X-RAYDIFFRACTION STUDIES IN THE BeO-In20a SYSTEM
Dec., 1953
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X-RAY DIFFRACTION STUDIES IN THE SYSTEM Be0-Inz03* BY L. M. WATTAND W. 0. MILLIGAN The Rice Institute, Houston, Texas Received March 8, 1965
Marked mutual protection against crystallization was obRerved in the system BeO-Inzoo. The composition ranges over which the two zones of mutual protection extend vary with the temperature level a t which the gels are heated. Heat treatment of the dual oxide gels for two hours a t 700 or 800" results in interstitial solid solution in the InzOcstructure of as much as 90 mole per cent. beryllium oxide.
Similar studies are reported here for the system Introduction The phenomenon of mutual protective action2in BeO-In20a, chosen for the distinctively different dual systems of hydrous oxides has been previously crystal structures of the two oxides. observed in the following systems: C~O-Fe203,~ Experimental N~O-AISO~,~ FezO~-CrzOs,~and BeO-A120~, Zr0.r Ala03 and Sn02-A120s.6 An examination of the Appropriate portions of beryllium and indium nitrate ternary systems NiO-Cr203-Zr02' and A1203- solutions (0.71 M with respect to the anhydrous oxides) Sn02-TiOzS revealed a similar behavior. In each were mixed together and recipitated with a slight excess of ammonium hydroxide Ca. 5.0 M ) to form eleven mixed of these systems each oxide prevents or retards the hydrous oxide gels containing 0, 10, 20, 30, 40, 50, 60, 70, crystallization of the other. Theidegree of mutual 80,90 and 100 mole per cent. InnOa. After being washed in protection varies from system to system and also a centrifuge with distilled water and dioxane until nitrate depends upon the temperature level a t which the free, the gels were poured into evaporating dishes and allowed to dry in air a t room temperature. Small portions dual gels have been heated. of the air-dried gels were heated for two hour periods in an (2 e)
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electric furnace at 300,400,500,600,700 and 800'. X-Ray diffraction patterns of the air-dried and the heattreated samples were obtained using CuK, X-radiation and a Norelco 90" recording X-ray spectrometer. Tracings of some of the 77 X-ray Spectrometer curves are given in Figs. 1-2 for samples heat treated at 300, 400, 500 and 600". The results at the higher temperatures are given in chart form in Figs. 3-4. (2 0) 20°
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(1) Preliminary results were presented before the 2nd Texas Regional Meeting of the American Chemical Society, Dallas, Texas, December, 1946, (2) W. 0.Milligan, Taxa JOURNAL, 55, 497 (1951). (3) W.0. Milligan and J. Holmes, 3. Am. Cham. Boc., 63,149 (1941). 50,465 (1946). (4) W. 0.Milligan and L. Merten, TEISJOURNAL, (5) W.0.Milligan and L. Merten, ibid., 51,521 (1947). (6) H. B. Weiser, W. 0. Milligan and G. A. Mills, ibid., 52. 942 (1948). (7) W. 0. Milligan and L. M. Watt, 8 i d . . 52, 230 (1948). (8) W. 0.Milliean and B. G. Holmes, ibid., 57, 11 (3958).
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Fig. 2.-X-Ray
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L. M. WATTAND W. 0. MILLIGAN
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The series of samples heated for two hours a t 400' and that heated for two hours at 500' exhibited very similar X-radiograms. At these temperatures the mutual protection phenomenon was clearly visible. The samples containing 100 and 90 mole per cent. In203gave the standard cubicIn& pattern; the 80 mole per cent. In203 sample was amorphous to X-rays; the X-radiogram of the 70% 1n&13-3070 Be0 sample also exhibited lines of the standard In& pattern; all samples containing 60 through 90 mole per cent. InzOawere again amorphous; and the pure Be0 sample gave the standard hex'agonal Be0 pattern. Thus, two zones of mutual protection against crystallization were observed, one between 90 and 70 mole per cent. In203and another between 70 and 0 mole per cent. Heat treatment a t 600" shifted these regions of mutual protection. Figure 2 shows that after two hours at this higher temperature all samples containing 100 through 60 mole per cent. In203 contain In203 crystals; the 50 and 40 mole per cent. In203 samples are amorphous; the 30 and 20 mole per cent. Inz03samples are crystalline; and the 10 mole per cent. sample is also amorphous. The pure Be0 sample is again crystalline. In this series of samples the zones of mutual protection lie between 60 and 30 mole per cent. In20a and 20 and 0 mole per cent.
of ions of one kind by ions of another having different effective radii. The deformation of the unit cell resulting from such substitutions is revealed in the X-ray diagrams by a shift in the positions of the diffraction lines and has been observed in other dual oxide systems such as that of the ferric and chromic oxides.6 However, if the packing of the ions in a crystalline compound leaves large enough holes between its ions, small incoming ions foreign to
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Dec., 1953
SORPTION-DESORPTION STUDIES IN THE BeO-In203 SYSTEM
random, no coherent scattering of the X-rays would be expected, and hence new diffraction lines would not appear. The small radius of the beryllium ion compared to that of the oxygen and indium ions and the lack
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of a detectable shift in the observed cubic In203 lines (Fig. 4) make this type of interstitial solid solution a likely explanation of the crystal structures giving rise to the X-radiograms obtained of the BeO-In20, system.
