In this study, the effects of crucible-introduced elements (Al3+, Ti4+, Mg2+ and Y3+) on the structure, crystallization behavior, and electric properties of BaO-Bi2O3-TiO2-B2O3 glasses and glass-ceramics (GCs) were systematically investigated. Raman spectroscopy, DSC, XRD, SEM, EDS, and Raman mapping analyses were used to elucidate the structural evolution of the glasses and crystal morphology of their GCs. After long time heat treatment at crystallization temperatures, most GCs contain only one crystal phase, the orthorhombic Bi4Ti3O12. Analysis of crystallization kinetics shows that crucible-introduced elements alter the glass stability, crystallization temperature and crystallization activation energy, thereby affecting crystal growth. Therefore, different crystallization behaviors are observed, and the crystal morphology evolves from fine spherulitic structures to coarser polycrystalline dendritic morphologies, with a significant increase in crystal size. The relative permittivity of GCs increases with the increasing crystal size, exhibiting superior dielectric performance, with a relative permittivity of approximately 130, which is nearly twice that of previously reported Bi4Ti3O12-based GCs. The relative permittivity remains nearly temperature-independent below 400 degrees C at a frequency of 1 MHz, and clear ferroelectric behavior is observed. These results provide new path into element-induced structural modification and crystallization control in Bi4Ti3O12-based GCs, which are promising for energy storage and optoelectronic applications.

Crucible-introduced elements regulate crystallization and microstructure evolution in BaO–Bi 2 O 3 –TiO 2 –B 2 O 3 GCs, enabling large Bi 4 Ti 3 O 12 crystals and enhanced dielectric performance with permittivity up to ∼130.

The domain structure of Sn-doped BaTiO 3 was examined with piezoresponse force microscopy and spatially resolved Raman spectroscopy, and derived reversible and irreversible contributions from Rayleigh analysis of the dielectric response.

Correction for ‘Unraveling the structural complexity of niobate units in aluminosilicate glasses and glass–ceramics’ by Maria Rita Cicconi et al. , Mater. Adv. , 2025, 6 , 3863–3874, https://doi.org/10.1039/D5MA00082C.

Lanthanide-doped Ca2Nb2O7 offers versatile and tunable luminescence properties. Previous studies have shown that Pr3+-doped and Pr3+/Er3+ co-doped Ca2Nb2O7 ceramics exhibit non-destructive mechanoluminescence, up- and down-conversion luminescence, and thermoluminescence, with potential for optical temperature sensing. However, to date, niobate glass–ceramics (GCs) remain largely unexplored, although they would offer excellent temperature resistance, high chemical durability, controllable crystallization, and the possibility to combine functional properties. This study investigates Pr3+ single doping and Pr3+/Er3+ co-doping in glass–ceramics prepared from niobium-containing calcium aluminosilicate glasses with the composition 55CaO-(35-x)Al2O3-10SiO2-xNb2O5 (mol%, where x = 0, 10). The aim is to obtain glass–ceramics containing Ca2Nb2O7 crystals with a layered perovskite structure and to evaluate their suitability as hosts for rare-earth ions. The luminescence properties of both parent glasses and GCs were investigated, and it is shown that the glasses show intrinsic luminescence which, when doped, enables sensitization of rare-earth elements via charge transfer. Furthermore, several interesting photoluminescence mechanisms were observed in the doped GCs, including (i) Er3+ up-conversion from the NIR to the visible, (ii) variations in the relative intensities of Er3+ hypersensitive transitions, reflecting changes in site symmetry, and (iii) a charge transfer process to the activator ions under UV excitation. These phenomena extend the accessible excitation range for rare-earth emission. Overall, the developed Ca2Nb2O7 GCs demonstrate efficient dopant integration, confirming their suitability as lanthanide hosts for advanced photonic, sensing and energy conversion applications.

