Low Doping Concentration Research Articles

High piezoelectric and dielectric constant of Fe/In Co‐doped KNN‐based ceramics regulated by lattice distortion

AbstractThe new (0.96‐x)(K0.48Na0.52Nb0.96Sb0.04)O3‐0.04(Bi0.5Ag0.5)ZrO3‐x(Fe2O3‐In2O3) ceramics with high dielectric, and electromechanical coupling properties were designed. In this work, the effect of KNN‐based ceramics lattice distortion (c/a) and microstructure on the electrical properties was explored by varying the doping amount of Fe3+ and In3+. The problem of a large number of oxygen vacancies generated by the volatilization of K and Na can be well solved by introducing Fe3+ and In3+. The bulk density increases significantly and the maximum value is about 4.52 g/cm3.The sample with x = 0.003 has the smallest c/a, and exhibits the best piezoelectric and dielectric properties (d33 = 536 pC/N, εr = 3432 and kp = 55.8 %). Low doping concentration of Fe2O3 is considered a “soft” addition for KNN‐based piezoelectric ceramics. The study of this mechanism provides a new idea to regulate the electrical performance of KNN‐based ceramics.

Cross‐Plane Thermal Transport in Acceptor‐Doped Thiophene‐Based Polymer Thin Films Investigated by the 3‐Omega Method

Thermal transport properties in acceptor‐doped thiophene‐based polymer films such as poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) and poly[2,5‐bis(3‐tetradecylthiophen‐2‐yl)thieno[3,2‐b]thiophene] (PBTTT) are investigated using the cross‐plane 3‐omega method. A bilayer structure consisting of polymer semiconductors sequentially doped with 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4TCNQ) and poly(methylmethacrylate) (PMMA) on a Si substrate is originally prepared by spin coating and employed to prevent leakage current from a heater wire during the 3‐omega measurements. Nondoped PBTTT thin film reveals an intrinsic cross‐plane thermal conductivity of 0.49 W m−1 K−1, which is higher than that for nondoped P3HT film (0.20 W m−1 K−1). X‐ray diffraction (XRD) analysis suggests that higher crystallinity of PBTTT films may result in higher thermal conductivity. The intrinsic thermal conductivity of P3HT and the interfacial thermal resistance between PMMA and P3HT are slightly increased at a low doping concentration (0.01 mg mL−1) and decreased at a higher doping concentration of 0.1 mg mL−1, whereas F4TCNQ doping reduces these values monotonously in the case of PBTTT layers. Furthermore, excess doping occurs only for P3HT and increments both intrinsic thermal conductivity and thermal resistance at PMMA/P3HT interface. The observed trend in the cross‐plane thermal transport caused by the sequential doping can be attributed to the differences between P3HT and PBTTT in their crystallinity and effective doping levels.

Spectral study and energy transfer analysis of Er:YAlO3 crystals

Er:YAP crystals have been proved promising mid-infrared gain materials but there is few systematic study focused on the relationship between the doping concentration and spectral properties. In this work, Er:YAP crystals with a series of doping concentrations(0.1 at.%, 1 at.%, 5 at.%, 10 at.%, 15 at.%, 30 at.%) were fast grown successfully by a modified laser-heated pedestal growth (LHPG) method. Through investigating doping concentration dependent spectral characteristics in detail, we found that the cross relaxation process (Er3+: 4S3/2+4I15/2 → 4I9/2+4I13/2) gets significantly enhanced with the doping concentration when it is below 5 at.%, and eventually tends to saturate. And the cooperative up-conversion process (Er3+: 4I13/2+4I13/2 → 4I15/2+4I9/2) conducive to high-efficiency ∼3 μm laser starts to dominate when the doping concentration is 5 at.% or even less. This result demonstrates the potential of Er:YAP crystals to achieve high-power and high-efficiency laser output under relatively low Er-doping concentration, and offers a valuable guidance for doping optimization of Er:YAP systems.