SORPTION-DESORPTION STUDIES IN THE SYSTEM BeO-In20a' BY W. 0. MILLIGAN AND C. R. ADAMS The Rice Institute, Houston, Texas Received March 9. 1868
Water vapor sorption-desorption isotherms a t 2 and 12" have been obtained for a series of eleven heat-treated (2-hour periods) gels selected a t every 10 mole per cent. in the system BeO-InzOs. Two zones of enhanced adsorption occur at compositions of about 40-60 and 90 mole per cent. BeO, in a plot of specific adsorptive capacity at constant p / p o as a function of composition. Plots of BET surface area as a function of composition lead to the same conclusion. The two zones of enhanced adsorptive capacit correspond to the zones of mutual protection against crystallization previously detected by X-ray diffraction methods. Losteric differential and integral heats of adsorption are likewise higher in the regions of mutual protection. The observed enhanced composition zones of amount of adsorption and the enhanced heats of adsorption confirm a prediction set forth in an earlier paper. The most frequent uncorrected Kelvin pore radii computed from the desorp, tion isotherms are 125 A. for pure In208 and 25 b. for pure BeO. As the amount of B e 0 is increased the pore radii decrease regularly, the greatest changes occurring at compositions of 10 and 90 mole per cent. BeO.
Introduction In a previous report from this Laboratory2 a systematic X-ray diffraction study of dual hydrous oxide gels in the system BeO-In203 demonstrated the existence of two composition zones of mutual protection against crystallization. In an earlier investigation3 the prediction was made that such zones of prot,ection may correspond to regions of maximum surface, and which, therefore, may exhibit enhanced adsorptive properties. The purpose of this present paper is to report the results of an extensive sorption-desorption study of gels in the system BeO-In20e which have been heat treated at 500 O. Experimental Preparation of Samples.-The samples employed in this investigation were prepared similarly to those previously used in X-ray diffraction experiments.2 Freshly prepared solutions of beryllium and indium nitrate (0.5 M with respect to the anhydrous oxides) in 0.01 N nitric acid were coprecipitated at a pH value of 9.4 in a rapid mixing device4 by the addition of a previously determined quantity of dilute freshly distilled ammonium hydroxide. The amounts of the beryllium and indium nitrate solutions were selected so that the eleven gels corresponded to 0, 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100 mole per cent. InlOs. The carefully washed2 gels were dried in air at room temperature, and then were heat treated at 500' for a period of two hours. After the heat treatment the samples were allowed to attain equilibrium with water vapor in the atmosphere, in order that samples for sorption-desorption isotherms and aliquot portions for water analysis would be identical in composition. X-Ray Analysis.-In order to ensure that the samples were closely similar to the ones used earlier in X-ray diffraction studies,2 monochromatic X-radiograms were obtained, using chromium Ka X-radiation from a sodium chloride crystal monochromator. "No-Screen" X-ray film was employed, and the exposure time was 60 hours. (1) Preliminary results presented before the Division of Colloid Chemistry at the 122nd meeting of the American Chemical Society in Atlantic City, N. J., September 14-19, 1952. (2) L. M. Watt and W. 0. Milligan, THISJOURNAL, 57, 883 (1963). (3) H. B. Weiser, W. 0. Milligan and G. A. Mills, ibid., 52, 942 (1948). (4) H. B. Weiser and W. 0. Milligan, ibid., 40, 1075 (1936).
Sorption-Desorption Isotherms.-The isotherms were obtained in a multiple sorption-desorption apparatus, fully described elsewhere.6 The temperature was held constant during each isotherm to approximately f0.001'.~ At the same time that the adsorption samples were placed in the apparatus, aliquot portiones were weighed and then ignited to constant weight at 750 . The loss in weight upon ignition was attributed to the loss of water, inasmuch as these samples had previously been heated at 500°, a t which temperature essentially all of the possible foreign volatile matter would have been lost. Complete sorption-desorption isotherms were obtained at 1 2 O , employing water vapor as the adsorbate. Barium chloride dihydrate, carefully degassed at liquid nitrogen temperature, was used as the source of water vapor. Water vapor was made available to the samples, while the temperature was being lowered from that of the room to 12' in order to maintain true equilibrium, after which the apparatus was evacuated at mm. before the commencement of the isotherms. Upon completion of the isotherms at 12", the temperature was lowered to 2', again in the presence of excess water vapor. Complete sorption-desorption isotherms were then obtained at 2", following the same procedure as at 12".
Results and Conclusions X-Ray Analysis.-The results of X-ray diffraction analysis were similar to those obtained previously2 at a temperature level of 500 or 600". Samples in a wide region of composition were found to be amorphous t o X-rays: namely, the region lying between 70% 1n203-30% Be0 and 10% 1n2O3--9O% BeO. The samples containing 30% or less Be0 gave only the pattern of In203with a decrease in crystallinity as the amount of Be0 increased. The X-ray results will not be discussed in detail here. Isotherms.-The sorption-desorption isotherms are plotted in Figs. 1-22. All of the samples gave similarly shaped isotherms, with the exception of the sample consisting of pure BeO. The isotherms for the ten samples containing In203 show that a considerable amount of water vapor is taken up at low relative pressures and that only a small amount of water vapor is taken up thereafter, until the relative pressure reaches a rather high value. At (5) W. 0. Milligan, W. C. Simpson, G. L. Bushey, H. H. Rachford, Jr., and A. L. Draper, Anal. Chem., 23,739 (1951).
