This study focuses on the preparation of nanostructured holmium oxide via the decomposition of holmium acetate precursor utilizing the non-isothermal strategy. Thermogravimetric analysis(TGA) was used to follow up the...This study focuses on the preparation of nanostructured holmium oxide via the decomposition of holmium acetate precursor utilizing the non-isothermal strategy. Thermogravimetric analysis(TGA) was used to follow up the various thermal events involved in the decomposition process. Dehydration completes approximately at 150℃, which is followed by the decomposition of the anhydrous acetate leading to the formation of holmium oxide. Based on the TGA results the acetate precursor was heated non-isothermally at the temperature range of 150 e700℃. The obtained solids were characterized using powder X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), Fourier transform infrared spectroscopy(FT-IR), field-emission scanning electron microscopy(FE-SEM) and transmission electron microscopy(TEM). It is found that nanocrystalline Ho_2 O_3 starts to form at 500℃ and presents the only phase detected at the 500 e700℃ range. The electrical conductivity of the solids that form at the temperature range of 300 e700℃ was investigated. The obtained values were correlated with the observed structural modifications accompanying the heat treatment. The electrical conductivity of the Ho_2 O_3 samples prepared at 500, 600 and 700℃ reaches the values of 1.92 × 10^(-7), 1.61 × 10^(-7) and 8.33 × 10^(-8) Ω^(-1)cm^(-1) at a measuring temperature of 500℃, respectively. These values are potentially advantageous for high-resistivity devices.展开更多
The doping effects of rare earth oxides Ho_2O_3 and Er_2O_3 on dielectric properties of BaTiO_3-based ceramics were studied. After adding rare earth elements, grain growth in this system was inhibited and the grain si...The doping effects of rare earth oxides Ho_2O_3 and Er_2O_3 on dielectric properties of BaTiO_3-based ceramics were studied. After adding rare earth elements, grain growth in this system was inhibited and the grain size was reduced evidently which realized the fine-grained effect. In this system, the trivalent oxides Ho_2O_3 and Er_2O_3 were added to BaTiO_3 ceramics. The rare earth oxides do not enter into inner lattice totally to replace A or B sites. Some of additives can improve dielectric strength by forming nonferroelectric phases, and the rest maintained at grain boundaries controls overgrowth of grains. The dielectric constant at room temperature is increased up to 3000 and the curve of TCC becomes flat. Meanwhile, the dielectric strength E_b becomes higher.展开更多
The perovskite-type-oxide solid solution Ba0.97Ce0.8Ho0.2O3-α was prepared by high temperature solidstate reaction and its single-phase character was confirmed by X-ray diffraction. The ionic conduction of the sample...The perovskite-type-oxide solid solution Ba0.97Ce0.8Ho0.2O3-α was prepared by high temperature solidstate reaction and its single-phase character was confirmed by X-ray diffraction. The ionic conduction of the sample was investigated using electrical methods at elevated temperatures, and the performance of the hydrogen-air fuel cell using the sample as solid electrolyte was measured, which were compared with those of BaCe0.8Ho0.2O3-α. In wet hydrogen, BaCe0.8Ho0.2O3-α almost exhibits pure protonic conduction at 600-1000℃, and its protonic transport number is 1 at 600-900 ℃ and 0.99 at 1000 ℃. Similarly, Ba0.97Ce9.8Ho0.2O3-α exhibits pure protonic conduction with the protonic transport number of 1 at 600- 700℃, but its protonic conduction is slightly lower than that of BaCe0.8Ho0.2O3-α, and the protonic transport number are 0.99-0.96 at 800-1000 ℃. In wet air, the two samples both show low protonic and oxide ionic conduction. For Ba0.97Ce0.8Ho0.2O3-α, the protonic and oxide ionic transport numbers are 0.01-0.11 and 0.30-0.31 respectively, and for BaCe0.8Ho0.2O3-α, 0.01-0.09 and 0.27-0.33 respectively. Ionic conductivities of Ba0.97Ce0.8Ho0.2O3-α are higher than those of BaCe0.8Ho0.2O3-α under wet hydrogen and wet air. The performance of the fuel cell using Ba0.97Ce0.8Ho0.2O3-α as solid electrolyte is better than that of BaCe0.8Ho0.2O3-α. At 1000 ℃, its maximum short-circuit current density and power output density are 465 mA/cm^2 and 112 mW/cm^2, respectively.展开更多
