Glass formation and crystallization in alkali-containing fluoride glasses

Journal ofNonCrystalline North-HoUand.Amstcrdam

Solids 95 &96 (1987)

481

GLASS FORMATION

Xiujian

487 - 494

AND CRYSTALLIZATION

ZHAO and

Sumio

IN

ALKALI-CONTAINING

FLUORIDE

GLASSES

SAKKA

Institute for Chemical Research, Kyoto and Division of Molecular Engineering, Kyoto University, Sakyo-ku. Kyoto-shi

University, Uji-shi. Graduate School of 606. Japan

Kyoto-fu Engineering,

611

Glass formation range, glass-forming ability and crystallization kinetics were studied with alkali-containing fluoride systems of compositions (~DO-X)(D.~Z~F~~D.~A~F~~O.~B~F~)~~L~(N~, K or Cs)F. Glass formation range decreases with increasing size of alkali ion. Maximum of glass-forming ability is found around the alkali fluoride (RF) concentration of 5-20 mol%. The composition corresponding to the maximum shifts to lower RF concentrations with increasing size of alkali ion. The glass-forming ability appears to be mainly determined by the difference between crystallization and glass transition temperatures. Crystallization kinetics study shows that the maximum of glass-forming ability corresponds to a minimum of the activation energy of crystallization for glasses containing LiF.

1.

INTRODUCTION Heavy

a1.l

metal

in

waveguides

excellent

(-250

nm)

glasses

to

have

mid-IR

very

is

yet.

clear

In

this

Alkali of

the

glass

With the

2.

in

LiF-containing activation

of

glasses energy

R is

for

range

the

and

in

K or

the

glass

crystallization growth

range

be

related

is the

are

(loo-x)(0.6ZrFq.

discussion

to

systems

ability

of

to

glass

fluoride

compositions

and

on these

contrast

as

of

formation

for UV

fluoride

considered

glass-forming

Cs.

near

studies In

kinetics is

of

formation

et

systems

from

alkali-containing

of

Poulain

optical

communication

a number

can

glass

glasses Na.

Li.

ions

crystal

in

by

for

applications. on

(RF)

ions

fluoride

alkali

reported

length

years, and

studies

formation

where role

wave

ten

fluoride

alkali-containing

structural

last

the

fundamental

alkali

first materials

repeatless in

systematic

few3-6.

D.1A1F3-D.3BaF2)-xRF. the

the

role

In

both

were

candidate

light

um)2.

the

paper, with

of

for

however,

but

reported

made

on ZrF4

strong

long-distance,

(a-10

been

are

based are

transmittance

modifier7*8. not

glasses

ultralow-loss.

glasses,

glasses

glasses

These

in

their

oxide

fluoride

1975.

will these

also

be made

on

glasses. reported

and

glass-forming

ability.

EXPERIMENTAL 2.1

Glass

The

compositions

preparation

the

present

Here

x ranges

from

0 Elsevier SciencePublishers Physics Publishing Division)

DO22-3D93/87/$03SD

(North-Holland

(lOD-x)(D.6ZrF4*0.1A1F3~D.3EJaF2)'xRF study.

0 to

B.V.

in 60,

0 to

45,

mol D to

have 35

been and

used

D to

30

Zhao Xiujiatt,

488

intervals

of

reagents

5 mol%

materials.

in

respectively

(NH4)2ZrFG, The

preheated

at

mixture

melt

were

Differential

cast

thermal

then

Li,

Na.

K and

Cs.

CsF

were

used

as

with melted

atmosphere

a brass

analysis of

KF and added

and

a nitrogen

made

and crysrollizorion

equaling

NaF,

materials 1 hour

thermal

DTA-30

R's

LiF.

into

were

mould

about at in

of

10 wt%

using

DTA in

The

an

pure

NH4HF2

for

was

20 minutes

electrically

heating

ZOO'C.

