La Doping Research Articles

The effect of La doping on multiferroic BiFeO3 ceramic through structural, dielectric, magnetic, ferroelectric, and optical studies

In this study, La-doped bismuth ferrite (BLFO), Bi1-xLaxFeO3 (x = 0.00, 0.005, 0.007, 0.01) compositions have been synthesized via a solid-state method to investigate their structural, electrical, magnetic, ferroelectric, and optical properties. All the synthesized ceramics were found to be in rhombohedral distorted perovskite structures with R3c symmetry. A significantly reduced grain size with improved dielectric properties (enhanced dielectric constant and reduced dielectric loss) was observed with La doping up to composition x = 0.007. The magnetization study revealed that substitution of La in BFO enhances remnant magnetization (Mr) and coercive field (Hc). The ferroelectric study manifested that composition x = 0.007 retained a higher polarization value among all the ceramics. Moreover, the optical study exhibited that with doping, the bandgap increased from 2.49 eV for BFO to 2.64 for x = 0.007 ceramic. For the last composition x = 0.01, the bandgap decreased to 2.43 eV, which can be advantageous for magnetic photocatalysts applications.

The effect of rare-earth element (Gd, Nd, La) doping of NiO films on UV photodetector

The semiconductor-based UV photodetectors are the most essential devices in the field of space observations, military, DNA sequencing, analysis of protein, medical imaging, checking of atmospheric pollution, optical communications radiation, etc. With such a wide range of possible applications, the nanostructured pristine and rare-earth (RE) doped NiO ((NiO: Gd(1%), NiO:Nd(1%), NiO:La(1%)) thin films were prepared and investigated for their suitability as UV photodetectors. The films were prepared by nebulized spray pyrolysis (NSP) at a substrate temperature of 450 °C. The x-ray diffraction studies confirm the cubic single phase with the polycrystalline nature of the prepared films. The spectroscopic studies such as absorbance and photoluminescence confirm that increase in the optical bandgap and 391 nm PL emission is attributed to the near band edge emission of the NiO. The x-ray photoelectron spectroscopy reveals the presence of nickel and the doped elements with their oxidation states. The UV photodetector performance of the prepared NiO films was carried out under the irradiation of 365 nm light. The NiO:Gd exhibits the best responsivity (0.353 AW−1), external quantum efficiency (120%), detectivity (1.72 × 1010 Jones) and rise time (2.0 s), and fall time (2.2 s). Importantly, strategies such as limited doping (1 at.%) and larger ionic radii of Gd incorporation into the host NiO cause a moderate increase in the lattice distortion and inhibit the recombination rate instead of behaving as a recombination center. In addition, the conduction band (CB) electrons are trapped by a greater number of oxygen vacancies residing at the Gd3+ 4f state and cause a good separation of charge carriers. Overall, these modifications enhance the mean lifetime of electrons, consequently reducing the recombination rate and enhancing the photoresponse.

Storage and release of rare earth elements in microsphere-based scaffolds for enhancing osteogenesis

In osteoporosis and diabetes, it is essential to accelerate the bone repair and regeneration process. Trace rare earth elements such as lanthanum (La) ions (La3+) with appropriate concentrations are bioactive and can effectively regulate bone tissue performances. However, few well-established bone tissue engineering scaffolds can precisely and stably release La3+ to promote bone regeneration significantly. Based on the advantages of biodegradable microspheres and microsphere-based scaffolds for controlled drug release, we developed poly(lactide-co-glycolide) (PLGA)-based microsphere-based scaffolds as both three-dimensional (3D) porous scaffolds and La3+ storage and release systems for osteogenesis. So far, there is no study about microsphere-based scaffolds to release trace La3+ to induce osteogenic differentiation of bone marrow mesenchymal stromal cells (BMSCs). PLGA microspheres co-embedded with La-doped mesoporous silica (LMS) with different amounts of doped La were sintered to prepare the LMS/PLGA (LMSP) microsphere-based scaffold. The La3+ release behavior of LMSP can be controlled by adjusting the doping amount of La in mesoporous silica (MS). All these scaffolds possessed a 3D network architecture. With the increase of La doping, LMSP can better compensate for the pH decrease caused by PLGA degradation. The combination of MS and PLGA can avoid the cytotoxicity of MS alone. All prepared LMSP scaffolds were non-cytotoxic. After BMSCs were implanted on scaffolds, LMSP could promote cells adhesion, proliferation, and osteogenic differentiation. Among these microsphere-based scaffolds, LMSP-3 with stable and higher dose La3+ release behavior showed the strongest ability to enhance the osteogenesis of BMSCs. The results showed that microsphere-based scaffolds with the ability to store and stably control the release of La3+ could effectively improve osteogenic performance, which provides a new idea for the construction of bone tissue engineering scaffolds.