As power devices become increasingly crucial to advanced technologies, the development of passive components, such as capacitors, has gained significant research attention. Among various candidate materials, CaTiSiO5 stands out as a particularly promising lead-free dielectric due to its positive-bias dependence of dielectric permittivity, which originates from its antipolar structure. Although considerable efforts have been devoted to studying the effects of chemical substitutions on the crystal structure and temperature-dependent dielectric properties of CaTiSiO5, research on its electrical response under large electric fields remains limited, particularly regarding its behavior across wide temperature ranges relevant to practical applications. Remarkably, CaTiSiO5 exhibits a positive DC-bias effect at room temperature, where the permittivity increases with applied electric field. This behavior is significantly different from conventional ferroelectric capacitors, arising from the coupled effects of electric field and temperature on phase structure modulation. In this work, the temperature-dependent DC-bias effect was characterized from -30 °C to 150 °C, where both positive and negative DC-bias effects were observed as temperature changes, providing important insight into the role of the high temperature antiferroelectric-paraelectric phase transition observed at approximately 170 °C using temperature-dependent Raman spectroscopy as well as small signal dielectric and elastic measurements. These data are contrasted to large-field polarization–electric field and electric-field-dependent relative permittivity measurements to more fully understand its antiferroelectric behavior and dielectric response under large electric fields, providing valuable guidance for the design of next-generation power electronic devices.

Ancient Romans exploited aesthetic natural stones from many sites across their Empire in the Mediterranean, transporting them for thousands of kilometres, to decorate their buildings. Petrographically, these metamorphic, sedimentary and igneous rocks display considerable differences, ranging from simple white stones to vividly coloured lithotypes. The source Region of these coloured stones is typically reconstructed from autoptic (visual and comparative examination of macroscopic or hand-sample scale) determinations, also taking advantage of the personal expertise of some specialists in the sector. Here, the ornamental stones of the 2nd-century AD thermal baths of Teate Marrucinorum (Chieti, Abruzzo region, Italy) are examined using a range of complementary methods. According to their autoptic features or mesoscopic textures, the initial 56 samples were divided into three categories: polychrome stones, grey-striped and white crystalline marbles. These rocks were analysed via bulk autoptic, mineralogical and geochemical methods; representative thin sections were also used for transmission optical microscope (TOM) petrographic and micro-Raman determinations. The δ¹⁸O and δ¹³C isotopic signatures were also characterised for white and grey-striped marbles. The complementary and multi-analytical approach unveils that the grey-striped marble is Greco Scritto (from Asia Minor), the white marbles come from Carrara (Marmor Lunense) and Marmara Island (Marmor Proconnesium) sources, whilst the four polychrome stones correspond to Pavonazzetto Antico (Marmor Phrygium), Cipollino Verde (Marmor Carystium), Portasanta (Marmor Chium) and Breccia di Settebasi (Marmor Scyreticum). The coupling of qualitative observations with quantitative measurements further constrains the provenance and features of the aesthetic rocks employed in the ancient town by the Romans.

CaO-Al2O3 based glasses are studied due to their presence in hydraulic binders/refractory cements. With the addition of Fe, an increased complexity in the phase diagrams and the liquid structure is observed as this element can exist in two different oxidation states which plays different roles in a liquid/glass matrix. The aim of this study is to understand the influence iron addition in a CaO-Al2O3-B2O3 glass. B2O3 was added to simulate a liquid phase present in some Belite-Ye'elimite-Ferrite clinkers in which a glassy phase is observed. Iron is mainly present in the Fe3+ form in four-fold coordination. Viscosity and glass transition temperatures decrease with the addition of Fe2O3 which has an important impact for the clinkering process. This decrease with iron correlates with the appearance of a new band at 650 cm-1 in the Raman spectrum which can be assigned to the vibration of Al—O—[4]Fe3+—O—Al links.

Oxide glasses are intrinsically brittle, lacking sufficient atomic-scale mechanisms that can relax mechanical stresses in the vicinity of a propagating crack. As a result, fracture is typically well-captured by considering local bond rupture at the crack tip. Here we demonstrate that barrier energies related to the low-temperature γ-relaxation mode in alkali-aluminosilicate glasses are inversely related to the fracture toughness measured via standardized three-point bending fracture experiments. This holds true for both a series with varying cations (Li, Na, K) and one with varying Li concentration. The structural rationale for this finding is gained via Raman spectroscopy. The findings suggest that a fundamental structural relaxation mode measured on bulk specimens can serve as an effective guideline for fracture toughness of oxide glasses. Data for additional silicate glasses support this conclusion.

