Phase Diagram, ZrO2 and Al2O3 System

Phase Diagram, Younes Sina, Zr-Al-O system, bainary system

1. Aluminum- Oxygen- Zirconium Phase diagram, Crystallographic and Thermodynamic Data Younes Sina

2. In principle it is possible to dope crystals in two different ways: Doping of an existing crystal 2) Growing the crystal from the normal constituents plus the desired amount of the foreign atoms

3. 1) Doping of an existing crystal There are 3 ways to introduce foreign atoms into an existing crystal: Bringing the crystal into contact with another phase which contains the desired foreign atoms. This then enter the crystal by solid state diffusion. Bombarding the crystal with appropriate ions Nuclear transmutation

4. There are no ternary phases in the Al-O-Zr system. Monoclinic αZrO 2 practically does not dissolve Al2O3. According to [1964Alp] the solubility of ZrO2 in Al 2 O 3 is 0.83 mol%. [2000Jer] found that it is even smaller (0.008 mol% ZrO 2 ).

5. Al 2 O 3 -ZrO 2   Fig. Zr-083 —System ZrO 2 -Al 2 O 3 , showing a new phase, e-Al 2 O 3 (Al 2 O 3 :ZrO 2 , 99:1 wt%). G. Cevales, Ber. Dtsch. Keram. Ges. , 45 [5] 216-219 (1968).   Starting materials were reagent-grade ZrO 2 and Al 2 O 3 (purity 99.88%) which had been heated to 1350°C for 15 h.  Mixtures were formulated at 5% intervals and additionally at 0.2% intervals in the regions 55 to 59% Al 2 O 3 and 95 to 100% Al 2 O 3 .  Ground mixtures with <70 wt% ZrO 2 were melted in W crucibles in a vacuum furnace.  Mixtures with >70 wt% ZrO 2 were heated in an electric arc furnace.  The melting temperatures were measured with a calibrated optical pyrometer, and observations were made on two series of compositions, one for heating and one for cooling.  The composition Al 2 O 3 :ZrO 2 (99.1 wt%), when fused in the arc furnace and quenched in H 2 O, yielded a new phase, e-Al 2 O 3 .  The phase was indexed on a hexagonal unit cell but with several low-angle peaks unaccounted for.  The new phase was verified by high-temperature X-ray diffractometry, using an IR strip furnace and optical pyrometry.  However, the high-temperature X-ray pattern reproduced is not convincing.  The solubility of Al 2 O 3 in ZrO2 was not studied because of the more general problem of the stabilization of tetragonal ZrO 2 . For a version of the system in an Ar atmosphere, see Fig. Zr-084. The polymorphism of pure ZrO 2 is shown in Figs. Zr-042 and Zr-043 .

6. Fig. Zr-083

7. Al 2 O 3 -ZrO 2   Fig. Zr-085 —System ZrO2-Al2O3 (calculated). P. Doerner, L. J. Gauckler, H. Krieg, H. L. Lukas, G. Petzow, and J. Weiss, CALPHAD: Comput. Coupling Phase Diagrams Thermochem. , 3 [4] 241-257 (1979 ).   The program used is for the calculation of condensed phase fields.1,2  The strategy for the calculation is outlined in[3] All thermodynamic data used are taken from the JANAF tables [4].   For ZrO2 only a monoclinic and a tetragonal modification were included.  In the case of the latter, the data were modified in such a manner as to yield the correct melting point.  Both solid phases are treated as purely stoichiometric. The mixing entropy of the liquid phase is described as an ideal mixture of molar units of AlO 1.5 and ZrO 2 ; therefore, only mixing of cation units is modeled.  For the diagram, the results have been transformed into the molar units Al 2 O 3 and ZrO 2 . The whole composition range is covered.  The temperature range of the calculation is 1527° to 2727°C.  The pressure is not included as a variable in the program (normal conditions in air are simulated). The corresponding experimental diagram in Fig. Zr-084 is reproduced reasonably well especially if one takes into account that only ideal mixing for the liquid phase was used and no higher terms were introduced . 1. B. Zimmermann; Ph.D. Dissertation. University of Stuttgart, Stuttgart, Germany, 1976. 2. L. J. Gauckler, H. L. Lukas, E. Th. Henig, and G. Petzow, CALPHAD: Comput. Coupling Phase Diagrams Thermochem. , 2 [4] 349-356 (1978). 3. H. L. Lukas, J. Weiss, and E. Th. Henig, CALPHAD: Comput. Coupling Phase Diagrams Thermochem. , 6 [3] 229-251 (1982). 4. D. R. Stull and H. Prophet; "JANAF Thermochemical Tables, 2nd ed.", Natl. Stand. Ref. Data Ser. (U. S., Natl. Bur. Stand.), Rep. No. NSRDS-NBS 37, National Bureau of Standards, U. S. Department of Commerce; Washington, D.C., 1141 pp. (1971).

