Chelate Bonding Mechanism in a Novel Magnesium Phosphate Bone Cement

A novel approach to harden magnesium phosphate cements was tested using phytic acid (C₆H₁₈O₂₄P₆) solutions as chelation agent. In addition to complex formation, a cementitious dissolution and precipitation reaction led to the formation of newberyite (MgHPO₄·3H₂O) as the hydrated form of the farringtonite [Mg₃(PO₄)₂] raw powder. The set cements showed good mechanical properties (up to 65 MPa in compression) displaying a doubling of the compressive strength of conventional newberyite forming cements despite of a significantly lower degree of cement conversion. An increasing phytic acid concentration from 10% to 30% had a retarding effect on the setting time (11–16 min), decreased the pH close to acidic conditions (pH = 5–4) and increased the maximum setting temperature (26°C–31°C), but none of these factors reached critical values. The presented strategy was successful in fabricating a good workable, novel mineral biocement with promising characteristics for biomedical applications.     

Pyrophosphate ions inhibit calcium phosphate cement reaction and enable storage of premixed pastes with a controlled activation by orthophosphate addition

The standard preparation routine of a calcium phosphate cement includes mixing a solid and a liquid component (reactive cement powder and mixing liquid) in an open bowl at the operating theatre. This poses the risk of preparation-related deviations of the resulting properties when the cements are mixed by different persons. Hence, facilitating this mixing procedure is highly desirable. It can be achieved by application of premixed cement pastes: The mixing liquid and a stable suspension of the cement powder are assembled and mixed in a special syringe, minimizing the impact of these preparation-related effects.In this study, a suspension of reactive α-tricalcium phosphate powder in water was stabilized by sodium pyrophosphate decahydrate (PP). Controlled activation of these premixed pastes was then accomplished by adding a concentrated Na₂HPO₄/NaH₂PO₄ (Na₂/Na) solution. Systematic assessment of the activation mechanism, including the effect of the PP concentration and the amount of Na₂/Na added, was performed by isothermal calorimetry, quantitative in-situ X-ray diffraction, rheological characterization and automated Gillmore needle measurements at 37 °C.Premixed pastes with addition of at least 0.05 wt% PP were successfully stabilized for up to 2 weeks at 25 °C, and even 4 weeks at 4 °C. This pre-storage had no significant impact on the setting performance of the pastes. Increasing the PP concentration at constant Na₂/Na amount systematically retarded the setting reaction, while an elevated quantity of Na₂/Na addition at constant PP concentration resulted in an acceleration.Based on these results, a composition stabilized with 0.05 wt% PP and activated with 20.8 vol% Na₂/Na related to the amount of liquid in the premixed pastes appears ideal with respect to the desired setting performance.     

Chemical stability of KNbO3, NaNbO3, and K0.5Na0.5NbO3 in aqueous medium

In recent years, potassium sodium niobate (K_0.5Na_0.5NbO₃, KNN) has become popular and promising among perovskite lead‐free piezoceramic systems. In this study, the chemical stability of KNN powders in aqueous medium was investigated as a function of pH, time, and powder surface area. To better understand the dissolution behavior of the complex KNN stoichiometry, subconstituents such as potassium niobate (KNbO₃, KN) and sodium niobate (NaNbO₃, NN) were investigated separately first. Results showed that all of the cations in the structure underwent dissolution in different values. Indicating that KNN undergoes incongruent dissolution in aqueous medium, the dissolution of A site cations was higher at lower pH while the dissolution of B site cations increased at higher initial pH. The order of released cation concentrations (C_A1 = K > C_{A2 = Na} > C_B = Nb) fits with inverse relationship of cation field strength (FS) order, B = Nb⁵⁺_FS > A₂ = Na⁺_FS>A₁ = K⁺_FS, at pH 4, 7 and 10 for NN, KN, and KNN. Calculated diffuse layer thickness from the ICP data confirmed to outer amorphous layer in TEM image. Also, the ratio of normalized cation concentration versus surface area of powders showed that incongruent dissolution kinetic was driven by the diffusion step.     

