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The present study delves into the significant impact of secondary phases created during the formation process of Y 2 W 3 O 12. Thermomiotic ceramic materials exhibit negative thermal expansion (NTE). Among those ceramics, Y 2 W 3 O 12 is distinct for having phase stability over a high-temperature range as well as high volumetric NTE. These properties make Y 2 W 3 O 12 an unprecedented additive for thermal expansion coefficient (CTE) engineering for high-temperature composites. Synthesis of this material is continuously concluded with a higher thermal expansion than the theoretical. To fully take advantage of this material's unique properties, the origin of the mismatched NTE should be fully understood. In this study, the popular solid-state synthesis approach of Y 2 W 3 O 12 across all synthesis steps was examined in detail. Each secondary Y-W-O phase's contribution to the CTE was calculated, and the final value closely aligns with the measured NTE within 3.7 %, demonstrating the impact of secondary phases on the material's thermal behavior. [ABSTRACT FROM AUTHOR]

The search for alternative energy sources is nowadays at the forefront of applied research. In this context, thermoelectricity for direct energy conversion from thermal to electrical energy plays an important role, in particular, for the exploitation of waste heat [G. J. Snyder and E. S. Toberer, Nat. Mater. 7, 105 (2008); M. S. Dresselhaus et al., Adv. Mater. (Weinheim, Ger.) 19, 1043 (2007)]. Materials for such applications should exhibit thermoelectric potential as well as mechanical stability. PbTe based alloys have been considered for many years as state of the art thermoelectric materials for mid-temperature power generation (500–900 K), with efficiency values that are still being improved by both alloying [P. F. P. Poudeu et al., Chem., Int. Ed. 45, 1 (2006); J. R. Sootsman et al., Chem. Mater. 18, 4993 (2006); P. F. P. Poudeu et al., Chem. Soc. 126, 14347 (2006); J. Androulakis et al., Adv. Mater. (Weinheim, Ger.) 18, 1170 (2006); K. F. Hsu et al., Science 303, 818 (2004)] and doping [Y. Gelbstein et al., Physica B (Amsterdam) 363, 196 (2005); Y. Gelbstein et al., Physica B (Amsterdam) 396, 16 (2007)] optimizations. However, the mechanical properties of PbTe based materials are highly dependent on the conductivity type (n or p) and carrier concentrations [Y. Gelbstein et al., Scr. Mater. 58, 251 (2008)]. This paper puts forward the mechanical durability of thermoelectric materials and, in particular, of PbTe as a dominant factor that is nondetachable from the transport properties, which should be considered in the search for high quality thermoelectric materials. Here we discuss the microhardness enhancement of p-type PbTe alloys with hole concentrations higher than 5×1018 cm-3. This anomaly is obtained while all the other investigated n-type (up to 1020 cm-3) and p-type (up to 1018 cm-3) compositions maintained a constant microhardness value of ∼30 HV. The origin of this microhardness enhancement is not yet understood on a fundamental level, however two possible mechanisms are discussed. One deals with the elastic interaction between dislocations and impurities with higher covalent radius than the sublattice vacancy. The other is correlated with the existence of a second valence band of heavy holes in PbTe, which begins to fill up at the same concentration where a hardness enhancement was observed. These mechanisms correlating between mechanical end electronic properties of PbTe based alloys can serve as guidelines for the search for potential candidates, obtaining both thermoelectric potential and mechanical stability for thermoelectric applications. [ABSTRACT FROM AUTHOR]

Global climate changes, due to rise of combustion of fossil fuels and greenhouse gas emissions, are becoming a major environmental concern, which can be approached by utilizing of waste heat into usable electrical energy, as in thermoelectric, TE, heat to electricity conversion. Among the recently developed TE materials classes, half-Heusler, HH, alloys gain a lot of attention due to their combined high electronic TE potential with a high temperature stability. So far the most efficient HH compositions are n -type. In the current research, based on ab-initio DFT and statistical thermodynamic calculations as well as an experimental validation, the temperature dependent solubility limit of Sc in HH (Ti 1- c Sc c )NiSn alloys is reported. It is shown that below the solubility limit p -type TiNiSn rich single phases are expected, while beyond the solubility limit a phase separation into ScNiSn and p -type TiNiSn rich phases is favored. This finding is of a high significance upon designing of TE devices with similar n - and p - type legs, as required for practical applications, with an addition of very interesting sub-micron phase-separation features, enabling scattering of phonons and enhancing of the TE performance. [ABSTRACT FROM AUTHOR]

In thermodynamic engines, such as thermoelectric (TE) converters, maximizing the Carnot efficiency, by applying large temperature differences, is required for maximizing the heat to electricity energy conversion. This requirement is a key factor for the desire to maximize the hot side temperature of TE converters as much as possible. Yet, practical stability considerations, such as sublimation of volatile species, composing many of the currently available TE materials, limit the hot side temperature to a certain level, depending on the specific composition. Pb 1- x Sn x Te based TE compositions are known as highly efficient and stable up to a temperature of around 500 °C. For a better understanding of the degradation mechanisms in such compositions, the current research is focused on accelerated degradation studies at a slightly higher temperature of 520 °C for periods of up to 900 h, following hot pressing. It was found that in this class of TE materials, besides of the already reported perferial surface sublimation, sublimation of volatile species from grain boundaries is also apparent, degrading the TE figure of merit, ZT , by up to 44%. The mechanisms for this performance degradation are discussed in details. Furthermore, ZT enhancement of up to 40% is currently being reported by using hot-pressing synthesis rather than the previously reported cold pressing and sintering. [ABSTRACT FROM AUTHOR]

For the first time, the temperature dependence of the solubility of Ti in PbTe is considered. The potential of Ti doping in PbTe was recently examined both theoretically and experimentally, in which a ∼9% efficiency enhancement was observed compared to an undoped PbTe. We present an experimental study of the system for different Ti concentrations indicating the solubility limit of Ti in PbTe and the effect of temperature on the morphology of the alloy. Exceeding the solubility limit leads to phase separation accompanied by formation of the TiTe 2 phase. At high temperatures, dissolution of the TiTe 2 secondary phase occurs for low Ti concentration, and the system transfers to the single-phase disordered solid solution. On the contrary, for the same temperatures, in the case of higher Ti concentrations the two-phase state is preserved. Theoretical explanation of the observed results is given using ab inito calculations combined with the statistical thermodynamic approach. The quasi-binary PbTe-TiTe 2 cross-section of the ternary Pb–Ti–Te phase diagram, indicating the Ti solubility in (Pb 1-c Ti c )Te is presented. [ABSTRACT FROM AUTHOR]