8. Fig. Zr-085

9. Al 2 O 3 -ZrO 2   Fig. Zr-086 —System ZrO 2 -Al 2 O 3 .  Binary phase relations under He atmosphere. G. R. Fischer, L. J. Manfredo, R. N. McNally, and R. C. Doman, J. Mater. Sci. , 16 [12] 3447-3451 (1981).   Approximately 20 samples were examined to determine liquidus temperature in situ using high-temperature X-ray diffraction.  Starting materials were coprecipitated from mixed metal chloride solutions using NH 4 OH.  The resultant gel was stirred, dried in air, and then calcined to 1000°C.  Chemical analysis of the resultant powders resulted in a maximum absolute error of ±1 wt% ZrO 2 .  (All reported ZrO 2 values include a relative 1.8 wt% HfO 2 ).  Semiquantitative spectrographic analysis for trace impurities indicated generally <1000 ppm total impurities with no detectable chlorine in any sample. A second set of samples were prepared by solid state reaction synthesis of "reagent-grade" oxides for determination of the eutectic composition through microstructural examination of fused samples.  For liquidus studies, the coprecipitated mixtures were ground to smaller than 325 mesh and mixed with xylene for application to the 5-mm Ta-foil strip heater substrate.  Approximately 0.05-g samples were used.  High-temperature X-ray diffraction studies were performed using a wide-angle goniometer with a detector panel, and equipped with a modified commercial high-temperature attachment.  All studies used Ni-filtered CuKa radiation, with an atmosphere of purified helium maintained to prevent oxidation of the sample holders.  Temperature measurement was performed optically, matching the apparent brightness of the Ta holder with the pyrometer filament.  Accuracy was assured by calibration curves established using known melting points of Pt, Au, and the end-member oxides and was said to be ±20°C.  Melting was determined through observance of the disappearance of characteristic diffraction lines as the sample temperature was increased step-wise.  The eutectic composition, 42.5 ±1 wt% (61.8 mol%) ZrO 2 , was confirmed by optical microscopy on polished sections of samples surrounding the apparent liquidus minimum composition.  These samples were fused in an induction furnace .

