Les matériaux tétraédrites de formule chimique [(Cu,Ag)10(Zn,Fe)2(Sb,As)4S13] sont des roches naturelles particulièrement abondantes sur Terre appartenant à la famille des sels sulfurés. Longtemps étudiées du point de vue structural et pour leur composition, ce n’est que récemment qu’ils ont suscité un intérêt pour la thermoélectricité en raison de leur très faible conductivité thermique. Afin d’étudier les performances de ces matériaux en terme de conversion d’énergie, les travaux de cette thèse ont consisté à les synthétiser par métallurgie des poudres puis à mesurer leurs propriétés thermoélectriques aussi bien à basse température (2 – 300 K) pour identifier les mécanismes microscopiques qui gouvernent les propriétés de transport qu’à haute température (300 – 700 K) pour déterminer leur domaine d’application optimal. L’étude de leur homogénéité chimique et de leur stabilité thermique a permis de confirmer l’existence d’une transition structurale pour certaines compositions menant à la séparation de phases lors du refroidissement, mécanisme connu en minéralogie et en géologie sous le terme d’exsolution. Celui-ci peut être responsable d’une modification des propriétés de transport et notamment d’une diminution de la conductivité thermique de l’ordre de 50%. De nombreuses substitutions ont été entreprises afin de tenter d’optimiser les performances de ces composés. Les matériaux tétraédrites présentent un caractère métallique qui évolue vers un état semi-conducteur selon la nature de l’élément en substitution et de sa concentration. D’autre part, une étude détaillée des propriétés thermiques de ces matériaux par diffusion inélastique des neutrons a permis de déterminer l’origine microscopique des très faibles valeurs de conductivité thermique observées dans ces matériaux / Tetrahedrite with general chemical formula [(Cu,Ag)10(Zn,Fe)2(Sb,As)4S13] are a family of natural minerals, widely spread on Earth, which belongs to the sulfosalt class of compounds. Discovered in the 19th century and extensively studied by mineralogists over the last 60 years from both structural and chemical points of view, it is not until recently however that they have focused attention in thermoelectricity due to their very low thermal conductivity. In order to study the performance of these materials in terms of energy conversion by thermoelectric effect, this thesis consisted in synthesizing tetrahedrite materials by powder metallurgy method and in determining their transport properties both at low (2-300 K) and high temperatures (300-700 K). This wide temperature range enabled us to identify the microscopic mechanisms that govern the transport properties and to assess their thermoelectric performances. The study of their chemical homogeneity and thermal stability has confirmed the existence of a structural transition for certain compositions leading to phase separation upon cooling, a mechanism known in mineralogy and geology as an exsolution process. This mechanism is responsible for a modification of the transport properties and especially an impressive decrease in the thermal conductivity of the order of 50%. Numerous substitutions have been undertaken in an attempt to optimize the thermoelectric performances of these compounds. Tetrahedrite materials exhibit a metallic character that evolves into a semiconductor state depending on the chemical nature of the substituting element and on its concentration. Moreover, a detailed study of the thermal properties of these materials by inelastic neutron scattering has unveiled the microscopic origin of the very low thermal conductivity values observed in these materials

The study of fluid inclusions proved the metamorphic origin of the cinnabar-pyrite mineralization at the deposit of Horní Luby. In addition, thermal conditions of the mineralization formation were determined. During the deposit forming processes, the primary homogenous H2O-CO2 fluid of the temperature of about 300řC was differentiated to fractions rich in H2O or CO2. The differentiation took place in several stages in the temperature range between 200 to 150řC. Quartz crystallized from the parent fluid at the temperature about 300řC, pyrite at temperatures in the range of 220řC to 210řC and cinnabar at temperatures in the range of 195řC to 160řC. The cinnabar is thus the youngest mineral at the deposit (crystallization succession. quartz - pyrite - cinnabar). At the deposit of Jedová hora, quartz crystallized at the temperature of about 160řC to 150řC, barite at temperature of about 115řC (the fluid boiling point) and cinnabar in the range between these temperatures. The origin of mercury at all Czech historical deposit of cinnabar can be very likely related to Lower Paleozoic submarine volcanism. In all cases, the pre-concentrated mercury was remobilized during the Variscian metamorphosis, followed by precipitation in form of veins with cinnabar or as cinnabar impregnation. Study of tetrahedrite...