Enhancement in room temperature ammonia sensing performance of the La substituted SnO2 (La:SnO2) thin films developed using spray pyrolysis technique

In this report, pristine SnO2 and La doped SnO2 (La:SnO2) thin films were synthesized using the spray pyrolysis technique and their gas sensing performance operated at room temperature in the presence of ammonia (50 to 250 ppm) were analyzed. The La:SnO2 thin films were developed in four different La concentration like 0, 1, 3 & 5% in SnO2. All the prepared thin film samples were characterized using different analytical techniques for analyzing their properties. The XRD result shows the prepared La:SnO2(0, 1, 3 & 5%) thin films exhibits a tetragonal rutile structure of SnO2 without any secondary impurities according the JCPDS data (41–1445). Also, the crystallite size increases with the La doping concentration at 1% and decreases with further increase in La concentration (3 & 5%) could due to the deterioration of the grain growth of the Sn-O lattice. The scanning electron microscope (SEM) results shows the La:SnO2 thin films possess a tetragonal structures with different nano size particles and the energy dispersive x-ray analysis (EDX) confirms the presence of Sn, O & La elements. The optical results suggest that the transparency increases with the introduction of the La dopants slightly shifted towards the blue region. The bandgap of the samples increases with the increase in La concentration which is according to the Moss- Burstein effect. The photoluminescence (PL) studies confirms the 1% La:SnO2 thin films has higher defect sites due to the presence of oxygen vacancies. Finally, the gas sensing properties of the samples shows that the 1% La:SnO2 exhibits high response of 128% for 250 ppm of ammonia gas at room temperature. Also, 1% La:SnO2 possess stable current value for the fixed concentration of ammonia (250 ppm) during five cycles. This results suggests that the fabricated 1% La:SnO2 thin film sensor can be better suited for the commercial gas sensing application.

A Mn4+ activated (Gd,La)2(Zn,Mg)TiO6 deep-red emission phosphor: The luminescence properties and potential application for full-spectrum pc-LEDs

Deep-red light emitting phosphors play vital roles in phosphor-converted light emitting diodes (pc-LEDs) for indoor plant growth and full-spectrum applications. Recently, Mn4+ activated red/deep-red phosphors have attracted considerable interests due to the advantages of cheap price and excellent luminescence properties. Herein, a series of (Gd,La)2(Zn,Mg)TiO6:Mn4+ phosphors were synthesized through high temperature solid state reaction. Morphology, structure and luminescence properties of the as-prepared phosphors were investigated. More importantly, the influences of Mg2+/La3+ doping on structure, luminescence spectra, decay curves and thermal quenching were discussed in detail. It is found that a certain amount of Mg2+ contributes positively to the emission intensity and can improve the luminescence thermal stability of Mn4+, while the doping of La3+ exhibits a negative effect. By employing the prepared phosphor as deep-red component, a full-spectrum high performance white LED with low correlated color temperature (4287 K) and extremely high color rendering index (Ra = 97.9) can be fabricated. The results indicate that the as-prepared phosphors may be potential for full-spectrum lightings and indoor plant growth after further improvement.

Enhanced visible light photocatalytic efficiency of La-doped ZnO nanofibers via electrospinning-calcination technology

A series of La-doped ZnO (La/ZnO) nanofibers were prepared by electrospinning-calcination technology and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet–visible (UV–Vis) absorption spectroscopy and specific surface area analysis. The effect of numerous operational parameters involving calcination temperature, La doping amount, La-doped ZnO concentration and initial Rhodamine B (Rh B) concentration on photocatalytic efficiency of the composite has been analyzed by using Rh B for degradation under the illumination of visible light. Under optimum conditions, ZnO doped with 1.5 ​at.% La achieved 94.31% Rh B degradation after 510 ​min of visible light illumination. The kinetic data of La/ZnO catalyst for Rh B photodegradation fitted the Langmuir-Hinshelwood first-order (LHFO) kinetic model well.