10. Fig. Zr-086

11. Al 2 O 3 -ZrO 2   Fig. Zr-087 —System ZrO2-1/2(Al 2 O 3 ). Calculated. F ss, T ss, and M ss = cubic, tetragonal, and monoclinic ZrO 2 solid solutions; Crn = corundum (Al 2 O 3 ). R. G. J. Ball, M. A. Mignanelli, T. I. Barry, and J. A. Gisby, J. Nucl. Mater. , 201 , 238-249 (1993).   Models were developed in this paper for phase equilibria of oxides subject to reactions between nuclear reactor core debris and concrete. Calculations were performed using thermodynamic and phase equilibria data from the literature. The optimized description of crystalline and liuqid phases obtained was then used to predict phase relationships in higher-order systems. The optimization programs used included one reported in Ref. [1]. The reference value for the Gibbs energy of a phase that was used was the weighted sum of the enthalpies of its constituent elements in their standard states at 25°C. The temperature dependence of the Gibbs energy is expressed in an equation that includes experimental enthalpy, entropy, and heat capacity data. For solution phases, the Gibbs energy mixing is included using an associated solution model.2 Thermodynamic data were obtained by critically assessing the results in Refs. [3-11].   1. H. L. Lukas, E. Th. Henig, and B. Zimmermann, CALPHAD: Comput. Coupling Phase Diagrams Thermochem. , 1 [3] 225-236 (1977). 2. F. Sommer, Z. Metallkd. , 73 [2] 72-76 (1982). 3. M. W. Chase, Jr., C. A. Davies, J. R. Downey, Jr., D. J. Frurip, R. A. McDonald, and A. N. Syverud, J. Phys. Chem. Ref. Data, Suppl. , 14 [1] 927-1856 (1985). 4. I. Ansara and B. Sundman, "The Scientific Group Thermodata Europe"; pp. 154-158 in Proc. Int. CODATA Conf., 10th (Computing, Handling and Dissemination of Data), 1986. Edited by P. S. Glaeser, Elsevier Science B.V., Amsterdam, Netherlands, 1987. 5. E. H. P. Cordfunke and R. J. M. Konings; Thermochemical Data for Reactor Materials and Fission Products, 695 pp. North-Holland, Amsterdam, Netherlands, 1990. 6. M. H. Rand, R. J. Ackermann, F. Groenvold, F. L. Oetting, and A. Pattoret, Rev. Int. Hautes Temp. Refract. , 15 [4] 355-365 (1978). 7. J. D. Cox, D. D. Wagman, and V. A. Medvedev; CODATA Key Values for Thermodynamics, 271 pp. Hemisphere Publishing, Bristol, Pennsylvania, 1989. 8. D. D. Wagman, W. H. Evans, V. B. Parker, R. H. Schumm, I. Halow, S. M. Bailey, K. L. Churney, and R. L. Nuttall, J. Phys. Chem. Ref. Data, Suppl. , 11 [2] 1-392 (1982). 9. V. P. Glushko, L. V. Gurvich, I. V. Veyts, C. B. Alcock, G. A. Bergman, G. A. Khachkuruzov, V. A. Medvedev, and V. S. Yungman; Thermodynamic Properties of Individual Substances: A Hand Book. Hemisphere Publishing, Bristol, Pennsylvania, 1981 & 1989. 10. I. Barin and O. Knacke; Thermochemical Properties of Inorganic Substances, 921 pp. Springer- Verlag , Berlin, Germany, 1973. 11. L. B. Pankratz, "Thermodynamic Properties of Elements and Oxides", Bull. - U.S., Bur. Mines, Bull. No. 672, U. S. Government Printing Office; Washington, D.C., 509 pp. (1982).

12. Fig. Zr-087

13. Al 2 O 3 -ZrO 2   Fig. Zr-088 —System ZrO 2 -Al 2 O 3 . T = tetragonal; M = monoclinic; F = fluorite-type (cubic). S. N. Lakiza and L. M. Lopato, J. Am. Ceram. Soc. , 80 [4] 893-902 (1997).   Powders of ZrO 2 and Al 2 O 3 (both 99.99% pure) were used to prepare specimens at 5 mol% intervals. Samples for 17 compositions were blended in an agate mortar with ethanol, pressed into pellets, and heated in Mo containers in a DTA apparatus under He to 2500°C. The investigation also used derivative thermal analysis to 3000°C with a solar furnace, X-ray powder diffraction, petrographic analysis, microstructural phase analysis, and electron microprobe X-ray analysis.     1. F. Schmid and D. J. Viechnicki, J. Mater. Sci. , 5 [6] 470-473 (1970). 2. J. Echigoya, Y. Takabayashi, K. Sasaki, S. Hayashi, and H. Suto, Trans. Jpn. Inst. Met. , 27 [2] 102-107 (1986). 3. A. V. Shevchenko, L. M. Lopato, G. I. Gerasimyuk, and V. D. Tkachenko, Izv. Akad. Nauk SSSR, Neorg. Mater. , 26 [4] 839-842 (1990); Inorg. Mater. (Engl. Transl.) , 26 [4] 705-708 (1990).

