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In the recent days, rare-earth doped phosphors have attracted an immense attraction in luminescence field for various solid-state lighting and electronic display device applications. However, need of efficient red phosphor is a prevalent challenge in this field. Herein, we report a bright red light emitting Na+ co-doped SrAl2O4:Eu3+ phosphor which is synthesized by modified sol–gel technique. These nanophosphors show excellent red emission due to characteristic 5D0 → 7Fj (j = 1, 2, 3, 4) transitions of the doped Eu3+ ions excited by 394 nm. Photoluminescence studies of both Eu3+ doped SrAl2O4 and Na+ co-doped SrAl2O4:Eu3+ has shown more than fourfold increase in the intensity for optimum Na+ addition. The improved decay time obtained from decay measurement has revealed that the co-doped Na+ has successfully reduced the nonradiative transitions. Thus, addition of monovalent Na+ to Eu3+ doped SrAl2O4 was found to be effective to address the charge imbalance problem along with significant enhancement in luminescence intensity and decay time. The results suggest that this nanophosphor could be a major candidate in the rapidly increasing field of solid-state lighting applications.

The crystallization behavior and melt structure of the CaO–SiO2–B2O3-based fluorine-free mold flux were investigated. The results show that the crystallization of the mold flux was first inhibited and then promoted with the increase in Al2O3 content from 4 to 12 wt.%. However, it was enhanced by MgO in the range of 2–10 wt.%. The results of Fourier transform infrared spectroscopy and Raman spectroscopy showed that Al2O3 worked as a network former in the mold flux melt when its content was in the range of 4–8 wt.%, whereas it worked as the network breaker to provide O2− when its content was in the range of 8–12 wt.%. In addition, the combined effects from the charge compensation by Mg2+ and the network broken by O2− led to the increase in some typical T–O–T (Al–O–Al, B–O–B, etc.) and simpler structural units (Q0(Si), B–O− in the [BO2O−], etc.) when the MgO content was in the range of 2–6 wt.%. The continuous increase in O2− provided by the addition of MgO from 6 to 10 wt.% further depolymerized the network of the melt and finally caused fast crystallization.

A class of high-entropy perovskite oxide (HEPO) [(Bi,Na)1/5(La,Li)1/5(Ce,K)1/5Ca1/5Sr1/5]TiO3 has been synthesized by conventional solid-state method and explored as anode material for lithium-ion batteries. The half-battery provides a high initial discharge capacity of about 125.9 mAh g−1 and exhibits excellent cycle stability. An outstanding reversible capacity of 120.4 mAh g−1 and superior delivering retention of ~ 100% can be obtained at 1000 mA g−1 after 300 cycles. Even at a high current density of 3000 mA g−1, a reversible capacity of 70 mAh g−1 can be retained, indicating excellent rate performance. Such outstanding cycle and rate performance can be ascribed to the entropy-stabilized structure offered by mixed aliovalent cations and the charge compensation mechanism in HEPO, respectively. This work highlights the great potential of perovskite high-entropy oxides as anode materials for lithium-ion batteries.

Immobilisation of Pu in a zirconolite matrix (CaZrTi2O7) is a viable pathway to disposition. A-site substitution, in which Pu4+ is accommodated into the Ca2+ site in zirconolite, coupled with sufficient trivalent M3+/Ti4+ substitution (where M3+ = Fe, Al, Cr), has been systematically evaluated using Ce4+ as a structural analogue for Pu4+. A broadly similar phase assemblage of zirconolite-2M and minor perovskite was observed when targeting low levels of Ce incorporation. As the targeted Ce fraction was elevated, secondary phase formation was influenced by choice of M3+ species. Co-incorporation of Ce/Fe resulted in the stabilisation of a minor Ce-containing perovskite phase at high wasteloading, whereas considerable phase segregation was observed for Cr3+ incorporation. The most favourable substitution approach appeared to be achieved with the use of Al3+, as no perovskite or free CeO2 was observed. However, high temperature treatments of Al containing specimens resulted in the formation of a secondary Ce-containing hibonite phase.