(OTA) the

analyzer.

glasses Powders

crystallization a heating

crystallization

powders

of

ANALYSIS

of

rate

range

occurred

574

urn were

at of

a heating

rate

of

674 urn (passing

LiF-containing

from

mainly

used

lO'C/min

through

200

with mesh)

1 to

from

glasses

are

in

a nitrogen

50 'C/min

the

surface

in

these

by using

the

Glass-forming

ability

The

glass-forming

ability

T g,

T,

and

temperatures, Fig.

studied

by

atmosphere.

glasses,

and

so

as samples.

was

calculated

formula

Tc - Tg

where

also

OF DTA DATA

3.1

-- Tm - Tc

Kgl T,

are

the

by

Hruby'

(1) glass

respectively.

transition,

They

are

crystallization

estimated

from

and

the

melting

DTA curve

as

shown

have

analyzed

in

1. 3.2

Kinetic

equations

Non-isothermal the

equations

where

o=

In

d (~p2)

depending

heating gas

on the

Kissinger-type

-$

Glass

rate

mechanism

formation

and

mE

= -m

Ozawa-type

RESULTS 4.1

crystallization

in

the

present

range

been

by

(2)

+ const

+ const

(=dT/dt), T and of

study

Sakka":

-+ln[-ln(l-x)]

constant,

and

non-isothermal obtained

by Matusita

ln

the R the

for

DTA data derived

ais

growth,

4.

of

B50-900°C

about

Extra starting

used. Non-isothermal

3.

raw for

under is

OTA measurements Shimadzu

of

/ Glass formation

for

BaF2,

45O'C

crucible

The

2.2

AlF3.

about

a platinum

furnace.

S. Sakka

E the Tp

the

activation

temperatures

crystallization. plots,

respectively.

Eqs.

energy and (2)

for

m and and

(3)

crystal n the are

parameters so-called

Zhoo Xiujion,

Temperature

containing

0

0

0

0

0

0

l

0 0 0

o 0 0

o 0 0

0 0 0

0 0 0

0 l 0 0

K system 0 0 Na system

0

0 0 0 0 l

10

Cs system

0

I

I

I

20

30

40

1

489

and crymdlizorion

0.81

0 0 0 I D

/ Glass formo~ion

("C)

Fig. 1 a glass

DTA curve of 15 mol% NaF.

S. Sokko

RF concentration

Li

I

I

50

60

system I

o-

70

0

(mol%)

10

20

30

40

RF concentration Fig. 2 Glass formation ranges of the alkali fluoride oglass @glass+crystal

The terms

glass of

formation

alkali

glass

formation

found

that

shown in terms concentration.

range glass

gl' of the

@crystal

ranges

fluoride

the

K

of

all

the

four

concentration. extends

to

formation

For

a LiF range

3 Tm as

are

shown

in

LiF-containing

concentration decreases

of

with

60

a function

RF concentration.

systems the

Fig. and

Tc-Tg

50 (mol%)

Fig.

2 in

system,

about

the

55 mol%.

increasing

It

is

size

of

alkali

T,

and

T,-Tg

around

the

ion. 4.2

Glass-forming

The

results

from

eq.

against

(1) the

concentration to the

lower

ability

of is

DTA are also

given

shown.

RF concentration. of

5-20

The

mol%.

RF concentrations

dependence

of

Kg1 on

in

Fig.

The with

the

Table

1.

Glass-forming

3 shows

the

plots

curves

for

Kg1 show

composition increasing

RF concentration

of

corresponding size

of is

alkali consistent

ability the

Kg,.

Kg1 estimated

a maximum to

the

ion. with

maximum

It

is that

RF shifts

found of

T,-T

that 9'

490

Zhao Xiujion.

Table

1.

OTA results 0.3BaF2)oxRF

and the glasses

Temperature co;,

x (mol%)

Tg

S. Sukko

values

K9l

c

Tm

0 glass 5 10 15 ;i

292

346

558

0.255

276 268 256 251 240

335 327 325 325 296

508 505 504 500 513

0.341 0.331 0.385 0.258 0.427

:i 40 45

226 220 216 209

281 275 268 261

490 492 492 491

0.256 0.261 0.232 0.226

:i K glass 5 10 ::

