Influence of iron ions on the structural properties of some inorganic glasses J Radioanl Nucl Chem...

Journal ofRadioanalyticalandNuclear Chemistry, Articles, Vol. 116, No. 1 (1987) 141-157

INFLUENCE OF IRON IONS ON THE STRUCTURAL PROPERTIES OF SOME INORGANIC GLASSES

s. Musld' M. GOTI~, S. POPOW~, ~. Cn~ETA

~ Rudjer Bo~kovi~ Institute, P,O. Box 1016, 41001 Zagreb (Yugoslavia)

(Received February 17, 1987)

The effects of iron on the structural properties of Zn-borosilieate glass and Pb-metaphosphate glass were studied using X-ray diffraction, s ~Fe M~ssbauer spectrosCopy and IR spectroscopy. Zn-borosilieate glass was prepared with varying amounts of Fe 203 (up to 30% wt.). It was found that the chemical form of added iron (,,-FeOOH, a-Fe203 or Fe304) affects the Fe3+/Fe 2§ ratio, as well as the distribution of iron ions at different coordination sites. At high concentration of iron the crystallization of zinc ferrite in the glass matrix takes place. X-ray diffraction and 5 ~Fe M6ssbauer spectroscopy showed that the amount of zinc ferrite in Zn-borosflieate glass decreases with the following order of addition: a-FeOOH~t~-Fe203-*F%O 4 . In Pb-metaphosphate glass doped with high concentration of a-Fe20 ~, the erystaUization of Fe3(PO,) 2 is pronounced. The assignments of IR band positions and the corresponding interpretation are given. The importance of this study for the technology of vitrification of high-level radioactive wastes is emphasized.

Introduction

Inorganic glasses are very important materials in modem technologies. Recently,

Zn-borosilicate and Pb-phosphate glasses gained importance, due to their potential

use as a matrix for the immobilization of high-level radioactive wastes. 1 - s

Zn-borosilicate glasses have already found application as surface passivants in the

fabrication of silicon power devices, such as thyristors, transistors and diodes. 6 - s

The principal composition, ZnO-B2 O3-SIO2, can be modified by doping the glass with Pb 2§ Sb 3+, Sn 2+, etc.

Pb-phosphate glasses are characterized by low preparation temperatures and low

softening points. Also, they tend to crystallize at temperature as low as 300 ~ Due to these properties, the Pb-phosphate glasses are suitable materials for fundamental

studies of t t~ devitrification and phase transitions in glasses. Pure Pb-phosphate glasses are very susceptible to corrosion in aqueous medium. SALES, BOATNER and

Elsevier Sequoia S. A., Lausanne Akaddmiai Kiad6, Budapest

S. MUSI~ et al.: INFLUENCE OF IRON IONS ON THE STRUCTURAL

coworkers have found 3 -s that the presence of 9% Fe203 (by weigllt) in Pb- metaphosphate glass increases the corrosion resistance of this glass in aqueous medium by a factor of 10. 4 Also, they found that the crjstallization of pure Pb-metaphosphate glass is greatly suppressed by the addition of Fez O3

The present study was undertaken (1) to determine the experimental conditions for the preparation of Zn-borosilicate glass and Pb-metaphosphate glass, (2) to determine the influence of iron ions on the structural properties of these glasses, and (3) to obtain information about valence and coordination of iron ions in glass mhtrix.

Experimental

The following chemicals were used for the preparation of glasses: H3 BO3, Na2 CO3, CaCO3, MgO, SrCO3, BaCO3, ZnO, K2 CO3, PbO and NH 4 H2 PO4. All chemicals were A. R. grade. Amorphous SiO2 was prepared by the precipitation method. 9 The characterization of o(-FeOOH, o~-Fe203 or Fe304 was described in a previous paperJ ~ The preparation of glasses was as follows.