Mitt i Europas växande beroende av extern antimonproduktion har Europeiska kommissionen konsekvent betonat ett växande gap mellan utbud och efterfrågan sedan 2014. Som svar på denna utmaning riktade sig denna studie mot sekundära antimonkällor från underutnyttjade rester av guld, koppar och blymalm, som för närvarande utgör ett miljöproblem. Genom noggranna experiment, fastställde vi att optimal antimonurlakning uppnås vid 120 °C inom 2 timmar med en 250 g/L Na2S och 60 g/L NaOH-blandning. Detta tillvägagångssätt accentuerar selektiv extraktion, förbättrar antimonåtervinningen och minimerar kopparinterferens. En innovativ aspekt av denna studie var användandet utav mikrovågsassisterad urlakning, vilket visar fördelar i både utvinningseffektivitet och bevarande av mineralstrukturer jämfört med traditionella metoder. Våra resultat stöds av flera analytiska verktyg och ger en första förståelse, även om detaljerna kring mikrovågsassisterad urlakning och dess skalbarhet motiverar ytterligare utforskning. Denna studie introducerar en metod för urlakning av antimon från koppargruvavfall och föreslår ett motsvarande återvinningssystem som kan vara ekonomiskt lönsamt. Sådana ansträngningar kan ge ett blygsamt bidrag till att lindra den nuvarande situationen. / Amid Europe's growing reliance on external antimony production, the European Commission has consistently emphasized an expanding supply-demand gap since 2014. Responding to this challenge, our research targeted secondary antimony sources from underutilized residues of gold, copper, and lead ore processing, which currently pose environmental concerns. Through meticulous experimentation, we determined that optimal antimony leaching is achieved at 120°C within 2 hours, using a 250 g/L Na2S and 60 g/L NaOH mixture. This approach accentuates selective extraction, enhancing antimony recovery and minimizing copper interference. An innovative facet of this study was the adoption of microwave-assisted leaching, demonstrating advantages in both extraction efficiency and mineral structure conservation over traditional methods. Our results, backed by multiple analytical tools, provide an initial understanding, though areas like the specifics of microwave-assisted leaching and its scalability warrant further exploration. This study introduces a method for leaching antimony from copper mining waste and suggests a corresponding recycling system that may be economically viable. Such endeavors might offer a modest contribution to alleviating the present situation.

Les matériaux thermoélectriques (TE) permettent de convertir directement de la chaleur en électricité et vice-versa. Les objectifs de cette thèse étaient de tenter d'améliorer les performances TE de trois familles de matériaux et de mieux comprendre le lien entre les propriétés physiques (électriques, thermiques, magnétiques) généralement mesurées dans une large gamme de température (5–700 K) et les microstructures/compositions chimiques observées. Généralement, les matériaux ont été synthétisés par des techniques de métallurgie des poudres et densifiés par spark plasma sintering. La majeure partie de nos travaux a concerné la famille des matériaux tétraédrites, dérivés du minéral naturel (Cu,Ag)10(Zn,Fe)2(Sb,As)4S13, présentant des propriétés TE prometteuses, récemment mises en évidence. D’abord, les propriétés TE de huit tétraédrites naturelles de provenance différente ont été étudiées. Nous avons montré que leurs propriétés physiques sont plutôt prévisibles selon leur composition chimique et finalement peu différentes selon leur origine. Les propriétés TE de mélanges de tétraédrites naturelles et synthétiques obtenus par broyage mécanique ont ensuite été déterminées. Ce procédé fortement énergétique produit des particules de taille nanométrique des deux phases qui forment une solution solide pendant le frittage. Par contre, un broyage manuel conserve la présence des deux phases, ce qui conduit à de plus faibles performances TE. Ensuite, nous avons montré que la substitution Sb <-> As, usuelle dans les spécimens naturels, n’influence que faiblement les propriétés TE. Enfin, les propriétés TE de manganites de calcium et de polymères conducteurs ont également été étudiées / Thermoelectric (TE) materials allow direct conversion between heat and electricity. The aim of this thesis was to try to improve the thermoelectric performance of three different families of materials and to better understand the link between the various physical properties (electrical, thermal, magnetic) generally measured in a broad temperature range (5–700 K) and the observed microstructure/chemical composition. In general, the