Liquidus determinations in the plane CaO·Nb2O5-CaO·SiO2-TiO2 within the quaternary system CaO-Nb2O5-TiO2-SiO2

Liquidus determinations in the plane CaO·Nb2O5-CaO·SiO2-TiO2 within the quaternary system CaO-Nb2O5-TiO2-SiO2

345 JOURNAL OF THE LESS-COMMON METALS Elsevier Sequoia S.A., Lausanne - Printed in The Netherlands LIQUIDUS DETERMINATIONS IN THE PLANE CaO.Nb,O&aO...

491KB Sizes 0 Downloads 103 Views

345

JOURNAL OF THE LESS-COMMON METALS Elsevier Sequoia S.A., Lausanne - Printed in The Netherlands

LIQUIDUS DETERMINATIONS IN THE PLANE CaO.Nb,O&aO.SiO,-Ti02 WITHIN THE QUATERNARY SYSTEM CaO-Nb205-Ti02-Si02

A. JONGEJAN

AND

A. L. WILKINS

Physicul Chemistry Section, Mineral Sciences Division, Mines Branch, Department of Energy, Mines and Resources, Ottawa (Canuda)

(Received May 20th, 1971)

SUMMARY

Liquidus temperatures of compositions in the plane CaO.Nb,O,-Ca0.Si02TiO, have been determined using the customary quench technique as well as hotstage microscopy. The boundaries between the fields of the following compounds have been outlined: TiOz (rutile), Ca0.Ti0,.Si02 (sphene), 8Ca0.7Nb,0,.6Ti02, CaO.Nb,O,, 3Ca0.Nb,0,.3Ti02(pyrochlore), CaO.TiO, (perovskite) and CaO.SiO, (pseudowollastonite). The pyrochlore and perovskite fields were wedged in between the others and both intersected the CaO.TiO,.SiO,-CaO.Nb,O, join.

INTRODUCTION

Studies of phase equilibria involving CaO, Nb,OS, TiO, and SiO, reported previously1*2 have been extended to those in the plane CaO.Nb,O,-CaO.SiO,Ti02. This plane is limited on two sides by the joins CaO.SiO,-Ti02 and CaO.SiO,CaO.Nb,O,. The CaO.Nb,O,-TiO, side, however, has been reported not to be a join because of the existence of the compound 8Ca0.7Nb205.6Ti02 located close to this side. The location of the plane in the quaternary phase tetrahedron CaO-Nb,O,Ti02-Si02 is shown in Fig. 1 together with that of the ternary system CaO.Nb,O,Ca0.Ti02-Si02 already studied2. These planes intersect along the join CaO.TiO,.SiO,-Ca0.Nb20,. The oblong shape of the Ca0.Ti02.Si02 field in the CaO-TiO,-Si02 system, as determined by Devries, Roy and 0sborn3, and that of the CaO.Nb,O, field in the CaO-Nb20,-Si02 system as determined by Prince, Ibrahim and Wilkins4, indicated that liquidus determinations in the CNCS-T* plane would give information about Crown Copyrights reserved. * The abbreviations commonly used in the literature dealing with the chemistry of ceramic oxides will be used in this paper, viz., C=CaO, N=Nb,O,, T=TiOz and S=SiOz. J. Less-Common Metals, 2.5 (1971) 345-351

346

A. JONGEJAN, A. L. WILKINS

Fig, 1. The quaternary system CaO-Nbz05-TiQ-SiOZ, showing the locations of theplanes Ca0.Nb20SCa0.Si02--TiO2 and CaO.Nb,Us-CaO.TiO2~0~ ~ters~ting along the CaO.TiO~SiO~-CaO.Nb~Os join.

the phase relations in the central part of the tetrahedron from a point of view different from that given by the CaO.Nb,O,-CaO.TiO,-SiO, system’. The liquidus temperatures along the CS-‘I’and the CS-CN joins used in this paper were obtained from the work cited above3s4,and those along the line CN-T from that reported elsewhere’. EXPERIMENTAL

