Function Of Mg Concentration Research Articles

Achievable hole concentration at room temperature as a function of Mg concentration for MOCVD-grown p-GaN after sufficient annealing

Relationship between the hole concentration at room temperature and the Mg doping concentration in p-GaN grown by MOCVD after sufficient annealing was studied in this paper. Different annealing conditions were applied to obtain sufficient activation for p-GaN samples with different Mg doping ranges. Hole concentration, resistivity and mobility were characterized by room-temperature Hall measurements. The Mg doping concentration and the residual impurities such as H, C, O and Si were measured by secondary ion mass spectroscopy, confirming negligible compensations by the impurities. The hole concentration, resistivity and mobility data are presented as a function of Mg concentration, and are compared with literature data. The appropriate curve relating the Mg doping concentration to the hole concentration is derived using a charge neutrality equation and the ionized-acceptor-density [ ] (cm−3) dependent ionization energy of Mg acceptor was determined as = 184 − 2.66 × 10−5 × [ ]1/3 meV.

Assessment of MgHf4P6O24 Solid-State Electrolyte in High-Temperature Electrochemical Mg-Sensors

The chemical synthesis of MgHf4P6O24 solid-state electrolyte was achieved using a modified sol-gel method by directly substituting the B-site in MgZr4P6O24 solid-state electrolyte [1], resulting in a considerably low activation energy of Ea = 0.74 ± 0.04 eV and a promising ionic conductivity of 4.52 x 10-4 Scm-1 at 747 oC. Using TGA-DSC measurement data, the synthesised xerogel powders were calcined at relatively low temperature of 800-900 oC, while the calcined nanopowders were pressed into pellets of 13 mm diameter (Ø) and 3.8 mm thickness with a uniaxial steel die at 5 kN compressive pressure, and later sintered at 1000 ≤ T oC ≤ 1550. However, 1300 oC was adapted as the sintering temperature in this study because the optimum samples density and composition stability were achieved at 1300 oC. X-ray diffraction reveals a good crystallinity of the calcined nanopowders phase having an average crystallite size of 20±2 nm and 42±2 nm at 800 oC and 900 oC, respectively, indicating that crystallite size increases as a function of calcination temperature, which is consistent with the TGA-DSC profiles and confirmed using HRTEM.The sintered MgHf4P6O24 solid-state electrolyte was subsequently characterised for their electrical and thermodynamic properties, identifying reliable ionic and transport data of the solid-state electrolyte. Furthermore, the average transport number of Mg2+-cations in the MgHf4P6O24 solid-state electrolyte measured as a function of Mg concentration in liquid Al is 0.84 ± 0.03. The ionic conductivity and emf data of the novel solid-state electrolyte in this study was compared with those of MgZr4P6O24 electrolyte [2-4], showing similar trend which defines the similarity in both chemical and structural properties of the B-site elements on the periodic table.Relying on the structural, chemical stability and ionic conductivity data characterised in this study, the electrochemical Mg-sensor was fabricated. The high-temperature electrochemical Mg-sensor was fabricated using the highly conducting Mg2+-cation solid-state electrolyte characterised in this study and a biphasic powder mixture of MgCr2O4 + Cr2O3 + O2 reference electrode in air, and testing in liquid Al alloys at 700 ± 5 oC after successful variation of Mg concentration using electrochemical method was achieved and the test rig is presented in Fig.1 [1-3]. The testing outcome shows a linear dependence of sensor voltage on the logarithm of Mg concentration. MgHf4P6O24 solid-state electrolyte has been identified in this study to have useful applications during refining, virgin metals alloying and scrap metal recycling for the benefit of our environment and depleting climate. Figure 1. Schematic of high-temperature electrochemical Mg-sensor test rig [1-3].