Appropriate amounts of the corresponding chemicals in powdered state were mixed, A small hmount of bidistilled water was added to this mixture, and after homogenization, the mixture was heated at 105 ~ NH4H2PO4 was used in prefer- ence to P2Os, because P2Os is extremely hygroscopic. Dried mi~ture of the chemicals was powdered, and then melted in contact with air. The temperature in the furnace was increased gradually to prevent uncontrolled foaming. The molten glass was poured into a preheated (200-300 ~ C) graphite mould, and then the glass was cooled to room temperature. Zn-borosilicate samples were doped with Fe2 O3, which was originally added to the mixture of chemicals in the form of a-FeOOH, ct-Fe203 or Fe3 04. Pb-metaphosphate glasses were prepared only with a -Fe 2 03. The experimental conditions for the preparation of glass samples are given in Table 1.

X-ray powder diffraction measurements were performed at room temperature using a counter diffractometer with monochromatized Cu Ks radiation (Philips diffractometer, proportional counter, graphite monochromator).

M6ssbauer spectra were recorded using a commercial spectrometer produced by Wissenschaftliche Elektronic GmbH (D-8130 Starnberg, West Germany). s 7 Co/Rh source was used. The standard absorbers ct-Fe, a-Fe203 and S TFe/Rh were also used.

The infrared spectra were recorded using Perkin-Elmer spectrometer, model 580B. The specimens (glass powder) were pressed in KBr discs.

142


Table 1 Experimental condffions for the preparation of glass samples

Heating time Temperature Sample Chemical composition, wt. % of melt of melt, ~

BSZn 37% SiO2, 15.2% B203, 5.5% Na20 4 h 1000 5.5% K20, 2.0% CaO, 2.0% MgO, 2.0% SrO, 2.0% BaO, 28.8% ZnO

BSZn-1 +5% Fe 2 03 (added as ~FeOOH)

BSZn-2 +15% Fe 203 (added as oL-FeOOH)

BSZn-3 +30% Fe 2 03 (added as a,-FeOOH)

BSZn4

BSZn~

BSZnM

BSZn-7

BSZn-8

BSZn-9

PbP-1

PbP-2

PbP-2: o o

PbP-3' o o

PbP-4

PbP-5

+5% Fe20~ (added as a-Fe203)

+15.% Fe203 (added as c~-Fe2 O3)

+30% Fe~O 3 (added as ceFe203)

+5% Fe203 (added as F%O 4)

+15% Fe203 (added as F%O4)

+30% Fe203 (added as Fe~ O4)

45% PbO, 55% P401 o

50% PbO, 50% P401 o

50% PbO, 50% P401 o

(50% PbO, 50% P401 o ) + 10% a-Fe 203

(50% PbO, 50% P40~ o) + 21% a-F%O 3

(50% PbO, 50% P401 o) + 40% ~-Fe~ O 3

4 h 1000

4 h 1000

4 h I000 5 rain 1100

4 h 1000

4 h 1000

3.5 h 1000 I h ii00

4 h 1000

4 h 1000

3.5 h 1000 1 h 1100

1 h 950

1 h 950 15 rain

1 h 800

1 h 900 10 min

1 h 1000

1 h 1000

143

S. MUSIC et al.: INFLUENCE OF IRON IONS ON THE STRUCTURAL

Results and discussion

In this study, X-ray diffraction, s 7 Fe M6ssbauer spectroscopy and IR spectroscopy

were used as experimental techniques to ascertain the influence of iron ions on the

structural properties of Zn-borosilicate glass and Pb-metaphosphate glass. The experimental results can be presented 'as follows.

X-ray diffraction

The results of X-ray diffraction" phase analysis of selected glasses are shown in

Table 2. Crystalline phases were identified according to the JCPDS Powder Diffrac- tion File (International Center for Diffraction Data, Swarthmore, Pennsylvania).

Measurements of highest possible Bragg angles enabled to make a distinction

between FeaO4 and ZnFe~ 04 in Zn-borosilicate glass. FeaO4 and ZnFe: 04 possess the same space group (Fd3m) and the ionic radii of Fe 2+ and Zn 2+ are very similar.

