Increasing Donor Concentration Research Articles

Effect of oxygen on regulation of properties of moderately boron-doped diamond films

Regulation of oxygen on properties of moderately boron-doped diamond films is fully investigated. Results show that, with adding a small amount of oxygen (oxygen-to-carbon ratio < 5.0%), the crystal quality of diamond is improved, and a suppression effect of residual nitrogen is observed. With increasing ratio of O/C from 2.5% to 20.0%, the hole concentration is firstly increased then reduced. This change of hole concentration is also explained. Moreover, the results of Hall effect measurement with temperatures from 300 K to 825 K show that, with adding a small amount of oxygen, boron and oxygen complex structures (especially B3O and B4O) are formed and exhibit as shallow donor in diamond, which results in increase of donor concentration. With further increase of ratio of O/C, the inhibitory behaviors of oxygen on boron leads to decrease of acceptor concentration (the optical emission spectroscopy has shown that it is decreased with ratio of O/C more than 10.0%). This work demonstrates that oxygen-doping induced increasement of the crystalline and surface quality could be restored by the co-doping with oxygen. The technique could achieve boron-doped diamond films with both high quality and acceptable hole concentration, which is applicable to electronic level of usage.

Properties of nitrogen-doped indium oxide films prepared using chemical vapor deposition technique for photoelectrochemical application

This study reports on the morphological, structural, and optical properties as well as photocatalytic activity of N–In2O3 films. The carbothermal reduction process was used to synthesized In2O3 films on Ni/Si substrates under atmospheric pressure, followed by annealing under ammonia flow for various durations. The effect of N-doping on the materials' properties was investigated using FE-SEM, EDX, HR-XRD, and UV–Vis. The narrowing of the bandgap from 3.09 eV for the un-doped to 2.95 eV for the sample with the highest N-concentration was observed. Photoelectrochemical study of In2O3 based electrodes shows enhancement in their photoanodic activity with increasing N-doping. The most efficient electrode generates 1.33 mA/cm2 photocurrent density at 0.46 V vs. Ag/AgCl, about three times more than the intrinsic electrode, achieving an applied bias to photon conversation efficiency (ABPE) of 1.03% and an incident photon to current conversion efficiency (IPCE) of 33.80% at λ = 420 nm. The enhanced PEC performance could be attributed to the increased donor concentration in the electrodes due to N-doping, as revealed by Mott-Schottky analysis. The result demonstrates that N-doping of CVD synthesized In2O3 films could be an excellent way of improving their PEC performance.

Optimizing the Efficiency of a Cytocompatible Carbon-Dots-Based FRET Platform and Its Application as a Riboflavin Sensor in Beverages.

In this work, the Förster resonance energy transfer (FRET) between carbon dots (CDs) as energy donors and riboflavin (RF) as an energy acceptor was optimized and the main parameters that characterize the FRET process were determined. The results were successfully applied in the development of an ultrasensitive ratiometric fluorescent sensor for the selective and sensitive determination of RF in different beverages. Water-soluble CDs with a high quantum yield (54%) were synthesized by a facile and direct microwave-assisted technique. The CDs were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), Zeta potential, and UV-visible and molecular fluorescence spectroscopy. The study of the FRET process at two donor concentrations showed that the energy transfer efficiency decreases as the donor concentration increases, confirming its dependence on the acceptor:donor ratio in nanoparticle-based systems. The results show the importance of optimizing the FRET process conditions to improve the corresponding output signal. The variation in the ratiometric signal with the concentration of RF showed linearity in a concentration range of 0 to 11 µM with R2 = 0.9973 and a detection limit of 0.025 µM. The developed nanosensor showed good selectivity over other possible types of interference. The sensor was then applied for the determination of RF in beverage samples using the standard addition method with recoveries between 96% and 106%. Preliminary cytocompatibility tests carried out with breast cancer cells (MDA-MB-231) revealed the nanosensor to be cytocompatible in its working concentration regime, even after long incubation times with cells. Altogether, the developed RF determination method was found to be fast, low-cost, highly sensitive, and selective and can be extended to other samples of interest in the biological and food sectors. Moreover, thanks to its long-lasting cytocompatibility, the developed platform can also be envisaged for other applications of biological interest, such as intracellular sensing and staining for live cell microscopy.