Reducing high carrier concentration in rocksalt-AlxSc1-xN with Mg acceptor doping

Aluminum scandium nitride (AlxSc1-xN) is an emerging III-nitride semiconductor that has attracted significant interest in recent years in surface and bulk acoustic resonators for its high piezoelectric coefficient and applications in high-power electronic devices. AlxSc1-xN stabilizes in the rock salt phase for x < 0.52 when deposited directly on (001) MgO substrates and has been utilized as a semiconductor in single-crystalline TiN/AlxSc1-xN metal/semiconductor superlattices for thermionic energy conversion, optical hyperbolic metamaterials, and the fundamental studies on heat and current transport in materials. However, due to the presence of oxygen impurities and native defects, such as nitrogen vacancies, sputter-deposited rock salt-AlxSc1-xN exhibits a high carrier concentration in the (2–4) × 1020 cm−3 range that leads to its Ohmic tunneling contact with metals and prevents observation of thermionic emission. In this Letter, we demonstrate that magnesium (Mg) acts as an efficient hole-dopant in r-AlxSc1-xN, increases its resistivity, and reduces its carrier concentration as a function of Mg concentration to as low as 1.4 × 1018 cm−3. A combination of spectroscopy, microscopy, and first-principles modeling demonstrate (a) epitaxial 001 oriented AlxSc1-xN:Mg growth for the first 35–75 nm and subsequent pyramidal growth with multiple in-plane orientations, (b) MgxNy to form a uniform and homogeneous solid solution with r-AlxSc1-xN without any precipitation, phase separation, or secondary phase formation, and (c) Mg-defect states are located deep inside the valence and conduction bands that leave behind a pristine r-AlxSc1-xN bandgap and band edges. The demonstration of Mg-hole doping in r-AlxSc1-xN marks significant progress in r-AlxSc1-xN thin film and superlattice-based devices.

Novel MgHf4P6O24 as a Solid Electrolyte in Mg-Sensors

In this study, a modified sol-gel chemical route was developed for synthesising MgHf4P6O24 multicomponent nanostructured ceramic oxide electrolytes. The chemical synthesis approach was determined by substituting the Zr4+ B-site in MgZr4P6O24 solid electrolyte [1-3] with Hf4+ reactive oxide, resulting in a considerably low activation energy (Ea = 0.74 ± 0.04 eV) and a promising ionic conductivity (4.52 x 10-4 Scm-1 at 747oC), for the novel MgHf4P6O24 solid electrolyte.The solid electrolyte was first calcined at a relatively low temperature range of 800-900oC, while the resultant calcined nanopowders were pressed into pellets of 13mm diameter (Ø) and 3.8mm thickness using a uniaxial steel press at 5kN compressive pressure. The pressed pellets were later sintered at 1000 ≤ T/oC ≤ 1550 temperature range. Meanwhile, calcination and sintering temperatures of the electroceramic electrolytes were maintained at 900 ≤ T/oC ≤ 1300oC after TGA-DSC thermal analysis and densification measurements; An optimum density and stable thermodynamic composition of the solid oxide pellets were also achieved at 1300oC. X-ray diffraction and rietveld analysis reveals a good crystallinity of the solid electrolyte with an average crystallite size of 20±2 nm and 42±2 nm at 800oC and 900oC, respectively, this indicates that crystallite size increases as a function of calcination temperature, which is consistent with the TGA-DSC thermal analysis profiles and confirmed using HRTEM. Interestingly, the refined crystallographic data and conductivity properties of the novel MgHf4P6O24 solid electrolyte characterised in this study was reported for the first time. The MgHf4P6O24 solid electrolyte characterised for their electrical and thermodynamic properties portray reliable ionic and transport properties of the solid electrolyte; The average transport number for Mg2+-cations in MgHf4P6O24 solid electrolyte measured as a function of Mg concentration in molten Al is 0.84±0.03. Ionic conductivity and thermodynamic stability of the solid electrolyte in this study was compared to those of MgZr4P6O24 electrolyte [1, 3], which shows novel improvement in the ionic conductivity and thermodynamic properties of both solid oxide electrolytes.Relying on the structural, thermodynamic stability and ionic conductivity data in this study, Mg-sensor probes were designed and fabricated, then tested in molten Al at 700±5oC, using the electrochemical method illustrated in Figure 1[3]. In application, a high-temperature Mg-sensor probe was fabricated using the Mg2+-cation conductors characterised in this study by incorporating a biphasic powder mixture of MgCr2O4+Cr2O3 ceramic reference electrode in air, showing promising trend after successfully sensing Mg dissolved in molten Al alloys at 700±5oC. A linear dependence of sensor voltage on the logarithm of Mg concentration was obtained. The thermodynamic activity of Mg in molten Al shows a rather negative deviation from Raoult's law [4]. MgHf4P6O24 solid electrolyte has useful potential applications in high-temperature Mg-sensors during refining, virgin metals alloying and scrap metal recycling for improved environmental sustainability and climate change. Figure 1. A schematic of high-temperature Mg-sensor test rig [3].