Influence of the addition of different radiopacifiers and bioactive nano-hydroxyapatite on physicochemical and biological properties of calcium silicate based endodontic ceramic

The purpose of this study was to investigate the influence of different radiopacifiers on the physicochemical and biological properties of novel calcium silicate based endodontic ceramic enriched with bioactive nano-particulated hydroxyapatite – ECHA. Namely, ECHA was used as a basis for mixing with the following radiopacifiers: strontium fluoride (SrF₂), zirconium dioxide (ZrO₂) and bismuth oxide (Bi₂O₃). For comparison, Portland cement (PC) and mineral trioxide aggregate (MTA) were used. The following physicochemical characteristics were examined: the radiopacity, setting time, compressive strength, porosity, wettability and pH value. The biocompatibility of the cements was assessed by crystal violet, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) and cell adhesion assays. The highest radiopacity was obtained for the ECHA + Bi₂O₃ mixture and MTA that were statistically significant in comparison to other materials (p < 0.05). Both initial and final setting times as well as compressive strengths were statistically lower for experimental cements than for PC and MTA (p < 0.05). The lowest total porosity was observed in the ECHA + ZrO₂ group when compared with the other two experimental cements (p < 0.05), but not when compared with PC and MTA (p > 0.05). Experimental cements exhibited statistically higher contact angles of glycerol than PC and MTA (p < 0.05). For blood plasma, a statistical difference was found only between ECHA + Bi₂O₃ and PC (p < 0.05). All investigated materials had alkalization ability. Cell viability assays revealed that the extracts of tested cements did not exhibit cytotoxic effect on L929 cells. Scanning electron microscopy had shown a high degree of cell proliferation and adhesion of cells from apical papilla on experimental cements’ surfaces. Novel endodontic ceramics with nano-hydroxyapatite addition have satisfactory biological and physicochemical properties when compared to MTA and PC controls. Considerable lower setting time of experimental cements might present a huge advantage of these synthesized materials in clinical practice. SrF₂ presents a novel promising radiopacifying agent for dental cements manufacturing.     

Impact of triethanolamine on the sulfate balance of Portland cements with mixed sulfate carriers

The differences between the hydration of Portland cements with single and with mixed sulfate carriers in the presence of triethanolamine (TEA) were investigated, and possible mechanisms were proposed. Without TEA, cements with different types of sulfate carriers (gypsum, hemihydrate, anhydrite, and mixture of these) have a comparable hydration process at the same molar amount of calcium sulfate. At a TEA dosage of 0.5 wt.%, the sample with a mixture of three sulfate carriers shows substantially stronger retardation of the C₃S (This publication uses the cement chemist notation: C₃S = Ca₃SiO₅, C₂S = Ca₂SiO₄, C₃A = Ca₃Al₂O₆, C₄AF = Ca₂(Al, Fe)₂O₅.) hydration than the cements with only one of these sulfate carriers, which is likely caused by the rapid formation of ettringite and the fast depletion of all sulfate carriers. These effects indicate that TEA influences the balance of sulfate carriers with aluminate-containing clinker phases. On the one hand, TEA can disturb the original sulfate balance due to the accelerated dissolution of aluminate-containing clinker phases, especially C₄AF. On the other hand, these effects are closely related to the types and amounts of the sulfate carriers in the cement. A higher amount of sulfate carriers can minimize the TEA-related retardation of the C₃S hydration, and hemihydrate shows the strongest impact at the same calcium sulfate quantity.     

Concentration effects of hydrochloric acid on the anodic behaviour of lead sulphide

The anodic dissolution of lead sulphide is studied at various chloride concentrations and at different pH values. At 25° C it is found that in hydrochloric acid the dissolution rate reaches a maximum around 3.0 mol dm^–3. It has also been observed that at concentrations between 0.7 and 1.2 mol dm^–3, a crystalline sulphur deposit formed during the dissolution process leads to an independent peak on theI-E curve whereas at higher concentrations it merges with the PbCl₂ peak formation. pH has no significant effect on the dissolution rate. The results of a systematic study on the kinetics of the dissolution process as a function of concentration, temperature and pH are discussed.     