Na-ion batteries (NIBs) have attracted significant attention owing to Na being an abundant resource that is uniformly distributed in the Earth’s crust. Several 3d transition metal (TM) ions have been thoroughly investigated as charge compensators in single or multiple composition systems to enhance the electrochemical performance of cathodes for the practical applications. In this review, the composition-structure-property relationship of Ni-based cathodes has been reviewed as a design perspective for NIB’s cathodes. The typical Ni-based cathode materials have been systematically summarized and comparatively analyzed, and it is demonstrated that Ni ions can be used to provide charge compensation. Moreover, Ni-based cathodes present high reversible capacity owing to the multi-electron redox reactions and suitable redox potential of Ni-ions redox. However, considering the abundance, cost, and hygroscopic properties of Ni element, the content of 0.15–0.35 per formula can be optimal for enhancing the performance of cathodes. Lastly, further perspectives on designing Ni-containing cathodes, including Ni-rich layered cathodes, have been discussed, which could promote the practical applications of NIBs for grid-scale energy storage in future.

A series of CaZrO3:Bi3+, CaZrO3:Eu3+, CaZrO3:Eu3+, Bi3+, and CaZrO3:Eu3+, Bi3+, Li+ phosphors are synthesized by high-temperature solid-state reaction method in air. Their luminescence properties are researched, compared, and analyzed. CaZrO3:Bi3+ phosphor under excitation at 310 nm emits deep-blue light with chromaticity coordinate (0.1612, 0.0254). CaZrO3:Eu3+ phosphor under excitation at 310 and 395 nm shows red-emitting with chromaticity coordinate (0.6386, 0.3611). CaZrO3:Eu3+, Bi3+ phosphor under excitation at 310 nm exhibits a systematically varied hue from deep-blue to red light by changing Eu3+ ion concentration, and that with excitation at 395 nm only emits red light with chromaticity coordinate (0.6386, 0.3611). The energy transfer process from Bi3+ to Eu3+ ions may be indicated by their spectral properties. The optimal Eu3+ and Bi3+ ions concentrations are 5 mol% and 0.9 mol%, respectively. The emission intensity CaZrO3:Eu3+, Bi3+ phosphor may be enhanced about 1.6 times due to the co-doping Li+ ion as charge compensator role. The luminous mechanism of CaZrO3:Eu3+, Bi3+ phosphor is explained by the simplified energy level diagrams of Bi3+ and Eu3+ ions.

A layered Zn-doped compound of Na0.7Zn0.15Mn0.75O2 is synthesized by a facile solid-state method. The product exhibits the same structure as P2-Na2/3Ni1/3Mn2/3O2, and some particles of the product are of lamellar shape with the thickness being about 0.6 μm. When the material is tested on the properties of intercalating/deintercalating Na+ in the voltage 2–4.4 V, it can deliver an initial discharge capacity of 158 mAh g−1. When the material is charged to different voltage, XPS spectra are performed on the surface of this material, and it is disclosed that oxygen activity makes the main part of contributions to charge compensation on the initial extracting Na+ process, while there is no apparent peak shift for the XPS spectra of Mn 2P3/2.

The study is based on the determination of trace elements in ruby samples, Ti in particular, using laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS). The samples were then divided into three groups: high (≥ 200 ppma), moderate (100–200 ppma), and low (≤ 50 ppma) Ti content. In addition, X-ray absorption spectroscopy (XAS) was employed to confirm that the Ti oxidation state was Ti4+. The heat experiment conditions were set at 800, 1200, and 1650°C to investigate the transformation of the –OH vibration in the FTIR spectra of ruby samples. The FTIR spectra showed that samples containing a low Ti concentration did not show the 3309-cm–1 absorption peak either before or after heating at any of the designed temperatures. An obvious 3309-cm–1 peak appeared only in samples with a moderate to high Ti content after heating at ≥ 1200°C. The results also suggest that, in addition of Ti4+, the occurrence of the 3309-cm–1 peak in the FTIR spectra is strongly affected by the charge compensation of –OH in Al sites, i.e., the structural –OH; thus, the structural –Ti–OH stretching in the ruby samples. Hence, for gemological identification, the 3309-cm–1 peak can be applied to indicate whether a ruby has undergone heat treatment if those samples contain enough Ti ions in their structure, i.e., Ti ≥ 100 ppma. This condition is usually found in ruby samples from major deposits such as Mong Hsu and Mogok, Myanmar; Luc Yen, Vietnam; and Montopuez, Mozambique.