204 194

231 255

493 512

0.132 0.214

289 280 271 278

358 355 333 345

484 490 557 493

0.548 0.556 0.277 0.453

25 30

263 257

312 293

573 582

0.188 0.125

Li

4

/ Glass /ormarion

of

Kg1 of

and crysrollizorior~

(100-x)(0.6ZrF4-0.1A1F3~

x (mol%)

K9l

Na glass 5 10 :z

35 :z

Cs glass 5 10 15 ;:

283 271 267 257 252 245 238

342 342 342 332 326 308 288

460 455 458 458 457 452 472

0.500 0.628 0.647 0.595 0.565 0.438 0.272

295 293 279 266 262

365 378 342 326 297

480 552 551 547 508

0.609 0.489 0.341 0.271 0.166

I,,,,,,

I 1.55 103/Tp

(K-l)

Fig. 4 Ozawa-type plots for glasses. The numbers concentrations.

I 1.65

I

I 1.75

103/Tp

LiF-containing show LiF

Fig. 5 Kissinger-type plots containing glasses. show LiF concentrations.

I

I 1.85

(K-l)

for LiFThe numbers

I 1

Zlrao

In

the

lower

increases

is.

S. Srrkka

RF concentration

which

concentration That

Xiujion.

is

the

the

dependence

Glass /orntotton

region,

consistent

region,

/

Tm decreases

with

the

behaviour

of

of

Kg1

and ctytollizatiot~

as the

increase

in

Tm is

on the

not

Kgl,

RF concentration but

always

491

in

higher

consistent

RF concentration

is

RF with

mainly

Kg,.

determined

by

T,-Tg. 4.3

Non-isothermal

It

is

assumed

straight

line

heating

rate.

is

that

seen

mainly

when

against

the

plot

of

In

a versus

crystallization

4 shows

plots

the by

the

the

Fig. the

from

estimated

crystallization that

such

are

surface,

plots

straight the

assuming

for

The

RF concentration

based

in

does

some

lines.

activation

n=m=l.

l/Tp

mechanism of

the

energies

Fig.

of

(2)

change

gives

with

LiF-containing

Since

values

on eq.

not

glasses.

crystallization

for

crystal

given

in

,

@from

Fig.

10

20

It

occurs

growth

E are

a

the

Table

can

be

2 and

plotted

6. 4

600 Table

2.

(mzl%)

Values of E determined from Figs. 4 and 5 in LiF-containing glass'es.

_

E (kJ/mol) Fig.4 from

5

from

0 5 15 20 25

The

plots

lower for

507 464 304 329 418 5ao 384 331

of

heating

growth

those It

is

growth Fig.

in

7 that

Table

and

corresponding

to For

Fig.

3.

with

increasing

the

higher

Fig.

of 6 that

kinds

energy

of for

reaches up to

minimum LiF

a LiF of

shown

plots

in

are

the

Fig.

crystal a minimum

are

given

to

in

that

for

energies

Table

close.

2 and

a LiF

the

for It

decreases

of

than

seen

activation

energies

growth

concentration

larger

is

in

Fig.

6

l/Tp.

very

at

50

(mol%)

It

6. The

activation

plots

40

Fig. 6 energy for crystal LiF concentration glasses.

lines.

In o versus

E corresponds

concentrations

RF concentration.

are straight

these

plots

two

activation

increases

l/Tp give

30

concentration

Activation growth vs. LiF-containing

from

RF concentration, then

LiF

the

2 and the

2001 0

plots

from

from

the

UJ 300

versus

these determined

estimated

increasing mol%.

(a/Tp2)

determined seen

Fig.5 497 454 295 320 409 571 375 322

rates,

crystal

with

In

500

E 2400

is first

crystal also

concentration 30 mol%.

maximum 30 mol%.

The

seen

in

with of

15-20

composition

of K as cl1 E decreases

shown again

in

4.4

The

The

crystals

BaZr2F10

kind

and

mol% were LiF

5.

precipitated in

unknown

Li2ZrFb

glasses

crystals,

crystals,

with whereas

different

from

LiF

from

in

glasses

the

15 to

35 mol%

with

crystals

LiF

were

higher

precipitated

than in

35

lower

glasses.

DISCUSSION 5.1

Glass

on glass tends

formation

to

induce

favoring

for the

ionicity.