Ba0.95Ce0.8Ho0.2O3-a was prepared by high temperature solid-state reaction. X-ray diffraction （XRD） pattern showed that the material was of a single perovskite-type orthorhombic phase. Using the material as solid el...Ba0.95Ce0.8Ho0.2O3-a was prepared by high temperature solid-state reaction. X-ray diffraction （XRD） pattern showed that the material was of a single perovskite-type orthorhombic phase. Using the material as solid electrolyte and porous platinum as electrodes, the measurements of ionic transport number and conductivity of Ba0.95Ce0.8Ho0.2O3-a were performed by gas concentration cell and ac impedance spectroscopy methods in the temperature range of 600---1000 ℃in wet hydrogen, dry and wet air respectively. Ionic conduction of the material was investigated and compared with that of BaCe0.8Ho0.2O3-a. The results indicated that Ba0.95Ce0.8Ho0.2O3-a was a pure protonic conductor with the protonic transport number of 1 during 600---700℃ in wet hydrogen, a mixed conductor of protons and electrons with the protonic transport number of 0.97--0.93 in 800---1000 ℃. But BaCe0.8Ho0.2O3-a was almost a pure protonic conductor with the protonic transport number of 1 in 600---900 ℃ and 0.99 at 1000 ℃ in wet hydrogen. In dry air and in the temperature range of 600---1000 ℃, they were both mixed conductors of oxide ions and electronic holes, and the oxide-ionic transport numbers were 0.24--0.33 and 0.17--0.30 respectively. In wet air and in the temperature range of 600---1000 ℃, they were both mixed conductors of protons, oxide ions and electronic holes, the protonic transport numbers were 0.11--0.00 and 0.09--0.01 respectively, and the oxide-ionic transport numbers were 0.41--0.33 and 0.27--0.30 respectively. Protonic conductivity of Ba0.95Ce0.8Ho0.2O3-a in both wet hydrogen and wet air was higher than that of BaCe0.8Ho0.2O3-a in 600--- 800 ℃, but lower in 900--1000 ℃. Oxide-ionic conductivity of the material was higher than that of BaCe0.8Ho0.2O3-a in both dry air and wet air in 600---1000 ℃.展开更多
Ceramic BaCe0.8Ho0.2O3-α with orthorhombic perovskite structure was prepared by conventional solid state reaction, and its conductivity and ionic transport number were measured by ac impedance spectroscopy and gas co...Ceramic BaCe0.8Ho0.2O3-α with orthorhombic perovskite structure was prepared by conventional solid state reaction, and its conductivity and ionic transport number were measured by ac impedance spectroscopy and gas concentration cell methods in the temperature range of 600-1000 ℃ in wet hydrogen and wet air, respectively. Using the ceramics as solid electrolyte and porous platinum as electrodes, the hydrogen-air fuel cell was constructed, and the cell performance at temperature from 600-1000 ℃ was examined. The results indicate that the specimen was a pure protonic conductor with the protonic transport number of 1 at temperature from 600-900 ℃ in wet hydrogen, a mixed conductor of proton and electron with the protonic transport number of 0.99 at 1000 ℃. The electronic conduction could be neglected in this case, thus the total conductivity in wet hydrogen was approximately regarded as protonic conductivity. In wet air, the specimen was a mixed conductor of proton, oxide ion and electron hole. The protonic transport numbers were 0.01-0.09, and the oxide-ionic transport numbers were 0.27-0.32. The oxide ionic conductivity was increased with the increase of temperature, but the protonic conductivity displayed a maximum at 900 ℃, due to the combined increase in mobility and depletion of the carriers. The fuel cell could work stably. At 1000 ℃, the maximum short-circuit current density and power output density were 346 mA/cm^2 and 80 mW/cm^2, respectively.展开更多
