The phase diagram for the system Bi2O3‐B2O3 has been determined experimentally. The melting point of Bi2O3 has been redetermined as 825° C with an estimated overall uncertainty of about ±3°C, and the molal heat of fusion of Bi2O3, calculated from the slope of the liquidus curve, is 2050 cal per mole. The system contains a body‐centered cubic phase of approximate composition 12Bi2O3·B2O3, which melts incongruently at 632°C. Four congruently melting compounds exist in the system: 2Bi2O3· B2O3·5B2O3, Bi2O3·3B2O3, and Bi2O3·4B2O3, with melting points, respectively, of 675°, 722°, 708°, and 715°C. The Bi2O3·4B2O3 compound exhibits a sluggish transformation at 696°C. Compositions containing up to 97.5 wt% (85 mole %) Bi2O3 can be partly or totally quenched to glass. Indices of the quenched glasses are greater than 1.74. A region of liquid immiscibility extends at 709°C from almost pure B2O3 to 19.0 mole % Bi2O3. The extent of immiscibility theoretically calculated agrees with the experimentally determined value when 1.20 A is used for the ionic radius of Bi3+.
(Janu ary 5, 1965) DT A was c hose n as a co nve ni ent method for resolvin g diffe re nces in th e re port e d he a t of tra ns iti o n a nd heat of fu s ion of Bi 20 3 • The heat of th e low to hi gh tra ns ition of K,SO. (at 583°C) a nd t he heat of fu s ion of Ag (at 960.8 °C) were used a s int e rn a l s ta nd a rd s. These s tand a rd s we re mix ed d irec tl y with th e Bi , O" in three weight ratios. Th e hea tin g sc hedule for eac h we ight rati o was 3°/ min , 9°/ min , a nd 3°/min. For e valu a tin g internal co ns is te ncy, DTA de te rm in ati ons we re mad e for mixtures of the tw o s tand a rd s. Linearity was obtained within limits be tween the weig ht rati o of Bi2 0" and s ta nda rd a nd th e correspo ndin g ratio of pea k a reas. Th e he at of tra ns iti on of Bi 20 " { m on~ °c c ubi c was found to . .m~.. be 9.9±0.S kcal/ mole a nd th e hea t of fu s IOn (c ubI c ...... Ilq .) 3.9± 0.2 kcal/ mo le. The un ce rta intI es are es timat ed limit s of error, based on interna l co ns is te ncy a nd on th e va lues of th e s tandard s.
The change in volume, AV, due to a triaxial tensiIe stress, P, for a material with effective compressibility pSfr is:Under constant load, the creep rate, A; , for a rate of change of the effective compressibility, p,,,, is:
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