14. Fig. Zr-088

15. Al 2 O 3 -ZrO 2   Fig. 11136 —System ZrO 2 -Al2O 3 . T - x sections of the phase diagram for the ZrO 2 -AlO 1.5 system. ( A ) Calculated T - x phase diagram; ( B ) calculated ToL ss curve together with the extended T ss data from Ref. 1. C ss, T ss, and M ss symbols denote cubic (fluorite-type) zirconia solid solution, tetragonal zirconia solid solution, and monoclinic zirconia solid solution, respectively. T. Wang and Z. P. Jin, J. Cent. South Univ. Technol. (Engl. Ed.) , 4 [2] 108-112 (1997).   Phase relations in the quasibinary ZrO 2 -AlO 1.5 system were assessed by means of the CALPHAD technique. The liquid phase, cubic (fluorite-type) zirconia solid solution, and tetragonal zirconia solid solution were described by a regular solution model. Monoclinic zirconia and a-AlO 1.5 were treated as stoichiometric phases. A consistent set of optimized parameters were obtained to agree with the available experimental data. The assessed data for invariant equilibria in the ZrO 2 -AlO 1.5 system are listed in the following table .   —————————————————————— Composition (mol% AlO 1.5 ) Temp. (°C) —————————————————————— C ss = Liquid + T ss 3.4 38.6 2.5 2263   Liquid = T ss + α -AlO 1.5 77.9 6.3 100 1862   T ss = M ss + a-AlO 1.5 1.1 0.0 100 1140 ——————————————————————   The calculated eutectic temperature is consistent with the results of Refs. 2-4. The calculated eutectic composition agrees well with that from Refs. 2-6 within the estimated errors. The accuracy of the phase diagram is dependent on the entire set of the experimental and thermodynamic information; further studies are needed for the equilibrium solubilities of AlO 1.5 in ZrO 2 phases. The results are applied to the production of highly corrosion resistant and refractory materials .   1. M. L. Balmer, F. F. Lange, and C. G. Levi, J. Am. Ceram. Soc. , 77 [8] 2069-2075 (1994). 2. F. Schmid and D. J. Viechnicki, J. Mater. Sci. , 5 [6] 470-473 (1970). 3. A. V. Shevchenko, L. M. Lopato, G. I. Gerasimyuk, and V. D. Tkachenko, Izv. Akad. Nauk SSSR, Neorg. Mater. , 26 [4] 839-842 (1990); Inorg. Mater. (Engl. Transl.) , 26 [4] 705-708 (1990). 4. S. N. Lakiza, L. M. Lopato, and A. V. Shevchenko, Poroshk. Metall. (Kiev) , 33 [9-10] 46-51 (1994); Sov. Powder Metall. Met. Ceram. (Engl. Transl.) , 33 [9-10] 486-490 (1994). 5. J. B. MacChesney and P. E. Rosenberg; pp. 114-165 in Phase Diagrams: Materials Science and Technology, Vol. I (Theory, Principles, and Techniques of Phase Diagrams). Edited by A. M. Alper. Academic Press, London/New York, 1970. 6. I. Shindo, S. Takekawa, K. Kosuda, T. Suzuki, and Y. Kawata, Adv. Ceram , 12 [Sci. Technol. Zirconia 2] 181-189 (1984).