Due to this" fact the diffraction lines of Fe3 04 and ZnFe: 04 have very similar posi-

Table 2 X-ray diffraction phase analysis of selected glass samples

Sample Composition

BSZn

BSZn-1

BSZn-3

BSZn~

BSZn~

BSZn-7

BSZn~

PbP-2

pbp~ 8~176

pbP-3 9oo

PbP~

Amorphous

Amorphous

Amorphous + ZnFe204 (~ 40%)

Amorphous

Amorphous (dominantly) + ZnFe 204 or F% 04 (~ 10%)

Amorphous

Amorphous (dominantly) + ZnFe 204 or Fe 304 (few percent)

Amorphous + unidentified crystalline phase (few percent)

Amorphous

Amorphous

F% (PO 4)2 (dominant) + amorphous + unidentified crystalline phase (few percent)

14a


tions. A significant amount of ZnFe2 04 ( " 40%) was found in sample BSZn-3. The X-ray diffraction results indicate a correlation between the amount of crystalline phase and the chemical form of iron. In Zn-borosilicate glass the amount of crystalline phase decreases in the following order of addition, a-FeOOH ~ tx-Fe203 -* Fe304. Evidently, Fe-oxyhydroxide, which is less stable, favours the crystallization of ZnFe2 04 in Zn-borosilicate glass. For samples BSZn-6 and BSZn-9 it was not possible

to measure precisely the positions of diffraction lines of the crystalline phase at highest Bragg angles, due to its low (content) amount. However, the crystalline phase in these samples may be ascribed to ZnFez 04 with much greater probability than to Fe304.

At lower concentrations of Fe2 03 (< 10%) the crystallization in Pb-metaphosphate glasses is not observed (sample PbP-39~176 However, with the increase in Fe20a content, the crystallization in Pb-metaphosphate ~ass occurs. The X-ray diffraction

analysis indicated the presence of well crystallized iron(III) phosphate, Fe3(P04) z (sample PbP-5). Also, in some phosphate glasses a small amount of unidentified crystalline phase is observed.

Table 3 shows angular positions of the amorphous maximum and the equivalent Bragg spacings for the selected glass samples. Diffraction pattern of each sample shows

Table 3 Angular positions of the amorphous maximum and the equivalent

Bragg spacings for the glass samples

Sample Amount of Angular position Equivalent of the amorphous Bragg spacing, A

added iron, wt. % maximum CO, Cu Ks)

BSZn Fe 203 not added 14.30

BSZn-1 5% Fe 2 O* 14.30

BSZn-3 30% Fe 2 O* 14.50

BSZn-6 30% ~-Fe 2 O 9 14.75

BSZn-7 5% Fe 2 O** 14.50

BSZn-9 30% Fe 20a** 14.60

pbP.2 s o o Fe2 03 not added 12.75

pbP.39 o o 10% ~-Fe 2 03 13.75

3.12

3.12

3.08

3.03

3.08

3.06

3.50

3.24

*Added as ~FeOOH. **Added as Fe3 O,.

10 145

S. MUSI(~ et aL: INFLUENCE OF IRON IONS ON THE STRUCTURAL

a broad maximum corresponding to the amorphous (glassy) component. The angular

position of this maximum is characteristic for a given (starting) chemical composition.

Addition of a-FeOOH, or a-Fe2 O3 or Fe 304 to the starting composition causes a shift of the amorphous maximum toward a higher diffraction angle. Generally, these

shifts may mean a change in interatomic distances and/or in the atomic environment

(coordination).

57Fe MOssbauer spectroscopy

M6ssbauer spectroscopy has been extensively used to obtain information about the structural properties of inorganic glasses. It is well known that s 7 Fe M6ssbauer

spectroscopy is able to give information on the oxidation state and the coordination

of iron ions. Also, M6ssbauer spectroscopy can be used to follow the crystallization

processes in glass materials. A review of M6ssbauer data on inorganic glasses has been published by DARBY DYAR. 11

The characteristic s 7Fe M6ssbauer spectra of Zn-borosilicate glasses prepared with

iron ions are shown in Figs 1, 2 and 3. These spectra were recorded at room temperature. They are characterized by the superposition of several doublets corresponding to the Fe 3§ and Fe 2§ ions. In the inorganic glasses the iron ions are not distinctly

distributed between different coordination sites. For this reason, in the M6ssbauer spectra the corresponding doublets are not well resolved. Table 4 shows the s 7Fe

M6ssbauer parameters of the quadrupole doubletg obtained for Zn-borosilicate glasses

doped with iron ions. M6ssbauer spectrum of sample BSZn-3 (Fig. 1) can be considered as the superposi-

tion of three doublets Q~, Q2 and Q3. In sample BSZn-2, the intensity of Q1 decreases

for account of the increase in Q2 and Q3 intensities. M6ssbauer spectrum of sample

BSZn-2 indicates the presence of quadrupole doublet Q4, which corresponds to a small amount of Fe(II). Evidently, the content of iron in Zn-borosilicate glass affects the shape of s 7 Fe M6ssbauer spectrum.