Effect of La addition on Ag-rich phase formation and mechanical properties of Cu-2Ag alloys

A series of novel Cu-2Ag-xLa alloys with reinforced mechanical properties and enhanced electrical conductivities are developed. The effects of La addition on the microstructural features and mechanical properties of as-cast and solution treated Cu-2Ag alloys are systematically investigated. The yielding strength of as-cast Cu-2Ag alloys with 0.02La and 0.07La (wt.%) is considerably reinforced by relative amounts of 55.56% and 30.16%, respectively. The strengthening mechanism for such increased yielding strength is mainly related to the shifting of interfacial relation between matrix and Ag-rich phase from original semi-coherent type to non-coherent type with La doping. Consequently, the interface barrier strength is enhanced by the non-coherent interface, and contributes to the increased yielding strength. Meanwhile, the strengthening effect from La addition closely depends on the exact contents of La element. As La content increases from 0.02 to 0.07 (wt.%), the strengthening effect becomes weaker because of the increased space of Ag-rich phases leading to an 16.33% decrease in yield strength. Additionally, La has dual effects on the dissolution of Ag-rich phases and precipitation of new La-rich phase in the as-cast alloys during solution treatment. Simultaneously, the precipitation of the La-rich phase abnormally enhances the electrical conductivity of the solution La-containing alloys when the solution time exceeds 24 h.

The formation mechanism of Al-RE tubular phase in AZ80-Ce magnesium alloy by La doping

In this paper, the effect of La addition on the Al-RE phase in Mg-Al-Zn-Ce magnesium alloy was studied. Melting method was used to prepare AZ80-Ce magnesium alloys with different La content, and the morphological transformation mechanism of Al-RE phase was proposed by XRD, SEM, EPMA, TEM and extraction. The results show that the Al11RE3 phase can be formed by adding RE (Ce/La) into AZ80 magnesium alloy. With the increase of La, the morphology of Al11RE3 phase in the alloy changes from acicular to tubular. La replaces part of Ce in the Al11Ce3 cell and the Al11Ce3 phase is transformed into Al11RE3 phase based on Al11RE3 cell when La is added. In the Al11RE3 phase, the doping of La will cause lattice distortion in the crystal, which increases the surface energy on the growth surface of the Al11RE3 phase and accelerates its growth rate in (001) direction, resulting in the formation of tubular Al11RE3 phase. After forming the tubular structure, the growing process of Al11RE3 phase is divided into three stages owing to different control factors.

La-RuO2 nanocrystals with efficient electrocatalytic activity for overall water splitting in acidic media: Synergistic effect of La doping and oxygen vacancy

The development of high-performance and durable Ru-based electrocatalysts in proton exchange membrane (PEM) water electrolyzers for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) remains a huge challenge due to the severe catalyst’s corrosion and high reaction overpotential in acid media. Herein, we reported a synergistic strategy of effectively combining hetero-atom doping and oxygen vacancy in the La-doped RuO2 nanocrystals, successfully realized by a hydrothermal and followed annealing process aiming for efficiently overall water splitting. The as-obtained La-doped RuO2 nanocrystals demonstrate superior electrocatalytic performances with ultra-low overpotential of 208 mV for OER and 71 mV for HER at the current density of 10 mA/cm2 together with robust long-term stability in 0.5 M H2SO4 electrolyte, which are 222 and 15 mV lower in overpotentials than that of bare RuO2 electrocatalyst. Moreover, the La-doped RuO2 nanocrystals only require a cell voltage of 1.53 V to drive the overall water splitting reaction and exhibit a remarkable stability. Density functional theory (DFT) calculations further reveal that the synergistic effect of La doping and oxygen vacancy engineering could tune the d-band center of Ru active sites and optimize the Gibbs free energy of intermediate state, thus enhancing the activity of RuO2. Such synergistic strategy of aliovalent doping and vacancy engineering for much enhanced acid electrocatalysis may offer important referential values for exploring efficient electrocatalysts towards overall water splitting in acidic media.