materials were synthesized by powder metallurgy techniques and densified by spark plasma sintering (SPS). The major part of our studies concerns the tetrahedrite family of materials, derived from the mineral tetrahedrite, (Cu,Ag)10(Zn,Fe)2(Sb,As)4S13, whose promising thermoelectric properties were only recently discovered. In a first approach, the TE properties of eight natural tetrahedrites of different geographic origin are studied. It is shown that they all behave rather predictably and uniformly. Next, the properties of ball milled mixtures of natural and synthetic tetrahedrites are investigated. This high-energy process yields nanoscale particles of the two phases, which form a solid solution during the sintering. Low-energy hand grinding preserves the two-phase nature and results in inferior TE performance. Because arsenic is a common substituent in natural specimens, several As-substituted tetrahedrites are synthesized and characterized. It is shown that the TE properties are only weakly influenced by the substitution of As for Sb. Besides tetrahedrites, calcium manganese oxides and conductive polymers are also studied

Abstract Polymetallic (Pb-Zn-Cu-Ag-Au-Sb-As-Bi-Cd-Te-Se-Ge…) quartz veins occur in an area from Eidsvoll in southeastern Norway to west of LakeVänern in southwestern Sweden. They most likely formed during the waning stage of the c. 1 Ga Sveconorwegian orogeny. In Värmskog parish, Värmland county, several mineralized quartz veins of different types are known. Of these, three of the larger vein deposits, Vegerbol, Karlsbol and Södra Gärdsjön, have been investigated. Despite a history of mining activities (mostly for silver) and exploration from the mid-1800s up until the present day, details about their ore mineralogy have remained essentially unknown. In order to classify and characterize them better, the present study was undertaken. The main ore minerals in the veins are galena, sphalerite, chalcopyrite, tetrahedrite sensu lato and pyrite. Additionally, this investigation showed the occurrence of an array of silver-bearing phases such as argentian tetrahedrite to freibergite, native silver, polybasite, pyrargyrite, jalpaite, aguilarite, cervelleite, hessite and matildite. These are the main and accessory silver carriers in the studied deposits. Gold (argentiferous) was also found, as well as the nickel-cobalt sulphide siegenite.    The silver contents of the tetrahedrites may vary within one deposit, ranging from tetrahedrite sensu stricto to freibergite. A weak positive correlation occurs between silver and iron in the tetrahedrites. Cadmium was found both in the tetrahedrites and in the sphalerites. Many sphalerites, however, are very pure ZnS. The complex accessory ore mineralogy, including native gold as well as tellurium and selenium-bearing phases (Vegerbol), makes these vein deposits comparable to mineralized veins to the west and southwest of the Värmskog area.    Combining mineralogical and textural observations with previous studies, the vein mineralizations most likely formed during a change in tectonic regime, in recurrently active brittle structures, at temperatures ranging from c. 350 down to below 100°C. The occurrence of pyrite and hematite and the lack of pyrrhotite and magnetite points to an oxidizing ore-forming environment with relatively high sulphur activity.    Finally, in order to assess the possibility of connecting two of the mined vein systems, VLF (Very Low Frequency) electromagnetic measurements were performed across the strike of a possible continuation between the Vegerbol and Karlsbol deposits. The VLF survey showed a significant anomaly where such a continuation was to be expected, thus indicating an overall strike length of at least 1 km for that vein system. / Sammanfattning Polymetalliska (Pb-Zn-Cu-Ag-Au-Sb-As-Bi-Cd-Te-Se-Ge…) kvartsgångar förekom­mer inom ett område från Eidsvoll, Norge i norr, till sydväst om Vänern i Sverige. De tros ha bildats under den svekonorvegiska orogenesens (ca 1 Ga) slutskede. I Värmskogs socken, Värmland, förekommer mineraliserade kvartsgångar av flera olika typer. Bland dessa har tre undersökts med avseende på malmmineralogi. Dessa kallas för Vegerbol, Karlsbol och Södra Gärdsjön, och de har brutits i huvudsak på silver. Trots att brytning och prospekteringsarbeten pågått från 1800-talet fram till i dag har det saknats detaljerade mineralogiska beskrivningar över fyndigheterna. Denna studie har genomförts för att bättre kunna karakterisera och klassificera dessa mineralis­eringar. Huvudmalmmineral vid dessa förekomster är blyglans, zinkblände, koppar­kis, pyrit och för Södra Gärdsjön även tetraedrit. Denna undersökning har påvisat förekomsten av silverförande faser som silverhaltig tetraedrit till freibergit, gediget silver, polybasit, jalpait, aguilarit, cervelleit, hessit och matildit, vilka utgör både huvudsakliga och accessoriska silverbärare i de undersökta förekomsterna. Guld (silverhaltigt) har också hittats, samt ett Ni-Co-förande mineral, siegenit.    