Soluble phosphate salts as setting aids for premixed calcium phosphate bone cement pastes

Recently, premixed calcium phosphate cement pastes have been proposed as biomaterials for bone tissue repair and regeneration. Use of premixed pastes saves the time and removes an extra step during a medical operation. α-Tricalcium phosphate (α-TCP) based cements set to form calcium deficient hydroxyapatite which has a moderate bioresorbtion speed. α-TCP cements require a setting aid, usually a sodium or potassium phosphate salt, to speed up the setting process. Within the current research we investigated which setting aid has significant advantage, if α-TCP is used in form of non-aqueous premixed paste. This approach offers the application of simple ingredients to produce a premixed calcium phosphate cement. The following properties of cement formulations were evaluated: cohesion, phase composition, microstructure, pH value of the liquid surrounding the cement, and compressive strength.Compositions using mixture of basic and acidic potassium phosphate salts (KH₂PO₄ and K₂HPO₄) in sufficient amounts give the best overall results (adequate cohesion and pH of the surrounding liquid, hydrolysis of starting materials within 48 h, and compressive strength of 12 ± 3 MPa). Cement prepared with basic sodium phosphate salt (Na₂HPO₄) as setting aid had considerably higher compressive strength 22 ± 1 MPa, but the pH of the surrounding liquid was basic (9.0).     

Mechanical activation and cement formation of trimagnesium phosphate

Magnesium phosphate cements have attracted an increasing attention for biomedical applications in the past years due to their high mechanical performance and fast in vivo degradation at bony implantation sites. Cements are usually multicomponent mixtures of cement raw powders and setting regulators, whereas the latter may have a detrimental effect on the biocompatibility. Here, we demonstrate that following prolonged grinding of trimagnesium phosphate (Mg₃(PO₄)₂, farringtonite), a mechanically induced disordering reaction strongly altered farringtonite reactivity such that self‐setting cements without further components were formed with a compressive strength of up to 11 MPa. Time‐resolved X‐ray diffraction analysis revealed that the formation of a nanocrystalline magnesium phosphate phase during grinding was responsible for cement setting to the highly hydrated magnesium phosphate mineral cattiite (Mg_3[(PO₄)₂?22H₂O), whereas crystalline farringtonite showed practically no setting reaction.     

Impact of precursor preparation on density of gadolinium iron garnets synthesized via reactive sintering

Gadolinium iron garnet was obtained from two different precursors, homogenized in isopropyl alcohol and in an aqueous environment with a fixed pH. In the first case, it was a mixture of goethite (FeO(OH)) and gadolinium oxide (Gd₂O₃); in the second, a mixture of GdIP (GdFeO₃) and α-Fe₂O₃. Conditions of homogenization in the aqueous environment were selected based on the zeta (ξ) potential measurements as the function of pH. DSC measurements of the output powder mixtures allowed the identification of the effects observed during the temperature rise. In the case of the material obtained from a mixture of goethite (FeO(OH)) and gadolinium oxide, with the increasing temperature, we observe three effects, the first of which corresponds to the phase transformation of goethite into α-Fe₂O₃, the second corresponds to the reaction of gadolinium iron perovskite (GdIP) formation, and the third to the reaction in which a gadolinium iron garnet (GdIG) is formed. However, in the case of heat treatment of the mixture of GdIP and α-Fe₂O₃, we only observe the effect responsible for a solid state reaction leading to the formation of gadolinium iron garnet. Dilatometric measurements allowed to determine the changes in linear dimensions at various stages of reaction sintering. The resulting materials were sintered at temperatures of 1200, 1300, and 1400 °C. In the case of the material obtained from a mixture of perovskite and iron (III) oxide, already at the temperature of 1300 °C, a density has been obtained at around 95% of the theoretical density, and the temperature of 1400 °C allowed achieving a density of 97% of the theoretical density. Whereas, for the material obtained from a mixture of goethite (FeO(OH)) and gadolinium oxide, a density above 95% of theoretical density was achieved only at 1400 °C.     

In situ synchrotron powder diffraction study of the setting reaction kinetics of magnesium-potassium phosphate cements

This work reports a kinetic study of the formation of magnesium-potassium phosphate cements accomplished using in-situ synchrotron powder diffraction. The reaction: MgO + KH₂PO₄ + 5H₂O → MgKPO₄ · 6H₂O was followed in situ in the attempt of contributing to explain the overall mechanism and assess the influence of periclase (MgO) grain size and calcination temperature (1400-1600 °C) on the reaction kinetics. Numerical kinetic parameters for the setting reaction have been provided for the first time. The best fit to the kinetic data was obtained using a weighted nonlinear model fitting method with two kinetic equations, representing two consecutive, partially overlapping processes. MgO decomposition could be described by a first order (F1) model followed by a Jander diffusion (D3) controlled model. Crystallization of the product of reaction was modelled using an Avrami model (A_n) followed by a first order (F1) chemical reaction. A reaction mechanism accounting for such results has been proposed.     

