Ceramics, Volume 7, Issue 2 (June 2024) – 10 articles

Optical materials with a tunable localized surface plasmon resonance (LSPR) are of great interest for applications in photonics and optoelectronics. In the present study, we explored the potential of generating an LSPR band with an ultra-broad range of over 1000 nm in gold nanoparticles (NPs), precipitated through a thermal treatment in ZnO-Al₂O₃-SiO₂ glass. Using optical absorption spectroscopy, we demonstrated that the LSPR band’s position and shape can be finely controlled by varying the thermal treatment route. Comprehensive methods including Raman spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy were used to study the glass structure, while computational approaches were used for the theoretical description of the absorption spectra. The obtained results allowed us to suggest a scenario responsible for an abnormal LSPR band broadening that includes a possible interparticle plasmonic coupling effect taking place during the liquid–liquid phase separation of the heat-treated glass. The formation of gold NPs with an ultra-broad LSPR band in glasses holds promise for sensitizing rare earth ion luminescence for new photonics devices. Full article

The study investigates alterations in the mechanical and thermophysical properties of ceramics composed of xLi₂ZrO₃–(1−x)Li₄SiO₄ as radiation damage accumulates, mainly linked to helium agglomeration in the surface layer. This research is motivated by the potential to develop lithium-containing ceramics characterized by exceptional strength properties and a resistance to the accumulation of radiation damage and ensuing deformation distortions in the near-surface layer. The study of the radiation damage accumulation processes in the near-surface layer was conducted through intense irradiation of ceramics using He²⁺ ions at a temperature of 700 °C, simulating conditions closely resembling operation conditions. Following this, a correlation between the accumulation of structural modifications (value of atomic displacements) and variations in strength and thermophysical characteristics was established. During the research, it was observed that two-component ceramics exhibit significantly greater resistance to external influences and damage accumulation related to radiation exposure compared to their single-component counterparts. Furthermore, the composition that provides the highest resistance to softening in two-component ceramics is an equal ratio of the components of 0.5Li₂ZrO₃–0.5Li₄SiO₄ ceramics. Full article

(1) Background: The presence of various dental ceramic materials with different chemical compositions complicates clinicians’ decision making, especially in cases with a highly acidic environment appearing in patients suffering from gastroesophageal reflux disease or other eating disorders. Thermal alterations in the oral cavity can also affect surface structure and roughness, resulting in variations in both degradation mechanisms and/or bacteria adhesion. The aim of the present in vitro study was to evaluate the effect of thermal cycling and exposure to simulated gastric acid on the surface roughness of different ceramics; (2) Methods: Five groups of different ceramics were utilized, and twenty specimens were fabricated for each group. Specimens were either thermocycled for 10,000 cycles in distilled water or immersed in simulated gastric acid for 91 h. The evaluation of surface roughness was performed with optical profilometry, while scanning electron microscopy, X-ray diffraction analysis and inductively coupled plasma atomic emission spectroscopy were also performed; (4) Conclusions: Based on the combination of the surface roughness profile and structural integrity, zirconia specimens presented the smallest changes after immersion in simulated gastric acid followed by lithium disilicate materials. Zirconia-reinforced lithium silicate ceramic presented the most notable changes in microstructure and roughness after both treatments. Full article