Ultrasonication-assisted liquid-phase exfoliation enhances photoelectrochemical performance in α-Fe2O3/MoS2 photoanode

This study successfully manufactured a p-n heterojunction hematite (α-Fe2O3) structure with molybdenum disulfide (MoS2) to address the electron–hole transfer problems of conventional hematite to enhance photoelectrochemical (PEC) performance. The two-dimensional MoS2 nanosheets were prepared through ultrasonication-assisted liquid-phase exfoliation, after which the concentration, number of layers, and thickness parameters of the MoS2 nanosheets were respectively estimated by UV–vis, HRTEM and AFM analysis to be 0.37 mg/ml, 10–12 layers and around 6 nm. The effect of heterojunction α-Fe2O3/MoS2 and the role of the ultrasonication process were investigated by the optimized concentration of MoS2 in the forms of bulk and nanosheet on the surface of the α-Fe2O3 electrode while measuring the PEC performance. The best photocurrent density of the α-Fe2O3/MoS2 photoanode was obtained at 1.52 and 0.86 mA.cm−2 with good stability at 0.6 V vs. Ag/AgCl under 100 mW/cm2 (AM 1.5) illumination from the back- and front-sides of α-Fe2O3/MoS2; these values are 13.82 and 7.85-times higher than those of pure α-Fe2O3, respectively. The results of electrochemical impedance spectroscopy (EIS) and Mott-Schottky analysis showed increased donor concentration (2.6-fold) and decreased flat band potential (by 20%). Moreover, the results of IPCE, ABPE, and OCP analyses also supported the enhanced PEC performance of α-Fe2O3/MoS2 through the formation of a p–n heterojunction, leading to a facile electron–hole transfer.

Simulation on Optimum Doping Levels in Si Solar Cells

The two key variables of an Si solar cell, i.e., emitter (n-type window layer) and base (p-type substrate) doping levels or concentrations, are studied using Medici, a 2-dimensional semiconductor device simulation tool. The substrate is ptype and 150 μm thick, the pn junction is 2 μm from the front surface, and the cell is lit on the front surface. The doping concentration ranges from 1 × 1010 cm−3 to 1 × 1020 cm−3 for both emitter and base, resulting in a matrix of 11 by 11 or a total of 121 data points. With respect to increasing donor concentration (Nd) in the emitter, the open-circuit voltage (Voc) is little affected throughout, and the short-circuit current (Isc) is affected only at a very high levels of Nd, exceeding 1 × 1019 cm−3, dropping abruptly by about 12%, i.e., from Isc = 6.05 × 10−9 A·μm−1, at Nd = 1 × 1019 cm−3 to Isc = 5.35 × 10−9 A·μm−1 at Nd = 1 × 1020 cm−3, likely due to minority-carrier, or hole, recombination at the very high doping level. With respect to increasing acceptor concentration (Na) in the base, Isc is little affected throughout, but Voc increases steadily, i.e, from Voc = 0.29 V at Na = 1 × 1012 cm−3 to 0.69 V at Na = 1 × 1018 cm−3. On average, with an order increase in Na, Voc increases by about 0.07 V, likely due to narrowing of the depletion layer and lowering of the carrier recombination at the pn junction. At the maximum output power (Pmax), a peak value of 3.25 × 10−2 W· cm−2 or 32.5 mW· cm−2 is observed at the doping combination of Nd = 1 × 1019 cm−3, a level at which Si is degenerate (being metal-like), and Na = 1 × 1017 cm−3, and minimum values of near zero are observed at very low levels of Nd ≤ 1 × 1013 cm−3. This wide variation in Pmax, even within a given kind of solar cell, indicates that selecting an optimal combination of donor and acceptor doping concentrations is likely most important in solar cell engineering.