Adsorptive removal of methyl orange using mesoporous maghemite

In this work, mesoporous maghemite (γ-Fe₂O₃) was prepared by the thermal decomposition of [Fe(CON₂H₄)₆](NO₃)₃ with the aid of cetyltrimethyl ammonium bromide (CTAB), and its adsorption ability for the removal of methyl orange (MO) from wastewater was investigated. X-Ray powder diffraction (XRD) together with nitrogen adsorption–desorption measurements show the formation of mesoporous γ-Fe₂O₃ with an average pore size of 3.5 nm and a specific surface area of 93.0 m²/g. Magnetic measurements show that the mesoporous γ-Fe₂O₃ exhibits ferrimagnetic characteristics with the coercivity of 141.5 Oe and remanent magnetization of 7.3 emu/g and has the maximum saturation magnetization of 55.2 emu/g. The adsorption of MO on the mesoporous γ-Fe₂O₃ reaches the maximum adsorbed percentage of ca. 90% within a few minutes, showing that most of MO can be removed in a short time when the mesoporous γ-Fe₂O₃ is used as an adsorbent. When the pH of MO solution is varied from 3 to 11, the adsorbed percentage of MO decreases from ca. 90 to ca. 81%, showing that the adsorption is slightly influenced by solution pH. The adsorption data for MO fit well with either Langmuir or Freundlich adsorption models. The maximum adsorption capacity of the mesoporous γ-Fe₂O₃ for MO is determined to be 385 mg/g, which suggests that the material could be an excellent magnetic adsorbent for MO.     

Tricalcium aluminate hydration in additivated systems. A crystallographic study by SR-XRPD

Synchrotron radiation X-ray powder diffraction has been used to monitor the evolution of ettringite in C3A-gypsum synthetic mixture and in commercial cement systems during the first hours of the hydration process. The hydration of the paste was achieved using a remote controlled system, in order to collect data as soon as water is added to the system. The use of full-profile Rietveld method during the analysis of the diffractograms collected allowed us to monitor the evolution of phases weight fraction. The rigorous measurement of the lattice parameters and of the diffraction peak shape proved to be very useful to obtain information on the structural evolution of ettringite and on the mean grain size of the crystal phases. Depending on the admixture added to the system, the precipitation of well crystalline ettringite takes some hours. During this “induction” period we observe a significant variation of a and c lattice parameter values for ettringite. In particular a increases from 11.8 Å to 11.24 Å, the value for pure ettringite. The c parameter decreases from 22 Å to 21.48 Å. The lattice parameter variation could be related to small crystallite size effect, but the large variation more likely reflects also crystallographic changes, such as defect re-organization during the nucleation and growth process or also changes in the SO₃ and H₂O content in the ettringite channel. Not surprisingly the amount and the grain dimensions of crystalline ettringite are affected by the chemistry of the system. We observed the same evolution trend during ettringite formation also in shrinkage-compensating commercial cements (composed by mixture of Ca-Al cements, Portland cement and bassanite), in which ettringite is the main hydrous phase present.     

Effect of annealing on the structure and magnetic properties of mechanically milled TiO2–Fe2O3 mixture

A mixture of Fe₂O₃ and TiO₂ oxides has been mechanically milled to form TiFe₂O₄ spinel phase. X-ray diffraction (XRD) pattern of the as-milled mixture shows the presence of both Fe₂O₃ and TiO₂ phases. The diffraction peaks become broader and their relative intensity drastically decreases due to the particle size reduction and accumulation of strains. The milled powder was then subjected to annealing at different temperatures (600, 750, 900, 1200 °C). Annealing at 600 °C and 750 °C does not show any significant change in the phase formation. Nonetheless, XRD patterns show a narrowing and an increase in the intensity of Fe₂O₃ peaks with respect to TiO₂, which was reflected by an evolution in particle nano-structure following SEM analysis. An increase in the intensity ratio of the major peaks belonging to Fe₂O₃ relative to the as-milled mixture, which was associated with a reduction of the amount of TiO₂, suggested a possible insertion of Ti into the Fe₂O₃ crystal lattice. However, in VSM measurements, annealing at 600 °C and 750 °C does not change the ferromagnetic phase but the effect of annealing was a notable reduction in the values of both Ms and Mr (saturation magnetization and remanence magnetization respectively) Ultimately, as the powder was heated to 900 °C a new phase seemed to have emerged, this phase was confirmed by SEM, XRD, and magnetic measurements (VSM) where it change phase from ferromagnetic to paramagnetic phase.     