The experimental methods used were the sazne as those described pre~ousIy. Mixtures ofthe required compositions were prepared from Ma~~nc~odt’s “Analytical Reagent”-grade calcium carbonate, 99 %-pure niobium pentoxide “Technical”-grade from Fansteel Metallurgical Corp., North Chicago, Illinois, heated to 1250°C,Baker’s “Analytical Reagent”-grade titanium dioxide and silicon dioxide prepared by dehydrating Baker and Adamson’s silicic acid overnight at 1250°C. A qu~tity of the chemicals, sufficient to yield 4 g of the required composi~ons, was mixed in an agate mortar. These mixtures were heated in platinum crucibles overnight at 1000°C to sinter them and partly to decompose the calcium carbonate. They were then heated to 1700°C in a gas-fired muffle furnace for one hour. The mixtures were ground to fine-grained powders so that the small quantities used in the Jiquidus determinations would be representative of the bulk composition. Reproducible results were obtained with this technique. The liquidus temperatures of samples that could produce clear glasses upon quenching were measured with the customary quench technique, whereby a small sample (3 mg) in a Pt enveiope was kept at an elevated temperature and quenched in water after reaching equilibrium conditions. The thermocouples used in measuring J. Lass-Common Met&,

25 (I 97i } 345-35 1

QUATERNARY SYSI-FM CaO-Nb20,-TX&-SiOz

341

Fig. 2. The compositions of the mixtures used in the liquidus determinations in the plane CaO.NbzOSCaO.SiOZ-TiO,. Liquidus temperatures determined by the quench technique are indicated l$& those determined by hot-stage microscopy are indicated by 0.

these temperatures were calibrated against the melting points of gold (1063’C) and palladia (1549OC). The liquidus temperatures of samples that could not produce glasses upon quenching were measured using a Griffin-Telin hot-stage microscope equipped with a Pt : 5 % Rh us. Pt :20 yQRh thermocouple. The use of this instrument has been describ ed previously6. The accuracy of the deter~nations using the quench technique was + l°C, but that of the determinations using the hot-stage microscope was + 5°C. RESULTS AND DISCUSSION

The compositions of the mixtures of which the liquidus temperatures were determined, have been indicated in Fig. 2, together with the field boundaries. The results of the liquidus determinations on these mixtures are listed in Table I and are represented graphically in Fig. 3. The perovskite and pyrochlore phase volumes lie in between that of sphene on the one side, and those of CN and C,N,T, on the other. The maximum temperature

A. JONGBJAN, A. L. WILKINS

348 TABLE

I

L~QUDUS

DETERMINATIONSIN

Sample reference numbers

THE

PLANE

CaO.SiO,~aO.Nb,O,-TiO, Method*

Composition (wt. %)

Liquidus temp.

CaO

NbzOs

TiO,

SiO,

CS

CN

(“C)

16.82 18.37 17.50 16.63 19.04 18.17 20.47 20.58 19.71 18.84 21.26 20.39 21.93

45.42 41.29 37.16 33.03 33.03 28.90 31.79 28.90 24.77 20.65 20.65 16.52 12.39

30.00 30.00 35.00 40.00 35.00 40.00 33.00 35.00 40.00 45.00 40.00 45.00 45.00

7.76 10.34

15 20

55 50

10.34 10.34 12.93

20 20 25

40 45 40

z

12.93 14.74 15.51

25 28.5 30

35 38.5 35

: Q

15.51 15.51

30 30

30 25

: Q

18.10 18.10 20.68

35 35 40

20 25 15

: Q

1315 1290 1353 1407 1335 1383 1286 1298 1361 1402 1339 1381 1368

SCaO.?NE ),0,.6TiO, (l’ rimary phasr4 7&32 CNTS 126 15.48 61.94 68-72 14.61 CNTS 67 57.81 7&31 CNTS 125 17.02 57.81 68-71 16.15 CNTS 66 53.68 71t30 CNTS 124 18.57 53.68 68-70 CNTS 65 17.70 49.55 7&29 20.11 CNTS 123 49.55 19.24 68-59 CNTS 64 45.42 68-96 41.29 CNTS 80 18.37 7&120 CNTS 129 18.99 39.64 68-47 CNTS $5 20.78 41.29 70-34 CNTS 128 21.55 39.23

20.00 25.00 20.00 25.00 20.00 25.00 20.00 25.00 30.00 30.00 25.00 25.00

2.59 2.59 5.17 5.17 7.76 7.76

5 5 10 10 15 15

75 70 70 65 65 60

H.S. H.S. H.S. H.S. H.S.