Assessment of MgHf4P6O24 Electroceramic Oxide Electrolyte in High-Temperature Electrochemical Sensor for Sensing Mg in Non-Ferrous Alloys

The chemical synthesis of MgHf4P6O24 multicomponent nanostructured ceramic oxide electrolyte was achieved using a modified sol-gel chemical process by substituting the tetravalent Zr4+ B-site in MgZr4P6O24 solid-state electrolyte [1, 2] with tetravalent Hf4+ ceramic oxide resulting in a considerably low activation energy (Ea = 0.74 ± 0.04 eV), promising ionic conductivity (4.52 x 10-4 Scm-1 at 747oC), electroceramic MgHf4P6O24 solid-state electrolyte.MgHf4P6O24 solid-state electroceramic oxide electrolyte was calcined at a relatively low temperature range of 800-900oC, the calcined nanopowders were pressed into pellets of 13mm diameter (Ø) and 3.8mm thickness with a uniaxial steel die at 5kN compressive pressure and sintered at 1000 ≤ T/oC ≤ 1550 temperature range. However, 1300oC was adopted as the sintering temperature in this study haven achieved optimum density and stable sample composition at that temperature. X-ray diffraction reveals a good crystallinity of the electroceramic oxide with an average crystallite size of 20±2 nm and 42±2 nm at 800oC and 900oC, respectively, indicating that crystallite size increases as a function of calcination temperature, which is very consistent with the simultaneous TGA-DSC thermal analysis profiles and confirmed using HR-TEM. The refined crystallographic data and ionic conductivity properties of the novel MgHf4P6O24 ceramic oxide solid-state electrolyte was reported for the first time in this study. SEM-EDS characterisation technique was used for determining both structural and compositional homogeneity. The sintered MgHf4P6O24 electroceramic oxide electrolyte was characterised for their electrical and thermodynamic properties thereby identifying reliable ionic and transport properties of the electroceramic oxide; The average transport number for Mg2+-cations in MgHf4P6O24 electroceramic oxide electrolyte measured as a function of Mg concentration in molten Al is 0.84±0.03. The ionic conductivity and thermodynamic analysis of the novel solid-state electroceramic oxide electrolyte in this study was compared with those of MgZr4P6O24 electrolyte [3], showing novel improvement in the trend of the ionic conductivity and thermodynamic properties of both electroceramic oxide electrolytes.Relying on the structural, chemical stability and ionic conductivity data characterised in this study, solid-state electrochemical Mg-sensor was designed and fabricated, then testing of the high-temperature Mg-sensor in molten Al alloys by the electrochemical method was achieved as shown in Figure 1 [3]. The novel high-temperature solid-state Mg-sensor was fabricated using the novel high conducting Mg2+-cation solid-state electroceramic oxide electrolyte characterised in this study by incorporating a biphasic powder mixture of MgCr2O4+Cr2O3 solid-state ceramic reference electrode in air, showing promising trend after successfully sensing Mg dissolved in molten Al alloys at 700±5oC. A linear dependence of sensor voltage on the logarithm of Mg concentration was obtained. The thermodynamic activity of Mg in molten Al alloy shows a rather negative deviation from Raoult's law. Solid-state MgHf4P6O24 electroceramic oxide electrolyte has useful potential applications in solid-state Mg-sensors during refining, virgin metals alloying and scrap metal recycling for the benefit of our environment and depleting climate.