Precipitation of Molybdenum Oxides in Supersaturated Zinc Oxide Thin Films

Zinc oxide thin films saturated with molybdenum were prepared by RF magnetron sputtering process using zinc oxide and molybdenum targets for the co-sputtering. The sputtering power for zinc oxide was kept constant while that for molybdenum was varied from 0 watt to 35 watt. We found that the molybdenum-doped zinc oxide thin film change their color from transparent to grayish color as molybdenum sputtering power increases. The color change of the zinc oxide film suggests that the molybdenum changes its valance state as the molybdenum sputtering power was varied.A surprising finding about the study is the electrical conductivity increases and then decreases with molybdenum sputtering power. The increase of electrical conductivity should be attributed to the increase of donor concentration as more molybdenum atoms are incorporated. The decrease of conductivity, on the other hand, is not so well reported. Hall measurement study shows that the conductivity decrease is caused by decreased electron concentration. However, the electron mobility increases steadily with increased molybdenum sputtering power even though the electron concentration decreases. This is an indication that the electrical conduction no longer occurs through the molybdenum-doped ZnO grains.We propose that the conduction changes from grains to grain boundaries as molybdenum sputtering power increases. It means molybdenum is precipitated at the grain boundaries and forms conducting channels besides zinc oxide grains. The high mobility conduction channel is desired for devices using electron transport layers in their structures. The electrochemical solar cells are one of the devices that may benefit from the finding of molybdenum-doped oxide. We would like to present the valance change of molybdenum along with the conduction behavior, and would also like to predict the band alignment between zinc oxide and molybdenum oxide in the molybdenum-doped zinc oxide thin films. X-ray diffraction, UV-vis spectrophotometry, and x-ray photoelectron spectroscopy will be presented to show the conclusion that the electron mobility increase was attributed to the grain boundary conduction.

The effect of silver doping on photoelectrochemical (PEC) properties of bismuth vanadate for hydrogen production

Bismuth vanadate (BVO) as one of the promising photoanodes suffers from low charge transport mobility and conductivity. Here, dip coating of successive layers of bismuth vanadate (BVO) precursor were utilized to prepared BVO photoanode. Ag-doped BVO electrodes were also prepared by adding a trace amount of Ag+ in the bismuth vanadate precursor and codepositing Ag with the BVO film. In the Ag-doped BVO, Ag+ ions substitutionally replaced Bi3+ ions and increased the electron concentration in BVO. The photocurrent density and photoconductivity of Ag-doped BVO were monitored by changing the loading percentage of Ag (1–5%). At optimum Ag-doping percentage (2% Ag-doped BVO), the photocurrent density is found to be 5.5-fold greater than that of pure BVO. Deterministic investigation indicated that the enhanced PEC performance of the 2% Ag-BVO was attributed to significantly increased donor concentration (30-fold), greater visible light absorption, decreased recombination process of charge carriers (9-fold), thinner space charge layer (6-fold) and reduced flat band potential (16%). The water splitting experiment showed that the total generated H2 after 2 h of irradiation for 2% Ag-BVO was estimated as 5.2 μmol cm-2 and the equivalent value for O2 was 2.70 μmol cm-2.

Influence of silicon donor doping on electron transport in quantum wells AlGaAs/InGaAs/GaAs at different temperatures

Electron transport in single delta-Si doped pseudomorphic quantum wells with increasing donor concentration analyzed in a temperature range 2–300K. Hall effect and Shubnikov-de Haas oscillations studied at low temperatures. Temperature dependences of electron sheet concentration differ: samples with higher doping show significant increase of electron consentration at high temperature, while for the lightly doped it has a minor temperature sensitivity due to the band peculiarities of donor ionization. Electron mobility increases and then decreases at higher electron concentration, although the second quantum well subband remains unpopulated.

The origin of carbon-related carrier compensation in p-type GaN layers grown by MOVPE

The role of carbon impurities in p-type GaN layers grown by metalorganic vapor phase epitaxy (MOVPE) was investigated. The lightly Mg-doped (∼1017 cm−3) p-type GaN samples with different carbon concentration [C] were prepared by controlling growth temperature and pressure. Temperature-dependent Hall-effect analyses exhibited an increase in donor concentration with increasing [C]. The low-temperature mobility also decreased with increasing [C], as a result of mobility limitation due to ionized impurity scattering. These results show that carbon atoms in MOVPE-grown p-GaN layers act as ionized donors and cause carrier compensation. Deep-level transient spectroscopy (DLTS) using bias pulses detected the existence of Hd traps (EV +0.88 eV) arising from the 0/−1 charge state of carbon on nitrogen sites (CN). The concentrations of Hd traps closely corresponded to [C] values in p-type GaN layers. Employing low-frequency capacitance DLTS to avoid carrier freeze-out at low temperatures, we newly discovered the Ha trap (EV +0.29 eV) whose concentration was directly proportional to the [C] value. These findings suggest that the Ha trap originates from CN identical to the Hd trap. Based on prior theoretical calculations of energy levels, the Ha trap can reasonably be assigned to a +1/0 donor state of CN. These results strongly suggest that a CN having two different charged states can compensate an electron and a hole in n-type and p-type GaN layers, respectively.