16. Fig. 11136

17. Al 2 O 3 -ZrO 2   Fig. Zr-084 —System ZrO 2 -Al 2 O 3 in Ar M . Alper, "Interrelationship of Phase Equilibriums, Microstructure, and Properties in Fusion-Cast Ceramics"; pp. 335-369, in Sci. Ceram, Vol. 3 . Edited by G. H. Stewart. Academic Press, London, United Kingdom, 1967 .   Experiments were conducted in an induction furnace, with setter materials of the same compositions as the mixtures being heated.  About 16 samples were melted in an Ar atmosphere, and temperature was measured with an optical pyrometer.  According to Ref. 1, <1% ZrO 2 goes into solid solution in a-Al 2 O 3 and up to ~7 % Al 2 O 3 can form a solid solution with ZrO 2 .  The distribution of phases obtained was found to be related to the phase diagram and was dependent on composition and cooling rate.      1. A. M. Alper, R. N. McNally, and R. C. Doman, Am. Ceram. Soc. Bull. , 43 [9] 643-643 (1964).

18. Fig. Zr-084

19. Zirconia was prepared by firing the coprecipitate from ZrOCl 2 and AlCl 3 mixed aqueous solution with ammonia . When fired above 600°C, the products were fine crystalline tetragonal zirconia of crystallite size <10 nm. In previous studies , the tetragonal phase had been assumed to be a (Zr 4+ 1-x Al 3+ x )O 2-x/2 solid solution, where x < 0.25. However , X-ray diffraction pattern simulation and Al K-edge X-ray a bsorption near-edge structure (XANES) spectroscopy confirmed the present product to be a mixture of t-ZrO 2 fine powder with a small amount of δ -Al 2 O 3 of very low crystallinity , even below the expected compositional range of x < 0.25 in the a ( Zr 4+ 1-x Al 3+ x )O 2-x/2 solid solution. Shinichi Kikkawa , Akio Kijima, Ken Hirota , and Osamu Yamamoto Department of Material Science and Engineering, Graduate School of Engineering , Hokkaido University, Sapporo, 060-8628, Japan

20. Growing the crystal from the normal constituents plus the desired amount of the foreign atoms

21. Because of a high melting point of sapphire ( Tm=2323 K), the growth of single crystals from melt is performed in most cases using tungsten or molybdenum–tungsten crucibles in heating units (furnaces) made of sheet molybdenum. For this reason, both metals are highly probable impurities in the final sapphire substrates . Additional impurities can pass to as-grown crystals from the initial materials.

22. Glow Discharge Mass Spectroscopy (GDMS) analysis of Heat Exchanger Method ( HEM) sapphire showed the following typical impurities (all values in ppm ): Na 1 Si 4 Fe 0.6 Ca 2 Mg 2 Ga 2 Cr 0.2 Ni 0.3 Ti <0.3 Mn 0.5 Cu 0.1 Mo < 0.5 Zn 1 Zr 1 Most of the impurities are close to the detectability limits of GDMS.

23. Diffusion studies coupled with doping data can also yield information about the likely defect types present in a solid. For example, zirconia, ZrO 2 , as an impurity in alumina, Al 2 O 3 . The Zr 4+ cations are accommodated on Al 3+ sites as substitutional defects with an effective positive charge, Zr • Al . As ZrO 2 is oxygen rich compared to alumina , the extra oxygen can either be accommodated as oxygen interstitials, O i 2 ’: 2 Zro 2 (Al 2 O 3 )→2 Zr • Al + 3 O o +Oi 2 ’ or balanced by Al 3+ vacancies, V 3’ Al : 3 ZrO 2 (Al 2 O 3 )→3 Zr • Al + 6 O o + V 3’ Al

24. Isothermal sections for the Al-O- Zr system were constructed based on diffusion couple studies. No ternary phases have been observed. [1977Guk, 1978Guk1, 1978Guk2, 1978Guk3 Al-O-Zr. Isothermal section at 1300°C

25. Isothermal sections for the Al-O- Zr system were constructed based on diffusion couple studies. No ternary phases have been observed . [1977Guk, 1978Guk1, 1978Guk2, 1978Guk3 Al-O-Zr. Isothermal section at 1130°C

26. Mahabad- Iran