Silverinnehållet i tetraedriterna varierar inom en och samma förekomst, några analyser har givit freibergitsammansättningar. En svag positiv korrelation finns mellan silver och järnhalt i tetraedrit. Kadmium förekommer både i tetraedrit och i zinkblände. Många zinkbländen består dock av rent ZnS. Förekomsten av relativt komplexa accessoriska mineral inklusive guld och Se-Te-faser (Vegerbol) visar att dessa gångar är jämförbara med liknande förekomster väster och sydväst om Värmskogs­området.    Genom att sammanföra data från denna undersökning med sådana från tidigare studier gjorda på gångarna kan man anta att de bildats vid vid en förändring av den tektoniska miljön, i upprepat aktiva spröda strukturer och vid temperaturer mellan ungefär 350 till under 100 °C. Förekomsten av pyrit och hematit samt avsaknad av magnetkis och magnetit tyder på att malmbildningen skett under oxiderade förhållan­den och relativt hög svavelaktivitet.      Elektromagnetiska mätningar i VLF-bandet (Very Low Frequency) utfördes tvärs över den förmodade strykningsriktningen för en möjlig fortsättning av gången mellan Karlsbol och Vegerbol. Mätningarna gav en tydlig anomali där en sådan fortsättning kan förväntas vilket skulle kunna betyda att det finns en sammanhängande mineralisering med ca 1 kilometers längd.

Thermoelectric (TE) materials directly convert heat energy into electrical energy. The conversion efficiency of the TE devices depends on the performance of the materials. The conversion efficiency of available thermoelectric materials and devices is low. Therefore, the development of new materials for improving thermoelectric device performance is a highly essential. As the performance of the TE materials depends on TE figure of merit [zT=S2P T ] which consist of three material properties such as Seebeck coefficient (S), electrical resistivity ( ) and thermal conductivity ( ). Thermoelectric figure of merit can be improved by either increase of power factor or decreasing of thermal conductivity or by both. In the present thesis, Cu based chalcogenide compounds are chosen for the study of thermoelectric properties because of their complex crystal structure, which leads to lower values of thermal conductivity. Also, the power factor of these materials can be tuned by the partial substitution doping. In the present thesis, Cu based chalcogenide compounds quaternary chalcogenide compound (Cu2ZnSnSe4), ternary compounds (Cu2SnSe3 and Cu2GeSe3) and tetrahedrite materials (Cu12Sb4S13) have been prepared by solid state synthesis. The prepared compounds are characterized by XRD for the phase identification, Raman Spectroscopy used as complementary technique for XRD, SEM for surface morphology and EPMA for the phase purity and elemental composition analysis respectively. For the evaluation of zT, thermoelectric properties of all the samples have been studied by measuring Seebeck coefficient, resistivity and thermal diffusivity. In the chapter 1, a brief introduction about thermoelectricity and its effects is discussed. Thermoelectric materials parameters such as electrical resistivity, Seebeck coefficient and thermal conductivity for different class of materials are mentioned. The selection of thermoelectric materials and the motivation for choosing the Cu based chalcogenide compounds for thermoelectric applications are discussed. In chapter 2, the details of the experiments carried out for Cu based chalcogenide compounds are presented. In chapter 3, the effect on thermoelectric properties by the cation substitution on quaternary chalcogenide compound Cu2+xZnSn1 xSe4 (0, 0.025, 0.05, 0.075, 0.1, 0.125, and 0.15) is studied. The electrical resistivity of all the samples decreases with an increase in Cu content except for Cu21ZnSn09Se4, most likely due to a higher content of the ZnSe. All the samples showed positive Seebeck coefficients indicating that holes are the majority charge carriers. The thermal conductivity of doped samples was higher as compared to Cu2ZnSnSe4 and this may be due to the larger electronic contribution and the presence of the ZnSe phase in the doped samples. The maximum zT = 0.23 at 673 K is obtained for Cu205ZnSn095Se4. In chapter 4, the effect of multi{substitution of Cu21ZnSn1 xInxSe4 (0, 0.05, 0.075, and 0.1) on transport properties were studied. The