Transition metal fluorophosphate glasses

Transition metal fluorophosphate glasses

Journal of Non.CrystallineSolids56 (1983) 111-116 North.HollandPublishingCompany 111 TRANSITION METAL FLUOROPHOSPHATE GLASSES Marc Matecki and Marc...

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Journal of Non.CrystallineSolids56 (1983) 111-116 North.HollandPublishingCompany

111

TRANSITION METAL FLUOROPHOSPHATE GLASSES

Marc Matecki and Marcel Poulain Universit~ de Rennes, Campus de Beaulieu Laboratoire de Chimie Min~rale D, L . A . C . N . R . S . n ° 254 Avenue du G~n~ral Leclerc, 35042 Rennes C~dex, France.

Glass formation has been investigated in the ternary systems NaPO3-BaF2-MF2 (M = Mg, Mn, Zn) or MF 3 (M = Fe, Ga). Large amounts of transition metals may be included, up to 75 mole %, with MnF 2 resulting in highly paramagnetic glasses. The values of characteristic temperatures, refractive index, density and thermal expansion coefficients have been measured for a set of samples with the formula : 0.5 NaPO3, 0.2 BaF2, 0.3 MF n (MFn = MgF2, CrF3, MnF2, FeF3, CoF2, NiF2, CuF2, ZnF2, GaF3). T~ lies between 240 and 370 ° C and melting between 600 and 700 ° C. Glass samples are stable at room atmosphere and soluble in water. The evolution of the physical properties is displayed for the two glass families : (I-x) NaPO3, x BaF 2 (0 < x < 0.25) and (0.8-x) NAP03, 0.2 BaF2, x MnF 2 (0 < x < 0.60). Some of these glasses appear as fluoride glasses stabilized by a small amount of phosphate. INTRODUCTION Numerous fluorophosphate glasses have been investigated for their optical properties as they display both low refractive index and low dispersion Ill. More recently, new compositions have been studied as Nd-laser hosts for high power delivery 121 131. Most of these glasses include aluminium metaphosphate AI(PO3) 3 as starting materials because it appears to be more stable to moisture than other metaphosphates. Other families derive from Ba(PO3) 2 141151, but usually alkali metaphosphates are excluded because they lead to hygroscopic glasses. In fact, it has been observed that the addition of fluoride to phosphate greatly increases the resistance to water, so that numerous NaPO -based fluorophosphate glasses are fairly stable at room atmosphere 161. Such 3glasses display a lower melting and working temperature range and, thereby, do not suffer alteration from volatilization of the melt. This paper describes a new family of fluorophosphate glasses in ternary systems NaPO3-BaF2-MF 2 or MF 3 in which MF 2 or MF 3 are 3d transition metals. EXPERIMENTAL The starting materials BaF2, ZnF2, MgF 2 and NaPO 3 were Rectapur PROLABO products. MnF 2 was prepared by the reaction of HF solution with manganese acetate or carbonate. GaF3 was prepared by the reaction of NH5F 2 on Ga203. Ga203 was provided by RHONE POULENC Chimie fine, NiF 2 and CoF 2 by OZARK, and the other difluorides by ~ R C K . The glass was prepared in a platinum crucible open to the room atmosphere. The calculated amount of fluorides and metaphosphate was gradually heated to fusion. The melt was then poured into a brass mold preheated to about the glass transition temperature. The sample obtained was annealed for one hour at Ta ~ Tg.

0022-3093/83/0000-0000/$03.00 @1983 North-Holland

112

M. Matecki, M. Poulain / Transition metal fluorophosphate glasses

BaF 2

BaF 2

/~ /VVVVVVV/,A,

(lb)

(la)~/VVVV\~ /VVW~~A NaPO 3

MgF 2

/~/VVVV'~C~

NaPO 3

MnF 2 BaF 2

(lc) / ~ (ld) /~ A/VVVVVA/XA /WVWX~xM

NaPO 3

ZnF 2

Figure 1

NaPO 3

(le)

FeF 3

/~

Vitreous areas in the system BaF 2NaPO3-MF_ (MF n = MgF 2 (la), MnF 2 (ib} ZnF 2 (ic~, FeF 3 (id) and GaF 3 (le)

NaPO 3

GaF 3

M, Matecki, M. Poulain / Transition metal fluorophosphate glasses

113

RESULTS The glass forming areas are shown in figure I for the five following systems : NaPO3-BaF2-HgF 2 (la), NaPO3-BaF2-MnF 2 (ib), NaPO3-BaF2-ZnF 2 (ic), NaPO 3BaF2-FeF 3 (id), NaPO3-BaF2-GaF 3 (le). Binary glasses (l-x) NaPO3-x BaV 2 exist in the range 0 < x < 0.3 so that it is a common edge for all the vitreous areas. The limits correspond to glasses obtained by pouring the melt onto a brass mold at 20 ° C.