Influence of lanthanum doping on the structural and optical properties of cerium tungstate nanocrystals

In this study, the effect of lanthanum (La) doping on the structural and optical properties of cerium tungstate nanocrystals synthesized by the chemical precipitation method is investigated. The X-ray diffraction studies confirmed the crystalline phase formation and observed no phase change with doping. It is interesting to note that the crystallite size is decreased with La doping. The characteristic vibrational peaks of W-O bonds are confirmed from the FTIR and Raman spectroscopic studies and found no appreciable changes in the spectral positions with doping. The optical properties are studied using UV-Vis spectroscopy and photoluminescence spectroscopy. The characteristic broad blue PL emission from the tetrahedral tungstate group is observed for the pure and doped samples, and the appreciable variation in PL intensity can be associated with the formation of defects that occurred while doping.

Mitigating the voltage fading and air sensitivity of O3-type NaNi0.4Mn0.4Cu0.1Ti0.1O2 cathode material via La doping

The practical application of O3-type layered oxides cathode materials for sodium ion batteries (SIBs) is hindered by two major difficulties, including capacity decay rooted in multiphase transitions and storage issue originated from sensitivity to moisture. Herein, we report a series of O3-type layered oxides Na(Ni0.4Cu0.1Mn0.4Ti0.1)1-xLaxO2 (x = 0, 0.001, 0.003, 0.005, termed as NMCT, NMCT-Lax, respectively) cathode materials synthesized via spray pyrolysis followed by high-temperature sintering method, which manifest enhanced electrochemical performance and air stability as compared to the NaNi0.5Mn0.5O2 (termed as NM) material. Optimum performance is achieved in the NMCT-La0.001 material that delivers a high initial discharge capacity of 170.1 mAh g−1 in the voltage range of 2.0–4.4 V at 0.1C (1C = 150 mA g−1). NMCT-La0.001 exhibits a highly reversible structural transformation during charging/discharging as demonstrated by in-situ XRD, and it keeps the original crystal structure after being exposed to the air for 30 days. The capacity decay of NMCT is effectively decelerated at high voltage (>4.2 V) after La doping, as which can stabilize the structure of the material by reducing the Mn3+ content through suppressing the Jahn-Teller effect. The research with respect to La doping provides a facile and instructive way for the design of high-performance cathode materials for SIBs.

The electrocaloric effect of Ba1-xLaxTi0.9Sn0.1O3 ceramics with excellent temperature stability near room temperature

The Ba1-xLaxTi0.9Sn0.1O3 ceramics (x = 0, 0.006, 0.007, 0.008) were prepared by the traditional solid-state reaction method. The influence of La3+ on the phase, dielectric properties, ferroelectric properties, and electrocaloric effect (ECE) was analyzed in detail. The results of refinement show that all ceramics are multiphase coexistence at room temperature, including the cubic phase, the tetragonal phase, and the orthogonal phase. With the increase of La3+, the polar phases decrease but the non-polar phase increases, which is the main reason for the decline in adiabatic temperature change (ΔT). The analysis of dielectric properties and ferroelectric properties demonstrate that the diffuse phase transition is strengthened by introducing La3+. It also means that polar nanoregions (PNRs) might be formed. Therefore, the temperature stability of the Ba1-xLaxTi0.9Sn0.1O3 ceramics in a wide temperature range near room temperature is improved. Simultaneously, the PNRs provide additional entropy to improve ECE. A higher ΔT = 0.88 K is obtained under 60 kV/cm for x = 0.007, which also possesses excellent temperature stability in the temperature range of 298 K–378 K. The doping of La3+ also improves the electric field threshold of the electrocaloric strength (ΔTmax/ΔE) and stabilizes the ΔTmax/ΔE under a higher electric field, which is conducive to improving ECE under a higher electric field and providing another possible solution for promoting the practical application of ECE.