Diamond offers great promise as a solution to some of the limitations of current state of the art semiconductor technologies. Yet, significant challenges associated with the doping process remain a primary impediment to the development of diamond-based electronic devices. At present, it is unclear which simple measurement methods are needed to evaluate the diamond doping process. We propose non-destructive inspection methods for evaluating the polycrystalline chemical vapor deposition (CVD) diamond doping process, by analyzing the wettability, optical absorption, photoluminescence emission spectroscopy and atmospheric scanning electron microscope (Air-SEM) tests. Our results show that the properties of the measured samples are distinctly changed due to the presence of the doping elements, thereby confirming the effectiveness of these non-destructive methods for the diamond production industry. [ABSTRACT FROM AUTHOR]

In an attempt to enhance the thermal to electrical conversion efficiency, novel complicated thermoelectric alloys are constantly reported. Most of these reports, correlate the low lattice thermal conductivity values, attributing to the enhanced efficiencies, to nanofeatures apparent in their systems. Yet, since most of the highly efficient thermoelectric materials ever reported are based on complicated alloys, a major reduction of the lattice thermal conductivity can be solely attributed to alloying/disordering effects. The current manuscript, explores by combined experimental and theoretical, using density functional theory and analytical modeling, approaches the lattice thermal conductivity values originated solely by alloying/disordering effects in the highly thermoelectrically efficient p-type Ge xPb1- xTe alloys. By comparing these calculated results to various reported experimental values following different synthesis routes, it is shown that solution-treated samples fit well to the calculated values while for phase-separated samples, a significant lattice thermal conductivity reduction of ∼50% might be expected. [ABSTRACT FROM AUTHOR]

We demonstrate the potential of metallurgical controlling of the phase separation reaction, by means of spark plasma sintering consolidation and subsequently controlled heat treatments sequence, for enhancement the thermoelectric properties of the p-type Ge0.87Pb0.13Te composition. Very high ZTs of up to ∼2, attributed to the nucleation of sub-micron phase separation domains and to comparable sized twinning and dislocation networks features, were observed. Based on the experimentally measured transport properties, combined with the previously reported phase separated n-type (Pb0.95Sn0.05Te)0.92(PbS)0.08 composition, a maximal efficiency value of ∼11.5% was theoretically calculated. These ZT and efficiency values are among the highest reported for single composition non-segmented bulk material legs. [ABSTRACT FROM AUTHOR]

Abstract: Seeking novel thermoelectric materials for power generation applications, the p-type Pb0.25Sn0.25Ge0.5Te composition is currently being investigated. This composition, lying in the miscibility gap of the quasi-ternary phase diagram of PbTe–GeTe–SnTe, exhibits a tendency for phase separation into fine submicron domains in addition to nearly optimized electronic properties. The maximal figure of merit, ZT, of ∼1.2 was obtained at 450°C, showing a high thermoelectric potential. Possible routes for further enhancement of ZT up to ∼1.8, upon precise controlling of the morphological alignment of the involved phases, are described. [Copyright &y& Elsevier]

Most high-performance thermoelectric materials require either expensive, rare, or toxic elements. By doping TiNiSn, a low-cost, abundant thermoelectric compound, with copper as an n-type donor, some optimization can be performed for such materials. Ti(Ni1-xCux)Sn was synthesized by arc melting followed by heat treatment and hot pressing. The resulting material was analyzed for its phases using XRD and SEM and its transport properties. Cu undoped and 0.05/0.1% doped samples showed no additional phases in addition to the matrix half-Heusler phase, while the 1% copper doping initiated some Ti6Sn5 and Ti5Sn3 precipitation. The transport properties showed that copper acts as an n-type donor while also lowing the lattice thermal conductivity of the materials. the sample containing 0.1% copper showed the best figure of merit, ZT, with a maximal value of 0.75 and an average value of 0.5 through 325–750 K showing a 125% improvement over the undoped sample of TiNiSn. [ABSTRACT FROM AUTHOR]

Demixing following a spinodal decomposition, takes place in Sn-lean compounds in the pseudo-ternary (Ge,Sn,Pb)Te system, giving rise to both Pb- and Ge-rich telluride areas. After quenching from the high-temperature single cubic phase in the course of an aging treatment at 663K, a Ge0.6Sn0.1Pb0.3Te sample undergoes several microstructural stages. The last stage consists of nucleation and growth of nanosize particles which maintain their dimensional stability for relatively extended periods of time. [Copyright &y& Elsevier]

Abstract: p-type (Pb,Sn,Ge)Te-based alloys for thermoelectric applications were prepared using Bridgman technique. Second-order, rhombohedral to cubic phase transitions are involved, as evaluated from anomalies in the temperature dependence values of Seebeck coefficient, electrical conductivity, heat flow and the elongation, in the vicinity of the phase transition temperature, T c. The correlation between these anomalies in both the electronic and thermodynamic properties was interpreted by means of the relationship of Fermi energy to the chemical potential (or to the molar Gibbs free energy). [Copyright &y& Elsevier]

Coherence is a major caveat in quantum computing. While phonons and electrons are weakly coupled in a glass, topological insulators strongly depend on the electron-phonon coupling. Knowledge of the electron−phonon interaction at conducting surfaces is relevant from a fundamental point of view as well as for various applications, such as two-dimensional and quasi-1D superconductivity in nanotechnology. Similarly, the electron−phonon interaction plays a relevant role in other transport properties e.g., thermoelectricity, low-dimensional systems as layered Bi and Sb chalcogenides, and quasi-crystalline materials. Glass-electrolyte ferroelectric energy storage cells exhibit self-charge and self-cycling related to topological superconductivity and electron-phonon coupling; phonon coherence is therefore important. By recurring to ab initio molecular dynamics, it was demonstrated the tendency of the Li3ClO, Li2.92Ba0.04ClO, Na3ClO, and Na2.92Ba0.04ClO ferroelectric-electrolytes to keep phonon oscillation coherence for a short lapse of time in ps. Double-well energy potentials were obtained while the electrolyte systems were thermostatted in a heat bath at a constant temperature. The latter occurrences indicate ferroelectric type behavior but do not justify the coherent self-oscillations observed in all types of cells containing these families of electrolytes and, therefore, an emergent type phenomenon where the full cell works as a feedback system allowing oscillations coherence must be realized. A comparison with amorphous SiO2 was performed and the specific heats for the various species were calculated. [ABSTRACT FROM AUTHOR]