Similar glasses may be prepared using CrF3, CoF2, NiF 2 and CuF 2 as transition metals, but the full vitreous system has not been investigated. A standard composition is 0.5 NAP03, 0.2 BaF~, 0.3 MF 2 or MF 3. It appears that large amounts of transition metal fluorldes may be included, up to 60 mole % MnF 2 and even 75 % by quenching. Sample thickness varies according to the composition, and although limiting glasses can hardly be more than 5 rmn thick, no crystallization is observed for the others at even slow cooling rates. PHYSICAL PROPERTIES Several physical properties have been measured, including thermal analysis, thermal expansion, refractive index and density. The more significant values are displayed in table i. Characteristic temperatures have been determined by D.T.A. at 15 Kmin -I heating rate; glass transition Tg and melting point Tm correspond to the intersection of the interpolated base line with the tangent at the inflection point; the liquidus temperature T I is the top of the melting peak which corresponds roughly to the onset of solidification on cooling. For some glasses, Tc is not observed or cannot be precisely measured. To get a better accuracy, Tc has been recorded at the top of the exothermic peak. The values of vitreous NAP03 are also reported. It appears that the incorporation of fluoride may decrease the devitrification tendency as for a glass containing FeF 3. TABLE i Physical characteristics of fluorophosphate glasses 0.5 NAP03, 0.3 MFn, 0.2 BaF 2

T1

~ IO-~K - I

HFn

nD

d

Tg

Tc

Tf

MgF 2

1.5105

3.28

364

488

592

707

189

CrF 3

1.$40

3.45

36S

454

539

620

200

HnF 2

1.5142

3~42

268

458

611

654

217

FeF 3

1.5452

3.43

323

641

(679)

199

CoF 2

1,526S

3,53

298

618

6S0

219

NiF 2

1.5325

3,59

346

542

685

198

CuF 2

1.5360

3.SS

248

424

580

659

220

ZnF 2

1.5208

3.47

246

4S4

587

60S

222

GaF 3

1.4970

3.58

298

634

678

195

513

The n D refractive indices have been measured using an Abbe refractometer and densities by the Archimedean method. Thermal expansion coefficients (DI 10 ISA ADAMEL dilatometer) are usually in the range 200-250"10 -7K-4 With ZnF2, MgF2 and GaF 3 as the third glass component, the optical transmission range lies from 370 nm

M. Matecki, M. Poulain / Transition metal fluorophosphate glasses

114

in the UV 2600 nm in the IR. The UV transmittance could be improved by using high purity starting materials, but it is probably more difficult to remove the OH groups inducing a strong absorption at 2900 nm. These fluorophosphates are stable at room conditions for several years if the NaPO 3 molar fraction is not greater than 0.4. In aqueous solutions, the sample behaviour depends on the phosphate content and on the te~nperature. For example, the NPBM-4 glass (Ba 2Mn ~Na 4(P03) 4F1.2 ) undergoes some surface attack after eight days in water at 2~ C'and a 12 % weight loss after 72 hours in a Soxhlet apparatus (T(H20) = 88 ° C). At the same conditions, the NPBZ-2 glass (Ba.4Zn.4 Na.2(PO3).2F1. 6) gives a 0.2 % weight loss at 20 ° C and 7 % in the Soxhlet apparatus. EVOLUTION OF PHYSICAL PROPERTIES WITH COMPOSITION Two sets of samples have been synthesized in the NaPO3-BaF 2 and NaPO 3BaF2-MnF 2 systems using the following composition rules : (l-x) NaPO3, x BaF 2 (0.8-x) NaPO3, 0.2 BaF2, x MnP 2

(0 < x < 0.3) (0 < x < 0.6)

We have reported in table 2 the measured values of characteristic thermal expansion, density and refractive index.

temperatures,

TABLE 2 Physical characteristics

of fluorophosphate glasses

(0.8-x) NaPO 3 , x MnF2, 0.2 BaF 2 nD

d

TI

0

I .S02

3.0

249

O,lO 0,30 0.30 0,36 O.$S 0.40 0,42 0,47 0,50 0,60

1.510 1.515 1,5182

3.16 3.28 3.42

240 265 270 276 285 Z~7 275 291 288 300

x

I,SI96

I .$ZOZ 1.5220

3,59

3.7? 3.96

TC~

Tf

398

6S6

38Z $23 603 541 472 555 {491) C$|0) {524) 634 (SZ) 643 {S29) 493 595 416 597 027 500

Tl

(l-x) NAP03, x BaF 2

a IO''K-'