A free-cobalt barium ferrite cathode with improved resistance against CO2 and water vapor for protonic ceramic fuel cells

The triple conducting (electron, oxygen-ion and proton) cathode is promising for protonic ceramic fuel cells (PCFCs). Heavy doping of Fe can impel BaZr 0.9 Y 0.1 O 3-δ to cross the electronic percolation threshold, forming the triple-conducting BaFe 0.8 Zr 0.1 Y 0.1 O 3-δ (BFZY) material. The partial A-site substitution with La is also designed to further optimize the properties of BFZY. Herein, a systematic study on Ba 0.95 La 0.05 Fe 0.8 Zr 0.1 Y 0.1 O 3-δ (BLFZY) cathode is conducted for searching potential free-cobalt PCFC cathodes with good tolerance for both CO 2 and water vapor. The XRD result indicates that BLFZY maintains stable cubic perovskite structure. The comprehensive analysis based on XRD, TG and TPD-CO 2 reveals that the BLFZY cathode exhibits an excellent tolerance for CO 2 and water vapor. The La doping also has a positive influence on the thermal expansion coefficient, electrical conductivity, and electrocatalytic activity. The anode-supported single cell with single-phase BLFZY cathode achieves a peak power density of 305 mW cm −2 and polarization resistance of 0.492 Ω cm 2 at 600 °C and maintains steady power output in the short-term durability test. This indicates that the BLFZY material is a good cathode candidate for PCFCs. • BLFZY shows good tolerance for both CO 2 and water vapor. • La dopant is favorable to reducing TEC and increasing electrical conductivity. • A peak power density of 305 mW cm −2 is reached at 600 °C.

From Doping to Dilution: Local Chemistry and Collective Interactions of La in HfO2

Lanthanum (La) doping is considered as a promising route to overcome reliability issues of switchable ferroelectric HfO2‐based devices. This study links the local chemistry at the La lattice sites with local and collective electronic properties of the La:HfO2matrix using hard X‐ray photoelectron spectroscopy. The satellite structure of the La 3dcore level, the plasmonic excitation energies, and core‐level rigid binding energy shifts are investigated for La:HfO2samples with a wide range of La doping, ranging from 3.5% to 33%, i.e., from the doping to dilution level. The emerging chemical phases and electronic properties are discussed as a function of La content. From the evolution of the plasmon excitation energies and rigid binding energy shifts, it is concluded that electronic charge compensation by oxygen vacancies occurs for increasing La content.

Differences between La substitution and doping strategies in dielectric properties of CaCu3Ti4O12 ceramics with low loss

Differences between La substitution and doping strategies in dielectric properties of CaCu3Ti4O12 ceramics with low loss

Machine Learning Guided Dopant Selection for Metal Oxide-Based Photoelectrochemical Water Splitting: The Case Study of Fe2 O3 and CuO.

Doping is an effective strategy for tuning metal oxide-based semiconductors for solar-driven photoelectrochemical (PEC) water splitting. Despite decades of extensive research effort, the dopant selection is still largely dependent on a trial-and-error approach. Machine learning (ML) is promising in providing predictable insights on the dopant selection for high-performing PEC systems because it can uncover correlations from the seemingly ambiguous linkages between vast features of dopants and the PEC performance of doped photoelectrodes. Herein, the authors successfully build ML model to predict the doping effect of 17 metal dopants into hematite (Fe2 O3 ), a prototype photoelectrode material. Their findings disclose the critical parameters from the 10 intrinsic features of each dopant. The model is further experimentally validated by the coherent prediction on Y and La dopants' behaviors. Further interpretation of the ML model suggests that the chemical state is the most significant selection criteria, meanwhile, dopants with higher metal-oxygen bond formation enthalpy and larger ionic radius are favored in improving the charge separation and transfer (CST) in the Fe2 O3 photoanodes. The generic feature of this ML guided selection criteria has been further extended to CuO-based photoelectrodes showing improved CST by alkaline metal ions doping.

Effect of La Doping on NiCr2O4 Properties and Catalytic Applications toward Decolorization of 4-Nitrophenol

We report the successful synthesis of urea as a fuel for low-temperature microwave combustion-based synthesis of NiCr2O4 and La-doped NiCr2O4. Synthesis parameters include the kind of precursor, fuel, and container, as well as how external heat is provided to achieve the combustion reaction. Crystal structures, morphology, surface area, solar cells, Fourier-transform infrared spectrometry, and catalytic activity were used to characterize the products. No impurities phase formed in the as-synthesized NiCr2O4 sample, confirmed by XRD. Surface area was measured with a Brunauer–Emmet–Teller adsorption isotherm. Schottky and Frenkel formation energies have been investigated. This demonstrates the time needed for full decolorization of 4-Nitrophenol (yellow color) by NiCr2O4 and La-doped NiCr2O4. The La-doped NiCr2O4 (0.03%) showed the greatest catalytic activity compared to pristine and other La-doped NiCr2O4. The decolorization occurs in 10 min. The chemical hardness and surface area of the chromites appear to be important in determining catalytic performance. For multi oxide systems, the counter-doped ions in the A and B sites may alter the metal ion-oxide bond, promoting this partial oxidation process at the interface. The results suggest multiple research subjects focusing on such materials for the future.

