Twin Crystals Research Articles

Chemical composition аnd morphology of pyrite and marcasite in blue clay from the Maritsa East lignite basin, Bulgaria

Pyrite and marcasite aggregates were found in a sample of blue silty clay from an exploration drill core at the northern edge of the Troyanovo North mine, Maritsa East lignite basin, Bulgaria. The aggregates have various sizes – from 50 µm (single crystal twins) to 0.5 cm (large twinned aggregates). Pyrite occurs as single cubic and cuboctahedral crystals, penetrative twins forming oval-shaped aggregates with visible cubic to truncated octahedral habits. Marcasite occurs as single tabular, pyramidal crystals, but often as twinned (penetrative, parallel, contact) composite oval-shaped aggregates. Marcasite has higher trace element contents than pyrite. In both minerals are detected Mn, Co, Ni, Cu, Zn, Mo, As, Sb, Hg, Tl and Pb with varying contents. The crystal aggregate growth is slow in varied supersaturation and pH due to the occurrence of both octahedral and cubic faces in pyrite and marcasite presence.

The effect of induced precipitations and pre-twins on the bending neutral layer migration behaviors of AZ80 Mg alloy sheet

To explore the effect of the precipitated phase particles and twins on the microstructure evolution and neutral layer evolution during bending, {10–12} tensile twins were introduced along the transverse direction (TD) on AZ80 Mg alloy sheets at room temperature. Then pre-compressed samples were aged to induce more precipitations. The reverse tensile tests were carried out at room temperature, and the three-point bending deformation was carried out at 100 °C. After aging treatment, precipitations increased. The results showed that twin crystals can promote precipitation formation. And the YS (yield strength) values of the pre-twinned aged samples were significantly larger than that before aging. During the bending process on the pre-compressed samples, the outside of the sample was dominated by the detwinning behaviors, while the inside region was dominated mainly by twinning. For pre-compressed bending samples, the k values were smaller than the initial bending sample. The tension and compression asymmetry in its inner and outer regions was weaker than that of the original bending sample. The existence of precipitations hindered the detwinning behaviors in outside the pre-twinning aged bending samples, and the twinning in inner region was restrained as well so that the inner and outer tension asymmetry decreased. The k values were smaller than that of the unaged samples, which was beneficial to weaken the bending springback of Mg alloy sheets.

Atomic insight into the BEOL thermal budget on phase transition of phase change memory cells

Research works on phase change random access memory (PCRAM) based on Ge–Sb–Te (GST) phase change materials have achieved exciting progress, but the industrialization of PCRAM still faces big challenges, including unsatisfied endurance property or unexpected cell structure failure during fabrication. Here, we investigate the impact of the thermal budget in back-end-of-line (BEOL) process on the microstructure evolution of carbon doped GST (CGST) cells. We demonstrate that the as-deposited amorphous CGST in the confined memory cell will transform to face centered-cubic (FCC) phase with uniform grain size during high temperature up to 400 °C in the BEOL process. However, if there is much more unexpected thermal budget during the BEOL process, the FCC-CGST grains will further grow and transform to highly ⟨0001⟩ oriented single crystalline hexagonal (HEX) GST, together with the formation of voids, leading to the structure failure of the storage cells. By virtue of the advanced spherical aberration corrected transmission electron microscopy (Cs-TEM), we find that there are randomly stacked seven-layered and nine-layered atomic arrangements in single crystalline HEX-GST, corresponding to the chemical stoichiometry of Ge2Sb2Te5 and Ge1Sb2Te4, respectively. Interestingly, twin crystal with the coexistence of vacancy-ordered FCC-GST and HEX-GST on the different twin boundary is observed, indicating that the twin crystals play a critical role in the coalescence and the growth of FCC-GST. This work not only sheds light on the structure failure mechanism of GST cell but also provided additional insight into the formation of HEX-phase in a confined GST memory cell.