Quadrupole doublet Q~ can be ascribed to zinc ferrite, due to the following

reasons. The X-ray diffraction showed the presence of crystalline phase in Zn-borosl-

licate glass, which can be ascribed to ZnFe204. Also, on the basis of the X-ray diffraction patterns, it can be concluded that this phase in the glass matrix is not in the form of superparamagnetic particles (particles of very small dimensions). The M6ss- bauer parameters obtained for the Q~ component are in agreement with those measured 12 for ZnFe2 04 (6 = 0.338 mm/s and A = 0.341 mm/s). SIMMONS and MUSI~ have.shown that M6ssbauer spectrum 12 of Zno .8 Fe2.2 04 is also characterized by a quadrupole doublet (6 = 0.371 mm/s and A = 0.323 ram/s). With further increase in the Fe 2+ content in Zno.s Fe2.2 04, at room temperature, the hyperfine magnetic lines appear.

146


BSZn -3

"..,.

11 . b

S I g � 9 .*

. . ,. : , . , �9 . . .'.~

�9 T,

BSZn-2 ~ ,'- ," %

t p " - �9 .

:. I I I I "1 [

-t , -3 -2 -1 o 1

~ , oo

.-: !

I I I 2 3 4

mml$

Fig. 1. M6ssbauer spectra of samples BSZn-2 and BSZn-3 recorded at room temperature

Quadrupole doublet Q2 can be ascribed to Fe a+ ions in octahedral positions, and Q3 to Fe a+ ions in tetrahedral positions.

Figure 2 shows the MOssbauer spectra of samples BSZn-6, BSZn-5 and BSZn-4, which were prepared with a varying amount of Fe2 03 (added in the ~-Fe20a form). This figure indicates a general tendency observed in our experiments with Zn-borosilicate glasses. With decreasing Fe2 03 content in Zn-borosilicate glass, there is an increase in the intensity of the Q4 component corresponding to Fe(II). Approximately 50% of the total iron is present as Fe(II) in Zn-borosilicate glass at the content of 5% a-Fe20a (by weight). Also, with the decrease in Fe20a content in Zn-borosilicate glass, there is a corresponding decrease in the content of zinc ferrite phase.

Figure 3 shows the M6ssbauer spectra of samples BSZn-9 and BSZn-8 recorded at room temperature. Samples BSZn-9 and BSZn-8 were prepared with Fe203, which was originally added in the chemical form of Fe3 04.

10, 147


BSZn - 6 " :

�9 ;

" v : "

:::f - :,, ....";k-

�9 ~ IIKll Ir

; ,

BSZn - 5 ,r a, ~ , .

" ,t '~

~ : . . , : : , . . �9 ,/~. ~'.'.~'~'."~'/ .~.., ad. S S Z n - ~ , ....:, �9

, . !

I I [ ] "r I I I I - 4 -~ - 2 -1 0 1 2 3 t,

m m / s

Fig. 2. M6ssbauer spectra of samples BSZn-4, BSZn-5 and BSZn-6 recorded at room temperature

In numerous studies of oxide glasses, the researchers did not pay proper attention to the effects of the chemical form of doped iron. For this reason, we studied the effects of the chemical form of doped iron (a-FeOOH, a-Fe203, Fe304) on the state of iron in Zn'borosilicate glass. There is also a great practical interest for the results of these experiments. Iron component can be present in a significant amount in high-level radioactive liquid, materials. High-level radioaetiv~ liquid wastes must be cherrdcally or thermally pretreated before the vitrification process. The chemical state of iron depends on the applied method of pretreatment of high-level radioactive wastes (derfitration with organic reductants or calcination).