GeTe-based alloys have been considered as p -type thermoelectric materials for decades. Yet the fact that they possess intrinsically high concentration of cation germanium vacancies have triggered the thermoelectric community in finding alternatives and strategies to optimize their efficiency. While most of the published studies mainly discuss the stoichiometric alloy, here we demonstrate the introduction of excess germanium/tellurium to the system. The nonstoichiometric alloy is doped with bismuth, acting as a donor simultaneously with an increased number of vacancies, enabling higher solubility of other impurities (iodine/indium). This strategy and the mechanisms involved, has been investigated and correlated to the microstructural characteristics. ZT of ~1.6 was obtained but more importantly, it opens the opportunity for a potential route for further thermoelectric enhancement. • GeTe -based alloys shows ZT enhancement throughout all temperature range, reaching a 60% improvement compared to pure GeTe. • Achieved by electronic optimization using doping nonstoichiometric Ge x Te 1-x with both BiTe and cationic/anionic impurities. • General effective media evaluation enables the assessment of other routes for further transport properties enhancement. [ABSTRACT FROM AUTHOR]

Multi-phase thermoelectric materials are widely investigated due to their high potential for thermoelectric efficiency enhancement as a result of lattice thermal conductivity reduction by phonon scattering from the involved interfaces. Yet, the electronic mutual influence of the involved phases on the thermoelectric efficiency has to date usually been neglected in designing novel multi-phase thermoelectric materials. In the current research, the influence of distribution and morphology alignment on the electronic thermoelectric properties of three-phase composite materials was analyzed. Such an analysis, based on defining interaction volumes of the relevant thermoelectric properties, for any distribution and relative amount of any three phases with known individual properties, can be utilized for thermoelectric efficiency enhancement by intentional alignment of the phases along the preferred thermoelectric direction. For the p-type Gex(SnyPb1-y)1-xTe thermoelectric alloys, following a phase separation reaction it was found that serially relative alignment between the involved phases is optimal from the thermoelectric point of view. [ABSTRACT FROM AUTHOR]

Solid oxide fuel cells typically operate at temperatures near 800 ​°C. One obstacle to reducing this temperature is finding a high-performance cathode for lower temperatures. La 2 NiO 4+δ (LNO) has shown promise as a good material as a cathode being a well-known mixed electronic and ionic conductor. However, increasing the surface exchange in LNO is important for high performance applications. Mn substitution has been shown to increase the surface exchange of LNO with Sr required to stabilize the structure. Changing the ratio of Mn:Sr will change the oxidation state of Mn and Ni and the fundamental properties of the material. Changing the Sr content in (La 1-x Sr x) 2 (Ni 0.9 Mn 0.1)O 4+δ was investigated with x ​= ​0.1-0.5. The XRD patterns shows a single phase K 2 NiF 4 structures. Above 35% Sr the 'a' parameter of the unit cell starts increasing and the 'c' parameter starts to decrease. Increasing Sr content showed increased electrical conductivity from 40 ​S ​cm−1 to 261 ​S ​cm−1. Impedance data of the 10% Sr sample showed behavior similar to LNO sample with slightly increased area specific resistance (ASR); any further increase in Sr content further increases ASR of the electrode. Image 1 • La 1-x Sr x (Ni 0.9 Mn 0.1)O 4 samples were synthesized using the modified Pechini method. • Samples with higher Sr content showed an increase in conductivity. • Half cells measured in air showed decreasing performance with increase of the Sr content. • The effects of Mn and Sr seem to compete. Mn increases surface exchange and decreases conductivity and Sr vice versa. [ABSTRACT FROM AUTHOR]

Silicides and especially Mg 2 X (X = Si, Sn, Ge) are considered as attractive thermoelectric materials, which are capable of an efficient heat to electricity energy conversion. They have low density, abundant and affordable raw constituents, and good mechanical properties. Yet, the synthesis of such Mg- based compounds is usually very challenging due to the reactivity, volatility and oxidation tendency of Mg. These challenges led many of the researchers exploring these materials, to low temperature synthesis routes, where, the most common is a solid-state mechanical alloying, using ball milling. In such synthesis approaches, Mg volatility was compensated upon the introduction of excess Mg into the source materials, beyond the stoichiometric composition. In the current research a novel synthesis route based on an induction melting in a closed Ta chamber is proposed. Using this technique undoped and Bi-doped Mg 2 X (X = Si, Sn, Ge) compounds were synthesized and analyzed. Phase separation into Mg 2 X- and Mg 3 Bi 2 -rich phases was observed for the Bi-doped compositions, with an associated significant reduction of the lattice thermal conductivity. • a novel synthesis route based on an induction melting in a closed Ta chamber of Mg 2 X (X = Si, Sn, Ge) is proposed. • Using this technique undoped and Bi-doped compounds were synthesized and analyzed. • Phase separation into Mg 2 X- and Mg 3 Bi 2 - rich phases was observed for the Bi-doped compositions. [ABSTRACT FROM AUTHOR]

(Hf,Zr,Ti)Co(Sb,Sn) Solid solutions were prepared by mechanical-alloying followed by hot-press method as an attempt to reduce Hf concentration and therefore the material's cost without negatively affecting the thermoelectric performance. To this end, two different methods were applied: (a) Hf substitution with its lighter and cheaper homologue Zr; and (b) fine tuning of carrier concentration by the substitution of Sb with Sn. The isoelectronic substitution of Hf with Zr was investigated in Hf0.6-xZrxTi0.4CoSb0.8Sn0.2 solid solutions and resulted in lower power factors and ZTs. However, the low thermal conductivity of Hf0.4Zr0.2Ti0.4CoSb0.8Sn0.2 contributed in achieving a relatively good ZT~0.67 at 970 K. The effect of charge carrier concentration was investigated by preparing Hf0.4Zr0.2Ti0.4CoSb1-ySny (y = 0.15–0.25) compounds. Hf0.4Zr0.2Ti0.4CoSb0.83Sn0.17 composition prepared by six hours milling reached the highest ZT of 0.77 at 960 K. [ABSTRACT FROM AUTHOR]

In an attempt to reduce the reliance on fossil fuels, associated with severe environmental effects, the current research is focused on the identification of the thermoelectric potential of n-type Pb1-xTixTe alloys, with x values of up to 3%. A solubility limit of 0.5 at. % Ti in PbTe was identified, while beyond this composition, a precipitation of a TiTe2 phase was occurred. An impressive maximal dimensionless thermoelectric figure of merit ZT of ~1.2 was obtained upon 0.1% Ti doping at 500 °C, indicating a ~9% efficiency enhancement compared to an undoped PbTe. It is shown that generating a functionally graded material based on undoped PbTe as a low temperature segment and a 0.1% Ti doped PbTe as a high temperature segment has a potential to enhance the efficiency by ~14% compared to the undoped sample. [ABSTRACT FROM AUTHOR]