Widespread development of bedding-parallel calcite veins in medium–high maturity organic-rich lacustrine shales (Upper Cretaceous Qingshankou Formation, Northern Songliao Basin, NE China): Implications for hydrocarbon generation and horizontal compression

Bedding-parallel calcite veins (BPCVs) occur widely in Upper Cretaceous lacustrine shales of the Qingshankou Formation in the Northern Songliao Basin, China. Research on the formation processes and geological significance of BPCVs has focused on the sources of fluid, timing of formation, initiation, dilation and growth mechanisms, and on relationships with hydrocarbon generation. In this study, we addressed these issues through a comprehensive study of drill cores containing BPCVs using petrographic observations, isotope geochemistry, rare earth element (REE) analysis, fluid inclusion analysis, in situ U–Pb dating, and basin modeling. BPCVs were observed in medium–high maturity shales with high organic matter contents with heterogeneous compositions. Similarities in δ13C, δ18O, 87Sr/86Sr, and REEs contents between BPCVs and the host shale indicate that locally derived formation fluids driven by chemical gradients were involved in BPCV formation. The in situ U–Pb age dating (70 ± 8.9 Ma and 70.6 ± 9.7 Ma) constrained BPCVs formation to the late Cretaceous, corresponding to a burial depth of ∼1600 m, indicating that the BPCVs formed in the oil window. The latter is also supported by fluid inclusions-derived temperatures (∼76–109 °C). BPCV formation included vein initiation and dilation, and the microstructures, e.g., domal and pincer structures, sigmoidal calcite veins, conjugate en-échelon calcite vein arrays, as well as mechanical crystal twins of the BPCVs, all indicate that tectonic compression influenced fracture development as also indicated in other basins where beef occur. Fluid overpressure caused by hydrocarbon generation, tectonic compression, and clay mineral transformation (mainly smectite to illite conversion) was responsible for vein dilatation. Antitaxial fibrous crystals with smooth crystal boundaries and high aspect ratios, containing sinusoidal solid inclusions as well as median planes, indicate that crystallization force promoted vein growth. Thus, BPCVs can be used as a good indicator of hydrocarbon generation, and horizontal tectonic compression.

Molecular dynamics analysis on the indentation hardness of nano-twinned nickel

Molecular dynamics simulations were employed to perform the nanoindentation analysis of nanocrystalline nickel with a variety of crystal structures (single-crystal, polycrystalline, and nano-twinned) and twin layer thicknesses under an indenter of spherical shape. To understand the effects of crystal structure and twin spacing on nanoindentation responses, the indentation force, strain, atomic rearrangement, dislocation, temperature, hardness, Young's modulus and elastic recovery rate of the indentation region were analyzed. It was noted that the three types of nanocrystalline nickel's mechanical properties and elastic recovery rate were greatly affected by their crystal structures. The results show that the hardness of the nano-twinned nickel is negatively correlated with the thickness of the twin layer, and the maximum hardness is 18.1 GPa when the thickness of twin layer is 1.2 nm. For the three structures, in the width direction, the elastic recovery ratio of the nano-twin structure is the largest, and the elastic recovery ratio of the nanotwin structure in the depth direction is the smallest. In the single crystal structure, the compression area is concentrated under the indenter and distributed in a ' V ' shape, and in the polycrystalline and twin structures, the compression area is scattered. In the polycrystalline structure, the compression area were distributed below the indenter and at crystal boundaries. In the nano-twinned structure, the compression area were mainly distributed below the indenter.

Microscopic Visualization of Crystal Twinning in Accessory Zircon

Abstract In general, crystal twinning in accessory zircon represents a rare, but in almost all granites and gneisses, encounterable phenomenon. Since only the crystal face {101} occurs as a twin plane, formation of crystal twins turns out to be relatively simple. Besides geniculate twins, which develop by rotation of the crystal structure about the line [101], parallel twins that are arranged parallel to the crystallographic main axis of zircon can also be observed by light and electron microscopy. While geniculate twins usually show a frequency within the region of a permille, the number of parallel twins can rise to several percent depending on the investigated rock. In the present contribution, a brief insight into the microscopic world of zircon twinning is provided.

Twin Zn1- x Cdx S Solid Solution: Highly Efficient Photocatalyst for Water Splitting.

Twins in crystal defect, one of the significant factors affecting the physicochemical properties of semiconductor materials, are applied in catalytic conversion. Among the catalysts serving for photocatalytic water splitting, Zn1- x Cdx S has become a hot-point due to its adjustable energy band structure. Via limiting mass transport to control the release rate of anions/cations, twin Zn1- x Cdx S solid solution is prepared successfully, which lays a foundation for the construction of other twin crystals in the future. On twin Zn1- x Cdx S, water tends to be dissociated after being adsorbed by Zn2+ /Cd2+ at twin boundary, then the fast-moving electrons at twin boundary quickly combine with the protons already attached to S2- to form hydrogen. According to the theoretical calculation, not only the intracrystalline electron mobility, but also the extracrystalline capacity of water-adsorption/dissociation and proton-adsorption on the twin boundary are superior to those of the counterpart plane in defect-free phase. The synthetic twin Zn1- x Cdx S apparent quantum efficiency of photocatalysis water splitting for hydrogen reached 82.5% (λ = 420nm). This research opens up an avenue to introduce twins in crystals and it hopes to shed some light on photocatalysis.