The results presented in Figs 1, 2 and 3 (see the M6ssbauer spectra of samples BSZn-3, BSZn-6 and BSZn-9) undoubtedly indicate the influence of the chemical

148


form of iron on the shape of s 7 Fe M6ssbauer spectrum of Zn-borosilicate glass. The chemical form of iron (a-FeOOH, a-Fe20a or Fea04.) affects the Fea*/Fe 2§ ratio, as well as the distribution of Fe a§ and Fe 2§ ions at different coordination sites. The asymmetry of Fe a§ ions increases in the sequence BSZn-3 ~ BSZn-6 ~ BSZn-9. Also, the Q4 component is not present in sample BSZn-3, but it is present in the M6ssbauer spectra of samples BSZn-6 and BSZn-9. For small concentrations of iron, its valence state is determined by the redox number of Zn-borosilicate glass. At high concentrations, the iron oxide strongly affects the resulting glass oxidation state. This is a result of the nonequilibrium conditions between the Zn-borosilicate melt and the furnace atmosphere during the preparation of glass. Therefore, different states of iron in Zn-borosilicate glass can be expected when the glass is prepared by using different chemical forms of iron oxides. These statements are confirmed by our M6ssbauer spectroscopic measurements.

, ,= . ,,;.,,,..-. '~" " " " ~ " "~:"'J~'~ r. : :" .I . : ~:':" ""

B S Z n - 9 " ~ o

.~',e~.. 'X. : ' . �9 ,

%

BSZn -8

I I I -4 -3 -2

�9 t ".~

I ~ I -1 0 1

1 I I 2 3

m m l s

Fig. 3. M6ssbauer spectra of samples BSZn-8 and BSZn-9 recorded at room temperature

s 7Fe M6ssbauer spectra of Pb-metaphosphate glasses prepared with ct-Fe2 03 (samples PbP-4 and PbP-5) are shown in Fig. 4. These spectra indicate the presence of crystalline phase, which can be ascribed to Fe3 (P04)2. The M6ssbauer spectrum of Fe3(PO4)2 has been published by MATTIEVICH and DANON. 13 They prepared Fe3(P04)2 by dehydration of Fe3(P04)2 �9 3H20 at 800 ~ Fe3(P04)2, graftonite,

149


Table 4 s 7 Fe M6ssbauer parameters of the quadrupole doublets obtainect

for Zn-borosilicate glass containing iron

Sample Lines Isomer shift,* Quadrupole mm/s splitting, mm/s Identification

BSZn-2 Qx 0.33 0.35 zinc ferrite

Q2 0.22 0.92 Fe~}et

Q3 0.24 1.38 Fete t

Q4 1.15 2.70 Fe 2+ (small amount)

BSZn-3

BSZ~6

BSZn-8

BSZn~

Q1 0.36 0.36 zinc ferrite 3 + Q2 0.29 0.71 Feoe t

Qs 0.33 1.20 Fe~ t

Q4 not observed

Q1 0.39 0.32 zinc ferrite 3+ Q~ 0.33 0.78 Feoe t

Qs 0.39 1.24 Fete ta+

Q4 Fe 2+ (small amount)

Q, 0.33 0.35 zinc ferrite 3+ Q2 0.26 0.99 Feoc t

Q3 0.34 1.24 Fele t

Q4 Fe 2+ (small amount)

Q1 0.33 0.35 zinc ferrite

Q2 0.28 0.81 Feoc ta+

Q3 0.33 1.14 Fete t

Q4 Fe 3+ (small mount)

*Relative to a-iron

is characterized by a specific structure; 14 it possesses three non-equivalent sites for

the Fe 2+ ions, two 5-coordinate and one 7-coordinate. The X-ray diffraction and

s 7Fe M6ssbauer spectroscopic results presented in this work indicate that the crystalli-

zation processes are very pronounced in Pb-metaphosphate glasses containing more

than 21% Fe20a (by weight).

150


IR spectroscopy

IR spectroscopy is an important technique for the investigation of the structural properties of inorganic glasses, and it can be considered as complementary to X-ray diffraction and to other techniques for the study of glass structure. IR spectroscopy has not been extensively used in the study of Zn-containing glasses in spite of the fact that zinc has an important role in the improvement of chemical durability I s ,1 of inorganic glasses.