The MNiSn (M = Ti; Zr; Hf); half-Heusler semiconducting alloys have a high potential for use as n-type thermoelectric materials at elevated temperatures (~1000 K). The alloys' durability is crucial for their commercial handling and use, and therefore it is required to characterize their surface oxidation behavior and stability at the working temperature. X-ray photoelectron spectroscopy was utilized to study the surface composition and oxidation of the ZrNiSn alloy at room and elevated temperatures. It was found that during heating in a vacuum, Sn segregates to the surface in order to reduce the surface energy. Exposing the alloy to oxygen resulted mainly in the oxidation of the zirconium to ZrO2, as well as some minor oxidation of Sn. At room temperature, the oxidation to ZrO2 was accompanied by the formation of a thin ZrO layer at the metal-oxide interface. In contrast to TiNiSn, where most of the oxide was formed on the surface due to oxygen-enhanced segregation of Ti, and in the case of ZrNiSn, the formed oxide layer was thinner. Part of the oxide is formed due to Zr segregation to the surface, and in part due to oxygen dissolved into the alloy. [ABSTRACT FROM AUTHOR]

Solid oxide fuel cells are characterized by a high efficiency for converting chemical energy into electricity and fuel flexibility. This research work focuses on developing durable and efficient anodes for solid oxide fuel cells (SOFCs) based on exsolving nickel from the perovskite structure. A-site-deficient La- and Ni-doped strontium titanates (La0.2Sr0.7Ti0.95Ni0.05O3−δ, LSTN) were synthesized using four different techniques and mixed with Ce0.8Gd0.2O2−δ (GDC) to form the SOFC anode. The synthesis routes of interest for comparison included solid-state, sol-gel, hydrothermal, and co-precipitation methods. LSTN powders were characterized via XRD, SEM, TPR, BET and XPS. In situ XRD during reduction was measured and the reduced powders were analyzed using TEM. The impact of synthesis route on SOFC performance was investigated. All samples were highly durable when kept at 0.5 V for 48 h at 800 °C with H2 fuel. Interestingly, the best performance was observed for the cell with the LSTN anode prepared via co-precipitation, while the conventional solid-state synthesis method only achieved the second-best results. [ABSTRACT FROM AUTHOR]

In thermoelectric (TE) generators, maximizing the efficiency of conversion of direct heat to electricity requires the reduction of any thermal and electrical contact resistances between the TE legs and the metallic contacts. This requirement is especially challenging in the development of intermediate to high-temperature TE generators. PbTe-based TE materials are known to be highly efficient up to temperatures of around 500 °C; however, only a few practical TE generators based on these materials are currently commercially available. One reason for that is the insufficient bonding techniques between the TE legs and the hot-side metallic contacts. The current research is focused on the interaction between cobalt-metallized n-type 9.104 × 10−3 mol % PbI2-doped PbTe TE legs and the Ag0.32Cu0.43In0.25 brazing alloy, which is free of volatile species. Clear and fine interfaces without any noticeable formation of adverse brittle intermetallic compounds were observed following prolonged thermal treatment testing. Moreover, a reasonable electrical contact resistance of ~2.25 mΩmm2 was observed upon brazing at 600 °C, highlighting the potential of such contacts while developing practical PbTe-based TE generators. [ABSTRACT FROM AUTHOR]

Thermoelectrics enabling a direct conversion of waste heat into useful electricity is widely investigated for renewable energy applications. n-type half-Heusler (HH) MNiSn (M = Ti,Zr,Hf) thermoelectric (TE) elements are known as attractive semiconducting candidates for such purposes. Yet, both electronic and phonon scattering optimization are still required for fulfilling their full potential. In the current research, Ti0.3Zr0.35Hf0.35Ni1.005Sn separating into a main Ti0.3Zr0.35Hf0.35NiSn HH matrix and a minority full-Heusler (FH) Ti0.3Zr0.35Hf0.35Ni2Sn phase is reported. Adverse electronic effects of the metallic FH phase are nearly avoided by its small relative amount and dimension, while maintaining nearly optimal electronic TE performance along with large phonon scattering, minimizing the lattice thermal conductivity. Consequently, a very high maximal TE figure of merit, ZT, of ∼1.04 is obtained, which is among the highest ever reported for n-type MNiSn HH compounds. [ABSTRACT FROM AUTHOR]

Thermoelectric generators (TEGs) are devices capable of transforming heat energy into electricity and vice versa. Although TEGs are known and have been in use for around five decades, they are implemented in only a limited range of applications, mainly extraterrestrial applications. This is due to their low technical readiness level (TRL) for widespread use, which is only at levels of 3–5 approaching laboratory prototypes. One of the most setbacks in reaching higher TRL is the lack of understanding of the mechanical and thermo-mechanical properties of TE materials. Out of ~105,000 entries about TE materials only ~100 entries deal with mechanical properties, while only 3 deal with thermo-mechanical properties. GeTe-based alloys with varying other elements, forming efficient p-type thermoelectric materials in the 200 ÷ 500 °C temperature range, have been intensively researched since the 1960s and have been successfully applied in practical TEGs. Yet, their temperature-dependent mechanical properties were never reported, preventing the fulfillment of their potential in a wide variety of practical applications. The combined effects of temperature and mechanical compression of GeTe were explored in the current research by implementing novel quantitative crystallographic methods to statistically describe dislocation activity and modification of the micro-texture as inflecting by the testing conditions. It is suggested, through utilizing these methods, that the combined effect of compression and temperature leads to the dissolving of twin boundaries, which increases dislocation mobility and results in a brittle-to-ductile transition at ~0.45 of the homologous temperature. [ABSTRACT FROM AUTHOR]