Heavy Mg Doping to Form Reliable Rh Reflective Ohmic Contact for 278 nm Deep Ultraviolet AlGaN-Based Light-Emitting Diodes

We investigated the electrical property of reflective non-alloyed Rh contacts to p-Al0.45Ga0.55N contact layers and the performance of 278 nm flip-chip (FC) LEDs with the Rh and Ni/Au contacts as a function of Mg concentration. The three contact layers contained Mg concentration of 5.7 × 1019 cm−3 (sample A), 1.0 × 1020 cm−3 (sample B), and 1.4 × 1020 cm−3 (sample C). The Rh contacts to the sample A showed non-ohmic behaviour, while the samples B and C were ohmic with contact resistivity of 3.2 × 10−1 and 3.4 × 10−2 Ωcm2, respectively. The FC-LEDs with the sample A, B, and C with the Rh contacts yielded forward voltages of 7.26, 6.24, and 6.30 V, and output power of 10.46, 10.85, and 10.44 mW at 50 A cm−2, respectively, whereas that with the sample C (Ni/Au contact) gave 6.51 V and 6.26 mW. The FC-LEDs with p-Al0.55Ga0.45N (sample D) and p-Al0.61Ga0.39N (sample E) contact layers (with Mg dopant of 8.0 × 1019 cm−3) displayed forward voltage of 7.41 and 8.72 V at 50 A cm−2 and output power of 11.88 and 15.25 mW, respectively. The Wall-plug efficiency of the sample C, D, and E was estimated to be 3.31, 3.21, and 3.50%, respectively. These results show FC-LEDs fabricated with highly Mg-doped p-AlGaN and Rh contact demonstrate reliable performance upon operating at 100 A cm−2.

Chemical controls on ikaite formation

ABSTRACTThe hydrated carbonate mineral ikaite (CaCO3·6H2O) is thermodynamically unstable at all known conditions on Earth. Regardless, ikaite has been found in marine sediments, as tufa columns and in sea ice. The reason for these occurrences remains unknown. However, cold temperatures (<6°C), high pH and the presence of Mg2+ and SO42– in these settings have been suggested as factors that promote ikaite formation. Here we show that Mg concentration and pH are primary controls of ikaite precipitation at 5°C. In our experiments a sodium carbonate solution was mixed with seawater at a temperature of 5°C and at a constant rate. To test the effect of Mg2+ and SO42– we used synthetic seawater which allowed us to remove these elements from the seawater. The pH was controlled by different ratios of Na2CO3 and NaHCO3 in the carbonate solution. We found that ikaite precipitated when both seawater and synthetic seawater from which SO4 had been removed were used in the experiments. However, ikaite did not precipitate in experiments conducted with synthetic seawater from which Mg had been removed. In these experiments, calcite precipitated instead of ikaite. By varying the Mg concentration of the synthetic seawater and the pH of the sodium carbonate solution, we constructed a kinetic stability diagram for ikaite and calcite as a function of Mg concentration and pH. One possible explanation of our finding is that Mg2+ inhibits calcite nucleation and thereby allows metastable ikaite to form instead.

Density functional theory calculations for evaluation of phosphorene as a potential anode material for magnesium batteries.

We have systematically investigated black phosphorus and its derivative – a novel 2D nanomaterial, phosphorene – as an anode material for magnesium-ion batteries. We first performed Density Functional Theory (DFT) simulations to calculate the Mg adsorption energy, specific capacity, and diffusion barriers on monolayer phosphorene. Using these results, we evaluated the main trends in binding energy and voltage as a function of Mg concentration. Our studies revealed the following findings: (1) Mg bonds strongly with the phosphorus atoms and exists in the cationic state; (2) Mg diffusion on phosphorene is fast and anisotropic with an energy barrier of only 0.09 eV along the zigzag direction; (3) the theoretical specific capacity is 865 mA h g−1 with an average voltage of 0.833 V (vs. Mg/Mg2+), ideal for use as an anode. Given these results, we conclude that phosphorene is a very promising anode material for Mg-ion batteries. We then expand our simulations to the case of bulk black phosphorus, where we again find favorable binding energies. We also find that bulk black phosphorous must overcome a structural stress of 0.062 eV per atom due to a volumetric expansion of 33% during magnesiation. We found that the decrease in particle size is good to increase its specific capacity.