High-Performance Ferroelectric Electromagnetic Attenuation Materials with Multiple Polar Units Based on Nanodomain Engineering.

The multirelaxation behavior is promising for high-performance dielectric materials based on polarization-controllable high-efficiency electromagnetic attenuation. However, a single polar unit is the main problem that restricts the development of dielectric materials in the field. Herein, by constructing multiple polar units based on nanodomain engineering, enhanced electromagnetic attenuation properties are achieved in La doping BiFeO3 ferroelectric ceramics. A dual-band attenuation with a maximum reflection loss of -43.4 dB together with a wide effective bandwidth (<-10 dB) of 3.3 GHz in X-band, is acquired in Bi0.85 La0.15 FeO3 which just has a thickness of 1.54 mm. A systematic experimental analysis coupled with potential well modeling suggests that the miniaturization of the ferroelectric domain, from micron to nanoscale, induces an additional interface polarization that is capable of responding to microwave frequency, leading to the formation of dual dielectric relaxation. The way that intrinsic polar unit induces another polar unit through size effect to obtain multiple contributions of electromagnetic loss provides a feasible and universal strategy to design high-performance electromagnetic attenuation materials based on the ferroelectric family.

Green synthesis of novel lanthanum doped copper oxide nanoparticles for photocatalytic application: Correlation between experiment and COMSOL simulation

Treatment of waste water via photocatalysis is one of the most effective, economical and environment friendly process. In this study, green method (leaf extract of Citrus Medica Linn.) is used to synthesize pure and lanthanum (La)-(1,2 & 3 wt%) doped copper oxide nanoparticles (CuO-NPs). Different characterization techniques such as XRD, SEM, EDS, UV/VIS, PL and FTIR are utilized to investigate their physical, chemical, optical and structural properties. The synthesized material is used as photocatalyst for degradation of methylene blue (MB) dye. Interestingly, the La doped CuO-NPs have exhibited unique results. Variation in dopant concentration reduces the particle size (40.82 ± 0.04 nm to 31.89 ± 0.02 nm) and band gap of material shifts towards visible region (3.03 eV–2.71 eV). During photocatalysis, doping reduces the electron-hole pair recombination rate which makes it a potential photocatalyst. Maximum degradation efficiency of 84% is observed in 150 min for 2% La doped CuO-NPs which reveals that 2% La doping is optimal. Further increase in dopant concentration increases band gap, therefore, degradation efficiency drops to 75%. Simulation of this work is carried out using COMSOL Multiphysics 5.3a Licensed version. A 2D model is constructed and CuO-NPs is considered as photocatalyst in order to correlate simulated and experimental photocatalytic degradation of MB and rhodamine B (RhB) dye. Comparative analysis of rate constants revealed that the trend given by simulation is very close to the experimental observations.

Influence of La and Si promoters on the anaerobic heterogeneous catalytic decomposition of ammonium dinitramide (ADN) via alumina supported iridium active sites

Structural origins of the promotional effects of the La or Si doping of alumina supported Ir catalysts in anaerobic ammonium dinitramide decomposition were investigated. Our findings reveal that Ir/Al2O3 and Ir/La-Al2O3 favorably lower the onset temperature of the ADN decomposition reaction, whereas Si doping boosts the pressure generation during the reaction. Formation of mostly metallic Ir nanoparticles for Ir/Al2O3 and Ir/La-Al2O3 enables the lowering of the activation energy of the reaction. On the other hand, enhancement due to Si promotion is associated to the generation of small oxidic Irnx+ clusters which are strongly interacting with the SiOx-AlOx surface domains of the support material. Fundamental structure-functionality relationships unraveled in the current work may allow design of novel catalytic systems for aerospace monopropellant propulsion systems with higher performance by simultaneous exploitation of Ir active sites with different electronic properties.