In an attempt to reduce our reliance on fossil fuels, associated with severe environmental effects, the current research is focused on the identification of the thermoelectric potential of p-type (GeTe)1-x(Bi2Te3)x alloys, with x values of up to 20%. Higher solubility limit of Bi2Te3 in GeTe, than previously reported, was identified around ∼9%, extending the doping potential of GeTe by the Bi2Te3 donor dopant, for an effective compensation of the high inherent hole concentration of GeTe toward thermoelectrically optimal values. Around the solubility limit of 9%, an electronic optimization resulted in an impressive maximal thermoelectric figure of merit, ZT, of ∼1.55 at ∼410° C, which is one of the highest ever reported for any p-type GeTe-rich alloys. Beyond the solubility limit, a Fermi Level Pinning effect of stabilizing the Seebeck coefficient was observed in the x=12%-17% range, leading to stabilization of the maximal ZTs over an extended temperature range; an effect that was associated with the potential of the governed highly symmetric Ge8Bi2Te11 and Ge4Bi2Te7 phases to create high valence band degeneracy with several bands and multiple hole pockets on the Fermi surface. At this compositional range, co-doping with additional dopants, creating shallow impurity levels (in contrast to the deep lying level created by Bi2Te3), was suggested for further electronic optimization of the thermoelectric properties. [ABSTRACT FROM AUTHOR]

An experimental demonstration of the combined photovoltaic (PV) and thermoelectric conversion of concentrated sunlight (with concentration factor, X, up to ~300) into electricity is presented. The hybrid system is based on a multi-junction PV cell and a thermoelectric generator (TEG). The latter increases the electric power of the system and dissipates some of the excessive heat. For X≤200, the system's maximal efficiency, ~32%, was mostly due to the contribution from the PV cell. With increasing X and system temperature, the PV cell's efficiency decreased while that of the TEG increased. Accordingly, the direct electrical contribution of the TEG started to dominate in the total system power, reaching ~20% at X ≈ 290. Using a simple steady state finite element modeling, the cooling effect of the TEG on the hybrid system's efficiency was proved to be even more significant than its direct electrical contribution for high solar concentrations. As a result, the total efficiency contribution of the TEG reached ~40% at X ≈ 200. This suggests a new system optimization concept that takes into account the PV cell's temperature dependence and the tradeoff between the direct electrical generation and cooling capabilities of the TEG. It is shown that the hybrid system has a real potential to exceed 50% total efficiency by using more advanced PV cells and TE materials. [ABSTRACT FROM AUTHOR]

Abstract The effect of a galia (Ga 2 O 3) addition on the crystallographic phase transformations and the grain growth behavior of yttria stabilized zirconia (YSZ) were investigated regarding powders containing different amounts of galia in the range of 0–25 mol %. Ternary compositions of galia- YSZ sponge-like cryogels were prepared by the sol-gel method combining freeze-drying process and calcination of dried powders at different temperatures for 2 h in air. Crystallographic phase transitions were analyzed via X-ray diffraction (XRD) and exceptional powder particle morphology of internal nano voids derived from the freeze-drying technique was investigated by using Scanning Transmission Electron Microscope (STEM). It was shown that galia supressed the grain growth process in yttria stabilized zirconia and had no effect on the internal voids obtained. Highlights • Galia addition inhibited 8YSZ crystallization and extended the amorphous range. • Galia addition elevated the activation energy for the grain growth process in 8YSZ. • Internal nano-voids were formed via sol-gel synthesis followed by freeze-drying. [ABSTRACT FROM AUTHOR]

Abstract A thermoelectric converter (TEC), an array of thermocouples composed of p -type and n -type semiconducting elements, directly converting heat to electricity, is subjected to large temperature gradients in practical operation conditions. To prevent mechanical fractures in the thermocouples, the coefficient of thermal expansion (CTE) between the p -type and n -type elements must be matched reasonably well. The current research paves a route for obtaining a TEC based on polycrystalline n -type and single-crystal based p -type half Heusler (HH) TiNiSn thermoelectric elements with practically the same CTEs. For this purpose, HH TiNiSn crystals were grown using the metal flux method, and their crystallographic and thermoelectric properties were characterized. It was experimentally validated that electron donor levels of 8 × 1019-8x1020 cm−3, originated by grain boundaries in poly-crystalline TiNiSn, can be reduced to the ∼7 × 1018cm−3 range, in single-crystals, allowing upon low acceptor doping concentration, to obtain electronically optimal p -type TiNiSn thermoelectric legs. Highlights • TiNiSn half-Heusler crystals were grown from metallic flux. • Reduced electron concentration compared to polycrystalline samples was obtained. • The electronic effect of grain-boundaries in TiNiSn is discussed in details. • For obtaining p -type TiNiSn, elimination of grain boundaries is essential. [ABSTRACT FROM AUTHOR]

Abstract Researchers have spent decades exploring strategies for reducing energy consumption in buildings worldwide, proposing passive solutions and optimizing active systems. However, no breakthrough technology has been developed. The use of thermoelectricity in buildings for heating, cooling and ventilation has been proposed as an alternative solution to many systems anchored in our day-to-day. This paper seeks to classify, analyze and summarize the possibilities of the thermoelectric technology integration in buildings. The results obtained from the search were divided into two main groups: systems that are integrated in the building envelope and non-integrated systems that operate independently. Among the analyzed parameters, on the one hand the characteristics of the prototypes' components needed for the construction were described. On the other, the thermoelectric specific parameters required for optimization under the operating scenarios' conditions were studied. The results of most of the studies showed that even though the technology can provide the comfort conditions, still the performance of these systems is not competitive compared to conventional vapor compression systems. However, the advantages of thermoelectricity such us the non-use of refrigerants or the high durability, makes this technology an alternative solution to consider, of which interest is growing in line with recent studies. Highlights • A novel classification of thermoelectric applications in buildings is carried out. • A wide characterization and building integration options are gathered. • The potential of thermoelectricity in buildings is demonstrated. • Classification optimized to future research in architecture. [ABSTRACT FROM AUTHOR]

The effect of a galia (Ga2O3) addition on the crystallographic phase evolution and the crystal growth behavior of zirconia (ZrO2) rich powder were investigated. Binary compositions of galia-zirconia powder (on the zirconia-rich side of the quasi-binary phase diagram) were obtained by the sol-gel method and calcined at different temperatures for 2 h. Rietveld refinement (FullProf program) was used to determine the crystallographic phase composition. Crystal size was approximated based on X-ray diffractions analysis combined with estimates of average crystal size obtained by processing high-resolution scanning electron microscopy images. The surface area of the powders obtained was measured via the Brunauer-Emmett-Teller method. Zirconia-galia sol-gel powders were found to form tetragonal or mixed tetragonal-monoclinic solid solution phases depending on both composition and calcination temperature. It was shown that galia suppressed crystal growth process in zirconia, producing finer nano-powders with higher surface area compared to pure zirconia. [ABSTRACT FROM AUTHOR]