A brief review of commonly encountered anions, cations and co-doped HA and Ca-deficient HA was given in the DFT studies. First, the charge compensation mechanism, the preference substitution sites and crystal structure changes of doped HA were described and discussed. And then conclusions were drawn and future challenges were discussed. The review is expected to provide theoretical guidance for the development of bioactive HA with special structures and functions.

In order to enhance the deep red emission intensities of CaAl12O19:Cr3+ and CaAl12O19:Mn4+ phosphors, the authors prepared a series of samples through doping a variety of ions with different valence states at 1500 °C by solid state reaction in air. Their doping effects and possible mechanisms were investigated, respectively. The results indicated that Sm3+ could enhance the emission intensity of CaAl12O19:Cr3+ through an energy transfer process, whereas it has not a similar effect for the CaAl12O19:Mn4+ phosphor. It is also shown that Cl−, Mg2+ and K+ could enhance the emission intensity of CaAl12O19:Mn4+ mainly due to their charge compensation effects. What is more interesting is that the doped Ge4+ ion, as a type of covalent ion of Mn4+, also has the ability to enhance the red emission intensity of CaAl12O19:Mn4+ through decreasing the concentration of Mn4+–Mn4+ pairs in the prepared phosphor.

A series of novel red-emitting Na2Ca3 − x Si2O8:xEu3+ phosphors were synthesized by solid state reactions. The phosphors can strongly absorb 395 nm light, and show red emission with a good color purity. The excitation and emission spectra properties of Na2Ca3Si2O8:Eu3+ were characterized. Na2Ca3Si2O8:Eu3+ with self-compensated and alkali metal ions charge compensated approaches (2Ca2+→Eu3+ + M+, M = Li+, Na+, K+) have investigated, which found that the red emission of luminescent intensity can be greatly enhanced, and shows superior luminescent property to the commercial Y203S:Eu3+. The present work implies that the efficient charge compensated phosphors are promising candidates as red-emitting phosphor for w-LEDs.

Novel CaSb2O6:Eu3+, Bi3+ phosphor is synthesized by solid-state reaction method in air. Their crystal structures are investigated. Luminescence properties of CaSb2O6:Eu3+, CaSb2O6:Bi3+, and CaSb2O6:Eu3+, Bi3+ phosphors are compared, analyzed and explained, respectively. Tunable emission of CaSb2O6:Eu3+, Bi3+ phosphor with excitation 298 nm can be observed by changing Eu3+ or Bi3+ concentration. Energy transfer (ET) and charge compensation in CaSb2O6:Eu3+, Bi3+ phosphor are observed and analyzed via its luminescence properties. Lifetimes of CaSb2O6:5 %Eu3+, yBi3+ phosphor (0.5 ≤ y ≤ 5 mol%) are investigated, which further confirm that ET process can be formed between Eu3+ ion and Bi3+ ion. The luminous mechanism is explained via the energy level diagrams of Bi3+ and Eu3+ ions. The emission properties indicate that CaSb2O6:Eu3+, Bi3+ phosphor has a potential application for white LEDs based on near UV (~394 nm) LED chip.

BaWO4:Sm3+, Mo6+/K+ phosphors are synthesized by a high temperature solid-state reaction method in air. The very strong emission bands peaking at ~600 and 644 nm and the strongest excitation band peaking at ~403 nm are assigned to the 4G5/2 → 6HJ (J = 7/2 and 9/2) and 6H5/2 → 4F7/2 transitions of Sm3+ ion, respectively. The optimal Sm3+ doping concentration is ~5 mol%. Emission intensity of BaWO4:Sm3+ phosphor is increased more than twice owing to charge compensation when the K+ ion is codoped as charge compensator, however, Mo6+ ions is small influence to its emission intensity. The energy transfers and luminous mechanism are explained by using energy level diagrams of WO42− group and Sm3+ ion. Lifetimes of Ba0.925WO4:0.05Sm3+, Ba0.925W0.9Mo0.1O4:0.05Sm3+, and Ba0.9K0.05WO4:0.05Sm3+ phosphors with excitation 403 nm are about 0.933, 0.882, and 0.693 ms, respectively. The experiment results indicate that BaWO4:Sm3+, Mo6+/K+ phosphors will be a potential red phosphor candidate for white LEDs based on near UV (~403 nm) LED chip and research contents are useful to improve luminescence properties of Sm3+-doped phosphors.