Two thin sections of Muong Nong-type tektites from the Australasian tektite strewn field have been analyzed by Fe K-edge X-ray absorption near edge spectroscopy (XANES), using a hundreds-of-micrometers-sized beam suitable for spatially resolved analysis of the Fe oxidation state across distinct regions of the samples. Earlier analyses with an unfocused beam were inconclusive regarding different amounts of oxidized iron in the Muong Nong-type tektites, but did indicate different chemical compositions of the lighter and darker colored layers. Experimental XANES spectra are very similar in shape to those of other tektites. However, small and reproducible changes were found in the pre-edge peak involving the centroid energy: the pre-edge peak of the spectra collected within the dark layers are reproducibly 0.2 eV at higher energy than those of the spectra collected within the light matrix. This difference in energy position is four times the estimated energy reproducibility and, therefore, is significant. By comparison with pre-edge peak data of Fe model compounds, we estimate the Fe3+/(Fe2++Fe3+) ratios in the light matrix and dark layers to be 5% and 15% (+/- 5), respectively. The heterogeneous distribution of the Fe oxidation state in Muong Nong-type tektites, as opposed to the homogeneous Fe oxidation state distribution in splash-form tektites, is consistent with previous hypotheses, based on volatile contents, of Muong Nong-type tektites resulting from melts that experienced lower temperatures compared to those of splash-form tektites.

Due to the growing significance of energy storage, ceramics for high energy density capacitors have become an increasingly prominent area of research. For this reason, current research primarily focuses on enhancing the energy storage performance and efficiency. Despite the importance for implementation in applications, however, there remain few investigations on the mechanical properties. Here, it is investigated the role of uniaxial compressive stress on polycrystalline NaNbO3, a lead-free antiferroelectric with significant potential for advanced energy storage applications. Through ex situ stress-dependent crystal structure analysis using XRD as well as Raman mapping, it is demonstrated that NaNbO3 ceramics, which initially exhibit an antiferroelectric P phase accompanied by a ferroelectric Q phase, undergo a stress-modulated change in the crystal structure and domain state. This is analogous to the well-known irreversible electric field-induced AFE-to-FE phase transition found in NaNbO3. Ex situ Raman mapping of unpoled and mechanically loaded samples revealed spatial variations in the AFE and FE phases, demonstrating the inhomogeneity of the stress-modulated structural phase transition in the polycrystalline microstructure. In addition, the large signal mechanical response of poled and unpoled samples is characterized, showing a significant decrease in the coercive stress of NaNbO3 and an increase in the backswitching rate due to the formation of a long-range ordered ferroelectric structure with orientation and non-180 degrees domain switching. Revealing the complicated role of compressive stress on NaNbO3 will help to understand real-world operating conditions and provide deeper insights into the underlying physical mechanisms, providing guidance for the design and application of antiferroelectric materials.

Niobium-containing glasses and glass–ceramics play an important role in several technological applications, but our understanding of the structure–property relationships of many Nb-containing compositions is still rudimentary. To address the current limitations, the present contribution reports data from synchrotron high-energy X-ray diffraction data to unravel the structural evolution of niobate entities in alkali–aluminosilicate glasses. The data obtained are compared with complementary Raman and solid-state NMR spectroscopy data to provide a better interpretation of the macroscopic properties of the glasses and their crystallization behavior in terms of the glass structure. The data show that the incorporation of niobium into the glass network (from 0.2 mol% to 10 mol%) causes a rearrangement of the units and induces large modifications, particularly in the medium-range order. Nb5+ is present in all glasses predominantly in the form of 6-coordinated [NbO6] units with rather invariant 〈Nb–O〉 bond distances around 2.0 Å. This observation correlates well with the 93Nb NMR data showing similarly small changes in the chemical shift values. A contrasting scenario is presented when looking beyond the first coordination sphere, with a particular focus on the A–Nb (A = alkali) and Nb–Nb correlations. Both are strongly dependent on bulk chemistry, which, in turn, is influenced by the availability and nature of charge-compensating alkali ions. The addition of Nb has a relatively minimal effect on Si and Al units, promoting the association of Nb with other Nb species, thereby initiating the formation of a subnetwork of [NbO6] units in a corner shared environment. Both alkali species and Nb5+ ions in the amorphous state tend to favor a structural arrangement very similar to that of the stable crystalline phase.

