**3. Germanium production and its main applications**

Germanium was initially used industrially in transistors due to its semiconductor properties. However, it was later replaced by silicon, which has better behavior with respect to temperature [9]. In 2016, Ge applications in solar cells, fiber optics, metallurgy, and chemotherapy and as catalyst for polymerization of polyethylene terephthalate (PET) comprised in 2016 almost 80% of the global consumption of Ge [20, 28–30].

Fiber optics are the major use of Ge worldwide since it is used as a doping element in optical fibers, which contain approximately 4% Ge, the rest being silicon oxide (SiO<sup>2</sup> ). Germanium increases the refractive index of the optical fiber which helps to contain the light within the fiber and enables the transmission of the digital signal. Germanium can also be used to make lenses and window panes for infrared detectors, infrared devices mainly destined to military guidance, and weapon-sighting applications and cameras because of its transparency to infrared radiation. It can, therefore, be used in numerous applications such as surveillance, night vision, and satellite systems [29–31]. With regard solar cell applications, Ge is used in high-performance multi-junction cells (typically III–V cells) in the domain of photovoltaics (PV) and in the bottom-cell part of triple junction PV, for the substrate, base, and emitter layers, because of its lattice constant, robustness, low cost, abundance, and ease of production.

Other diverse uses of Ge could be as an alloying element (0.35%) for Sn, or Al-Mg alloys, to increase their hardness; soldering material (12%Ge/88%Au) for gold-based dental prosthesis; luminescent material; photographic and wide-angle lenses; ceramics, with Na<sup>2</sup> O/TiO<sup>2</sup> or K<sup>2</sup> O/ Ta2 O5 ; gamma-ray detector Bi<sup>2</sup> (GeO3 )3 ; bismuth germanate oxide crystals (BGO- Bi<sup>4</sup> Ge<sup>3</sup> O12) for various detection technologies (scintillation, tomography, gamma spectroscopy); fluorescent paint (MgGeO3 ); superconductors (Nb3 Ge); thermocouple; and thermoelectricity. Germanium dioxide is also used as a polymerization catalyst in the production of PET, giving rise to a wide range of PET bottles and containers [29–31].

produce GeO<sup>2</sup>

reduction of GeO<sup>2</sup>

with hydrogen.

electronic and optic are recycled in short cycle [36, 37].

in last year 1300 US \$/kg for Ge metal only in the USA [20].

, which is used in the manufacture of certain types of optical lenses and as a

Germanium: Current and Novel Recovery Processes http://dx.doi.org/10.5772/intechopen.77997 15

catalyst in the production of PET resin. Germanium metal powder is produced through the

In 2017, the worldwide production of Ge was estimated to be about 134,000 kg that is mainly recovered from Zn concentrates, coal deposits, coal fly ashes, and recycled materials [20]. While several authors have reported an increase (~30%) of the Ge production in the last decade, it is known that Ge reserve is scarce and it is estimated to be 8600 tons [9, 28, 34, 35]. The contradiction between the increasing consumption and the scarce reserve of Ge is becoming more notorious and has been contributed to a strong recycling process for Ge. In 2016, about 30% of the total Ge consumed was supplied from scrap (recycled materials), e.g., from windows in decommissioned tanks and military vehicles. In special, recycling rates for fiberoptic scrap are reported as high as 80%. As a consequence, about 50% of the Ge metal used for

As shown in **Figure 2**, the worldwide production of Ge is led by China (65.7%) followed by Russia (5%) and other countries such as Canada, Belgium, and Germany (30%) [20]. In China, Ge use in fiber optics increased substantially from 2012 to 2016 which supposed the highest consumption growth of Ge. Moreover, countries such as the USA and China treat Ge a strategic reserve, due to important value for the high-tech industry for civilian and military purposes [38]. Several authors indicate that reliable information about global Ge prices for public domain is very little published [1, 38, 39]. From the point of view of the authors, the last statements have partially contributed to the extremely global Ge price fluctuations, exceeding

**Figure 2.** Germanium refinery production of (a) global main producers between 2014 and 2017 excluding the USA—\*

includes Belgium, Canada, Germany and others [20, 29, 30, 34]—And (b) of USA between 2009 and 2012.