In this paper, the influence of MgO/Nb2O5 co-doping on the microstructure and microwave dielectric properties of Al2O3 ceramics has been investigated. Comparing with only MgO doped samples, the introducing of Nb2O5 can further promote the densification progress and improve the microwave dielectric properties. A high Q × f value of 216,894 GHz could be obtained with 500 ppm MgO/500 ppm Nb2O5 co-doped sample. Besides, MgO/Nb2O5 co-doping could increase the stability of the Q × f value of the Al2O3 ceramics. Charge compensation and low content of the second phase are believed to be the main reason of this high and stable Q × f value.

Co-precipitated Y3Al5O12:Ce nanophosphors with enhanced photoluminescence (PL) intensity were synthesized by introducing SiO2 in the precursor. The role of SiO2 on morphologies, PL enhancement and valence state of Ce was investigated by varying the amounts of SiO2 from 0 to 1.0 wt%. The SiO2 addition inhibited the crystal growth owing to the appearance of second phase. However, the PL intensity of YAG:Ce was largely improved with SiO2 addition. The reason for the PL enhancement was that the incorporation of Si4+ into the YAG host suppressed the further oxidation of Ce3+ to Ce4+ owing to charge compensation.

The empirical models of sulfide capacity calculated by traditional optical basicity do not consider the charge compensation of alkaline metal ions to Al3+ in the molten slags, so that the deviations between the calculated values and measured ones of sulfide capacity are inevitable. The relation between sulfide capacity and the corrected optical basicity put forward by Mills considering the charge compensation was investigated. Combined with the relation between sulfide capacity and temperatures, a novel and accurate calculation model of sulfide capacity was proposed, which was applied to calculate the sulfide capacities of CaO-Al2O3-SiO2-MgO and CaO-Al2O3-SiO2-MgO-TiO2 sys-tems, where the sum of the CaO and MgO concentrations in the slags must be not lower than the Al2O3 concentra-tion. It was also found that the calculated values were in a good agreement with the measured values, and the mean deviations were 2.57 and 2.65 %, respectively.

A model has been developed that enables the viscosities of the fully liquid slag in the multi-component Al2O3-CaO-FeO-Fe2O3-MgO-Na2O-SiO2 system to be predicted within experimental uncertainties over a wide range of compositions and temperatures. The Eyring equation is used to express viscosity as a function of temperature and composition. The model links the activation and pre-exponential energy terms in the viscosity expression to the slag internal structure through the concentrations of various Si0.5O, \( {\text{Me}}^{n + }_{2/n} {\text{O}} \) , and \( {\text{Me}}^{n + }_{ 1/n} {\text{Si}}_{0. 2 5} {\text{O}} \) viscous flow structural units (SUs). The concentrations of these SUs are derived from a quasi-chemical thermodynamic model of the liquid slag using the thermodynamic computer package FactSage. The model describes a number of slag viscosity features including the charge compensation effect specific for the Al2O3-containing systems. The predictive capability of the model is enhanced by the physical aspects of the model parameters—the correlation with other physicochemical properties as well as experimental viscosity data is used to determine model parameters. The present series of two papers outlines (a) recent significant improvements introduced into the model formalism and (b) application of the model to the Al2O3-CaO-MgO-SiO2 system, review of experimental viscosity data, and optimization of the corresponding model parameters for this system.

Viscosity is an important physical property of blast furnace slags and has a great influence on blast furnace operations. Because of time consumption and difficulties encountered during high temperature experimental measurement, viscosity data are also limited, so a reasonable and accurate estimation model is required to provide the data for controlling and optimizing the blast furnace process. In the present study a viscosity model was proposed for blast furnace slags. In the model the activation energy was calculated by the optical basicity corrected for cations required for the charge compensation of AlO 4 5− , and the temperature dependence was described by the Weymann-Frenkel equation. The estimated viscosity values of the CaO-Al2O3-SiO2, CaO-Al2O3-SiO2-MgO, and CaO-Al2O3-SiO2-MgO-TiO2 systems fit well with experiment data, with the mean deviation less than 25%.