Synthesis and structural properties of GaN particles from GaO2H powders

Gallium nitride(GaN) powders have been synthesized by nitriding gallium oxyhydroxide (GaO₂H) powders in the flow of NH₃ gas at a nitridation temperature of 950 °C for 35 min. X-ray powder diffraction (XRD) patterns and Fourier transform infrared (FTIR) spectra reveal that simple heat treatment of GaO₂H in the flow of NH₃ leads to the formation of hexagonl GaN with lattice constants a = 3.191 Å, and c = 5.192 Å at 950 °C through intermediate conversion of β-Ga₂O₃. X-ray photo-electron spectroscopy (XPS) confirms the formation of bonding between Ga and N, and yields that the surface stoichiometry of Ga : N approximates 1 : 1. Transmission electron microscopy (TEM) image indicates that GaN particle is a single crystal, and its morphology is ruleless.     

Strontium-loaded magnesium phosphate bone cements and effect of polymeric additives

Magnesium phosphate-based cements (MPCs) are nowadays regarded as promising materials in the field of bone repair. The inclusion of Sr ions in the formulations may represent a valuable strategy to improve their bone regeneration performances, but the effect that such ion exerts on the physico-chemical properties of the material have not been investigated so far. In this work we describe the development of Sr-MPCs obtained including Sr ions in different forms, i.e., using Sr-substituted tri-magnesium phosphate precursor powder or including in the formulation Sr-based salts (SrCl₂ and SrHPO₄). The materials were characterized both in the form of pastes and hardened cements, finding that according to the type of Sr precursor used we can tune the setting time, the amount of binding phases in the cements, their morphology and thermal behavior. The dissolution behavior and the release kinetics of Mg²⁺ and Sr²⁺ can as well be modulated, and in particular the use of SrCl₂ in the formulation leads to a higher dissolution and a faster release of a significant amount of both Mg²⁺ and Sr²⁺, compared to the other samples. Given the unsatisfying performances obtained during the injectability and anti-washout tests, we also included two polymeric additives, namely poly(N-isopropylacrylamide) and mucin, in the Sr-MPCs formulations. The results demonstrate that it is possible to obtain Sr-MPCs with promising properties for applications as bone cements, that can be tuned according to the form under which Sr is included in the formulation. In addition, mucin markedly improves the cohesion and injectability of the Sr-MPC pastes, providing a simple but effective strategy to develop materials of interest in the orthopedic field.     

Synthesis of Y2O3 nano-powders by precipitation method using various precipitants and preparation of high stability dispersion for backlight unit (BLU)

Nano-sized yttria powder was successfully synthesized by precipitation method. Three different precipitants such as NH₄OH, mixture of NH₄OH and NH₄HCO₃, and NH₄HCO₃ were used. It was observed that the size of yttria powder is significantly affected by type of precipitant depending on the rate of formation of precipitate. It is seen that NaHCO₃ shows the most significant pH decrease during the formation of Y₂CO₃, thus leading to the formation of large crystal. The result also shows that the crystal size depends on calcinations temperature and the agglomeration have become more significant beyond 800 °C where the morphology have changed from flake to spherical shape interconnected each other. It was observed that the dispersity of yttria powder can be affected by bead size of ball mill, rpm and dispersion time where the physical, agglomeration has become more significant beyond 4 h of dispersion. Finally, the nano-sized yttria powder of on the average 114 nm shows excellent uniform coating, sufficient transmittance and excellent brightness for lamp.     

Controlling the reaction kinetics of sodium carbonate-activated slag cements using calcined layered double hydroxides

In this study, Na₂CO₃-activated slag cements were produced from four different blast furnace slags, each blended with a calcined layered double hydroxide (CLDH) derived from thermally treated hydrotalcite. The aim was to expedite the reaction kinetics of these cements, which would otherwise react and harden very slowly. The inclusion of CLDH in these Na₂CO₃-activated cements accelerates the reaction, and promotes hardening within 24 h. The MgO content of the slag also defines the reaction kinetics, associated with the formation of hydrotalcite-type LDH as a reaction product. The effectiveness of the CLDH is associated with removal of dissolved CO₃^2 − from the fresh cement, yielding a significant rise in the pH, and also potential seeding effects. The key factor controlling the reaction kinetics of Na₂CO₃-activated slag cements is the activator functional group, and therefore these cements can be designed to react more rapidly by controlling the slag chemistry and/or including reactive additives.     