x

nD

d

T0

TOp

Tf

T|

a 10''1 - I

737

333

0

1.482

2,S1

263

455

600

029

243

652 613 636 636 660 680 642 630 586 626

239 223 212 209 206 191 192 197 195 186

0.03 0.65

1.401

2.63

277 275

458 o

49? 501

000 503

203 240

528 503 StZ 534 615 656

615 601 615 615 689 737

237 240 ZZ8 220 224 333

3 6 1 1 568

663

Z3O

0,07 0,10 0,12 0,15 0,17 O,ZO 0,25

1.4995

2,87

1.502

3.0

256 2?2 ! 2011 262 259 467 2 4 9 308

1.505

3.12

Z46

1,496

2.77

Figure 2 shows the evolution of Tm, T c and Tg with respect to composition for both systems. While the variation of T g is monotonic, the phase diagram displays a congruent melting compound for the composition Na2BaMn2(PO3)2F6. As shown in figure 3, introducing fluoride leads to an increase in the refractive index n D which indicates that the refractivity of MnF 2 and BaF 2 in the glass is greater than that of NaPO 3. The change in density with respect to composition is shown in figure 4. A comparison is made between the experimental points and the values computed from the summation of the starting compound densities weighted by the molar fraction (full line). For the (l-x) NaP03,x BaF 2 system, glass formation leads to an increase in density with increasing x. For the (0.8-x) NAP03,0.2 BaF2, x MnF 2 system, there is no significant difference between experimental and computed values for 0 < x < 0.4; then the change in glass density becomes faster, resulting in a change in the slope of the line. The thermal expansion coefficient is also decreased by the fluoride incorporatiQn, but some peculiarities occur in its change. As shown in figure 5, a deviation from the straight line occurs and reaches a maximum value at x = 0.4 in the (O.8-X) NAP03, 0.2 BaF2, x MnF 2 and at x = 0.15 in the (l-x) NAP03, x BaF 2

M. Matecki, M. Poulain / Transition metal fluorophosphate glasses

T°C

115

T°C 750.

750

NaPO3( 1-x) BaF2x

/x

--X

500-

NIPO3

500.

--x~

.1

.2

MnF BaF2 2x .2

./

+ X-- Tg

250

0

(.8- x)

+

.t.~+--+

+%

"+~+

+- .

Tg

250.

X

.25

.50

X

Figure 2 Change in the characteristic temperature with respect to the composition index x for the glasses (l-x) NAP03, x BaF 2 and (0.8-x) NAP03, x MnF2, 0.2 BaF 2

n~ NePO3(.8-x) MnF2x BIF2.2 MnF2 BIF 2 (.8-x) • .2 + f +-----"+'---" + ~

, , ~

NePO3 1.52

3.5

/J/ 1.50

~,jx

3.

/

/

x

x

X NIPO3(I_x)BIF2x

/ S a P O 3 ( I _ x ) BaF2

/, 1.48 .25

.5

]-X

Figure 3 Change in the refractive index n D with respect to the composition index x for the glasses (l-x) NAP03, x BaF 2 and (0.8-x) NAP03, x MnF2, 0.2 BaF 2

2.5 0

.25

.5

X

Figure 4 Change in the density with respect to the composition index x for the glasses (l-x) NAP03, x BaF 2 and (0.8-x) NAP03, x MnF2, 0.2 BaF 2

systems which also corresponds to a maximum in the change in melting temperature. Van Uitert has pointed out that in most glasses the product ~Tm 2 is constant and close to 11 171. As the melting temperature increased rapidly for 0.3 < x < 0.4, a decrease in ~ leads to keeping ~T m constant. However, this first explanation is hampered by the lack of physical support to this empirical rule and it is also likely that this composition range corresponds to some change in Mn 2+ coordination.

M. Matecki, M. Poulain / Transition metal fluorophosphate glasses

1 16

iC~ (10"6.K -1) 26. C~X~X

NiPO 3

\

~:~ ~ X xX /

22

(l-x)

BiF 2

x

X

Figure 5

24-

~ + ~ + ~ ~'~-4-NaPO3('8"x) MnF2x BmF2"2

Change in the expansion coefficient with respect to the composition index x for the glasses (l-x) NaPe3, x BaF 2 and (0.8-x) NAP03, x MnF2, 0.2 BaF 2

20

16 0

.25

.50

=X

CONCLUSION The main feature of these glassy systems deriving from the NaPO3-BaF 2 association is their ability to dissolve large amounts of transition metal fluorides, resulting in highly paramagnetic materials. When looking at the glass forming areas, in some extreme range, these glasses appear to be binary fluoride glasses BaF2-MnF 2 or BaF2-ZnF 2 stabilized by a small amount of NaPe 3. The same conclusion arises from the observation of several Nd-laser fluorophosphate glasses 13]. Thus, a convenient structural model for these glasses is an aperiodic packing of F- and (PnOm)x- anions with cations randomly inserted in this anionic array. REFERENCES W. Jahn - Glasstechn. Ber. 34, 107 (1961). M. Faulstich, W. Jahn, G. Krolla and N. Neuroth - US Patent 4225439 (1980). S.E. Stokowski, R.A. Saroyan and M.J. Weber - Report M-095, Nov. 1978, Lawrence Livermore Laboratory, CA. 14J W.D. Chalilev, J.P. Wasylak, J.G. Igitchanjan, R.M. Oganesjan and M.A. Pogosjan - Proceedings of the XII Internat. Congress on Glass, Prague (1977), p. 133-147. M.L. Petrovska, T.N. Smirnova and N.G. Suikovskaya - Izv. Akad. Nauk SSSR, Neorg. Mat. 8, 1526 (1974) Engl. Transl.: Inorg. Mat. M. Poulain - unpublished results. L.G. Van Uitert - J. Appl. Phys. 50, 8052 (1979).

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