 Ω-1

cm-

1

ZrV2O7(sol gel), sintered using conventional heating at 500°C followed by microwave

radiation for 30min.

0.037 Ω-1

cm-

1

ZrV2O7(sol gel), sintered using conventional heating only at 600°C for 30min. 0.09 Ω-1

cm-1

ZrV2O7(sol gel), sintered using conventional heating at 600°C followed by microwave

radiation for 30min.

0.12 Ω-1

cm-1

ZrV2O7 ( hydrothermal), without heat treatment 3.5 Ω-1

cm-1

ZrV2O7(hydrothermal), sintered using conventional heating only at 500°C for 30min. 0.056 Ω-1

cm-

1

ZrV2O7(hydrothermal), sintered using conventional heating at 500°C followed by

microwave radiation for 30min.

0.12 Ω-1

cm-1

ZrV2O7(hydrothermal), sintered using conventional heating only at 600°C for 30min. 0.2 Ω-1

cm-1

ZrV2O7(hydrothermal), sintered using conventional heating at 600°C followed by


0.32 Ω-1

cm-1


[193]

Cs doped ZrV2O7 (sol-gel), without heat treatment 0.4 Ω-1

cm-1

Cs doped ZrV2O7(sol gel), sintered using conventional heating only at 500°C for 30min. 0.04 Ω-1

cm-1

Cs doped ZrV2O7(sol gel), sintered using conventional heating at 500°C followed by


0.05 Ω-1

cm-1

Cs doped ZrV2O7(sol gel), sintered using conventional heating only at 600°C for 30min. 0.07 Ω-1

cm-1

Cs doped ZrV2O7(sol gel), sintered using conventional heating at 600°C followed by


0.29 Ω-1

cm-1

Cs doped ZrV2O7(hydrothermal), without heat treatment 1.83 Ω-1

cm-1

Cs doped ZrV2O7(hydrothermal), sintered using conventional heating only at 500°C for

30min.

0.07 Ω-1

cm-1

Cs doped ZrV2O7(hydrothermal), sintered using conventional heating at 500°C followed

by microwave radiation for 30min.

0.13 Ω-1

cm-1

Cs doped ZrV2O7(hydrothermal), sintered using conventional heating only at 600°C for

30min.

0.12 Ω-1

cm-1

Cs doped ZrV2O7(hydrothermal), sintered using conventional heating at 600°C followed

by microwave radiation for 30min.

2.91 Ω-1

cm-1

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