Electron Effective Mass and Momentum Relaxation Time in One-Sided δ-Doped PHEMT AlGaAs/InGaAs/GaAs Quantum Wells with High Electron Density

Using the Shubnikov–de Haas effect, the dependences of electron effective mass m* and transport and quantum momentum relaxation times in Al0.25Ga0.75As/In0.2Ga0.8As/GaAs pseudomorphic quantum wells with one-sided silicon δ-doping on the electron density in the range of (1.1–2.6) × 1012 cm–2 have been established. Nonparabolicity coefficient m* in the linear approximation was found to be 0.133m0/eV. Both the transport and quantum momentum relaxation times depend nonmonotonically on Hall electron density nH, which is related to the competition between growth mechanisms of the Fermi momentum and the increasing contribution of large-angle scattering with increasing donor concentration.

Improved photoelectrochemical performance of molybdenum (Mo)-doped monoclinic bismuth vanadate with increasing donor concentration

Molybdenum (Mo)-doped Monoclinic Bismuth Vanadate (Mo-BiVO4; BVO) catalysts were fabricated via a simple dip coating method. We systematically studied the effect of Mo-doping with various concentration (1–5%) in BVO electrode through photoelectrochemical (PEC), Mott-Schottky and impedance measurement. Intermediate heat treatment and number of successive dip coating deposition were utilized to control the monoclinic crystallization and thickness of Mo-BVO photoanodes. Furthermore, the effect of Mo-doping in morphology, structure, chemical states and optical properties of the obtained electrodes were characterized by different physico-chemical and morphological methods BVO with 2% Mo doping (2% Mo-BVO) showed the best PEC performance, of about 15 times higher than that of the pure BVO. Improved charge carrier transport and optimized light absorption obtained upon Mo doping into the BVO crystal lattice while the monoclinic scheelite structure with small band-gap was retained. To understand the effect of Mo-doping, Mott Schottky and Impedance measurement carried out, in order to evaluate the donor concentration and conductivity of pure BVO and Mo-BVO. Interestingly, 2% Mo-BVO showed the maximum donor concentration (5.7E + 27) and minimum flat band potential (Vfb = −0.45) compared to other prepared electrodes. Furthermore, we attempt to discuss the improved PEC performance of Mo-BVO using high donor concentration, up-shifting of Fermi level and consequently facilitating electrons transport in Mo-BVO compared to pure BVO.

Screening of novel feruloyl esterases from Talaromyces wortmannii for the development of efficient and sustainable syntheses of feruloyl derivatives

The feruloyl esterases Fae125, Fae7262 and Fae68 from Talaromyces wortmannii were screened in 10 different solvent: buffer systems in terms of residual hydrolytic activity and of the ability for the transesterification of vinyl ferulate with prenol or l-arabinose. Among the tested enzymes, the acetyl xylan-related Fae125 belonging to the phylogenetic subfamily 5 showed highest yield and selectivity for both products in alkane: buffer systems (n-hexane or n-octane). Response surface methodology, based on a 5-level and 6-factor central composite design, revealed that the substrate molar ratio and the water content were the most significant variables for the bioconversion yield and selectivity. The effect of agitation, the possibility of DMSO addition and the increase of donor concentration were investigated. After optimization, competitive transesterification yields were obtained for prenyl ferulate (87.5–92.6%) and l-arabinose ferulate (56.2–61.7%) at reduced reaction times (≤24 h) resulting in good productivities (>1 g/L/h, >300 kg product/kg FAE). The enzyme could be recycled for six consecutive cycles retaining 66.6% of the synthetic activity and 100% of the selectivity.