Glass properties play crucial roles in ensuring the safety and reliability of electronic packaging. However, challenges, such as thermal expansion and resistance to acid corrosion, pose long-term service difficulties. This study investigated the impact of the microstructure on acid resistance by adjusting the glass composition. A glass material with excellent acid resistance was obtained by achieving a similar coefficient of thermal expansion to tantalum; it exhibited a weight loss rate of less than 0.03% when submerged in 38% sulfuric acid at 85 °C for 200 h. Theoretically, this glass can be used to seal wet Ta electrolytic capacitors. Differential scanning calorimetry (DSC) was used to analyze the glass transition temperature and thermal stability of borosilicate glasses. X-ray diffractometry (XRD), scanning electron microscopy (SEM), and Raman spectroscopy were used to study the microstructure of the amorphous phase of the borosilicate glass, which revealed a close relationship between the degree of network phase separation in the borosilicate glass and the degree of polymerization (isomorphic polyhedron value, IP) of the glass matrix. The IP value decreased from 3.82 to 1.98 with an increasing degree of phase separation. Boron transitions from [BO₄] to [BO₃] within the glass network structure with increasing boron oxide content, which diminishes the availability of free oxygen provided by alkaline oxide, resulting in a lower acid resistance. Notably, the glass exhibited optimal acid resistance at boron trioxide and mixed alkaline oxide contents of 15% and 6%, respectively. Raman experiments revealed how the distributions of various bridging oxygen atoms (Q_n) affect the structural phase separation of the glass network. Additionally, Raman spectroscopy revealed the depolymerization of Q₄ into Q₃, thereby promoting high-temperature phase separation and highlighting the unique advantages of Raman spectroscopy for phase recognition. Full article

Reusing waste as raw materials to produce other materials can entail a decrease in production costs and in the abusive use of natural resources. Furthermore, it can even improve the properties of the end product or material. In this sense, a review of the most relevant literature published in recent decades shows that numerous solutions have been proposed or implemented, such as its use to produce construction materials, catalysts, pigments, pozzolana, refractory materials, glass-ceramic products, etc. Our research group has verified the viability of using different types of waste as secondary raw materials to obtain several types of ceramic, glassy and glassceramic materials, as well as frits. This article highlights several types of industrial waste that have both non-toxic (Li, Ca and Mn) and highly toxic (Cr VI) differentiating elements that can be used in sintering and vitrification industrial processes to immobilise them or render them inert. We studied the compositions and characterised the various materials obtained, conducting toxicity and leaching tests on waste/materials designed with high amounts of chromium. A suggestion for future lines of research has been proposed. Full article

In this work, we analyze the electrical behavior of strontium ferromolybdate below room temperature. We demonstrate that in SFMO ceramics, SFMO thin films deposited by pulsed laser deposition including (100) and (111) textured thin films, as well as in nonstoichiometric SFMO ceramics, an intergrain tunneling mechanism of charge carrier conduction leads to a decrease in resistivity with increasing temperature in the low-temperature region. This intergrain tunneling can be attributed to fluctuation-induced tunneling. On the other hand, bulk metallic resistivity of the grains, which increases with temperature, becomes dominant at higher temperatures and magnetic fluxes. The interplay of these conduction mechanisms leads to a resistivity minimum, i.e., a resistivity upturn below the temperature of minimum resistivity. Several mechanisms have been discussed in the literature to describe the low-temperature upturn in resistivity. Based on available literature data, we propose a revised model describing the appearance of a low-temperature resistivity minimum in SFMO ceramics by an interplay of fluctuation-induced tunneling and metallic conductivity. Additionally, we obtained that in the region of metallic conductivity at higher temperatures and magnetic fluxes, the pre-factor R_m of the temperature-dependent term of metallic conductivity written as a power law decreases exponentially with the temperature exponent m of this power law. Here, the value of m is determined by the charge scattering mechanism. Full article

Indium nitride is an excellent semiconductor that belongs to the group of III nitride materials. Due to its unique properties, it is applied to various optoelectronic applications. However, its low thermal stability makes it difficult to synthesize. The present study introduces the synthesis of indium nitride nanoparticles, using ultrasound power (sonochemistry). The sonochemical method provides a low-cost and rapid technique for nanomaterial synthesis. InN nanoparticles were produced in only 3 h through the sonochemical reaction of InCl₃ and LiN₃. Xylene was used as a reaction solvent. X-ray powder diffraction (XRD) as well as high-resolution transmission electron microscopy (HRTEM) were adopted for the characterization of the obtained powder. According to our results, ultrasound contributed to the synthesis of InN nanocrystals in a cubic and a hexagonal phase. The obtained InN nanoparticles were further used to decorate titanium dioxide (TiO₂) by means of ultrasound. The contribution of InN nanoparticles on the processes of photocatalysis was investigated through the degradation of methylene blue (MB), a typical organic substance acting in place of an environment pollutant. According to the obtained results, InN nanoparticles improved the photocatalytic activity of TiO₂ by 41.8% compared with commercial micrometric titania. Full article