In this study, a series of lead-free, Bi-based glasses were designed and investigated for potential applications in radiation shielding. The glasses, based on the system xBaO-(90-x)(40Bi2O3-25TiO2-35B2O3)-10Al2O3 (x = 0-30 mol%), were synthesized via a melt-quenching process at 1000 degrees C. The physical and optical properties of the glasses, as well as the valence states of Bi and the local oxygen environments, were systematically explored. The non-linear variation in physical and optical properties with composition is explained by the structural changes related to Bi, Ti, and B, as revealed by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and solid-state nuclear magnetic resonance (NMR) spectra. Simulations of radiation shielding ability were performed using the XCOM tool. The simulation results show that the glasses exhibit high mass attenuation coefficients (MAC), reaching up to 4 cm2/g, and low half layer value (HLV), reaching 0.031 cm at 100 keV photon energy, which are better than many previously reported Bi-containing glass systems. As photon energy increases, MAC values decrease and HLV increases, as expected. The addition of BaO slightly reduces the MAC and increases the HLV, while it can modify physical and optical properties, including density, glass stability, refractive index, optical band gap, ultraviolet-visible (UV-vis) absorption, and luminescence behavior, thereby offering flexibility for different applications in medical field and nuclear industry. Moreover, when the BaO content reaches 30 mol %, the glass exhibits optimal transparency and is almost colorless. These results suggest that the studied glass system is a promising candidate for lead-free radiation shielding applications, combining high MAC, low HLV with tunable physical and optical characteristics.

Barium calcium zirconium titanium oxide (BCZT) is a lead‐free piezoelectric ceramic material with exceptional electromechanical properties, making it highly valuable in applications such as sensors, actuators, and transducers. Among various synthesis methods for BCZT, the sol–gel (SG) route is chosen here because it allows precise control of the composition and a lower processing temperature compared to solid‐state sintering. However, achieving high electromechanical response through the SG synthesis route remains challenging. In this study, the response is increased up to 359 pC N −1 by coating the powder surface with a 0.69 nm stearic acid (SA) layer. The SG derived Ba 0.85 Ca 0.15 Zr 0.1 Ti 0.9 O 3 (BCZT50) is uniaxially pressed and then subjected to cold isostatic pressing to evaluate its properties without the influence of advanced shaping techniques. After heat treatment and corona polarization, the piezoelectric coefficient d 33 is determined to be 21–46 pC N −1 . The SA coating enhances powder flowability and compressibility during pressing, due to chemical interactions at the particle surfaces. To better understand the nature of the SA‐BCZT interaction and the formation of surface stearates, attenuated total reflectance‐Fourier transform infrared spectroscopy, X‐ray diffraction, and Raman spectroscopy are employed. These analyses help clarify the influence of the coating on the powder characteristics and its contribution to improved electromechanical performance.

In this study, Bi- and Ti-rich glasses have been designed and investigated for the development of ferroelectric glass-ceramics (GCs). The glass formation range, the structure of the glass network and the crystalline phases obtained in the glass-ceramics were explored. Glass compositions within the xBaO-(90-x)(40Bi2O3-25TiO235B2O3)-10Al2O3 system were synthesized through rapid press quenching of the melt, with a controlled melting temperature of 1000 degrees C. Raman spectroscopy was carried out to investigate the impact of Bi2O3, TiO2 and BaO on the arrangement of the structural units in these glasses. Subsequent thermal treatment in the temperature range of 500-700 degrees C led to the formation of glass-ceramics containing the ferroelectric Bi4Ti3O12 crystal phase in all compositions. Notably, glass-ceramics containing 10-16 mol% of BaO exhibited a single Bi4Ti3O12 crystal phase upon complete crystallization. The microstructure and temperature-dependent dielectric properties of glasses and GCs were investigated as a function of the Ba content. The permittivity epsilon r of the glasses is quite high compared to other glass systems, ranging between 22 and 28, and it is greatly increased in the crystallized samples (up to 70). Furthermore, no phase transitions up to 300 degrees C are observed, especially in GCs with a single Bi4Ti3O12 crystal phase, making these materials strong candidates for energy storage dielectrics. The samples developed in this study demonstrate the potentiality of obtaining piezoelectric glass-ceramics in network formerpoor matrices.