Influence of sintering time and donor concentration on the PTCR effect of La-doped BaTiO3-Na0.5Bi0.5TiO3 ceramics

Lead-free positive temperature coefficient of resistivity (PTCR) materials with higher Curie point are important for their high temperature applications. In the present study, 0.99BaTiO3 −0.01Na0.5Bi0.5TiO3-xLa2O3 (99BT-1NBT-100xLa, x = 0.001, 0.002, 0.003, 0.004) ceramics were prepared by a conventional solid-state reaction method. The phase structure, microstructure, and PTCR effect of these ceramics were investigated. X-ray diffraction analysis indicates that all the samples are of a single tetragonal perovskite structure. The SEM images of all samples show the grain shape is irregular. And the grain size is around 3–30 µm. The PTCR effects occur at a temperature of about 150 °C. The room-temperature resistivity (ρ25) drops with the increase of donor concentration and the decrease of sintering time. The resistivity ratio (ρmax/ρmin) first increased and then decreased with increasing sintering time and donor concentration. The optimum composition for a large PTCR effect is 99BT-1NBT-0.3La, having a high jump of resistivity of 2.63 orders of magnitude sintered at 1400 °C for 30 min in air. A possible relation between the PTCR effect with the dopant behavior are discussed. This work may help on the study of lead-free PTCR ceramics from the view of control of doping elements and sintering procedure.

WITHDRAWN: Influence of sintering time and donor concentration on the PTCR effect of La-doped BaTiO3-Na0.5Bi0.5TiO3 ceramics

Abstract Lead-free positive temperature coefficient of resistivity (PTCR) materials with higher Curie point are important for their high temperature applications. In the present study, 0.99BaTiO3 −0.01Na0.5Bi0.5TiO3-xLa2O3 (99BT-1NBT-100xLa, x = 0.001, 0.002, 0.003, 0.004) ceramics were prepared by a conventional solid-state reaction method. The phase structure, microstructure, and PTCR effect of these ceramics were investigated. X-ray diffraction analysis indicates that all the samples are of a single tetragonal perovskite structure. The SEM images of all samples show the grain shape is irregular. And the grain size is around 3–30 µm. The PTCR effects occur at a temperature of about 150 °C. The room-temperature resistivity (ρ25) drops with the increase of donor concentration and the decrease of sintering time. The resistivity ratio (ρmax/ρmin) first increased and then decreased with increasing sintering time and donor concentration. The optimum composition for a large PTCR effect is 99BT-1NBT-0.3La, having a high jump of resistivity of 2.63 orders of magnitude sintered at 1400 °C for 30 min in air. A possible relation between the PTCR effect with the dopant behavior are discussed. This work may help on the study of lead-free PTCR ceramics from the view of control of doping elements and sintering procedure.

Electrochemical Behavior Assessment of As-Cast Mg-Y-RE-Zr Alloy in Phosphate Buffer Solutions (X Na3PO4 + Y Na2HPO4) Using Electrochemical Impedance Spectroscopy and Mott–Schottky Techniques

In the present study, electrochemical behavior of as-cast Mg-Y-RE-Zr alloy (RE: rare-earth alloying elements) was investigated using electrochemical tests in phosphate buffer solutions (X Na3PO4 + Y Na2HPO4). X-ray diffraction techniques and Scanning electron microscopy equipped with energy dispersive x-ray spectroscopy were used to investigate the microstructure and phases of the experimental alloy. Different electrochemical tests such as potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS) and Mott–Schottky (M–S) analysis were carried out in order to study the electrochemical behavior of the experimental alloy in phosphate buffer solutions. The PDP curves and EIS measurements indicated that the passive behavior of the as-cast Mg-Y-RE-Zr alloy in phosphate buffer solutions was weakened by an increase in the pH, which is related to formation of an imperfect and less protective passive layer on the alloy surface. The presence of the insoluble zirconium particles along with high number of intermetallic phases of RE elements mainly Mg24Y5 in the magnesium matrix can deteriorate the corrosion performance of the alloy by disrupting the protective passive layer that is formed at pH values over 11. These insoluble zirconium particles embedded in the matrix can detrimentally influence the passivation. The M–S analysis revealed that the formed passive layers on Mg-Y-RE-Zr alloy behaved as an n-type semiconductor. An increase in donor concentration accompanying solutions of higher alkalinity is thought to result in the formation of a less resistive passive layer.