Direct observation of the ledge-typed twin boundary in a martensitic steel

The structure at the {112} twin boundaries in martensitic steels has been extensively debated recently. On the one hand, it was claimed to be the omega phase, similar to Ti alloys. On the other hand, it was considered artifacts induced by the double diffraction effect from the overlaps of twin-matrix crystals at their boundaries. In this study, we clarify the twin structure in a martensitic steel providing a detailed investigation of the α′ martensite twin boundaries using experiment and simulation. The fundamental for rejecting the existence of the omega phase in steels is based on the atomic resolution imaging from the <111> direction of twin structure, which was so far challenged to be acquired for such nano-sized twinned systems. The obtained result confirms the ledge-typed twin boundary that causes the visually omega-like forms when observed from other zone axes. The ledges occurred on {110} planes, making them secondary twin planes with coherent characteristics. Furthermore, these ledges were found to transit in a gradual manner from the primary (112) twin plane to (011) and then to (1¯10) secondary twin planes; a perpendicular transition from (112) to (1¯10) was not observed. Such a transitional behavior was explained in view of lowering total twin boundary energy, evaluated by the theoretical prediction of system energy and the geometric phase analysis of the twin planes. Double diffraction and rotational Moiré effects clarified the extra spots in the diffraction pattern obtained at the twin-matrix overlapped regions. This study gives light of understanding twinning in the bcc crystals.

Crystal Structures and Twinning of RuBr3

AbstractThe concerted experimental and computational study reports on the polymorphic behavior of RuBr3. Highly‐resolved X‐ray powder diffraction measurements of the modification lt‐RuBr3 give direct evidence for peak splitting substantiating an orthorhombic unit cell with additional weak intensities confirming a primitive lattice. The crystal structure of lt‐RuBr3 is determined using the intensities of a “Drilling” individuum. For lt‐RuBr3, findings of density functional theory calculations suggest that the deviation from hexagonal symmetry is mainly driven by electronic correlations. Reinvestigation of the recently reported high‐pressure modification hp‐RuBr3 essentially confirms the rhombohedral BiI3‐type crystal structure (space group R ). Simulations of the atomic arrangement of hp‐RuBr3 indicate that spin‐orbit coupling and corrections for the van‐der‐Waals dispersive forces are mandatory to reach a reasonable agreement with the experimentally determined crystal structure.

Microstructural understanding of CrN layer as a barrier against Cr-Zr interdiffusion in Cr-coated zirconium alloy for accident tolerant fuel claddings

In this study, a Cr-CrN-Cr coating was fabricated on Zr alloy to explore the barrier effect of the CrN layer on Cr-Zr interdiffusion. Steam oxidation tests were conducted using both a thermogravimetric analyzer and a tube furnace to examine the oxidation resistance and coating evolution of the sample under high-temperature conditions. Atomic scale characterizations were performed on the sample after exposure. After HT annealing, a ZrN layer composed of nano equiaxed grains was successfully formed between the residual coating and Zr substrate, serving as a diffusion barrier for both the Cr-Zr interdiffusion and nitrogen/oxygen inward diffusion. Nano twin crystals were observed within the ZrN grains, and the growth of twin boundaries was along multi-directions. The coating evolution during HT annealing was analyzed, and the impact of ZrN layer on the inhibition of Cr-Zr interdiffusion was discussed.