The history of research on voltage-gated proton channels is recounted, from their proposed existence in dinoflagellates by Hastings in 1972 and their demonstration in snail neurons by Thomas and Meech in 1982, to the discovery (after a decade of controversy) of genes that unequivocally code for proton channels in 2006. Voltage-gated proton channels are perfectly selective for protons, conduct deuterons half as well, and the conductance is strongly temperature dependent. These properties are consistent with a conduction mechanism involving hydrogen-bonded-chain transfer, in which the selectivity filter is a titratable amino acid residue. Channel opening is regulated stringently by pH such that only outward current is normally activated. Main functions of proton channels include acid extrusion from cells and charge compensation for the electrogenic activity of the phagocyte NADPH oxidase. Genetic approaches hold the promise of rapid progress in the near future.

A enhanced photoluminescence red phosphor of CaTiO3:Pr,Al has been synthesized by a peroxide-based route (PBR) and high temperature sintering method. The synthesizing conditions have been optimized in this work. The effect of sintering temperature and boron on the preparation, structure, and photoluminescence were studied by X-ray powder diffraction (XRD), emission, and excitation spectra at room temperature. The red emission is attributed to 1D2 → 3H4 transition of Pr3+, and the excited energy comes from the UV absorption of host and transfers to 4f–5d band of Pr3+. Also, the studies include analysis of charge compensation and Pr3+ concentration effects. Compared with conventional solid-state reaction methods, the PBR significantly lowered temperatures of synthesis, shortened reaction time, and enhanced the photoluminescence intensity.

The effect of compensator on optical properties of Ca2Al2SiO7:Eu3+ is systematically investigated by the X-ray powder diffraction, photo-luminescence (PL) properties and lifetime. It is obviously observed that the PL intensity of Eu3+ under 394 nm excitation increases in the order of Ca1.86Eu0.14Al2SiO7 (CAS), Ca1.72Na0.14Eu0.14Al2SiO7 (CASNa) and Ca1.86Eu0.14Al2.14Si0.86O7 (CASAl), the intensity of Eu3+ are 100%, 134%, 184%, and the lifetime of Eu3+ are 0.75 ms, 1.28 ms and 1.39 ms, respectively. A charge compensation model is proposed to explain the changes in the emission intensity and lifetime of Eu3+ in Ca2Al2SiO7 with different compensation methods.

The 3-amino-1,2,4-triazole (AmTAZ) ligand is a promising molecular species for formation of robust porous coordination polymers. We have recently crystallized two unusual cubic cage structures which possess μ2−O2− and μ3−S2− bridges, respectively. Although nitrate anions occupy the pore in these two cationic frameworks, we anticipate that similar materials with open pores can be formed by the incorporation of the charge-compensating anion into the framework structure.

Three new noncentrosymmetric cyclohexaphosphates with the general formula M(C6H5NH3)4 P6O18⋅8H2O (M: Cd, Cu, Co) are synthesized. They crystallize in the monoclinic system, space group P21, Z = 2 and are isostructural. We have determined their structure from the Cd salt. This Cd salt exhibits the following unit-cell parameters: a = 9.852(1), b = 24.784(4), c = 9.2078(8) A, β = 107.92(9)∘, V = 2139.2(9) A3. The structure has been solved using direct method and refined to a reliability R factor of 0.042. The structure can be described as infinite anionic layers with composition of [Cd(P6O18)(H2O)8]4− and parallel to the (1 0 1) plane. The charge compensation and the three-dimensional cohesion are performed by the protonated amine located between these inorganic layers.

The stability and electronic structure of cation- and anion-compensated interfaces between (0001) lattice-matched slabs of GaN and ZnO have been considered. It was found that, irrespective of interfacial polarity, cation-compensated interfaces are by approximately 20 meV/unit cell more stable than the corresponding anion-compensated interfaces. Valence band offsets of 1.0 and 0.5 eV have been found at the cation- and anion-compensated interfaces, respectively.

Potassium tantalate powders were hydrothermally synthesized at 100 to 200 °C in 4 to 15 M aqueous KOH solutions. A defect pyrochlore, Kta2O5(OH).nH2O (n≈ 1.4), was obtained at 4 M KOH, but at 7–12 M KOH, this pyrochlore was gradually replaced by a defect perovskite as the stable phase. At 15 M KOH, there was no intermediate pyrochlore, only a defect perovskite,0.85Ta0.92O2.43(OH)0.570.15H2O. Synthesis at higher KOH concentrations led to greater incorporation of protons in the perovskite structures. The potassium vacancies required for charge compensation of incorporated protons could accommodate water molecules in the perovskite structure.