. .,,..,h,~ ."

~. : :

PbP-5

"�9

r

. f : . .

pbla-4

I I I I - 5 - 4 - 3 - 2 - 1

I ~ I I "~l I I 0 1 2 3 4 5

mm/s

Fig. 4. M6ssbauer spectra of samples PbP-4 and PbP-5 recorded at room temperature

Figure 5 shows the characteristic parts of the IR spectra of samples BSZn, BSZn-4, BSZn-5 and BSZn-6. Table 5 shows the characteristic IR band positions of Zn-borosilicate samples prepared with iron ions. The characteristic IR band positions for sample BSZn (not doped with Fe) are measured at 3440, 1400, 1255, 1000, 715 and 480 cm-1. The broad absorption band at 3440 cm-1 is typical for the O-H stratcbing

151

s. MUSIC et al.: INFLUENCE OFIRON IONS ON THE STRUCTURAL

vibration. Absorption peak at 1400 cm -1 can be related to the ring stretching vibrations of BOs triangles, and the peak at 1255 cm -1 to the bond stretching vibration

of the boron sublattice against oxygen sublattice) 7 A broad absorption peak of

strong intensity is observed at 1000 cm - t . This absorption peak can be considered

as the superposi~tion of two or more peaks which are not well separated. The strong

absorption band at 1000-980 "cm -~ can be ascribed to the stretching vibrations of Si-O and B - O bonds of 4-coordinated Si 4+ and B 3+. Absorption peak at 715 cm -a

is due to the B--O-B bond bending motion in the glass network. The strong and

broad absorption band at 480 era- a can also be considered as the superposition of several peaks which are not well separated. This band can be ascribed to the stretching vibration of ZnO4 tetrahedra as well as to the bending vibrations within Si04

tetrahedra (O-Si--O) and between SiO4 tetrahedra ( S i - O - S i ) J s -2

1400 I000 600 20O ~Icm "I

Fig. 5. Parts of IR spectra of samples BSZn, BSZn-4, BSZn-5 and BSZn-6

The presence of iron in Zn-borosilicate glass affects the corresponding IR spectrum. A general tendency of the shifts of IR band positions can be observed. Absorption

peaks at 1400, 1000 and 715 era-~ slightly shift toward lower wave numbers with the increase in the iron content. Broad absorption peak at 480 era-1 transforms to

152


".N

0

t ~

0

, m

~ t ~ ~10 ~ ~ ~ t ~

, D e'~ , G

0

II

0

II

t! . G

II

IJ

.g N II

0

II

153


a doublet at 15% Fe2Oa (by weight). With further increase in Fe20a content the separation of doublet peaks increases. In sample BSZn-3 the IR band at 480 cm- 1 shifts to 535 cm-1, and also there is a corresponding IR band shift in the opposite direction from 480 to 425 cm-1

PbP-4

1400 1000 600 200 q l c m -~

F~.6. Parts oflR spe~raofsamp~sPbP-2, PbP~ and PbP~

In a study of the Na20-ZnO-SiO2 system, HURT and PHILLIPS have observed 22

a shift of an IR band from 495 cm -1 (15 mole % ZnO) to 525 cm -1 (35 mole % ZnO). They explained this effect by the increase of Zn 2§ in tetrahedral sites. In the present work, the shift from 480 to 535 cm-1 is ascribed to an increase in the con- densed Fe 3§ in octahedral sites (sample BSZn-3). This conclusion is in agreement with the s 7Fe M6ssbauer spectroscopic results, which showed that the symmetry of iron ions increases with the increase in Fe2 03 content in Zn-borosilicate glass. The shift of IR band from 480 to 425 cm- 1 can be explained as the resultant effect of (a) the increase in isolated Fe3+O6 octahedra, 22 (b) the (Si, Fe)-O stretching vibration and (Si, Fe) -O deformation vibration, 23 and (c) the presence of S i - O - F e 2+(vI) bond. 2a The absorption band of the S i - O - F e 2+(vI) bonding is at lower frequency

owing to the larger Fe2+-(O-Si) distance and the more ionic character of the Fe2§ bond, than the Fe3+-(O-Si) bond. This IR absorption is more characteristic for the samples prepared with Fe304. Since the X-ray diffraction and M6ss-

154


bauer spectroscopy detected zinc ferrite, one could expect the IR absorpt ion in the

3 0 0 - 1 0 0 cm -~ range, due to the presence of ZnO6. However, in the present work

the IR recordings in the 3 0 0 - 1 0 0 cm- 1 range were not performed.