Porous yttria-stabilised zirconia ceramics have been gaining popularity throughout the years in various fields, such as energy, environment, medicine, etc. Although yttria-stabilised zirconia is a well-studied material, voided yttria-stabilised zirconia powder particles have not been demonstrated yet, and might play an important role in future technology developments. A sol-gel synthesis accompanied by a freeze-drying process is currently being proposed as a method of obtaining sponge-like nano morphology of embedded faceted voids inside yttria-stabilised zirconia particles. The results rely on a freeze-drying stage as an effective and simple method for generating nano-voided yttria-stabilised zirconia particles without the use of template-assisted additives. [ABSTRACT FROM AUTHOR]

Prediction of the mechanical behavior of thin foils (~25 µm) requires special characterization techniques. The current work is focused on the mechanical and microstructural characterization of 25 µm HAVAR alloy foils following annealing, cold rolling, and subsequent heat treatments, using small punch testing (SPT), X-ray diffraction (XRD), and transmission-scanning electron microscopy (TEM). The SPT technique revealed that the annealed specimens exhibited the largest maximal load to failure and deformation (more than two-fold), compared to the cold rolled and heat treated conditions. The microscopy observations revealed high dislocation density following cold rolling and subsequent heat treatments. Following annealing, a cubic crystallographic structure (FCC) with equiaxed grains and a limited dislocation population was observed. Following cold rolling and subsequent thermal treatment, a preferred orientation texture (i.e., ‘deformation texture’) was observed with a very high dislocation density. The correlation between the mechanical behavior and the microstructural observations is discussed in detail. [ABSTRACT FROM AUTHOR]

The quest for improving eco-friendly renewable energy conversion methods due to the declining resources of conventional energy reserves and a rise in environmental awareness is constantly growing. The thermoelectric method of directly converting thermal into electrical energy is attracting increased attention for such applications and thus enhancing its efficiency is of great importance. The most efficient n -type thermoelectric materials for temperatures up to 300 °C are currently Bi 2 Te x Se 3- x based. By optimizing the preparation process while considering the inherent crystallographic anisotropy, the efficiency of such materials can be further improved. In this study the Bi 2 Te 2.4 Se 0.6 composition was optimized by CHI 3 doping, preferred alignment of the crystallographic orientation, and lattice thermal conductivity minimization. The synthesis route included rocking furnace melting, energetic ball milling and hot pressing with optimal parameters for enhancement of the thermoelectric figure of merit, ZT , at temperatures higher than 200 °C, commonly applied in low temperature power generation applications. The transport properties in the directions parallel and perpendicular to the pressing direction were examined. In the direction perpendicular to the pressing axis, a maximal ZT of ∼0.9 was obtained at ∼175 °C, which is as far as we know among the highest ever reported for n -type Bi 2 Te x Se 3- x based alloys. [ABSTRACT FROM AUTHOR]

The recent energy demands affected by the dilution of conventional energy resources and the growing awareness of environmental considerations, had positioned the research of renewable energy conversion methods in general and of thermoelectric direct conversion of thermal into electrical energies in particular, in the forefront of the currently active applicative sciences. IV-VI thermoelectric compounds (e.g. GeTe, PbTe and SnTe) and their alloys comprise some of the most efficient thermoelectric compositions ever reported. Yet a proper utilization of such materials in practical thermoelectric devices, still requires an overcoming the so-called technological “valley of death”, including among others, transport properties' degradation, due to sublimation of volatile Te rich species, while being subjected to elevated temperatures for long periods of time. In an attempt to establish practical operation criteria for extending the operation periods of such thermoelectric converters, it is currently shown based on thermal gravimetric and metallurgical considerations that such harmful sublimation can be practically bridged over by limiting the maximal operating temperatures to the 410–430 °C range for GeTe rich alloys and to 510–530 °C for PbTe and SnTe rich alloys, depending of the thermoelectric leg's diameter. [ABSTRACT FROM AUTHOR]

In this research it is shown that thermoelectric higher manganese silicides (HMS) compounds produced by arc-melting followed by hot pressing exhibited textured behavior, due to the different number of Mn–Si bonds on the [00l] direction over the [hk0] direction, leading to ∼10% ZT enhancement in parallel to the pressing direction compared to the transverse direction. This shows that more carful considerations are required while assuming isotropic behavior in non-cubic polycrystalline thermoelectric materials. [ABSTRACT FROM AUTHOR]

Thermoelectrics is a renewable energy method, capable of a direct conversion of waste heat into useful electricity, which can be applied for tackling global warming, high pollution levels and dilution of fossil energy sources. For this purpose novel and highly efficient thermoelectric compositions should be developed and analyzed under practical operation conditions. In the current research the effects of grain size and thermal treatment under operation conditions on the thermoelectric performance of Ge 0.962 Bi 0.038 Te 1.057 were investigated. Following hot-pressing both positive electronic and lattice effects were identified for sub-micron grained samples, enabling very high figure of merit, ZT , values of up to 1.8. These values were slightly degraded down to ≈ 1.4 following thermal treatment, mainly due to grain coarsening, highlighting the requirement of grain growth inhibition for maximizing the potential of this composition. • Nano-grained Ge 0.962 Bi 0.038 Te 1.057 was found to exhibit a very high ZT of 1.8 following hot-pressing. • This impressing ZT was attributed to both enhanced phonon scattering and electronic donor states at grain boundaries. • Reduction of ZT to 1.4 was noticed after thermal treatment, highlighting the requirement of grain growth inhibition [ABSTRACT FROM AUTHOR]

High thermoelectric conversion efficiencies can be achieved by making use of materials with, as high as possible, figure of merit, ZT, values. Moreover, even higher performance is possible with appropriate geometrical optimization including the use of functionally graded materials (FGM) technology. Here, an advanced n-type functionally graded thermoelectric material based on a phase-separated (PbSn0.05Te)0.92(PbS)0.08 matrix is reported. For assessment of the thermoelectric potential of this material, combined with the previously reported p-type Ge0.87Pb0.13Te showing a remarkable dimensionless figure of merit of 2.2, a finite-element thermoelectric model is developed. The results predict, for the investigated thermoelectric couple, a very impressive thermoelectric efficiency of 14%, which is more than 20% higher than previously reported values for operating under cold and hot junction temperatures of 50 °C and 500 °C, respectively. Validation of the model prediction is done by a thermoelectric couple fabricated according to the model's geometrical optimization conditions, showing a good agreement to the theoretically calculated results, hence approaching a higher technology readiness level. [ABSTRACT FROM AUTHOR]