On the role of Gd3+ ions in enhancement of UV emission from Yb3+–Tm3+ up-converting LiYF4 nanocrystals

Materials capable of emitting ultraviolet (UV) radiation are sought for applications ranging from theranostics or photodynamic therapy to specific photocatalysis. The nanometer size of these materials, as well as excitation with near-infrared (NIR) light, is essential for many applications. Tetragonal tetrafluoride LiY(Gd)F4 nanocrystalline host for up-converting Tm3+–Yb3+ activator-sensitizer pair is a promising candidate to achieve UV–vis up-converted radiation under NIR excitation, important for numerous photo-chemical and bio-medical applications. Here, we provide insights into the structure, morphology, size and optical properties of up-converting LiYF4:25%Yb3+0.5%Tm3+ colloidal nanocrystals, where 1, 5, 10, 20, 30 and 40% of Y3+ ions were substituted with Gd3+ ions. Low gadolinium dopant concentrations modify the size and up-conversion luminescence, while the Gd3+ doping that is exceeding the structure resistance limit of the tetragonal LiYF4 results in appearance of foreign phase and significant decrease of luminescence intensity. The intensity and kinetic behavior of Gd3+ up-converted UV emission are also analyzed for various gadolinium ions concentrations. The obtained results form a background for further optimized materials and applications based on LiYF4 nanocrystals.

Defect evolution and effect on structure and electric properties of A/B site Sm doped BaTiO3 sintered in different atmospheres

BaTiO3 ceramics doped with different contents of Sm (0.5-7 mol%) are prepared by a homogeneous precipitation method and sintered in air (A-xSm) and reducing (R-xSm) atmosphere respectively. With the increase of doping amount, the phase structure of Sm-doped BaTiO3 ceramics gradually changes from tetragonal phase to cubic phase, and the cubic phase is stronger in R-xSm. In the air atmosphere, Sm ions preferentially replace Ba sites as donors at low doping concentration, which is easy to convert Ti4+ ions into Ti3+ ions, resulting high dielectric constant (>104) and semiconductor like properties. As the doping amount increases, Sm ions start to replace Ti sites as acceptors to generate oxygen vacancies, which capture the electrons generated by donor doping, thus decreasing the percentage of Ti3+ ions. As a result, the dielectric loss and permittivity are decreased, and the electrical insulation properties of A-xSm ceramics are gradually improved. However, in the reducing atmosphere, oxygen atoms in the lattice are easy to escape, resulting in many oxygen vacancies and free electrons. The increase of oxygen vacancy inhibits the substitution of Sm ion to Ti site, and the free electron leads to the increase the percentage of Ti3+ ions and R-xSm ceramics exhibit semiconductor like properties. Thermally stimulated depolarization currents (TSDC) testing verified that oxygen vacancies of A-xSm ceramics mainly capture space charges, and a small part of oxygen vacancies form defective dipoles [2SmTi′−VO..]. The complex impedance test shows that the change of resistivity of A-xSm ceramics is mainly closed to the influence of Sm doping on the grain not grain boundary of BaTiO3 ceramic.

Influence of non-magnetic ions doping on structural, morphological, optical, and magnetic properties of nanocrystalline zinc oxide powders