Electronic changes at polar interfaces between transition metal oxides offer the tantalizing possibility to stabilize novel ground states yet can also cause unintended reconstructions in devices. The nature of these interfacial reconstructions should be qualitatively different for metallic and insulating films as the electrostatic boundary conditions and compensation mechanisms are distinct. Here we directly quantify with atomic-resolution the charge distribution for manganite-titanate interfaces traversing the metal-insulator transition. By measuring the concentration and valence of the cations, we find an intrinsic interfacial electronic reconstruction in the insulating films. The total charge observed for the insulating manganite films quantitatively agrees with that needed to cancel the polar catastrophe. As the manganite becomes metallic with increased hole doping, the total charge build-up and its spatial range drop substantially. Direct quantification of the intrinsic charge transfer and spatial width should lay the framework for devices harnessing these unique electronic phases.

The charge states of intrinsic point defects and the thermodynamic parameters of defect formation processes in undoped lead chalcogenides were determined. The results provide an adequate description of the transport properties of the materials as a function of synthesis temperature and partial pressures of vapor species. Earlier and present experimental data are analyzed in terms of isolated point defects using the complete electroneutrality condition and taking into consideration the high-temperature band structure of the chalcogenides. The concentrations of charge carriers and predominant defects are evaluated for partial pressures corresponding to the stoichiometry ranges of the materials studied.

The effect of non-stoichiometric ordering on the electrostriction of Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) compositions (65/35) close to morphotropic phase boundary (MPB) has been studied using electrically induced strain and polarization methods. La was substituted (1 to 10 at %) on the A-site to control the degree of B-site cation ordering. The charge imbalance due to La3+ was compensated by two different mechanisms: (1) creation of B-site vacancies, and (2) changing the B-site cation ratio. Electrostriction coefficient measurements revealed dependencies on the degree of non-stoichiometric ordering and the charge compensation mechanism. A high value of the electrostriction coefficient was found to be accompanied by larger electrically-induced strains and smaller polarizations. In addition, the temperature dependence of the electrostriction coefficient was studied.

Careful reanalysis of EPR spectra of Cr3+ ions in KTiOPO4 has been carried out in order to resolve the weaker lines not considered in our previous study. Two additional centers denoted as C and D have now been identified and the respective spin Hamiltonian parameters have been determined. The reanalysis of the results for the centers A and B identified previously and those for the new centers C and D indicates that the centers A and C originate from Cr3+ ions at Ti(2) sites, whereas the centers B and D originate from Cr3+ ions at Ti(1) sites. Sixteen magnetically inequivalent Cr3+ sites are assigned to two crystallographically different titanium sites: Ti(1) and Ti(2). Possible charge compensation models for the two different centers arising from Cr3+ ions at each of the two Ti sites are also suggested.

The expectation that the hydroxyl analogue state of positive muons implanted in quartz should be stabilized by a suitable charge compensation centre is supported by preliminary data. The diamagnetic fraction correlates with aluminium content over the narrow range investigated.

Native defects and dopants in GaN grown by organometallic chemical vapor deposition have been studied with photoluminescence and optically detected magnetic resonance. For undoped samples, the combined results indicate the presence of residual shallow donors and acceptors and deep donors. A model for the capture and recombination among these defects is developed. For Mg-doped samples, the experiments reveal shallow and perturbed acceptors and shallow and deep donors. Hence, shallow and deep states for the native donor or donors appear in all samples. The Mg-acceptor is perturbed from its effective-mass state by nearby point defects.

The dc gain behaviour of GaAs photoconductors realized utilizing a partially compensated buffer layer of an epitaxial MESFET structure as well as a Cr-doped semiinsulating substrate is studied. The light-power dependence of the gain hints to the dominant role of the bimolecular recombination process and trapmediated gain, and only a minor role of the surface photovoltaic effect. The possible correlation between dark current and gain mechanism in the MESFET-like device is pointed out.

An EPR study of Fe3+ centres in single crystal KTiOAsO4 (KTA) has been performed at the Q-band frequency. Two Fe3+ centres have been observed for which all spin-Hamiltonian parameters were calculated. The comparison of the pseudosymmetries obtained from fourth-order constants of the spin-Hamiltonian and from a fourth-order crystal field calculation for the two Ti-octahedra, allowed us to locate one Fe3+ at both Ti sites in KTA. The deviation from cubic symmetry is similar and not very large for the two centres showing that the charge compensation mechanism is not at short distance.