10.34

20

60

:

10.34 10.34

20 20

50 55

:

12.93 11.38 14.22

25 22 27.5

50 48 47.5

z Q

Pyrochlore (Primary phase) 70-120 CNTS 129 68-46 CNTS 54 70-34 CNTS 128 68-157 CNTS 84 68-180 CNTS 92 68-45 CNTS 53 70-307 CNTS 157 7ct176 CNTS 133

18.99 19.91 21.55 22.33 21.89 21.46 22.77 23.69

39.64 37.16 39.23 37.16 35.10 33.03 34.68 36.75

30.00 30.00 25.00 25.00 27.50 30.00 26.00 22.50

11.38 12.93 14.22 15.51

22 25 27.5 30

48 45 47.5 45

15.51 15.51

30 30

42.5 40

:

16.55 17.07

32 33

42 44.5

: Q

Perovskite (Primary phase) 68-178 CNTS 90 7@-181 CNTS 138 70-177 CNTS 134 68-155 CNTS 82 70-122 CNTS 131 68-173 CNTS 85 68-51’ CNTS 59 68-55 CNTS 60

23.56 24.13 25.01 25.67 26.46 27.27 28.70 30.24

33.86 34.27 33.86 34.68 33.86 34.27 33.03 28.90

25.M 23.50 22.00 20.00 19.00 17.00 15.00 15.00

17.58 18.09 19.13 19.65 20.68 21.46 23.27 25.86

34 35

41 41.5

38 37

42 41

:

41.5 40 45 50

41.5 41 40 35

;

TiO, (PIimary phase) 68-174 CNTS 86 68-96 CNTS 80 68-95 CNTS 79 68-94 CNTS 78 68-89 CNTS 73 68-88 CNTS 72 70-180 CNTS 137 68-58 CNTS 63 68-87 CNTS 71 68-86 CNTS 70 7&21 CNTS 115 CNTS 114 7(r20 7&19 CNTS 113

* Q = Quench technique. H.S. = Hot-stage microscopy. J. Less-Common Metals, 25 (1971) 345-351

Q

1423 1392 1415 1375 1377 1368 1366 1350 1290 1283 1317 1293

1283 1283 1293 1286 1285 1277 1283 1281

1285 1290 1284 1290 1277 1260 1262 1264

QUATERNARY TABLE

SYSTEM

349

I (continued)

Sample reference numbers CuO.Nb,Os 70--29 70-33 7@-308 68-93 68-92 68-154 70-121 68-50 70-27 68-57 68-179 68--156 XI-179

Composition CaO (Primary phase) CNTS 123 20.11 CNTS 127 22.23 CNTS 158 23.55 CNTS 77 26.48 CNTS 76 25.61 CNTS 81 24.74 CNTS 130 24.88 CNTS 58 27.16 CNTS 121 26.81 CNTS 62 29.57 CNTS 91 29.13 CNTS 83 30.15 CNTS 136 30.28

CaO. TiOJi02 70-305 70-25 70-306 70-24 68-44 68-85 70-123 68-49 68-48 70-28 68-91 68-90 68--177 68-176 71--7 70-23 70.-22

CaO-NbzO,-TiO,-SiO,

(wt. %)

Method*

Liquidus temp.

Nb,O,

TiO,

SiO,

CS

CN

(“Cl

49.55 41.29 38.40 45.42 41.29 37.16 35.51 37.16 35.51 37.16 35.10 33.03 31.38

20.00 22.00 21.50 10.00 15.00 20.00 21.00 15.00 17.00 10.00 12.50 12.00 13.00

10.34 14.48 16.55 18.10 18.10 18.10 18.62 20.68 20.68 23.27 23.27 24.82 25.34

20 28 32 35 35 35 36 40 40 45 45 48 49

60 50 46.5

1267 1302 1285 1360 1340 1285 1279 1291 1273 1298 1270 1253 1244

Q

50 55 45

::

45 43

z

45 43 42.5

: Q

38 40

:

37.5 39 39

;

36 35

z

30

:

40 20

:

37.5 25

:

30 35 32

:

23 27 15

:: Q

10

Q

Q

(Primary phase)

CNTS CNTS CNTS CNTS CNTS CNTS CNTS CNTS CNTS CNTS CNTS CNTS CNTS CNTS CNTS CNTS CNTS

CaO.SiO, (Priory 70-179 CNTS 68-56 CNTS 70-26 CNTS 70-178 CNTS 68-175 CNTS 71-s CNTS

155 119 156 118 52 69 132 57 56 122 75 74 89 88 202 117 116

21.04 21.02 22.25 22.21 23.00 22.13 22.32 26.28 23.67 28.26 27.83 26.96 29.72 31.26 32.98 34.00 35.54