In this research study, nanocrystalline non-magnetic ion-doped zinc oxide powders are synthesized through sol-gel auto combustion with a variety of different ions (Mg, Al, and Ca) at a range of concentrations (0, 5%, 10%, 20% mol). X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), filed-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectrometer (XPS), UV–visible diffuse reflectance spectroscopy (UV-DRS), photoluminescence spectroscopy (PL), and vibrating sample magnetometry (VSM) were then used to investigate the calcined products, whereupon the structures, chemical bonds, surface texture, chemical composition, morphologies, particle size, surface elemental composition, electronic state, optical and fluorescence properties including magnetism were reported for each of the samples. From XRD it could be determined that the introduction of minuscule quantities of magnesium and calcium ions to the zinc oxide powder produced solutions of hexagonal solid MgZnO and CaZnO, while composites of Mg/ZnO, CaO/ZnO, Al2O3/ZnO could also be observed, without impurity phases. Textural properties of these modified samples observed from SEM, FE-SEM, and TEM were superior to that of the pure ZnO. XPS studies confirmed the substitution of Zn2+ by Mg2+ and Ca2+ for the samples of low doping concentration. UV-DRS analysis showed that samples which had been optimally modified exhibited improved levels of absorption when compared to visible spectral observations of the pure sample. In comparison to the pure sample, the modified samples also showed higher bandgap energy (Eg). In the pure sample, violet and blue emission bands were seen in the PL spectra ranging from 350 to 430 nm, but these emissions showed significant changes in intensity as the concentration of non-magnetic ions was increased. Furthermore, VSM results revealed that diamagnetism of zinc oxide can be adjusted through the introduction of non-magnetic ions to paramagnetism and ferromagnetism.

Study of the Mechanisms of Polymorphic Transformations in Zirconium Dioxide upon Doping with Magnesium Oxide, as Well as Establishing the Relationship between Structural Changes and Strength Properties

The aim of this work is to study the mechanisms of polymorphic transformations in ZrO2 ceramics doped with MgO with different concentrations during thermal isochronous annealing, as well as the effect of the phase composition of ceramics on the change in strength properties and resistance to mechanical stress. Solving the problem of polymorphic transformations in zirconium dioxide by doping them with MgO will increase the resistance of ceramics to external influences, as well as increase the mechanical strength of ceramics. According to the data of X-ray phase analysis, it was found that the addition of the MgO dopant to the composition of ceramics at the chosen thermal annealing temperature leads to the initialization of polymorphic transformation processes, while changing the dopant concentration leads to significant differences in the types of polymorphic transformations. In the case of an undoped ZrO2 ceramic sample, thermal annealing at a temperature of 1500 °C leads to structural ordering due to the partial removal of deformation distortions of the crystal lattice caused by mechanochemical grinding. During the study of the effect of MgO doping and polymorphic transformations in ZrO2 ceramics on the strength properties, it was found that the main hardening effect is due to a change in the dislocation density during the formation of a ZrO2/MgO type structure. At the same time, polymorphic transformations of the m—ZrO2 → t—ZrO2 type have a greater effect on hardening at low dopant concentrations than t—ZrO2 → c—ZrO2 type transformations.

Acceptor doping and actuation mechanisms in Sr-doped BiFeO3[sbnd]BaTiO3 ceramics

BiFeO3-BaTiO3 (BF-BT) ceramics are important multiferroic materials, which are attracting significant attention for potential applications in high temperature lead-free piezoelectric transducers. In the present study, the effects of Sr2+ as an acceptor dopant for Bi3+, in the range from 0 to 1.0% (in mole), on the structure and ferroelectric/piezoelectric properties of 0.7BiFeO3-0.3BaTiO3 ceramics were evaluated. The use of a post-sintering Ar annealing process was found to be an effective approach to reduce electrical conductivity induced by the presence of electron holes associated with reoxidation during cooling. A low Sr dopant concentration (0.3%, in mole) yielded enhanced ferroelectric (Pmax ∼ 0.37 C/m2, Pr ∼ 0.30 C/m2) and piezoelectric (d33 ∼ 178 pC/N, kp ∼ 0.27) properties, whereas higher levels led to chemically heterogeneous core-shell structures and secondary phases with an associated decline in performance. The electric field-induced strain of the Sr-doped BF-BT ceramics was investigated using a combination of digital image correlation macroscopic strain measurements and in-situ synchrotron X-ray diffraction. Quantification of the intrinsic (lattice strain) and extrinsic (domain switching) contributions to the electric field induced strain indicated that the intrinsic contribution dominated during the poling process.

