Studies on the Determination of the Valence Forms of Germanium in Germanium Monoxide and of the Main Components in a Mixture of Germanium Monoxide and Lead Dioxide by the APN Method

N. P. Pikula, L. F. Zaichko, A. A. Kaplin

(Presented by the scientific seminar of the Department of Physical and Colloid Chemistry)

At the present time, in radioelectronics and communications technology, the use of integrated circuits obtained by depositing oxides or mixtures of oxides of two metals onto appropriate substrates is becoming increasingly important. In the present work, the objects of study are films of germanium monoxide (GeO) and films of germanium monoxide containing some amount of lead dioxide ($\mathrm{GeO} + \mathrm{PbO_2}$), obtained by deposition onto sitall substrates at high temperatures and pressures.

In the opinion of a number of authors [1, 2], under the conditions of depositing films from germanium monoxide, it disproportionates into metallic germanium and its dioxide according to the reaction

\[ 2\mathrm{GeO} = \mathrm{Ge} + \mathrm{GeO_2}. \]

It is therefore of interest to determine the valence forms of germanium in the bulk of the initial powdered and crystalline black-gray germanium monoxide and in the films deposited from it onto sitall substrates, which, depending on the deposition conditions, have colors ranging from yellow to dark brown.

Tananaev and Shpirt indicate [2] that germanium(II) is quantitatively determined in the presence of germanium(IV) by volumetric methods based on its oxidation to germanium(IV), by polarographic methods using the cathodic reduction wave in hydrochloric acid medium, and by photocolorimetric methods based on measuring the intensity of colored germanium(II) complexes.

However, these methods are very poorly developed and are not suitable for small weighed portions of germanium monoxide, as is the case in the analysis of films whose weight is approximately 0.001 gram. In the present work we have attempted to determine the different valence forms of germanium, based on the selection of a specific solvent for each valence form of germanium, followed by quantitative amalgam-polarographic determination of germanium by the method of standard additions, using a stationary electrode in the form of a mercury drop.

Below are presented data on the behavior of different forms of germanium in a series of solvents.

On the basis of the data listed above, specific solvents were selected: for metallic germanium—hot sulfuric

acid; for dioxide, water; for germanium in any form, a diluted mixture of ammonia and hydrogen peroxide. The starting material and the films of germanium monoxide were successively dissolved in water, hot sulfuric acid, and a diluted mixture of ammonia and hydrogen peroxide. Then an aliquot was taken from each solvent for determination of germanium by amalgam polarography with accumulation. The work was carried out on OH-101 and OH-102 polarographs; the reference electrode was a saturated

Table 1 [1–3]

Solubility of germanium and its oxides in various media

* — denotes the absence in the literature of data on solubility.

calomel electrode, and the indicator electrode was a stationary electrode in the form of a mercury drop on a silver contact ($r = 0.04$ cm). As the supporting electrolyte for the determination of germanium, a solution of 0.2 M Na$_2$CO$_3$ + 0.025 M Trilon B, proposed by O. S. Stepanova [4], was used. Electroaccumulation of germanium was carried out for 3–5 min at a potential of −1.9 V; the potential of the anodic peak of germanium in this supporting electrolyte is −0.3 V; the quantitative content of germanium in this supporting electrolyte was estimated by the method of standard additions. The results of the analyses performed are presented in Table 2.

The experimental data on the content of various forms of germanium in germanium monoxide should be regarded as approximate, since the solubility of germanium compounds in various media, according to data from different authors, differs. However, on the basis of the investigations performed it is possible to conclude that different valence forms of germanium are present in GeO films.

Of special interest is the analysis of a mixture of germanium and lead oxides for the content of the principal components (germanium and lead) by the APN method.

The aim of this part of the work was to establish the conditions for the determination of lead in the presence of germanium and of germanium in the presence of lead by the APN method in the initial powder mixtures GeO + PbO$_2$ and in films deposited from them.

As a result of the studies carried out, we have shown that, against a background of \(0.2\,M\ \mathrm{Na_2CO_3} + 0.025\,M\) Trilon B, used for the determination of germanium, lead can also be determined. The potentials of the anodic peaks of germanium and lead on this background are, respectively, \(-0.30\ \mathrm{V}\) and \(-0.52\ \mathrm{V}\). The plots of the dependence of the heights of the anodic peaks of germanium and lead on a background of \(0.2\,M\ \mathrm{Na_2CO_3} + 0.025\,M\) Trilon B, using a stationary electrode in the form of a mercury drop, are straight lines passing through the origin.

Table 2

Experimental data on the determination of the valence forms of germanium in the initial germanium monoxide and in GeO films

Studies of the effect of germanium on the lead peak showed that the simultaneous determination of Ge and Pb on this background is possible when the concentration ratio of the indicated elements is \(\mathrm{Ge}:\mathrm{Pb} \ge 10:1\). When germanium is present in more than a 10-fold excess, lead must be determined on a background of \(0.1\,N\ \mathrm{NH_4F}\), where germanium gives no anodic peak, and the potential of the lead peak is \(-0.47\ \mathrm{V}\). On a background of \(0.1\,N\ \mathrm{NH_4F}\), even a 300-fold excess of germanium does not cause a decrease in the anodic peak of lead and, consequently, does not interfere with its quantitative determination.

On the basis of the studies carried out, procedures have been proposed for determining the main components in a mixture of germanium monoxide and lead dioxide and in films deposited from this mixture. The procedures are based on dissolving the sample in a dilute mixture of ammonia and hydrogen peroxide and then in hydrochloric acid, followed by the simultaneous determination of lead and germanium from an aliquot on a background of \(0.2\,M\ \mathrm{Na_2CO_3} + 0.025\,M\) Trilon B at a germanium-to-lead ratio of less than \(10:1\), respectively, or by determining germanium on a background of \(0.2\,M\ \mathrm{Na_2CO_3} + 0.025\,M\) Trilon B and lead on a background of \(0.1\,M\ \mathrm{NH_4F}\). The results of the analysis are presented in Table 3.

Table 3

Results of analysis of the initial mixture and of films deposited from it for the content of the main components by the APN method

This method is distinguished by its simplicity, the rapidity of the analysis (30–40 min, including decomposition of the sample), and the minimal use of reagents for the analysis.

Conclusions

1. On the basis of the investigations carried out, the presence of different valence forms of germanium (metallic germanium, its monoxide and dioxide) in the initial mixture of germanium monoxide and in films deposited from it onto sitall substrates has been experimentally demonstrated.

2. Methods have been developed for analyzing the initial mixture \( \mathrm{GeO} + \mathrm{PbO}_2 \) and the films deposited from it for the content of the principal components.

Literature

1. V. M. Andreev, A. S. Kuznetsov, G. I. Petrov, L. N. Shigina. Production of Germanium. Metallurgiya Publishing House, 1969.

2. I. V. Tananaev, M. Ya. Shpirt. Chemistry of Germanium. Moscow, Khimiya, 1967.

3. Chemist’s Handbook, vol. 2. Moscow–Leningrad, Khimiya Publishing House, 1964.

4. O. S. Stepanova. Candidate’s dissertation, Tomsk, TSU, 1964.