In the frame of the current research, the p-type Bi2Te3 doped (GeTe)0.95(Bi2Te3)0.05 alloy composed of hot pressed consolidated submicron structured powder was investigated. The influence of the process parameters (i.e., powder particles size and hot pressing conditions) on both reduction of the lattice thermal conductivity and electronic optimization is described in detail. Very high maximal ZT values of up to ~1.6 were obtained and correlated to the microstructural characteristics. Based on the various involved mechanisms, a potential route for further enhancement of the ZT values of the investigated composition is proposed. [ABSTRACT FROM AUTHOR]

The world energy crisis had increased the demand for alternative energy sources and as such is one of the topics at the forefront of research. One way for reducing energy consumption is by thermoelectricity. The rmoelectric effects enable direct conversion of thermal into electrical energy. Higher manganese silicide (HMS, MnSi1.75) is one of the promising materials for applications in the field of thermoelectricity. The abundance and low cost of the elements, combined with good thermoelectric properties and high mechanical and chemical stability at high temperatures, make it very attractive for thermoelectric applications. Recent studies have shown that Si-rich HMS has improved thermoelectric properties. The most interesting of which is the unusual reduction in thermal conductivity. In the current research, transmission (TEM) and scanning (SEM) electron microscopy as well as X-ray diffraction methods were applied for investigation of the govern mechanisms resulting in very low thermal conductivity values of an Si-rich HMS composition, following arc melting and hot-pressing procedures. In this paper, it is shown that there is a presence of submicron dislocations walls, stacking faults, and silicon and HMS precipitates inside each other apparent in the matrix, following a high temperature (0.9 Tm) hot pressing for an hour. These are not just responsible for the low thermal conductivity values observed but also indicate the ability to create complicate nano-structures that will last during the production process and possibly during the application. [ABSTRACT FROM AUTHOR]

• The variables of temperature, pressure and crystal size were examined separately. • The lattice parameters in HT-XRD are affected by both temperature and size effects. • The lattice parameter of Y 2 O 3 in MgO is higher than pure Y 2 O 3 according to HT-XRD. • A non-monotonic lattice variation (NMLV) in Y 2 O 3 due to the nano-effect was shown. • The NMLV was modeled combining the surface tension effect and the Madelung model. Yttrium oxide (Y 2 O 3) is a ceramic material in use in various fields such as catalysis, thermal barrier coatings, dental ceramics, solid-state lasers, solid oxide fuel cells and etc. In nanoscale metal oxides, unlike metals, the dependence of the lattice parameter on the crystal size is in dispute. Y 2 O 3 and 5 vol% Y 2 O 3 in MgO powders were synthesized via the sol-gel technique. The latter was made in order to produce Y 2 O 3 inclusions in MgO, allowing for the study of differences resulting from crystal size with inhibited thermal growth. However, the lattice parameters of the C-type Y 2 O 3 were significantly lower than expected due to misfit high compression stress. High-temperature X-ray diffraction (HT-XRD) was used in order to investigate in situ crystal structure and microstructure variations of Y 2 O 3 imbedded in MgO as formed at high temperatures free of misfit strain, comparing with in situ study of pure Y 2 O 3 formation at the same temperature range. It was found that nanocrystalline C-type Y 2 O 3 was formed at a temperature range of 873–1163 K. Lattice parameters and crystal size were evaluated by using Rietveld refinement and high resolution scanning electron microscopy (HR-SEM). The relative lattice parameter changes as a function of crystal size were obtained by analyzing the in situ HT-XRD data from 873 to 1573 K. Those results along with those obtained at room temperature showed a non-monotonic trend: lattice contraction versus decreasing crystal size at the range of 60–45 nm crystal size and lattice expansion versus decreasing crystal size for smaller crystals (approximately 0.11%). The non-monotonic lattice variation was modeled by assuming two effects acting simultaneously as a function of crystal size: lattice contraction due to hydrostatic pressure caused by the surface tension and Madelung model predicting lattice expansion due to weakening of bonding force in small ionic crystals. The calculated theoretical lattice parameters values which were obtained by using this model were compared to the experimental results yielding a better understanding of the lattice variations in nano-Y 2 O 3. [ABSTRACT FROM AUTHOR]

• half-Heusler (HH) High entropy alloy (HEA) MNiSn (M=Ti,Zr,Hf) with addition of Al and Sc in the M sub-lattice was studied. • The thermoelectric figure of merit showed an improvement of ~40% in comparison with (Ti 0.3 Zr 0.35 Hf 0.35)NiSn. • Ab-initio DFT calculations are applied to calculate the binary interaction parameters in the M sub-lattice. • A new HEA parameter for multi-component alloying in only one sub-lattice of a compound is proposed. [Display omitted] Half-Heusler (HH) High entropy alloy (HEA) MNiSn (M=Ti,Zr,Hf) with addition of Al and Sc in the M sub-lattice was studied. The micro-structure of (Ti 0.33 Zr 0.33 Hf 0.33 Al 0.005 Sc 0.005)NiSn compound was examined and its transport properties were measured. The measurements showed the improvement of ~40% in the thermoelectric figure of merit in comparison with a similar composition of (Ti 0.3 Zr 0.35 Hf 0.35)NiSn without Al and Sc. The thermodynamic stability of the alloy was examined using the HEA methodology, including a new proposed HEA parameter for multi-component alloying in only one sub-lattice of the compound. Ab-initio density functional theory (DFT) calculations were carried out to obtain the binary interaction parameters between the components in the sub-lattice of M atoms. The thermodynamic stability of the alloy as a function of the atomic fraction of the elements occupying the same sub-lattice in the compound is analyzed using the new HEA parameter. [ABSTRACT FROM AUTHOR]

The MNiSn (M = Ti, Zr, Hf) n-type semiconductor half-Heusler alloys are leading candidates for the use as highly efficient waste heat recovery devices at elevated temperatures. For practical applications, it is crucial to consider also the environmental stability of the alloys at working conditions, and therefore it is required to characterize and understand their oxidation behavior. This work is focused on studying the surface composition and the initial oxidation of HfNiSn alloy by oxygen and water vapor at room temperature and at 1000 K by utilizing X-ray photoelectron spectroscopy. During heating in vacuum, Sn segregated to the surface, creating a sub-nanometer overlayer. Exposing the surface to both oxygen and water vapor resulted mainly in Hf oxidation to HfO2 and only minor oxidation of Sn, in accordance with the oxide formation enthalpy of the components. The alloy was more susceptible to oxidation by water vapor compared to oxygen. Long exposure of HfNiSn and ZrNiSn samples to moderate water vapor pressure and temperature, during system bakeout, resulted also in a formation of a thin SnO2 overlayer. Some comparison to the oxidation of TiNiSn and ZrNiSn, previously reported, is given. [ABSTRACT FROM AUTHOR]