In this study, the photoluminescence (PL) behavior of two aluminosilicate glass series containing alkali-niobates ranging from 0.4 to 20 mol% was investigated. The glasses exhibit an intense visible emission centered at ~18,400 cm−1 for the peralkaline series and at higher energies (~19,300 cm−1) for the metaluminous glasses. However, the photoluminescence emission intensity varies significantly with the niobate content and the bulk chemistry. PL and fluorescence lifetime measurements indicate that the broad emission bands result from the overlap of different niobate populations, whose distribution changes with niobate content. The distinct PL behavior in the two glass series was related to the structural evolution of the niobate units upon niobium addition. An enhancement of the visible emission was observed for a higher fraction of distorted [NbO6] units. Eu-doping was carried out as a structural probe of the glass network, and also to determine if these glasses could be used as potential rare earth element (REE) activators. The crystal field strength around Eu ions is strongly dependent on the bulk chemistry and the niobate content. Furthermore, the peralkaline series showed energy transfer from the host [NbO6] to Eu3+, confirming the feasibility of exploring niobate glasses and glass-ceramics as lanthanide ion-activated luminescent materials. In addition, glass-ceramics (GCs) containing alkali-niobate phases with a perovskite-like structure were developed and studied to verify the optical performance of these materials. It was verified that the bulk chemistry influences crystallization behavior, and also the photoluminescence response. The transparent GC from the metaluminous series exhibits a quenching of the Eu3+ emission, whereas an enhanced emission intensity is observed for the peralkaline GC. The latter shows a strong excitation-dependent PL emission, suggesting energy transfer and migration of electronic excitation from one Eu population to another. Additionally, Eu3+ emissions arising from the D15 and D25 excited states were observed, highlighting the low phonon energy achievable in niobo-aluminosilicate hosts.

Coextrusion by robocasting is a suitable process for fabricating multimaterial ceramic structures. Herein, the robocasting process is used to fabricate core–shell structures, combined with subsequent liquid silicon infiltration (LSI). Thus, reaction‐bonded silicon carbide (RBSC), reaction‐bonded boron carbide (RBBC), and reaction‐bonded silicon–boron carbide composites are produced. The LSI process offers the possibility to circumvent high temperatures and pressures used in traditional fabrication. Pastes with high solid loading and necessary carbon content are used in order to combine the robocasting with the subsequent LSI process. The influence of the paste rheology on the sample fabrication of multimaterial core–shell structures of reaction‐bonded carbides is investigated. The key rheological data, such as the viscosities of the combined pastes, are correlated with the observations from the microstructural investigation using scanning electron microscopy. A correlation between the difference in viscosity and the core geometry can be established. Crack formation in the material combination of RBSC and RBBC is found and compared with layered multimaterial structures of reaction‐bonded carbides. Residual stresses, which can be used to explain the crack formation, are investigated using Raman spectroscopy.

In this study, the structural phase transitions are investigated as a function of composition and temperature for polycrystalline x(Ba0.7Ca0.3)TiO3-(1-x)Ba(Zr0.2Ti0.8)O3 (x = 0.40, 0.45, 0.50, 0.55, and 0.60) through a combination of Raman spectroscopy, synchrotron X-ray diffraction, and dielectric spectroscopy. The aim is to gain insight into the complex phase boundary region responsible for the excellent electromechanical properties. The results demonstrate the correlation between local site substitutions based on the stoichiometric variations to the microstructure and dielectric properties. The dielectric response has been correlated with the BCT/BZT content displaying a maximum depending on the phase content. Additionally, in situ temperature-dependent Raman, permittivity, and pair distribution function (PDF) studies were performed from -60 °C to 130 °C to highlight the structure and phase evolution. In particular, the in situ temperature-dependent Raman measurements reveal sudden discontinuities in the vibrational modes that correspond to the structural changes in the perovskite structure. Therefore, the results of the permittivity response, based on the average of a large volume, are consistent with the local structural changes obtained by other techniques. Indeed, correlations of Raman, X-ray diffraction, and PDFs obtained from synchrotron X-ray total scattering data, along with permittivity measurements allowed the identification of the discrete ferro- to paraelectric phase transitions and a more robust characterization. The rotation and distortion of the octahedral caused by oxygen displacement are driving forces behind symmetry changes and phase transitions, explaining the mechanism of polymorphic phase transition based on A- and B-site substitution. Therefore, this work provides a comprehensive understanding of temperature and composition-dependent phase transitions in BCZT.