Effect of magnesium substitution on the magnetic properties of diluted magnetic spinels Ni1-xMgxFe2O4

The magnetic properties of Ni-Mg ferrites with compositions Ni1-xMgxFe2O4, have been studied using the mean field theory and high temperature series expansion theory (HTSE), extrapolated with the Padé approximants method. The nearest neighbour super-exchange interactions for intra-sites and inter-sites of the Ni-Mg ferrites in the range 0 ≤ x ≤ 1 have been computed using the distribution method of magnetic cations. The transition temperature TC is calculated as a function of Mg concentration. The critical exponent associated with the magnetic susceptibility was then deduced. The obtained results are in good agreement with experimental results and critical exponent values are consistent with those suggested by the universality hypothesis.

Temperature-dependent optical transitions of sol–gel derived Zn1−xMgxO alloy films

The effect of alloy-composition on optical properties of sol–gel derived Zn1−xMgxO films (0⩽x⩽0.12), was investigated by absorption and photoluminescence spectroscopy. Alloy-clustering induced broadening of emission-linewidth is negligible in the sol–gel derived Zn1−xMgxO alloys. Analyzing the temperature-dependent band-gap shrinkage in the Zn1−xMgxO alloys based on Pässler’s two-oscillator model enables us to precisely determine the strength of electron–phonon interaction as a function of Mg-concentration. The results reveal that the coupling-strength slightly decreases as Mg-composition increases in the Zn1−xMgxO alloys. Moreover, the phonon-dispersion coefficient, associated with an average effective phonon-energy (∼38meV), is approximately 0.5 and hardly changes with Mg-composition in the Zn1−xMgxO alloy films.

OH− absorption and nonvolatile holographic storage properties in Mg:Ru:Fe:LiNbO3 crystal as a function of Mg concentration

Mg:Ru:Fe:LiNbO3 crystals with various concentrations of MgO (in mole) and fixed content of RuO2 and Fe2O3 (in mass) are grown with the Czochralski method from the congruent melt. Their infrared transmission spectra are measured and discussed to investigate the defect structure. With the increase of Mg2+ concentration the blue nonvolatile holographic storage capability is enhanced. The nonvolatile holographic storage properties of dual-wavelength recording of Mg(7 mol%):Ru:Fe:LiNbO3 nonvolatile diffraction efficiency, response time, and nonvolatile sensitivity reach 59.8%, 70 s, and 1.04 cm/J, respectively. Comparing Mg(7 mol%):Ru:Fe:LiNbO3 with Ru:Fe:LiNbO3 crystal, the response time is shortened apparently. The nonvolatile diffraction efficiency and sensitivity are raised largely. The mechanism in blue photorefractive nonvolatile holographic storage is discussed.

Effect of Mg substitution on electromagnetic properties of NiCuZn ferrite

Mg substituted NiCuZn ferrites were prepared through sol–gel method using polyvinyl alcohol (PVA) as a chelating agent. The samples after annealing at 500°C to remove PVA were sintered at 950°C for 1h. The structural and electromagnetic properties of the samples were investigated. All the samples showed single phase spinel structure with increased lattice constant as a function of Mg concentration. The morphology reveals polyhedral shaped grains with increased grain size as a function of Mg composition. Dielectric parameters showed low values at higher frequencies. The initial permeability increased with Mg substitution in place of Ni in accordance with the microstructure. The samples sintered at low temperature having low dielectric losses and improved permeability along with the high frequency stability of permeability find applications in multilayer chip inductors.