Mechanical alloying synthesis was applied on the thermoelectric half-Heusler materials in order to explore the potential of such scalable synthesis method in this family of compounds. (Hf,Ti)Co(Sb,Sn) solid solutions were prepared by mechanical alloying followed by hot pressing and their thermoelectric properties were studied in the temperature range of 300–980 K. After successful synthesis, two different methods were applied to enhance the thermoelectric performance of p-type (Hf,Ti)Co(Sb,Sn) materials: (a) adjustment of the Ti/Hf ratio and (b) fine tuning of carrier concentration by the substitution of Sb with Sn. The isoelectronic substitution of Ti with Hf led to an important reduction in the lattice thermal conductivity and a high ZT of 0.84 at 980 K for Hf 0.6 Ti 0.4 CoSb 0.8 Sn 0.2. The effect of charge carrier concentration was investigated by preparing Hf 0.6 Ti 0.4 CoSb 1−y Sn y (0.15, 0.17, 0.20, 0.23, 0.25) compounds, using different mechanical alloying durations. The Hf 0.6 Ti 0.4 CoSb 0.83 Sn 0.17 composition, prepared by 4 h ball-milling, reached an impressive ZT ~1.1 at 973 K. • Half-Heusler solid solutions were synthesized via mechanical alloying as single phases. • Hf 1−x Ti x CoSb 0.80 Sn 0.20 and Hf 0.6 Ti 0.4 CoSb 1−y Sn y series were studied. • The Hf 0.6 Ti 0.4 CoSb 0.83 Sn 0.17 composition reached the maximum ZT of 1.1 at 973 K. [ABSTRACT FROM AUTHOR]

Rare-earth (RE) oxides are important in myriad fields, including metallurgy, catalysis, and ceramics. However, the phase diagram of RE oxides in the nanoscale might differ from the phase diagrams for bulk, thus attracting attention nowadays. We suggest that grain size in the nanoscale also determines the obtained crystallographic phase along with temperature and pressure. For this purpose, nanoparticles of Sm2O3 and Eu2O3 were mixed in an inert MgO matrix via the sol-gel method. This preparation method allowed better isolation of the oxide particles, thus hindering the grain growth process associated with increasing the temperature. The mixed oxides were compared to pure oxides, which were heat-treated using two methods: gradual heating versus direct heating to the phase transition temperature. The cubic phase in pure oxides was preserved to a higher extent in the gradual heating treatment compared to the direct heating treatment. Additionally, in MgO, even a higher extent of the cubic phase was preserved at higher temperatures compared to the pure oxide, which transformed into the monoclinic phase at the same temperature in accordance with the phase diagram for bulk. This indicates that the cubic phase is the equilibrium phase for nanosized particles and is determined also by size. [ABSTRACT FROM AUTHOR]

Next-generation solid oxide fuel cells (SOFCs) require rapid start up times to fit the requirements for automotive and aviation industries. However, rapidly started SOFCs suffer from degradation and failure of the fuel cell components. This is due to the difference in the thermal expansion coefficients (CTE) between the different components of the fuel cell, and especially the low thermal shock resistance (TSR) of the ceramic electrolyte. Introducing multi-phase materials to SOFC components can help manage the difference in CTE and improve the thermal shock resistance where it is lacking. In this research, we aim to change the electrolyte's CTE. This is made possible by incorporating secondary phases, with a negative thermal expansion (NTE) coefficient. These can be formed during the sintering process by adding tungsten oxide to the powder. The produced composite electrolytes showed reduced effective CTE in the operating temperatures and an increase in the thermal shock resistance. Introduction of varied amounts of such a secondary phase, could allow tailoring of the CTE and therefore improving the durability of the SOFC in rapid start up times. Image 1 • Using a sol-gel approach and a solid-state synthesis to obtain a ceramic composite. • Investigating a ceramic composite of yttrium stabilized zirconia and Y 2 W 3 O 12. • Lower thermal expansion coefficient effect on the composite's thermal shock resistance. • Testing the composite's ionic conductivity in against a solid oxide fuel cell electrolyte. [ABSTRACT FROM AUTHOR]

TiNiSn-based half-Heusler semiconducting compounds have the highest potential as n-type thermoelectric materials for the use at elevated temperatures. In order to use these compounds in a thermoelectric module, it is crucial to examine their behaviour at a working temperature (approximately 1000 K) under oxygen and a humid atmosphere. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) were utilized to study the surface composition and oxidation of the TiNiSn alloy at elevated temperatures. It was found that during heating in vacuum, Sn segregates to the surface. Exposing the alloy to oxygen at room temperature will cause surface oxidation of Ti to TiO2 and Ti2O3 and some minor oxidation of Sn. Oxidation at 1000 K induces Ti segregation to the surface, creating a titanium oxide layer composed of mainly TiO2 as well as Ti2O3 and TiO. Water vapor was found to be a weaker oxidative gas medium compared to oxygen. [ABSTRACT FROM AUTHOR]

PH13-8Mo is a precipitation hardened martensitic stainless steel, known for its high strength but also for its high sensitivity to hydrogen embrittlement. Small punch test, SPT (also referred to as the ball punch test, BPT), is a relatively simple and new technique to assess the mechanical properties of samples under biaxial loading conditions. The current study utilizes the unique loading conditions of SPT to investigate the mechanical behavior and fracture prior to and after the hydrogen charging of PH13-8Mo steel. The mechanical characteristics were investigated at different metallurgical conditions: solution and quenched (SQ); fully-aged (550 °C for 4 h) and over-aged (600 °C for 4 h). Samples were cathodically hydrogen charged in a 1 M H2SO4 solution containing NaAsO2 (0.125 mg/L) at 50 mA/cm2 for different durations of 0.5 h, 2 h, and 19 h, and compared to the as-heat-treated condition. A fractographic examination was performed following the SPT measurements by scanning electron microscopy (SEM). Transmission electron microscopy (TEM) and x-ray diffraction (XRD) analyses were used as complementary characterization tools. It is shown that upon hydrogen charging, the SPT fracture mode changes from ductile to completely brittle with a transition of mixed mode cracking also affecting the SPT load-displacement curve. [ABSTRACT FROM AUTHOR]