From

the

region.

first

will

decrease

in

shown

it

RF mainly

with

decreases the

size

region,

of

composition

total

Then

alkali

the

ion.

the

alkali-free

is

enough

high

glass-forming

is,

K

to ability

versus

RF

addition

of

91

lower

RF concentration

increases T,-Tg.

region,

T,-Tg As

shown

and in

in

the

the

the

higher

next

section,

dependence

in

RF to

RF concentration the

the

addition

of

crystallization

glasses.

alkali in

with

the

ion, the

increases,

corresponding

ionicity

ion.

RF concentration

the

That

RF

Rt

increasing

RF to

lower

effect,

of of

radius. of

of

the

limit

a maximum.

RF concentration,

ionicity

concentrations

glass

of

its size

RF concentration second

viscosity-temperature

increases

Kgl

total

the

mainly

same

show

mainly

modifies

increasing

the

in

the the

in

covalency liquid

ionicity with

addition

the

as glass

the

with

the

in

upper

decrease

RF concentration.

should

glass

range

the

where than

increasing

above,

temperature At

region

stronger

the

tendency

enhances

the

increasing

modifier.

generally

species

by

increases with

effects

character

be considered

will

ionicity

decrease glass

it the

be controlled

glass-forming

the

curves

alkali-free

the

of

effect

concentration

region

ions,

contradictory

ionic

modifier,

RF concentration

should

the

of

glass

will

two

high

simultaneously

RF may as

formation

effects

However, the

As

effect

increase

make

the

formation.

first

range two

will

glass

of

has 1)

polymerization

the

alkali

formation

glass

systems:

the

limit

ability modifier

2) the

glass

upper For

glass

glass

multicomponent

increasing

concentration is,

glass-forming

al.",

a recrystallization.

From

That

and

et

in

former, and

range

Cottrant

formation

glass

phase

to

modifier7*B.

in

crystals

other

According

of

of

precipitated

and order

is

Li

the to

assumed

of

in

glass

the

glass

of

of

alkali

increase

in

to

increase

ion, order

< K glass

< Cs glass. Then

to

lower

RF

because

the

rate

Li

with

RF concentration

crystallization.

Kg1 shifts

the

will

lower

< Na glass tends

maximum size

to

ionicity

system

the

increasing

total therefore,

glass

of

As

the

increase

< Na glass

< K

< Cs glass. 5.2 If

crystal

Activation the

crystal growth

energy

for

crystal

growth

growth

rate

is

diffusion-controlled,

E can

be

related

to

that

for

viscous

the flow

activation in

the

similar

energy

for

temperature

range.

The

fluorozirconates

is

generally,

E decreases

temperature

ranges

constant the

from

Tg,

This

means

has

a larger

the

the

dependence

the

the

that

of

concentration

increasing directly

related This

to

ZBL glasses.

discussion

may

The

above

compound

the

Li2ZrF6

has

assumed

that

be

also

suitable

controlled

for

crystal

may than

no

not 30

of

the

growth

for

will

Glass

is. et

decreases

for

other

alkali-containing

be

suitable

mol%,

for

because different

atom

decrease

its

of Li

Li

atom

with

that

increasing

the the

in

LiF crystalline

the

or

atom. If

this

These These

region

of

unknown

will

the

530

it

is

be a very

crystallization

region, LiF

Then

There the

LiF

crystals.

structure14.

Li

atom.

in

the ability.

with

BaZr2F10

be

glass-forming and modified

systems.

crystal

may

diffusion of

is

in

be

the

in

region

from

in

species

this

is

may

concentration.

glasses

in

and

ZBL

viscosity

LiF

LiF

glass

glass-forming

the

lower increasing

range

on

explained

the

alkali-free

al.13

the the

be

E with

increasing

Bansal

on

formation

studied

range,

with

glass-forming

with

increasing

appear the

around maximum The

ability

alkali-containing

size the shifts

dependence

K or

of

alkali

ion.

RF concentration to of

lower

and

fluoride

(0.6ZrF4~0.1AlF3~0.3BaF2)*xLi(Na.

ion.

that

LiF

can

rate

activation

energy

concentration.