Regenerated Fiber Bragg Gratings in Large Mode Area Fibers for High-Temperature Sensing

Regenerated fiber Bragg gratings (RFBGs) have been created in large mode area (LMA) fibers, and their key properties for their application as high-temperature sensors were experimentally characterized for the first time. UV written Type-I seed gratings in standard single-mode fibers (SMF-28) and in low numerical aperture LMA fibers with 125 μm and 250 μm cladding diameters were regenerated, and their wavelength drift characteristics at high temperatures, their temperature sensitivities, and their mechanical strengths were tested and compared with each other. We found that low dopant concentrations in the fiber cores led to lower wavelength drift rates during and after regeneration. A temperature calibration from room temperature to 800 °C showed that LMA fibers have generally similar but slightly lower temperature sensitivities than SMF-28 fibers. The tensile strength tests showed that LMA fibers with 250 μm cladding diameter have similar tensile fracture stresses as SMF-28 fibers but four times larger tensile force tolerances because of their twofold fiber diameter. Our research shows that using LMA fibers for RFBGs offers significant advantages for high-temperature sensing than their counterparts in standard fibers, which are also applicable to other silica fiber-based high-temperature sensors.

Balance between thermal stability and operation speed realized by Ti gradient doping in Sb2Te3 phase-change memory

Phase-change memory (PCM) is one of the leading candidates for the next generation nonvolatile memory. As a growth-dominated crystalline material, Sb2Te3 is of rapid crystallization speed while its poor thermal stability limits its application. Doping Ti can significantly enhance its amorphous stability but inevitably slows down its crystallization speed. How to balance the contradiction between thermal stability and operation speed remains challenging. In this work, we proposed a gradient Ti-doped Sb2Te3 phase-change material and device. This gradient doping strategy compensates for the negative effect of Ti doping on the crystallization rate of Sb2Te3 via the template effect of the lower doping concentration layer. Very small lattice mismatch between the Sb2Te3 layers with different Ti doping concentrations is verified by x-ray diffraction characterization. The crystallization temperature of a gradient Ti-doped Sb2Te3 thin film is raised up to 172.6 °C and the same 50 ns operation speed as a pure Sb2Te3 device is achieved in the corresponding PCM device. Furthermore, the gradient distribution of Ti elements and the corresponding progressive crystallization phenomenon are verified by transmission electron microscopy revealing the microscopic origin of rapid crystallization speed. Therefore, with our gradient doping strategy, the amorphous stability is improved without sacrificing the crystallization speed in PCM.

2.1 kV (001)- β -Ga2O3 vertical Schottky barrier diode with high-k oxide field plate

We report a vertical β-Ga2O3 Schottky barrier diode (SBD) with BaTiO3 as field plate oxide on a low doped thick epitaxial layer exhibiting 2.1 kV breakdown voltage. A thick drift layer of 11 μm with a low effective doping concentration of 8 × 1015 cm–3 is used to achieve high breakdown voltage. Using the high-k dielectric with a dielectric constant of 248, the breakdown voltage increases from 816 V for the non-field-plated SBD to 2152 V (>2× improvement) for the field-plated SBD without compromising the on-state performance. The diode dimensions are varied to analyze the effect of edge high-field related leakage with reverse bias and also the effect of current spreading during forward operation. Very uniform distribution of breakdown voltages of 2152 ± 20 V are observed for the diode diameters from 50 to 300 μm for the field-plated SBDs. The on and off state power losses are also analyzed and compared with the non-field-plated devices and the switching losses are estimated analytically.