Electron Transport in PHEMT AlGaAs/InGaAs/GaAs Quantum Wells at Different Temperatures: Influence of One-Side δ-Si Doping

The influence of the concentration of δ doping with Si on the electron transport properties of Al0.25Ga0.75As/In0.2Ga0.8As/GaAs pseudomorphic quantum wells is studied in a broad temperature range of 4.2–300 K. A decrease in the doping efficiency at an electron concentration of >1.8 × 1012 cm–2 is found. This is caused by the effects of incomplete impurity ionization, which is also reflected on the temperature dependence of the electron concentration. A nonmonotonic variation in the electron mobility with increasing donor concentration, which is not associated with filling of the upper subband of size quantization, is observed. An increase in the mobility is associated with a rise in the Fermi momentum and screening, while its subsequent drop with increasing Si concentration is caused by the tunnel degradation of the spacer layer with a decrease in the conduction-band potential in the region of the δ-Si layer.

Эффективная масса и время релаксации импульса электронов в односторонне delta-легированных PHEMT квантовых ямах AlGaAs/InGaAs/GaAs с высокой электронной плотностью

AbstractUsing the Shubnikov–de Haas effect, the dependences of electron effective mass m * and transport and quantum momentum relaxation times in Al_0.25Ga_0.75As/In_0.2Ga_0.8As/GaAs pseudomorphic quantum wells with one-sided silicon δ-doping on the electron density in the range of (1.1–2.6) × 1012 cm^–2 have been established. Nonparabolicity coefficient m * in the linear approximation was found to be 0.133 m _0/eV. Both the transport and quantum momentum relaxation times depend nonmonotonically on Hall electron density nH, which is related to the competition between growth mechanisms of the Fermi momentum and the increasing contribution of large-angle scattering with increasing donor concentration.

Электронный транспорт в квантовых ямах AlGaAs/InGaAs/ GaAs РНЕМТ при различных температурах: влияние одностороннего дельта-легирования Si

AbstractThe influence of the concentration of δ doping with Si on the electron transport properties of Al_0.25Ga_0.75As/In_0.2Ga_0.8As/GaAs pseudomorphic quantum wells is studied in a broad temperature range of 4.2–300 K. A decrease in the doping efficiency at an electron concentration of &gt;1.8 × 10^12 cm^–2 is found. This is caused by the effects of incomplete impurity ionization, which is also reflected on the temperature dependence of the electron concentration. A nonmonotonic variation in the electron mobility with increasing donor concentration, which is not associated with filling of the upper subband of size quantization, is observed. An increase in the mobility is associated with a rise in the Fermi momentum and screening, while its subsequent drop with increasing Si concentration is caused by the tunnel degradation of the spacer layer with a decrease in the conduction-band potential in the region of the δ-Si layer.

Control of Electrical Potential Distribution for High-Performance Perovskite Solar Cells

Summary The electrical potential distribution within photovoltaic devices plays critical roles in governing charge carrier dynamics and the device performance. Here we present the electrical potential distribution within highly efficient perovskite solar cells (PSCs) in working status. We found the major potential drop existing at the perovskite/mesoporous TiO 2 interface, indicating one diode junction in mesoporous PSCs. In contrast, the major potential drop was found on both sides of the perovskite layer in planar PSCs, exhibiting two diode junctions where the charge carriers could be recombined more easily than single-junction PSCs. We further controlled the position of diode junctions in planar PSCs by changing the dopant concentration. The undesirable charge recombination was largely suppressed, which enabled a better ideality factor and a higher efficiency 20.12% for planar PSCs with the increase of donor concentration. The present study will be helpful for understanding the fundamental mechanism within PSCs and achieving high device efficiency.

Quantitative calculation of barium vacancy formation mechanism effects on the room-temperature resistance and PTCR effect in donor-doped BaTiO3 ceramics

A modified barium vacancy formation mechanism in donor-doped barium titanate (BaTiO3) ceramics is proposed. Assuming a uniform distribution of barium vacancies at sintering temperature and only oxygen partial pressure and sintering temperature related concentration of unionized barium vacancies, the electrical characteristics have been calculated by solving a differential equation about electron level. The room-temperature resistivity and positive temperature coefficient of resistivity (PTCR) behaviors of donor-doped BaTiO3 semiconducting ceramics have been quantitatively computed. The results pointed out that the room-temperature resistivity changes as a U-type curve with an increase of donor concentration. Moreover, the PTCR effect of BaTiO3 semiconductive ceramics was calculated quantitatively under different conditions. Theoretical and experimental results for BaTiO3 semiconductive ceramics are compared and discussed.