The effect of Mg doping on the dielectric and tunable properties of Pb0.3Sr0.7TiO3 thin films prepared by sol–gel method

Mg doped Pb0.3Sr0.7TiO3 (PST) thin films were fabricated by the sol–gel method on a Pt/Ti/SiO2/Si substrate. The microstructure, surface morphology, dielectric and tunable properties of PST thin films were investigated as a function of Mg concentration. It is found that proper Mg doping dramatically improves the dielectric loss (0.0088 @ 1 MHz), furthermore, the crystallinity, dielectric constant, and tunability of films simultaneously decrease with the increase of Mg content. The 2 mol% Mg doped PST thin film shows the highest figure of merit (FOM) value of 36.8 for its the smallest dielectric loss and upper tunability. The dependence of Rayleigh coefficient on the doping concentration was examined, which indicated that the reduction of dielectric constant and tunability of films should be related to the \(\mathrm{Mg}''_{\mathrm{Ti}}\)–\(\mathrm{V}_{\mathrm{O}}^{\bullet\bullet}\) defect dipoles pinning the domain wall motion of residual polar clusters in PST.

Electrical Properties of Magnesium Incorporated Zinc Tin Oxide Thin Film Transistors by Solution Process

Zinc tin oxide (ZTO) films were fabricated on SiO2/Si substrate as a function of Mg concentration (the ratio of 3 to 10 atomic%) using a spin-coating process. For the characterization of thin film transistors (TFTs), Zn0.3Sn0.70 channel TFT exhibited a higher on/off ratio compared to Zn0.5 Sn.0.5O channel TFT because the higher Sn concentration can induce more charge carriers. 3 atomic% Mg incorporated Zn0.3Sn0.7O channel TFTs showed stable electrical performances such as I(on/off) - 1 x 10(7), micro(sat) = 1.40 cm2 V(-1) s(-1), and S = 0.39 V/decade. However, 10 atomic% Mg incorporated Zn0.3Sn0.7O channel TFTs deteriorated their electrical performances due to Mg segregation. The Mg incorporated Zn0.3Sn0.7O channel TFTs effectively suppress off-current and threshold voltage change during positive gate bias stress due to their strong bonding with oxygen.

Synthesis and magnetic properties of ferrites spinels Mg xCu 1− xFe 2O 4

Polycrystalline Mg 0.6Cu 0.4Fe 2O 4 ferrites have been prepared using solid-state reaction technique. Their structural and magnetic properties have been studied, using X-ray diffraction and magnetic measurements. Using mean field theory and high-temperature series expansions (HTSE), extrapolated with the padé approximants method, the magnetic properties of Mg 1− x Cu x Fe 2O 4 have been studied. The nearest neighbor super-exchange interactions for intra-site and inter-site of the Mg 1− x Cu x Fe 2O 4 ferrites spinels, in the range 0≤ x≤1, have been computed using the probability approach, based on Mössbauer data. The Curie temperature T c is calculated as a function of Mg concentration. The obtained theoretical results are in good agreement with experimental ones obtained by magnetic measurements.

Carrier dynamics in (ZnMg)O alloy materials

AbstractCarrier recombination dynamics in Zn1–xMgxO alloys were studied by time‐resolved photoluminescence as function of Mg concentration and lattice temperature for different emission and excitation energies. Disorder and carrier localization effects are found to play a significant role, becoming increasingly important for lower temperatures and higher Mg concentrations.Emission energy dependent dynamics were analyzed by the application of a theoretical model, yielding a characteristic localization energy of 60 ± 15 meV for the sample with the highest Mg concentration of x = 0.21. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Determination of the solubility range and crystal structure of the Mg-rich ternary compound in the Ca–Mg–Zn system

The homogeneity range and crystal structure of the Mg-rich ternary solid solution has been determined using SEM, EPMA/WDS, TEM and X-ray diffraction. This compound has the Ca 3Mg xZn 15−x (4.6 ≤ x ≤ 12) formula at 335 °C. The refinement of the XRD patterns was carried out by Rietveld analysis, XRD data has shown that this solid solution crystallizes in hexagonal structure having P63/mmc (194) space group and Sc 3Ni 11Si 4 prototype. The lattice parameters decrease linearly with decreasing Mg content obeying Vegard’s law. The fractional atomic occupancy of 6h, 4f, 2b and 12k sites of this compound are function of Mg concentration. Focused Ion Beam has been used to lift TEM specimen of the ternary compound and the hexagonal structure has been confirmed by means of selected area electron diffraction data. Based on the atomic occupancy results and the crystallographic details, a three sublattice (Ca)(Zn)(Mg, Zn) 4 model is proposed for this compound.