Dual Electric/Magnetic Field-Modulated Nematic Liquid Crystal Smart Window Based on the Supramolecular Doping Effect of Halloysite Nanotube Directors

Nowadays in the environmentally friendly society, smart windows have been viewed as one of the attractive energy-saving technologies for green buildings. However, some inherent defects on anisotropy and compatibility still greatly limit their practical applications. Thus, we first utilized hollow heterocharged halloysite (HAL) nanotubes as the doping agent to build up a 4-cyano-4′-pentylbiphenyl (5CB)-based supramolecular liquid crystal (LC) composite with excellent electro-optical properties. In particular, the chemical modification of 5CB blocks on the surface of HAL nanotubes (5CB-HAL) greatly improved HAL’s compatibility with the host 5CB. In the applied alternating current (AC) electric field with a low frequency (60 Hz), the vertically aligned 5CB-HAL-doped LC composites with a low doping concentration of 1.0 wt % exhibited outstanding electrochromic performances, including high contrast (82%), a rapid response of about 200 ms, low driving threshold (0.157 V/μm), a wide viewing angle (120°), and a smooth running of at least 10,000 cycles. In particular, in situ grown superparamagnetic iron (II, III) oxide nanoparticles above the HAL nanotube surface further endowed this LC system with fresh magnetic modulation and better light tuning. It is anticipated to provide a cheap, facile, reliable, and promising technology for high-performance bimodal smart windows.

Graded Mxene-Doped Liquid Metal as Adhesion Interface Aiming for Conductivity Enhancement of Hybrid Rigid-Soft Interconnection.

Hybrid rigid-soft electronic system combines the biocompatibility of stretchable electronics and the computing capacity of silicon-based chips, which has a chance to realize a comprehensive stretchable electronic system with perception, control, and algorithm in near future. However, a reliable rigid-soft interconnection interface is urgently required to ensure both the conductivity and stretchability under a large strain. To settle this demand, this paper proposes a graded Mxene-doped liquid metal (LM) method to achieve a stable solid-liquid composite interconnect (SLCI) between the rigid chip and stretchable interconnect lines. To overcome the surface tension of LM, a high-conductive Mxene is doped for the balance between adhesion and liquidity of LM. And the high-concentration doping could prevent the contact failure with chip pins, while the low-concentration doping tends to maintain the stretchability. Based on this dosage-graded interface structure, the solid light-emitting diode (LED) and other devices integrated into the stretchable hybrid electronic system could achieve an excellent conductivity insensitive to the exerted tensile strain. In addition, the hybrid electronic system is demonstrated for skin-mounted and tire-mounted temperature-test applications under the tensile strain up to 100%. This Mxene-doped LM method aims to obtain a robust interface between rigid components and flexible interconnects by attenuating the inherent Young's modulus mismatch between rigid and flexible systems and makes it a promising candidate for effective interconnection between solid electronics and soft electronics.

Slightly doped hydroxyapatite pigments of subtractive color with high near-infrared reflectance

A novel series of high near-infrared (NIR) reflective Ca5(PO4)3OH based pigments were synthesized by a solid-phase method. Slight single doping of Fe, Mn, and Cu can change white hydroxyapatite into yellow-orange, cyan, and red-violet, respectively. In the apatite-type structure, Fe ions would occupy the site of the Ca2+, Mn ions preferred to form MnO43− in place of PO43−, and Cu ions tended to stay in the hexagonal channel substituting the protons of OH−. When two of the elements were introduced into hydroxyapatite, the color of the co-doped materials followed the principle of subtractive color mixture. Because of the extremely low concentration of dopant, the structure of hydroxyapatite was kept undisturbed, and its high NIR reflectance was also maintained. This paper discussed chromatic properties, spectral analysis, crystalline structure, and morphology of both single-doped and co-doped samples. The economics, environment-friendly, and colorful Ca5(PO4)3OH based material is a potential cool pigment.