文摘This study focuses on the preparation of nanostructured holmium oxide via the decomposition of holmium acetate precursor utilizing the non-isothermal strategy. Thermogravimetric analysis(TGA) was used to follow up the various thermal events involved in the decomposition process. Dehydration completes approximately at 150℃, which is followed by the decomposition of the anhydrous acetate leading to the formation of holmium oxide. Based on the TGA results the acetate precursor was heated non-isothermally at the temperature range of 150 e700℃. The obtained solids were characterized using powder X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), Fourier transform infrared spectroscopy(FT-IR), field-emission scanning electron microscopy(FE-SEM) and transmission electron microscopy(TEM). It is found that nanocrystalline Ho_2 O_3 starts to form at 500℃ and presents the only phase detected at the 500 e700℃ range. The electrical conductivity of the solids that form at the temperature range of 300 e700℃ was investigated. The obtained values were correlated with the observed structural modifications accompanying the heat treatment. The electrical conductivity of the Ho_2 O_3 samples prepared at 500, 600 and 700℃ reaches the values of 1.92 × 10^(-7), 1.61 × 10^(-7) and 8.33 × 10^(-8) Ω^(-1)cm^(-1) at a measuring temperature of 500℃, respectively. These values are potentially advantageous for high-resistivity devices.
文摘The doping effects of rare earth oxides Ho_2O_3 and Er_2O_3 on dielectric properties of BaTiO_3-based ceramics were studied. After adding rare earth elements, grain growth in this system was inhibited and the grain size was reduced evidently which realized the fine-grained effect. In this system, the trivalent oxides Ho_2O_3 and Er_2O_3 were added to BaTiO_3 ceramics. The rare earth oxides do not enter into inner lattice totally to replace A or B sites. Some of additives can improve dielectric strength by forming nonferroelectric phases, and the rest maintained at grain boundaries controls overgrowth of grains. The dielectric constant at room temperature is increased up to 3000 and the curve of TCC becomes flat. Meanwhile, the dielectric strength E_b becomes higher.
基金V. ACKN0WLEDGMENT This work was supported by the National Natural Science Foundation of China （No.20171034） and the Natural Science Foundation of Education Department of Jiangsu Province （No.04KJD150218）.
文摘The perovskite-type-oxide solid solution Ba0.97Ce0.8Ho0.2O3-α was prepared by high temperature solidstate reaction and its single-phase character was confirmed by X-ray diffraction. The ionic conduction of the sample was investigated using electrical methods at elevated temperatures, and the performance of the hydrogen-air fuel cell using the sample as solid electrolyte was measured, which were compared with those of BaCe0.8Ho0.2O3-α. In wet hydrogen, BaCe0.8Ho0.2O3-α almost exhibits pure protonic conduction at 600-1000℃, and its protonic transport number is 1 at 600-900 ℃ and 0.99 at 1000 ℃. Similarly, Ba0.97Ce9.8Ho0.2O3-α exhibits pure protonic conduction with the protonic transport number of 1 at 600- 700℃, but its protonic conduction is slightly lower than that of BaCe0.8Ho0.2O3-α, and the protonic transport number are 0.99-0.96 at 800-1000 ℃. In wet air, the two samples both show low protonic and oxide ionic conduction. For Ba0.97Ce0.8Ho0.2O3-α, the protonic and oxide ionic transport numbers are 0.01-0.11 and 0.30-0.31 respectively, and for BaCe0.8Ho0.2O3-α, 0.01-0.09 and 0.27-0.33 respectively. Ionic conductivities of Ba0.97Ce0.8Ho0.2O3-α are higher than those of BaCe0.8Ho0.2O3-α under wet hydrogen and wet air. The performance of the fuel cell using Ba0.97Ce0.8Ho0.2O3-α as solid electrolyte is better than that of BaCe0.8Ho0.2O3-α. At 1000 ℃, its maximum short-circuit current density and power output density are 465 mA/cm^2 and 112 mW/cm^2, respectively.
