Liquidus in the Alumina‐Rich System La₂O₃—Al₂O₃

Abstract

TEMPERATURE ("C) 950 900 850 aoo 750 10.10 0 a l -< N -k k lo-'' s Iz w 0 W z l n 3 LL 0 0 LL Fig. 3. Autoradiograph of coarse-grained specimen with 0.001 5 in. removed from the original surface. %,a 0.82 0.86 0.90 0.94 0.98 0.102 VT ( 1 6~0~)The diffusion of 95Zr was attributed to "short circuit" paths, grain boundaries: and dislocations,' as well as volume diffusion for two reasons: (1) The data in the "tail" showed a linear relation when plotted as log of activity vs. depth; (2) an autoradiograph, made after 0.0015 in. of the specimen was ground away, showed gross inhomogeneities, Fig. 3 (for coarse-grained mate-(~2 ' -XI') 6.45 X Dt rial). "Short circuit" diffusion also may be associated with twin boundaries since they contain atomic disarraysK characteristic of short circuit paths4J Twin boundaries were abundant at room temperature but were not investigated a t the annealing temperatures in these specimens.Concentrated activity is present on part of the specimen circumference (Fig. 3) an indication that edge effects were not completelyThe data in Fig. 2 may be regarded as "effective" diffusion coefficients, including volume as well as short circuit components, although some of the short circuiting effects were removed from the data with the tail corrections noted in the foregoing. Fig. 2. Diffusion coefficients of Zr in ZrH1.a and Zrl.To. squares analysis. cients': The slope was related to the diffusion coeffilog Az -log A I --0.1086 A1 = activity a t depth XI mils. A z = activity a t depth r2 mils. D = diffusion coefficient, cm2/sec. t The diffusion coefficients and their estimated error for 2rHI.S and ZJH,,;~ are shown in an Arrhenius ~i~, 2, A leastsquares fit of these data gives values for the activation energy, Q = 33,000 f 6000 cal/mole and for the constant, DO = 1 X 10-6 to I x 10-4 cmz/sec. The diffusion coefficients for z~H~.~ are higher than those for ZrHl.iO, and a real difference may exist because of variations in impurity content and/or other factors previously noted. The Acknowledgment data were treated together since the respective errors overlapped in Fig. 2. = time of diffusion in seconds. in this specimen. R. S. Carpenter performed most of the experimental work and A. J. Moses carried out the Zr-Nb separations.

Phase relations in the ZrO2–La2O3–Y2O3–Al2O3 system: Experimental studies and phase modelling

“…2. Calculated data for invariant reactions are compared with available experimental information [44][45][46][47] in Table 3.…”

Thermodynamic Modeling of the HfO2–La2O3–Al2O3 System

“…The reassessed phase diagrams of La 2 O 3 –Al 2 O 3 and HfO 2 –Al 2 O 3 systems are shown in Figs. and compared with the experimental data, and the invariant reactions are presented in Table . The calculated results are in good agreement with most experimental data.…”

“…Because the source of thermodynamic data of oxide components is different between this work and Badu and Nagarajan, 28 the calculated entropy of formation from oxide components of La 2 Hf 2 O 7 at 298 K is not zero but 1.39 JÁ(molÁK) À1 . Ushakov et al 27 [38][39][40][41][42][43][44] and the invariant reactions are presented in Table 2. The calculated results are in good agreement with most experimental data.…”

Phase diagram estimation of the Al2O3-SiO2-Re2O3 systems

“…Bondar and Vinogradova [33] found in 1964 that there existed two intermediate compounds: (A1203) 0.5 (La203) 0.5 and 18-A1203 ( 11% --12 % mol A1203), the former melted at 2100 + 20~C congruently and the later at 1930 +-20~C uncongruently. Fritsche and Tensmeyer [34] agreed in the melting point of 13-A1203 but they considered this compound melted congruently. Rolin and Thanh [35] conducted the experiment again with thermal analysis, X-ray diffraction technique.…”

“…Experimental results from various authors [33][34][35][36] showed some similarities in the AlzO3-La203 system in the composition range of ~0--50 % (mol) La203. Bondar and Vinogradova [33] found in 1964 that there existed two intermediate compounds: (A1203) 0.5 (La203) 0.5 and 18-A1203 ( 11% --12 % mol A1203), the former melted at 2100 + 20~C congruently and the later at 1930 +-20~C uncongruently.…”