Mixed Microscopic Eu2+ Occupancies in the Next‐Generation Red LED Phosphor Sr[Li2Al2O2N2]:Eu2+ (SALON:Eu2+)

AbstractRed‐emitting narrow‐band phosphors are of utmost importance for next‐generation white‐light phosphor‐converted light‐emitting diodes (pc‐wLEDs) for improved efficacy and optimized correlated color temperatures. A promising representative crystallizing in an ordered variant of the UCr4C4 structure type is Sr[Li2Al2O2N2]:Eu2+ (SALON:Eu2+) emitting at a desirable wavelength of 614 nm. Despite an expected eightfold coordination of the Eu2+ ions by four N3− and O2− ions, respectively, the exact local coordination symmetry and a 1:1 ratio between the two types of ligands is not straightforwardly proven by X‐ray diffraction. Low‐temperature luminescence spectroscopy in conjunction with ligand field theory are powerful alternatives to resolve local features of Eu2+ as its excited 4f65d1 configuration reacts sensitively to the polarity of the ligands. The dominant emission at 614 nm shows pronounced vibronic fine structure at 10 K. In addition, weak emission bands can be resolved at 570 and 650 nm even at a low doping concentration of 0.5 mol% and are assigned to Eu2+ ions being eightfold coordinated by N3− and O2− ions in a ratio different from 1:1. Due to the feature of vierer ring‐type channels in SALON:Eu2+, those Eu2+ centers are sufficiently close for mutual energy transfer, which is characterized by time‐resolved luminescence at 10 K.

Insights into the role of Nb segregation on grain boundary structural transition and mechanical response in a Ni–Nb system

The role of Nb segregation on the grain boundary (GB) structural transformation and mechanical response has been studied in a binary Ni–Nb system through atomistic simulation. To investigate the effect of dopant concentration on the GB structural transitions, a Σ5 (310) GB has been created with the help of molecular statics simulation. Thereafter, hybrid Monte Carlo and Molecular dynamics (MD) simulations have been performed to segregate Nb atoms at the Σ5 (310) GB. At lower dopant concentrations, the Nb atoms preferably segregated at the tip of the kite structure. With an increase in dopant concentration and temperature, the Nb atoms segregated at other sites in the GB as well as in the matrix and the GB structure becomes disordered. The effect of doping on the mechanical behavior has been investigated by applying constant strain rate along X-direction through MD. The stress-strain curve of the Ni–Nb system at 300 K revealed an increase in the strength and ductility with the dopant concentration up to a certain limit (0.4 at. % Nb) and decreased thereafter. The superior mechanical response of the Ni-0.4Nb system is attributed to the formation of stacking faults and sessile dislocations during deformation. Stacking faults delay the formation of cracks while sessile dislocations impede the dislocation motion, resulting in higher ductility and strength. Contrarily, nucleation of voids and cracks takes place at a lower extent of strain, resulting in an early fracture in the pure Ni. However, the strength of the doped specimen is found to be lower than the undoped one at 700 K due to the early initiation of cracks in the disordered GB region of the former specimen. The comprehensive understanding of the effect of interfacial segregation on the structural and mechanical behaviour would open up new avenues for alloy design and the development of advanced materials.

Characterization of unintentional doping in localized epitaxial GaN layers on Si wafers by scanning spreading resistance microscopy

Localized epitaxy of gallium nitride (GaN) on silicon (Si) is studied, with the aim of achieving material compatible with 1200 V vertical devices, in particular an unintentional doping level <1 × 1016 cm−3, which is essential to have high quality devices. In this study, three mask materials (SiN, SiO2, Al2O3) are examined and the unintentional doping concentration in GaN layers grown by metal organic vapor phase epitaxy (MOVPE) is investigated by scanning spreading resistance microscopy (SSRM). The results from SSRM are verified by secondary ions mass spectroscopy (SIMS) and show that an unintentional doping concentration lower than 1016 cm−3 is achieved when Al2O3 is used as the mask material. This value is lower than any previous studies of localized GaN growth, and in addition, this is the first time that SSRM has been used to observe such low doping concentrations in GaN.