基金Project supported by theNat-ional Natural Science Foundation of China （No. 20171034） and the Natural Science Foundation of Education Department of Jiangsu Province （No. 07KJB 150126）.
文摘Ba0.95Ce0.8Ho0.2O3-a was prepared by high temperature solid-state reaction. X-ray diffraction （XRD） pattern showed that the material was of a single perovskite-type orthorhombic phase. Using the material as solid electrolyte and porous platinum as electrodes, the measurements of ionic transport number and conductivity of Ba0.95Ce0.8Ho0.2O3-a were performed by gas concentration cell and ac impedance spectroscopy methods in the temperature range of 600---1000 ℃in wet hydrogen, dry and wet air respectively. Ionic conduction of the material was investigated and compared with that of BaCe0.8Ho0.2O3-a. The results indicated that Ba0.95Ce0.8Ho0.2O3-a was a pure protonic conductor with the protonic transport number of 1 during 600---700℃ in wet hydrogen, a mixed conductor of protons and electrons with the protonic transport number of 0.97--0.93 in 800---1000 ℃. But BaCe0.8Ho0.2O3-a was almost a pure protonic conductor with the protonic transport number of 1 in 600---900 ℃ and 0.99 at 1000 ℃ in wet hydrogen. In dry air and in the temperature range of 600---1000 ℃, they were both mixed conductors of oxide ions and electronic holes, and the oxide-ionic transport numbers were 0.24--0.33 and 0.17--0.30 respectively. In wet air and in the temperature range of 600---1000 ℃, they were both mixed conductors of protons, oxide ions and electronic holes, the protonic transport numbers were 0.11--0.00 and 0.09--0.01 respectively, and the oxide-ionic transport numbers were 0.41--0.33 and 0.27--0.30 respectively. Protonic conductivity of Ba0.95Ce0.8Ho0.2O3-a in both wet hydrogen and wet air was higher than that of BaCe0.8Ho0.2O3-a in 600--- 800 ℃, but lower in 900--1000 ℃. Oxide-ionic conductivity of the material was higher than that of BaCe0.8Ho0.2O3-a in both dry air and wet air in 600---1000 ℃.
基金Project supported by the National Natural Science Foundation of China （No. 20171034） and the Natural Science Foundation of Education Department of Jiangsu Province （No. 04KID150218）.
文摘Ceramic BaCe0.8Ho0.2O3-α with orthorhombic perovskite structure was prepared by conventional solid state reaction, and its conductivity and ionic transport number were measured by ac impedance spectroscopy and gas concentration cell methods in the temperature range of 600-1000 ℃ in wet hydrogen and wet air, respectively. Using the ceramics as solid electrolyte and porous platinum as electrodes, the hydrogen-air fuel cell was constructed, and the cell performance at temperature from 600-1000 ℃ was examined. The results indicate that the specimen was a pure protonic conductor with the protonic transport number of 1 at temperature from 600-900 ℃ in wet hydrogen, a mixed conductor of proton and electron with the protonic transport number of 0.99 at 1000 ℃. The electronic conduction could be neglected in this case, thus the total conductivity in wet hydrogen was approximately regarded as protonic conductivity. In wet air, the specimen was a mixed conductor of proton, oxide ion and electron hole. The protonic transport numbers were 0.01-0.09, and the oxide-ionic transport numbers were 0.27-0.32. The oxide ionic conductivity was increased with the increase of temperature, but the protonic conductivity displayed a maximum at 900 ℃, due to the combined increase in mobility and depletion of the carriers. The fuel cell could work stably. At 1000 ℃, the maximum short-circuit current density and power output density were 346 mA/cm^2 and 80 mW/cm^2, respectively.