Synthesis of a novel nanostructured zinc oxide/baghdadite coating on Mg alloy for biomedical application: In-vitro degradation behavior and antibacterial activities

In this research, zinc oxide (ZnO) and zinc oxide/baghdadite (ZnO/Ca₃ZrSi₂O₉) were prepared on the surface of Mg alloy using physical vapor deposition (PVD) coupled with electrophoretic deposition (EPD). For this purpose, the nanostructured ZnO was prepared with a thickness of 900 nm and crystallite sizes of 64 nm as under layer while nanostructured baghdadite with a thickness of 10 µm was deposited on the Mg alloy substrate as an over-layer. Electrochemical measurement exhibited that the ZnO/Ca₃ZrSi₂O₉-coated specimen has a higher corrosion resistance and superior stability in simulated body fluid (SBF) solution in comparison with the ZnO-coated and bare Mg alloy samples. Antibacterial activities of the uncoated and coated specimens were evaluated against various pathogenic species (Escherichia coli, Klebsiella pneumoniae, and Shigella dysenteriae) via disc diffusion method. The obtained results showed that ZnO and ZnO/Ca₃ZrSi₂O₉ coatings have great zones of inhibition (ZOI) against E. coli, Klebsiella, and Shigella. However, less ZOI was found around the bare Mg alloy. Therefore, ZnO/Ca₃ZrSi₂O₉ is a promising coating for orthopedic applications of biodegradable Mg alloys considering its excellent antibacterial activities and high corrosion resistance.     

Organic template-directed indium phosphite-oxalate hybrid material: Synthesis and characterization of a novel 3D |C6H14N2|[In2(HPO3)3(C2O4)] compound with intersecting channels

A novel anionic three-dimensional indium phosphite-oxalate hybrid material, formulated as |C₆H₁₄N₂|[In₂(HPO₃)₃(C₂O₄)] (1) was prepared under hydrothermal conditions by using 1,4-diazabicyclo[2.2.2]octane (dabco) as a structure directing agent (SDA). Single-crystal X-ray diffraction analysis reveals that compound 1 crystallizes in the orthorhombic system space group Pna2₁ (No. 33) having unit cell parameters a = 12.4143(13) Å, b = 7.7166(8) Å, c = 18.327(2) Å, V = 1755.6(3) Å³, and Z = 4 with R₁ = 0.0282, wR₂ = 0.0632. The novel 3D open framework is constructed from InO₆ octahedra, HPO₃ pseudo-tetrahedra and C₂O₄ units. The assembly of these building units generates intersecting 8- and 12-membered ring (MR) channels along two different directions. To the best of our knowledge, it is the first reported indium phosphite-oxalate hybrid material. Further characterization of compound 1 was performed using X-ray powder diffraction (XRD), infrared (IR) spectra, thermal gravimetric analyses (TGA), inductively coupled plasma (ICP) and elemental analyses.     

Structure and lithium-ion mobility in Li1.5M0.5Ge1.5(PO4)3 (M = Ga,Sc, Y) NASICON glass-ceramics

This work reports structural and lithium-ion mobility studies in NASICON single- or multiple phase Li_1+xM_xGe_2−x(PO₄)₃ (M = Ga³⁺, Sc³⁺, Y³⁺) glass-ceramics using solid-state NMR techniques, X-ray powder diffraction, and impedance spectroscopy. X-ray powder diffraction data show the successful incorporation of Ga³⁺ and Sc³⁺ into the Ge⁴⁺ octahedral sites of the NASICON structure at the levels of x = 0.5 and 0.4, respectively. The glass-to-crystal transition was further characterized by multinuclear NMR and electrical conductivity measurements. Among the studied samples, the gallium-containing glass-ceramic presented the highest DC conductivity, 1.1 × 10⁻⁴ S/cm at room temperature, whereas for the Sc-containing samples, the maximum room temperature conductivity that could be reached was 4.8 × 10⁻⁶ S/cm. No indications of any substitution of Ge⁴⁺ by Y³⁺ could be found.