As explained in last sections, Ge recovery is associated with currently produced Zn and Cu-polymetallic ores and coal deposits [11, 31–33]. None of the Ge-bearing minerals is mined solely for its content, and most of the recovered Ge is a by-product from ores and coal processing [1]. Therefore, the extraction of Ge is mostly carried out through the typical extraction methods by mining facilities (pyro- and hydrometallurgy) [1, 25]. **Figure 1** shows the pathway processing for Ge recovering either by Zn refining residues and scrap. In general, after physical separation or pyro- and hydrometallurgical processes, a concentrate of Ge with around 30% content is obtained. Thus, the Ge concentrate, regardless of its source, is chlorinated, distilled, and purified to form the first usable product, GeCl<sup>4</sup> , which is primarily used in fiber-optic cable production [3]. Germanium tetrachloride can be hydrolyzed and dried to

**Figure 1.** Germanium processing pathway, modified from Melcher and Buchholz [3].

produce GeO<sup>2</sup> , which is used in the manufacture of certain types of optical lenses and as a catalyst in the production of PET resin. Germanium metal powder is produced through the reduction of GeO<sup>2</sup> with hydrogen.

various detection technologies (scintillation, tomography, gamma spectroscopy); fluorescent

dioxide is also used as a polymerization catalyst in the production of PET, giving rise to a

As explained in last sections, Ge recovery is associated with currently produced Zn and Cu-polymetallic ores and coal deposits [11, 31–33]. None of the Ge-bearing minerals is mined solely for its content, and most of the recovered Ge is a by-product from ores and coal processing [1]. Therefore, the extraction of Ge is mostly carried out through the typical extraction methods by mining facilities (pyro- and hydrometallurgy) [1, 25]. **Figure 1** shows the pathway processing for Ge recovering either by Zn refining residues and scrap. In general, after physical separation or pyro- and hydrometallurgical processes, a concentrate of Ge with around 30% content is obtained. Thus, the Ge concentrate, regardless of its source, is chlori-

in fiber-optic cable production [3]. Germanium tetrachloride can be hydrolyzed and dried to

Ge); thermocouple; and thermoelectricity. Germanium

, which is primarily used

paint (MgGeO3

); superconductors (Nb3

nated, distilled, and purified to form the first usable product, GeCl<sup>4</sup>

**Figure 1.** Germanium processing pathway, modified from Melcher and Buchholz [3].

wide range of PET bottles and containers [29–31].

14 Advanced Material and Device Applications with Germanium

In 2017, the worldwide production of Ge was estimated to be about 134,000 kg that is mainly recovered from Zn concentrates, coal deposits, coal fly ashes, and recycled materials [20]. While several authors have reported an increase (~30%) of the Ge production in the last decade, it is known that Ge reserve is scarce and it is estimated to be 8600 tons [9, 28, 34, 35]. The contradiction between the increasing consumption and the scarce reserve of Ge is becoming more notorious and has been contributed to a strong recycling process for Ge. In 2016, about 30% of the total Ge consumed was supplied from scrap (recycled materials), e.g., from windows in decommissioned tanks and military vehicles. In special, recycling rates for fiberoptic scrap are reported as high as 80%. As a consequence, about 50% of the Ge metal used for electronic and optic are recycled in short cycle [36, 37].

As shown in **Figure 2**, the worldwide production of Ge is led by China (65.7%) followed by Russia (5%) and other countries such as Canada, Belgium, and Germany (30%) [20]. In China, Ge use in fiber optics increased substantially from 2012 to 2016 which supposed the highest consumption growth of Ge. Moreover, countries such as the USA and China treat Ge a strategic reserve, due to important value for the high-tech industry for civilian and military purposes [38]. Several authors indicate that reliable information about global Ge prices for public domain is very little published [1, 38, 39]. From the point of view of the authors, the last statements have partially contributed to the extremely global Ge price fluctuations, exceeding in last year 1300 US \$/kg for Ge metal only in the USA [20].

**Figure 2.** Germanium refinery production of (a) global main producers between 2014 and 2017 excluding the USA—\* includes Belgium, Canada, Germany and others [20, 29, 30, 34]—And (b) of USA between 2009 and 2012.