We have calculated the thermal equilibrium concentrations of the various negatively charged Ga vacancy species in GaAs. The triply-negatively-charged Ga vacancy, V Ga 3− , has been emphasized, since it dominates Ga self-diffusion and Ga-Al interdiffusion under intrinsic and n-doping conditions, as well as the diffusion of Si donor atoms occupying Ga sites. Under strong n-doping conditions, the thermal equilibrium V Ga 3− concentration, $$C_{V_{_{Ga} }^{3 - } }^{eq} (n)$$ , has been found to exhibit a temperature independence or a negative temperature dependence, i.e., the $$C_{V_{_{Ga} }^{3 - } }^{eq} (n)$$ value is either unchanged or increases as the temperature is lowered. This is quite contrary to the normal point defect behavior for which the point defect thermal equilibrium concentration decreases as the temperature is lowered. This $$C_{V_{_{Ga} }^{3 - } }^{eq} (n)$$ property provides explanations to a number of outstanding experimental results, either requiring the interpretation that V Ga 3− has attained its thermal equilibrium concentration at the onset of each experiment, or requiring mechanisms involving point defect non-equilibrium phenomena.

Electrical charging during SIMS-analysis (secondary ion mass spectrometry) is a severe limitation for the analysis of non-conductive samples. In most cases this charging can be compensated with the aid of an electron gun. This is an already established method to analyze insulating samples. In this work results of a systematic study of electron gun charge compensation in our CAMECA ims5f ion microprobe are described.

The local potential at domains on ferroelectric surfaces results from the interplay between atomic polarization and screening charge. The presence of mobile charge affects surface domain configuration, switching behavior, and surface chemical reactions. By measuring the temperature and time dependence of surface potential and piezo response with scanning probe microscopies, thermodynamic parameters associated with charge screening are determined. This is illustrated for the case of BaTiO3 (100) in air, for which the charge compensation mechanism is surface adsorption and enthalpy and entropy of adsorption are determined. The local electrostatic fields in the vicinity of the domains have a dominant effect on chemical reactivity. Photoreduction of a large variety of metals can be localized to domains with the appropriate surface charge. It has been demonstrated that proximal probe tips can be used to switch polarization direction locally. Combining the ability to ‘write’ domains of local polarization with domain specific reactivity of metals, vapors of small molecules, and organic compounds leads to a new approach to fabricating complex nanostructures.

The incorporation of cerium, as a simulant for plutonium, has been investigated in both zirconolite and perovskite under oxidising and reducing conditions. The Ce valence in zirconolite was very sensitive to the processing atmosphere, whilst in perovskite the valence of the Ce was determined essentially by the chemical design of the perovskite. Charge compensation in zirconolite and perovskite samples displaying an apparent excess of positive charge was inferred to occur by the formation of cation vacancies, in samples prepared under oxidising conditions, and by trivalent Ti being produced in samples subject to a reducing atmosphere. Oxygen vacancies are inferred to be present in samples exhibiting an apparent excess of negative charge.

XPS and chemical titration both were carried out on Bi2+xSr1.8CaCu2Oz and Bi2Sr1.8−yCa1+yCu2Oz prepared by solid state reaction in order to investigate the correlation between the structural modulation and the mutual substitution of atoms. There was no clear evidence about the correlation between the modulation period by XRD and the site occupancies of Sr and Ca by XPS. However, there was a tendency that Bi mean valence by titration increased with increasing excess oxygen content and modulation period. The former one indicates the charge compensation and the latter one suggests the possibility of the origin of the structural modulation except for the excess oxygen.

A new charge-compensation method in monochromatized X-ray photoelectron spectroscopy has been successfully applied to the surface analysis of nonconductive materials such as ETFE and PET films, In this method unmonochromatized Mg X-rays are used effectively as an electron source for neutrallizing the sample chrging. Continuity of secondary electron energies produced by Bremsstrahlung radiations may play an important role in charge-neutralization process.

Partial substitution of Ce in place of Y has been achieved by taking care of charge compensation and compounds with the general formula Y1-2 xCexBa2+ xCu3O6·5+δ have been successfully prepared. X-ray powder diffraction analysis reveals that this substitution gives orthorhombic single phase for 0⩽x⩽0·3. TheT c remains nearly unchanged between 94-90 K.