Highly transparent yttria ceramics with Nb2O5/Ta2O5 as novel sintering additives by pressureless vacuum sintering

AbstractHighly transparent yttria ceramics were fabricated by pressureless sintering with Nb2O5 or Ta2O5 as a novel sintering additive. The optical transmittance, microstructural evolution, and thermo‐mechanical properties of the samples were investigated. The optimal doping concentrations of Nb2O5 and Ta2O5 are 0.3 and 0.2 at.%, respectively, which are much lower compared to those of previously reported counterparts. The transmittance of the sample with 0.3 at.% Nb2O5 reaches 81.6% at 1100 nm and 72.4% at 400 nm (2 mm in thickness), similar transmittance was obtained in the sample with 0.2 at.% Ta2O5. The microhardness (∼7 GPa), fracture toughness (∼0.85 MPa·m1/2), and biaxial strength (∼200 MPa) of the present samples were confirmed to be comparable or even better compared to those of previously reported transparent yttria ceramics fabricated by pressureless sintering. Furthermore, the present samples, by virtue of the low doping concentrations, possessed relatively high thermal conductivity values (&gt;10 W/m·K), which substantially guaranteed high thermal shock resistance.

Phase equilibria and non-transformable tetragonal zirconia in ZrO2-RETaO4 systems and their stabilization mechanism: Experiments and calculations

The non-transformable tetragonal zirconia (t-ZrO2) in ZrO2-RETaO4 systems offers significant promise in the development of next generation thermal barrier coatings. This work focuses on the effects of rare-earth dopants on phase equilibria and phase stability of tetragonal zirconia in ZrO2-RETaO4 systems. Precursor-derived oxides were heat treated at 1500 °C to elucidate phase constitution by X-ray diffraction. The composition ranges of non-transformable t-ZrO2 in ZrO2-YbTaO4, ZrO2-DyTaO4 and ZrO2-GdTaO4 are measured to be about 30–41, 22–29 and 16–19 mol% RE0.5Ta0.5O2, respectively. However, non-transformable t-ZrO2 cannot be found in ZrO2-NdTaO4 and ZrO2–LaTaO4. Formation abilities of t-ZrO2 in ZrO2-RETaO4 systems are determined to be inversely proportional to the ionic radius of RE3+. Based on our calculations, stabilization mechanisms of non-transformable t-ZrO2 were considered to be related to degree of strain energy release and high-temperature decomposed reactions of the doped t-ZrO2. Firstly, RE-Ta pair dopants could relieve the strain energy of the strained tetragonal zirconia structure, which would prevent the displacive transformation of t-ZrO2→m-ZrO2. Secondly, the solid solubilities of RE-Ta dopants should be large enough to ensure the doped t-ZrO2 phase cannot decompose before inhibiting t-ZrO2→m-ZrO2. For large ionic radius of Nd3+ and La3+ dopants, the decomposed reactions of doped t-ZrO2 can take place even at very low dopant concentration, which explains the observations that t-ZrO2 cannot be detected in their whole compositions. The emerging results are useful to the development of appropriate thermal barrier coatings.

1651-V All-Ion-Implanted Schottky Barrier Diode on Heteroepitaxial Diamond With 3.6 × 10⁵ On/Off Ratio

In this letter, we have reported a lateral diamond Schottky barrier diode (SBD) that was fabricated on a heteroepitaxial diamond substrate using all ion-implantation processes. The SBD exhibited a lower reverse leakage current, which resulted in an unprecedentedly high rectification ratio of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.6\times 10^{{5}}$ </tex-math></inline-formula> when compared to ion-implanted diamond diodes. The reverse breakdown voltage was measured to be 1.65 kV- the highest measurement ever reported among ion-implanted diamond devices. In addition, the ideality factor and Schottky barrier height were determined as 4.9 and 1.4 eV, respectively, under the forward bias conditions. This study revealed the improvement of ion-implanted diamond SBD by using high-quality heteroepitaxial diamond substrates and low channel doping concentration.