CONCLUSIONS

were

to

the

growth

Therefore,

In

temperature

compound

diffusion

to

manner. crystal

on the mol%

energy

LiF

increases

range.

630

T,-Tg

is

diffusing

energy by

of

decreasing

fluorine

main

the

comparable

for

growth

activation

of

LiF

crystallizing

bridging

the

the

results

the

dependence.

addition

precipitated first

activation

is

6.

dependence

(Li2ZrF6)

mol% where

and

give

a different

energy

crystal

crystallization

of

the

larger

may

in

in

concentration

of

range,

to

discussion

concentrations

small

addition

temperature

correlated

molten

temperature

temperature

formation, the

are As

decreases

for

LiF

the the

glass with

Further

crystallization

which

glasses

activation

energy

that

the

most

temperature,

crystallization

small

value.

crystallization

decrease

in

agrees

all

same

viscosity-temperature

the

viscosity

ability.

the

where

the

means

its

Tg,

a smaller

activation

region,

in of

The

very

glasses

having in

of

are

the

different

region

modification

glasses

have

glass

the

viscosity

a function

temperature.

temperature

for

the

in

of

E is

E.

viscosities

the

i.e..

present

viscosity13

concentration

are

the

viscosity

concentration

LiF

of

transition

and

dependence

increasing

energy

glass

condition

by

with

activation

At

temperature

non-Arrhenian'*.

of

Cs)F.

of

Glass

formation

of

glass-forming

5-20

mol%.

The

RF concentration

kinetics

compositions

Maxima

RF concentrations

Kg1 on the

crystallization

systems

with

decreases

abilities

composition

Kg1 corresponding

increasing indicates

(100-x)

range

size that

Kg1

of

alkali is

mainly

determined

by Tc-Tg.

shows

the

that

temperature appears

Crystallization

addition

of

dependence in

the

kinetics

RF to

and

the

a minimum

composition

study

alkali-free of

the

corresponding

on LiF-containing

glass

modifies

activation

to

that

energy

of

glasses

the for

viscositycrystal

growth

Kg1 maximum.

ACKNOWLEDGEMENT This for

the

work

was

partially

Ministry

of

supported

Education,

by a Grant-in-Aid

Science

and

Culture,

P.Brun,

Mat.

for

Scientific

Japan

(Prof.

Research S.

Sakka.

No.

60430020). REFERENCES 1) M.Poulain, 2)

M.Poulain.

J.Siscavage

O.H.El-Bayoumi,

3) A.Lecoq

and

4)

J.Senegas, Solids 85

5)

P.L.Higby.

6)

Xiujian

7)

C.M.Baldwin

8)

M.Poulain,

9)

A.Hruby.

J.Lucas

and

J.

M.Poulain,

J.M.Reau. H.Aomi. (1986) 315. J.E.Shelby

Zhao

and and

Submitted

J.

Phys.

11)

J.F.Cottrant,

B.Dubois

12)

Hefang

J.D.Mackenzie.

Hu and

N.P.Bansal, (1985)

70

G.Brunton.

S.Sakka.

A.J.Bruce. 379. Acta

Cryst.

to

J.

(1981)

K.Matusita

14)

and

M.Suscavage.

S.Sakka.

293

Solids

Am.

Appl.

J.

Non-Cryst.

Ceram.

10 (1975) Solids

Phys.

Sot.

243.

73 (1985)

613.

101.

J.

M.Poulain.

J.

58

Non-Cryst.

(1985)

4142.

Solids. 62

(1979)

537.

279. (1972)

1187.

Bull.

Inst.

Chem.

J.Portier,

J.

R.H.Doremus

829

Bull.

Non-Cryst.

and

B 22

and

Res.

34 (1979)

P.Hagenmuller

J.D.Mackenzie.

Nature Czech.

and

J.

B.Bendow.

Non-Cryst.

10)

13)

and

(1973)

Mat.

Non-Cryst. and

2294.

Res., Res. Solids

C.T.Moynihan,

Kyoto

Univ.

Bull.

20

(1985)

54 (1983)

J.

20

(1981)

159.

203.

241.

Non-Cryst.

Solids