Rietveld powder X-ray diffraction data accompanied by electron probe microanalysis (EPMA) and Raman spectra of all the samples con firmed the formation of a tetragonal kesterite structure. The electrical resistivity of all the samples exhibits metallic-like behavior. The positive values of the Seebeck coefficient and the Hall coefficient reveal that holes are the majority charge carriers. The co-doping of copper and indium leads to a significant increase of the electrical resistivity and the Seebeck coefficient as a function of temperature above 650 K. The thermal conductivity of all the samples decreases with increasing temperature. Lattice thermal conductivity is not significantly modified as the doping content may infer negligible mass fluctuation scattering for copper zinc and indium tin substitution. Even though, the power factors (S2 ) of indium-doped samples Cu21ZnSn1 xInxSe4 (x=0.05, 0.075) are almost the same, the maximum zT=0.45 at 773 K was obtained for Cu21Zn09Sn0925In0075Se4 due to its smaller value of thermal conductivity. In chapter 5, thermoelectric properties of Zn doped ternary compounds Cu2ZnxSn1 xSe3 (x = 0, 0.025, 0.05, 0.075) were studied. The undoped com\pound showed a monoclinic crystal structure as a major phase, while the doped compounds showed a cubic crystal structure confirmed by powder XRD (X-Ray Diffraction). The electrical resistivity decreased up to the samples with Zn content x=0.05 in Cu2ZnxSn1 xSe3, and slightly increased in the sample Cu2Zn0075Sn0925Se3 . This behavior is consistent with the changes in the carrier concentration confirmed by room temperature Hall coefficient data. Temperature dependent electrical resistivity of all samples showed heavily doped semiconductor behavior. All the samples exhibit positive Seebeck coefficient (S) and Hall coefficient indicating that the majority of the carriers are holes. A linear increase in Seebeck coefficient with increase in temperature indicates the degenerate semiconductor behavior. The total thermal conductivity of the doped samples increased with a higher amount of doping, due to the increase in the carrier contribution. The total and lattice thermal conductivity of all samples decreased with increasing of temperature, which points toward the dominance of phonon scattering at high temperatures. The maximum zT = 0.34 at 723 K is obtained for the sample Cu2SnSe3 due to a low thermal conductivity compared to the doped samples. In chapter 6, thermoelectric properties of Cu2Ge1 xInxSe3 (x = 0, 0.05, 0.1, 0.15) compounds is studied. The powder X-ray diffraction pattern of the undoped sample revealed an orthorhombic phase. The increase in doping content led to the appearance of additional peaks related to cubic and tetragonal phases along with the orthorhombic phase. This may be due to the substitutional disorder created by indium doping. The electrical resistivity ( ) systematically decreased with an increase in doping content, but increased with the temperature indicating a heavily doped semiconductor behavior. A positive Seebeck coefficient (S) of all samples in the entire temperature range reveal holes as predominant charge carriers. Positive Hall coefficient data for the compounds Cu2Ge1 xInxSe3 (x= 0, 0.1) at room temperature (RT) con rm the sign of Seebeck coefficient. The trend of as a function of doping content for the samples Cu2Ge1 xInxSe3 with x = 0 and 0.1 agrees with the measured charge carrier density calculated from Hall data. The total thermal conductivity increased with rising doping content, attributed to an increase in carrier thermal conductivity. The thermal conductivity decreases with increasing temperature, which indicates the dominance of Umklapp phonon scattering at elevated temperatures. The maximum thermoelectric figure of merit (zT) = 0.23 at 723 K was obtained for Cu2In01Ge09Se3. In chapter 7, thermoelectric properties of Cu12 xMn1 xSb4S13 (x = 0, 0.5, 1.0, 1.5, 2.0) samples were studied. The Rietveld powder XRD pattern and Electron Probe Micro Analysis revealed that all the Mn substituted samples showed a single tetrahedrite phase. The electrical resistivity increased with increasing Mn due to substitution of Mn2+ on the Cu1+ site. The positive Seebeck coefficient for all samples indicates that the dominant carriers are holes. Even though the thermal conductivity decreased as a function of increasing Mn, the thermoelectric figure of merit (zT) decreased, because the decrease of the power factor is stronger than the decrease of the thermal conductivity. The maximum zT = 0.76 at 623 K is obtained for Cu12Sb4S13. In chapter 8, the summary and conclusion of the present work is presented.