The characteristic IR spectra of phosphate glasses are shown in Fig. 6, and the

corresponding IR band positions are given in Table 6. The spectra of undoped Pb-

metaphosphate glasses (samples PbP-1, PbP-2, PbP-28~176 can be related to the IR

spectra of other glasses based on the metaphosphate composit ion. Generally, i t is

established that the metaphosphate glasses are composed o f polyphosphate chains

with the metal cations between these chains. In the l i terature 2s -27 two structural

models of the metaphosphate glasses, viz. straight chain model and zig-zag chain

model, were discussed.

The absorption band measured in the 1255 -1200 cm-1 range can be ascribed to

the stretching vibration of the P = 0 double bond. The P - O - stretching frequency

Table 6. Characteristic infrared band positions of Pb-me~aphosphate samples (em-~ )

PbP-1 PbP-2 pbP_2 s o 0 PbP-3 PbP-4 PbP-5

1210 s, shr 1200 s, shr 1255 vs 1195 s, sht 1120 s, shr~ b 1130 s, shr

1140 ~, shr

1075 d 1075 d 1070 d 1060 d 1060 d 1070 s, shr

910 d 915 d 910d 910 d 9 9 0 d 9 9 5 d

750 s, b 760 m 765 s 740 s

520 s 520 s, b 480 s, b 510 s

635 s, shr 640 s, shr

615 s, shr 615 s, shr

595 do s 595 d, s

545 d, s 545 d, s

515 w, sht 510w, shr

420 m, shr

385 s 385 s

330 m, b 330 s

Key: s = s t r o n g , m = m e d i u m , w = w e a k , v = v e r y , b = b r o a d , shr = s h o u l d e r , d = d o u b l e t .

155

S MUSIC et al.: INFLUENCE OF IRON IONS ON THE STRUCTURAL

is measured at 1075-1070 cm-1~ Antisymmetric stretching v a POP and symmetric

stretching v~ POP are meast~red at 915-910 cm -1 and 765-750 cm -1 , respectively.

The shoulder at 1140 cm-1, observed in sample PbP-28~176 can be ascribed to the

symmetric PO2 stretching vibration. Absorption band at 520-480 cm-1 may be

associated with the bending vibrations of the metaphosphate group. The IR spectrum of sample PbP-3900 does r~ot differ~ significantly from the IR spectra of samples

PbP-1, PbP-2 and PbP-28~176 However, changes are observed in the IR spectra of

samples PbP-4 and PbP-5, which were prepared with >i 21% Fe203 (by weight). This is in accordance with X-ray diffraction and M6ssbauer spectroscopy, which showed the presence of Fe3(t'O4)2 crystalline phase (dominant component in PbP-5 sample). SITZIA recorded 2 s IR spectrum of Fe3(PO4)2 in the range 4000-700 cm -1 ,

and the strong band consisting of three peaks at 1050, 1010 and 990 crn -1 is

observed. The IR spectra of samples PbP-5 and PbP-4 indicate a strong influence of

iron on b e stretching vibrations at > 990 cm- i and bending vibrations of the

phosphate group at < 640 era- 1. Absorption peaks observed in the 420-330 crn- 1

(samples PbP-4 and PbP-5) can be related to the vibrations of Fe cations. 2 9 -31

References

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2. R. P. TURCOTTE, J. W. WALD, Devitrification behaviour in a zinc borosilicate nuclear waste glass, Report PNL-2247, Battelle Pacific Northwest Laboratories, March 1978, Richland, Wa. 99352.

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Influence of iron ions on the structural properties of some inorganic glasses J Radioanl Nucl Chem...

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