The Stability of Silica

Abstract

Chipman1 recently reviewed five lines of evidence that indicate that the presently accepted heat of formation of silica (-209.9 kcal./mole)2 calculated from the heat of combustion of silicon in an oxygen bomb may be as much as 5 kcal./mole too positive.Still more recently, Good3 measured the heat of formation of aqueous fluosilicic acid and calculated a value of -217.5 ± 0.5 kcal./mole for AHf°m (c, quartz) which is 7.6 keal./mole more negative than the literature value. Some recent effusion

Oxygen Doping of Solution-Grown GaP

“…[aGa] 4 [aGa203] K had been obtained as a function of T by Cochran and Foster (15). The Ga20 pressure calculated from [9], together with the known free space in the capsule and the ideal gas relation, pv = nRT, permits the calculation of the correction that is to be subtracted from the measured weight loss.…”

The Reaction of GaP(s) with H[sub 2]O(g) and the Range of Stability of GaP(s) under Pressures of Ga[sub 2]O and P2

“…We have obtained a new heat of formation of SiO from the recent measurements Ramstad and Richardson (12) who studied the following reactions SiOf(quartz) -~ Hf(g) ----SiO(g) ~-HfO(g) [16] and Si(s and 1) + SiOf(quartz) : 2SiO(g) [17] The thermodynamic functions for SiOf, SiO, Si, H20, and H2 needed in this calculation were obtained from the JANAF Tables (13). The heat of formation of SiOe was corrected using the recent value recommended by Good ( 14) and corroborated by others (15,16) It is now possible to calculate the heat of formation of Ga20 from the measurements of Cochran and Foster (11) of the reaction of Ga with SIO2, Eq. [13].…”

“…SiO and Ga20.--Cochran and Foster (11) and Frosch and Thurmond (4) have given values for the heat of formation of Ga20. Cochran and Foster studied the two reactions 2Ga(1) ~-SiO2(s) ----Ga20(g) -t-SiO(g) [13] and 2Ga(1) ~-MgO(s) : GafO(g) -~ Mg(g) [14] while Frosch and Thurmond studied the reaction 4 1 -~-Ga(1) + -~ GafO~(s) ----Ga~O(g) [15] Recently, new experimental data have become available which lead to revised heats of formation for SiO2 and SiO. These revisions lead to a revision in the heat of formation of Ga20 as obtained from the reaction described by Eq.…”

Thermodynamic Analyses of Open Tube Germanium Disproportionation Reactions

“…The AH*p for the complete process represented by Eq. [4] at a given temperature [4] 0 ~ AHp* ~ AHp will be positive in sign but slightly less in magnitude than AHp. If subsequent experiments are performed in which the quantity of D is increased, a point will be reached ultimately at which reaction [1] now represents a perturbation on reaction [3], and AH*p will be negative in sign and transport will occur from the cold to hot regions of the system.…”

“…The epitaxial growth of GaAs using various transporting agents has become well established among many investigators (1)(2)(3)(4)(5)(6). Little has been reported, however, on the nature of incorporation of impurities during the growth process.…”