32.21 30.97 32.21 29.73 28.90 24.71 16.52 33.03 20.65 30.97 28.90 24.17 26.43 22.30 18.99 12.39 8.25

31.50 32.50 29.00 31.00 30.00 35.00 41.00 20.00 35.00 17.50 20.00 25.00 18.00 18.00 17.00 20.00 20.00

15.25 15.51 16.55 17.06 18.10 18.10 20.17 20.68 20.68 23.27 23.27 23.27 25.86 28.44 31.03 33.61 36.20

29.5 30 32 33 35 35 39 40 40 45 45 45 50 55 60 65 70

phase) 136 61 120 135 87 203

30.28 31.11 30.59 30.86 31.79 34.87

31.38 33.03 30.55 27.25 24.77 16.52

13.00 10.00 13.00

25.34 25.86 25.86 26.89 28.44 33.61

49 50 50 52 55 65

15.00 15.00 15.00

Q

38 40 37

::

30 33 20

:

~-

Q Q

1279 1281 1285 1290 1311 1316 1343 1280 1330 1271 1287 1311 1292 1298 1302 1315 1349

1245 1262 1248 1267 1279 1349

* Q = Quench technique. H.S. = Hot-stage microscopy.

in the narrow perovskite field occurs near the CTS-CN join. Previous results1 have indicated that the maximum temperature on the intersection of that field with the CTS-CN join is 1290°C. Because of the complexity in the directions of the isotherms near the intersecJ. Less-Common

Metals,

2.5 (1971) 345-351

350

A. JONGEJAN, A. I.. WILKINS

Fig. 3. Field boundaries (heavy lines) and isotherms (thin lines) in the plane CaO.NbzO,-CaO.SiCQ-TiO,. Dashed lines are inferred.

Pyrochlod Fig. 4. A detail of Fig. 3 showing the direction of the isotherms (thin lines) near the intersection of the CNCTS join with the phase voiumes of pyrochlore, sphene, TX&, C,N,T,, CN, and parts of the perovskite volume, together with the relevant parts of the field boundaries {heavy lines). J. Less-Common Metals, 25 (1971) 345-351

QUATERNARY SYSTEM CaO-Nbz05-Ti02--Si02

351

tion of the pyrochlore and perovskite phase volumes, a few isotherms in the area concerned, which are not shown in Fig. 3, are shown in Fig. 4. The distinction between the primary phases in the CN and the C,N,T, fields was based on the microscope observation that the needle-like crystals of the latter compound had not as sharp an outline as that of crystals of CN, and appeared to be more blade-like. Because the work reported here was confined to liquidus determinations only, any solid-solution phenomena, which could undoubtedly exist in this phase, have not been studied. According to the results, the perovskite seems to exist at high SiOz contents. However, since this conclusion may be ~slea~n~ due to the particular location of the CN-CS-T plane in the phase tetrahedron, additional liquidus determinations are being made on three planes parallel to the C-N-T base at the 15 %, 20% and 25 % SiOz levels, respectively. The results obtained will give a better indication of the true extent of the perovskite phase volume and will be detailed in later pub~cations. ACKNOWLEDGEMENTS

The authors wish to express their thanks to Dr. N. F. H. Bright and to Dr. D.A. Reeve for critically reading and editing the manuscript, and to Mr. E. J. Murray for the preparation of the X-ray diffraction powder patterns. Dr. Bright and Mr. Murray are members of the staff of the Mineral Sciences Division, while Dr. Reeve is a member of the Metals Reduction and Energy Centre, Department of Energy, Mines and Resources, Ottawa. REFERENCES 1 A. JONGEJAN AND A. L. WILKINS,J. Less-Common Metals, 24 (1971) 44.5. 2 A. JONGEJAN ANDA. L. WILKINS,J. Less-Common Metals, 25 (1971) 1pS. 3 R. C. DEVRI&S, R. ROY AND E. F. OSBORN,J. Am. Ceram. See., 38 (1955) 161. 4 A. T.PRINCE, M. IBRAHR.S ANDA. L. WTLKINS, M&z. Sci. Div. Rept. MS 63-52, Mines Branch, Department of Energy, Mines and Resources, Ottawa, Canada, 1963. 5 A. JONGEJAN ANDA. L. WILKINS,J. Less-Common Metals, 2i (1970) 225. 6 A. JONGEJAN ANDA. L. WILKINS,J. Less-Common Metals, 19 (1969) 185.

J. Less-Common Metals, 25 (1971) 345-351