Laser powder bed fusion of full martensite Cu-Al-Mn-Ti alloy with good superelasticity and shape memory effect

A copper-based shape memory alloy Cu-11.85Al-3.2Mn-0.1Ti with desirable superelasticity and shape memory effect was printed by laser powder bed fusion (LPBF), which demonstrated the feasibility of engineering applications through the deformation and recovery of complex corrugated structural components. The microstructure of LPBF-printed Cu-11.85Al-3.2Mn-0.1Ti was composed of full β1' martensite with a high density of stacking faults and twin crystals. The abnormal phase constitution of full martensite in the printed Cu-11.85Al-3.2Mn-0.1Ti is correlated to substrate preheating and thermal cycling during LPBF. The start and finish transformation temperatures of martensite (Ms and Mf) and austenite (As and Af) were 172.5 °C, 144.4 °C, 180.2 °C and 209.2 °C, respectively. The printed samples exhibited compressive strength of 1319 MPa with a compressive fracture strain of 16.1%. The printed alloy displayed remarkable superelasticity and shape memory effect. The superelastic recovery rate reached a maximum value of 87% at 6% pre-strain, corresponding to a superelastic recovery strain of 5.22%. The mechanism of superelasticity is attributed to the rubber-like deformation behavior. Moreover, the pre-strained samples demonstrated a desirable shape memory effect under the temperature stimulation, where the shape memory recovery rate of up to 100% at a pre-strain of 6%, corresponding to a shape memory recovery strain of 0.78%. The reasons for the favorable shape memory effect were: (i) the thermoelastic inversion of martensitic transformation and (ii) the precipitation of γ2(Cu9Al4) phase along the grain boundaries. As a result, these findings suggest that the LPBF technique can produce Cu-Al-Mn-Ti parts with superelasticity and good shape memory properties, which provided valuable references for printed copper-based shape memory alloys with full martensitic structures.

Visualizing crystal twin boundaries of bismuth by high-spatial-resolution ARPES

Visualizing crystal twin boundaries of bismuth by high-spatial-resolution ARPES

Pseudo-cubic trigonal pyrite from the Madan Pb–Zn ore field (Rhodope Massif, Bulgaria): morphology and twinning

Abstract. A new occurrence of pyrite crystals with rhombohedral habit, up to several centimeters in length, is described from the Madan Pb–Zn ore field (Rhodope Massif, south Bulgaria), where it constitutes a late pyrite generation. As observed in the past in other deposits, the ideal rhombohedron is derived from the pyritohedron by suppression of half of its faces (six “polar faces”) around a ternary axis. In studied crystals, together with six main “equatorial faces”, additional minor faces correspond to cube faces as well as polar faces. Such a dissymmetry indicates that the crystallographic point group of these crystals is 3‾, a subgroup of the eigensymmetry 3‾2/m of a rhombohedron taken as geometric face form. Twinning by metric merohedry confirms such a symmetry decrease and permits the definition of this type of pyrite as a dimorph of cubic pyrite, i.e., pseudo-cubic trigonal pyrite (pyrite-R). Twin operations belong to the set of symmetry operations absent in point group 3‾ relative to pyrite symmetry m3‾: reflection about the {100} plane or two-fold rotation about the &lt;100&gt; direction. Four twin types have been distinguished (name, chromatic point group): three contact twins (reflection, m′; rotation, 2′; trapezoidal, (m(2)m(2)2(2))(4)), as well as one penetration twin (crossed, 2′/m′). Composition planes always correspond to {100}, but there are two types of twin interfaces. More complex twinned samples may develop erratically during crystal growth. Other twin variations as well as genetic aspects of such a type of pyrite are discussed.

101 contact twins in gypsum experimentally obtained from calcium carbonate enriched solutions: mineralogical implications for natural gypsum deposits.

Gypsum twins are frequently observed in nature, triggered by a wide array of impurities that are present in their depositional environments and that may exert a critical role in the selection of different twin laws. Identifying the impurities able to promote the selection of specific twin laws has relevance for geological studies aimed at interpreting the gypsum depositional environments in ancient and modern deposits. Here, the effect of calcium carbonate (CaCO3) on gypsum (CaSO4·2H2O) growth morphology has been investigated by performing temperature-controlled laboratory experiments with and without the addition of carbonate ions. The precipitation of twinned gypsum crystals has been achieved experimentally (101 contact twin law) by adding carbonate to the solution, and the involvement of rapidcreekite (Ca2SO4CO3·4H2O) in selecting the 101 gypsum contact twin law was supported, suggesting an epitaxial mechanism. Moreover, the occurrence of 101 gypsum contact twins in nature has been suggested by comparing the natural gypsum twin morphologies observed in evaporitic environments with those obtained in experiments. Finally, both orientations of the primary fluid inclusions (of the negative crystal shape) with respect to the twin plane and the main elongation of sub-crystals that form the twin are proposed as a fast and useful method (especially in geological samples) to distinguish between the 100 and 101 twin laws. The results of this study provide new insights into the mineralogical implications of twinned gypsum crystals and their potential as a tool to better understand natural gypsum deposits.