Investigating the microwave dielectric properties of ceramics prepared through the conventional solid-state route, such as x[(Mg_0.6Zn_0.4)_0.95Co_0.05]_1.02TiO_3.02-(1−x)Ca_0.6(La_0.9Y_0.1)_0.2667TiO₃, reveals notable characteristics. [(Mg_0.6Zn_0.4)_0.95Co_0.05]_1.02TiO_3.02 shows a permittivity (ε_r) of approximately 20, a high quality factor (Q × f) ranging between 250,000 and 560,000 GHz, and a temperature coefficient of resonant frequency (τ_f) of approximately −65 ppm/°C. To enhance the temperature stability, Ca_0.6(La_0.9Y_0.1)_0.2667TiO₃ featuring a τ_f value of +374 ppm/°C was incorporated into the [(Mg_0.6Zn_0.4)_0.95Co_0.05]_1.02TiO_3.02 composition. τ_f demonstrated an increase with rising Ca_0.6(La_0.9Y_0.1)_0.2667TiO₃ content, reaching zero at x = 0.95. A ceramic composition of 0.95[(Mg_0.6Zn_0.4)_0.95Co_0.05]_1.02TiO_3.02-0.05Ca_0.6(La_0.9Y_0.1)_0.2667TiO₃, incorporating 3wt.% BaCu(B₂O₅) as sintering aids, exhibited outstanding microwave dielectric properties: ε_r~22.5, Q × f~195,000 (at 9 GHz), and τ_f~0.1ppm/°C, with a sintering temperature at 950 °C. This material is proposed as a prospective candidate for 6G band components and GPS antennas. Full article

Negative temperature coefficient (NTC) materials are usually based on ceramic semiconductors, and electrons are involved in their transport mechanism. A new type of NTC material, adequate for alternating current (AC) applications, is represented by zeolites. Indeed, zeolites are single charge carrier ionic conductors with a temperature-dependent electrical conductivity. In particular, electrical transport in zeolites is due to the monovalent charge-balancing cations, like K⁺, capable of hopping between negatively charged sites in the aluminosilicate framework. Owing to the highly non-linear electrical behavior of the traditional electronic NTC materials, the possibility to have alternative types of materials, showing linearity in their electrical behavior, is very desirable. Among different zeolites, natural clinoptilolite has been selected for investigating NTC behavior since it is characterized by high zeolite content, a convenient Si/Al atomic ratio, good mechanical strength due to its compact microstructure, and low toxicity. Clinoptilolite has shown a rapid and quite reversible impedance change under heating, characterized by a linear dependence on temperature. X-ray diffraction (XRD) has been used to identify the natural zeolite, to establish all types of crystalline phases present in the mineral, and to investigate the thermal stability of these phases up to 150 °C. X-ray photoelectron spectroscopy (XPS) analysis was used for the chemical characterization of this natural clinoptilolite sample, providing important information on the cationic content and framework composition. In addition, since electrical transport takes place in the zeolite free-volume, a Brunauer–Emmett–Teller (BET) analysis of the mineral has also been performed. Full article

Polymer-infiltrated ceramic network (PICN) materials have gained considerable attention as tooth-restorative materials due to their mechanical compatibility with human teeth, especially with computer-aided design and computer-aided manufacturing (CAD/CAM) technologies. However, the designed geometry affects the mechanical properties of PICN materials. This study aims to study the relationship between manufacturing geometry and mechanical properties. In doing so, zirconia-based PICN materials with different geometries were fabricated using a direct ink-writing process, followed by copolymer infiltration. Comprehensive analyses of the microstructure and structural properties of zirconia scaffolds, as well as PICN materials, were performed. The mechanical properties were assessed through compression testing and digital image correlation analysis. The results revealed that the compression strength of PICN pieces was significantly higher than the respective zirconia scaffolds without polymer infiltration. In addition, two geometries (C-grid 0 and C-grid 45) have the highest mechanical performance. Full article