The Effect of Mg Incorporation on Structural and Optical Properties of Zn2GeO4 : Mn Phosphor

The effect of Mg incorporation on structural and optical characteristics of rhombohedral doped with manganese was systematically studied, fixing the concentration of manganese at 2 atom %. The phosphors were prepared by a high-temperature solid-state-reaction technique. The structural properties were studied using X-ray diffraction (XRD) and optical properties were characterized by diffuse reflectance spectra (DRS), photoluminescent excitation (PLE), and photoluminescent (PL) emission spectra. The XRD and DRS analyses reveal that Mg can be successfully alloyed in up to and forms a solid solution. The PL emission was maximum when 5 atom % Zn was replaced with Mg in comparison to an Mg-free sample. The mechanism of luminescence is identified as resonant transfer from a subbandgap state in the host to . The PLE and DRS spectra of exhibited a blue shift with an increase in Mg concentration. The cell volume was found to be a monotonously increasing function of Mg concentration up to , beyond which it varied randomly.

The influence of Mg doping on the dielectric and tunable properties of (Ba 0.6Sr 0.4) 0.925K 0.075TiO 3 thin films fabricated by sol–gel method

(Ba 0.6Sr 0.4) 92.5%K 7.5%TiO 3 (BSTK) thin films doped by Mg from 0 to 6 mol% were fabricated by sol–gel method on a Pt/TiO 2/SiO 2/Si substrate. The structure and surface morphology of Mg-doped BSTK thin films were investigated as a function of Mg concentration by X-ray diffraction and scanning electron microscopy. The dielectric measurements were conducted on metal–insulator–metal capacitors at the frequency from 100 Hz to 1 MHz and at room temperature. It is found that the Mg concentration in Mg-doped BSTK thin films has a strong influence on the material properties including surface morphology, dielectric and tunable properties. Increasing of Mg content leads to simultaneous decreasing of grain size, dielectric constant, dielectric loss and tunability of Mg-doped BSTK films. The effects of Mg doping on the microstructure, dielectric and tunable properties of Mg-doped BSTK thin films were analyzed. The BSTK thin film exhibited the highest dielectric constant of 1040 and the largest tunability of 73.6%. Mg-doped BSTK thin film (6 mol%) showed the smallest dielectric loss of 0.0088 at 1 MHz. Figure of merit (FOM) of Mg-doped BSTK thin films with the optimal Mg content of 4 mol% showed maximum value of approximately 31.21 and its dielectric constant, dielectric loss and tunability were about 336, 0.014 and 44.45%, respectively. These results suggest that improved dielectric properties such as tunability and dielectric loss of 4 mol% Mg-doped BSTK films show the potential in tunable devices.

Effect of Mg concentration on the domain reversal of Mg-doped LiNbO3

MgO-doped LiNbO3 (MgLN) crystal has been produced using the Czochralski method. The domain reversal characteristics of the MgO-doped LiNbO3 single crystals with different Mg doping levels have been investigated, and the switching field is found to decrease with the increasing of Mg concentration. The switching field for the domain reversal in the MgLN crystal doped with 6.5 mol % MgO was ∼4.6kV∕mm. This is about one-fifth of the switching field for the congruent crystal. The resistance of the poling MgLN crystals as a function of Mg concentration was measured, and the influence of doping Mg on domain reversion for Mg-doped LiNbO3 is discussed, and explain the physical mechanism of the polarization switching of the MgLN crystals.