Crystallization between (100) Goethite and (001) Orientation of Hematite – A Review

Abstract The purposes of this study were: (1) to review the preparation and characterization of the intergrowth between goethite and hematite crystals; and (2) to propose a schematic diagram of the epitaxial relationships among three sets of (100) goethite twin crystals associated with the (001) orientation of the hexagonal prism of hematite. The Fe(ClO4)3 solution was prepared and aged at 70°C, which precipitated goethite initially and produced hematite later with prolonged aging. Goethite and hematite aged for 20 days were observed as star-shaped and hexagonal prisms, respectively. The results suggest that hematite could form later using goethite as a template surface. A selected area electron diffraction (SAED) pattern showed the epitaxial relationship among three sets of (100) goethite intergrowth crystals and hexagonal prisms with the (001) orientation of hematite. Goethite can be produced as lath-, X-, K-, or star-shaped crystals on the (100) orientation, depending on the Fe(ClO4)3 concentrations and the addition of HClO4 to Fe solution samples which were aged for a prolonged period at room temperature. The initial solubility products [(Fe3+)(OH–)3] of the sample solution, rather than the nature of the nuclei, are the key factors governing the formation of goethite or hematite. The addition of acids and high concentrations of iron solutions extend the secondary hydrolysis and induction period (IP) and favor the formation of hematite. The index of the SAED pattern of the star-shaped goethite intergrowth twin crystal has a (100) plane parallel to this basal plane and rotates at a 60° angle between two or three sets of lath-shaped goethite crystals, which share the (011) plane and form goethite twins with ‘interpenetrated’ crystal growth. Stereoscopic viewing using Oak Ridge Thermal Ellipsoid Plot (ORTEP) and CrystalMaker software was deployed to explore the relationship and configuration of oxygen atoms between pseudo-hexagonal (100) goethite associated with hexagonal (001) hematite lattice planes. A schematic diagram of the epitaxial relationship between star-shaped (100) goethite, which is acting as a template facilitating later precipitation of (001) hexagonal prisms of hematite on it, is presented.

Direct Crystal Growth Control: Controlling Crystallization Processes by Tracking an Analogue Twin

Due to the dynamic interactions of various crystallization phenomena, crystallization processes are notoriously difficult to control. In some applications, supersaturation control is aimed for as it affects various phenomena. Direct nucleation control aims at controlling the number of crystals in suspension. Here, we propose direct crystal growth control (DGC). The new method avoids parametrization of the thermodynamic relation between concentration, temperature, and solubility. Instead, a single crystal is fixed in the crystallization vessel, and it acts as an analogue twin. The analogue twin enables inline growth rate measurement and serves as a proxy for the growth of the suspended crystals. Via temperature manipulation, the analogue twin’s growth rate can be controlled to be kept constant. Growth rate of suspended crystals is then observed to be constant, too. However, hydrodynamic conditions for the analogue twin and suspended crystals were different and need to be further explored for a more accurate application of DGC. Temperature-dependent growth rates, the existence of molecular clusters in solution, and the potential use of the new growth rate probe for parameter estimation are discussed.

Complex Assessment of X-ray Diffraction in Crystals with Face-Centered Silicon Carbide Lattice

X-ray diffraction analysis is essential in studying stacking faults. Most of the techniques used for this purpose are based on theoretical studies. These studies suggest that the observed diffraction patterns are caused by random stacking faults in crystals. In reality, however, the condition of randomness for stacking faults may be violated. The purpose of the study was to develop a technique that can be used to calculate the diffraction effects of the axis of the thin plates of twin, new phases, as well as other variations in defective structures. Materials and methods. This was achieved through modern X-ray diffraction methods using differential equations (transformations and Fourier transforms) and the construction of the Ewald sphere, mathematical analysis, mathematical logic, and mathematical modeling (complex Markov chain). Conclusion. The study made it possible to develop a technique for the calculation of the diffraction effects of the axis of the thin plates of twin, new phases and other variations in defective structures. The technique makes it possible to solve several complex, urgent problems related to the calculation of X-ray diffraction for crystals with face-centered lattices containing different types of stacking faults. At the same time, special attention was paid to the correlations between the relative positions of faults. The calculations showed that the proposed method can help to determine the nature and structure of stacking faults by identifying the partial and vertex dislocations limiting them in twin crystals with a face-centered cubic structure of silicon carbide based on X-ray diffraction analysis.