On adapting brackish waterAnguilla anguilla to fresh water it was noted that, while the plasma sodium, magnesium,pCO2 and pH were held reasonably constant, there was a substantial fall in chloride concentration (−33 mEq). The gradient of the linear correlations between plasma sodium and chloride also fell (brackish water gradient=0.92, fresh water gradient=0.21) indicating that a new pattern of plasma ion interrelationships was being established. Comparison with plasma Na/Cl ion ratios from other fishes suggested that this phenomenon was peculiar toA. anguilla. Corresponding with the very low plasma chloride levels plasma bicarbonate was four to five times that found in other fishes, and this was thought related to the finding that the haematocrit value almost doubled during adaptation to fresh water. In fresh water adapted fish a fall in plasma chloride was associated with a rise in plasma bicarbonate, however the charge compensation effect of this response was only partial as summing the common plasma cations and anions left an anion deficit of about 34 mEq to be accounted for.

The electron paramagnetic resonance (EPR) spectrum of Cr3+ in synthetic crystals of forsterite consists primarily of lines of Cr3+ “isolated” at the M1 and M2 positions in a “perfect” crystal environment without local charge compensation. In addition it shows two nonequivalent superhyperfine-split sextets with different intensities which are due to strong interaction of the Cr3+ electron spin S (S=3/2) with an adjacent nuclear spin I(I=5/2). Electron nuclear double resonance (ENDOR) experiments revealed that the sextets result from Cr3+ (M1) - Al3+ and Cr3+ (M2) - Al3+ pairs, Al being located at adjacent tetrahedral Si sites. The g, D, A, and A′ tensor components of the Cr3+ - Al3+ pairs have been determined at room temperature. The values of the pairs are distinct although they are not very different from the corresponding data of “isolated” Cr3+. From the intensities of the EPR spectra the relative concentration of the Cr3+ - Al3+ pairs with respect to “isolated” Cr3+ has been estimated.

ESR and optical absorption studies have been carried out on Cu2+-doped lithium hydrazinium sulphate single crystals at 303 K. The spin-Hamiltonian parameters evaluated indicate a N2O2 square planar environment for Cu2+ ion in this lattice. The correlation ofESR and crystal structure data leads us to conclude that Cu2+ ion enters the lattice interstitially. Charge compensation is achieved by the release of protons. Using the optical absorption andESR data, bonding parameters and orbital reduction factors are also evaluated.

Rapid and reliable SIMS profiling of insulators can be achieved by using negative primary ions and a diaphragm placed on the specimen for charge compensation. Results with garnet LPE layers demonstrate the compositional variations arising from non-steady state growth conditions.

Three different operation modes of secondary neutral mass spectrometry have been applied for bulk and depth profile analysis of various insulators and insulating surface layers. Sample charging by ion bombardment has been compensated by different experimental techniques.

Crystal chemistry of alpha-quartz is discussed in relation to the nature, concentration and distribution of the common impurities. Two schemes for incorporation of impurities in the host structure,viz., the charge compensation model for untwinned natural quartz, and the broken-bond model for synthetic quartz to accomodate excess impurity residue after charge compensation, are critically reviewed. Another model for the presence of Al-H defects independent of alkali association in natural quartz is suggested. It is pointed out that the growth pressure influences the nature and distribution of impurities as well as generation of planar and line defects in synthetic quartz. It is also established that mechanicalQ (which is a measure of the acoustic loss) of synthetic crystals grown at low pressure deteriorates with increase in impurity content in excess of what is required for satisfying the charge compensation rule.

The conditions for the synthesis of the powdery calcium halophosphates fluorapatite, chlorapatite, and fluorochlorapatite, which takes place at T = 1000~ in the air, suggest that there is a high concentration of point defects in the anionic and cationic sublattices of the crystal. Diffusion of the halogen vacancies along the 63 axis results in the formation of complicated defects when they combine with the oxygen ions replacing the halogens. In [i, 2] it was shown that the formation of such complexes in unactivated fluorapatite and chlorapatite takes place according to a mechanism involving charge compensation of vacancies of different sign, which is highly probable from the point of view of the maintenance of the electrical neutrality of the crystal.