Engineering triple internal electric fields in Ag NWs@BaTiO3 composites for ultrasonic-visible-light driven antibacterial activity

Sono-photodynamic antibacterial therapy (SPDAT) is considered to be one of the most effective biomedical treatments, offering both practical flexibility and excellent performance. However, sono-photosensitizers with good biocompatibility, low cytotoxicity, and high antibacterial efficiency under harsh conditions are lacking nowadays. This paper presented attractive Ag NWs@BaTiO3 core–shell composites, which integrates three elements of piezoelectric effect, twin crystals, and heterojunction to engineer triple internal electric fields. Continuous co-disturbances induced by ultrasound and light disrupted the electrostatic balance and saturation effects of the triple internal electric field on composites, thereby regulating its own electrical properties and increasing its affinity and adhesion to bacterial cells through electrostatic attraction. Remarkably, the antibacterial efficiency of Ag NWs@BaTiO3 against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) reached 92.5% within 60 min and ∼ 100% within 30 min under low-power visible light irradiation and ultrasonic vibration, respectively. Moreover, the composites also exhibited good biocompatibility and low cytotoxicity. Intrinsically, the constructed triple internal electric fields could effectively extend the charges transfer pathway, accelerating the spatial separation of excited-charges pairs and thereby producing sufficient reactive oxygen species (ROSs) to boost the synergistic piezo-photocatalysis activity. Finally, we proposed a combined piezo-photocatalysis mechanism of energy band bending theory and screening charge effect under triple internal electric fields.

Crystallogenetic Causes of the Unique Shape of the Matryoshka Diamond: The Effect of Capturing a Diamond Inclusion of Twin Diamond Crystals

The unusual shape of the Matryoshka diamond, which is a diamond crystal with a cavity containing a diamond crystal freely moving in it, continues to attract keen interest of many researchers in the context of its seemingly paradoxical origin for a mantle mineral. The discovery sparked lively discussions and multiple attempts to explain the nature of the unique shape of this crystal. A comprehensive mineralogical and crystallographic analysis of the unusual specimen, as well as other analogous diamond crystals, suggests that it was formed as a consequence of the mutual disorientation of the crystals during their growth and the presence of a twin of diamond subindividuals that formed both the core (inclusion) and the sheath (host) diamonds. The twinning planes (111) in the contacting crystals of the inclusion and the host were in a sub-perpendicular position to each other during their simultaneous growth. The captured diamond of the inclusion prevented the normal development of the diamond that became the host. The diamond host rapidly grew along the direction of its own twin boundary and constantly generated new growth layers, which eventually converged around the small captured twin crystal cluster during metric selection. Analysis of diamond crystals of similar shape from the Nyurbinskaya pipe and from elsewhere worldwide confirms the ontogenic model of their origin as a consequence of the capture of diamond inclusions that hampered the rapid growth of the twin crystal (spinel-law twins) in the direction of the twin boundary.

KIT-5-Assisted Synthesis of Mesoporous SnO2 for High-Performance Humidity Sensors with a Swift Response/Recovery Speed

Developing highly efficient semiconductor metal oxide (SMOX) sensors capable of accurate and fast responses to environmental humidity is still a challenging task. In addition to a not so pronounced sensitivity to relative humidity change, most of the SMOXs cannot meet the criteria of real-time humidity sensing due to their long response/recovery time. The way to tackle this problem is to control adsorption/desorption processes, i.e., water-vapor molecular dynamics, over the sensor's active layer through the powder and pore morphology design. With this in mind, a KIT-5-mediated synthesis was used to achieve mesoporous tin (IV) oxide replica (SnO2-R) with controlled pore size and ordering through template inversion and compared with a sol-gel synthesized powder (SnO2-SG). Unlike SnO2-SG, SnO2-R possessed a high specific surface area and quite an open pore structure, similar to the KIT-5, as observed by TEM, BET and SWAXS analyses. According to TEM, SnO2-R consisted of fine-grained globular particles and some percent of exaggerated, grown twinned crystals. The distinctive morphology of the SnO2-R-based sensor, with its specific pore structure and an increased number of oxygen-related defects associated with the powder preparation process and detected at the sensor surface by XPS analysis, contributed to excellent humidity sensing performances at room temperature, comprised of a low hysteresis error (3.7%), sensitivity of 406.8 kΩ/RH% and swift response/recovery speed (4 s/6 s).