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Copyright of Low-Carbon Chemistry & Chemical Engineering is the property of Low-Carbon Chemistry & Chemical Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The essential role of metal–support interaction in ammonia synthesis was investigated by using a Pr6O11 supported Ru nanoparticles (NPs) catalyst system. Loading of Ru NPs onto the Pr6O11 support with relatively low surface area yields similar metal dispersion with respect to conventional SiO2 support. The Ru NPs on the Pr6O11 was found to exhibit excellent catalytic performance in ammonia synthesis, superior to free-standing Ru NPs and Ru NPs on conventional SiO2 support. Detailed structure analysis results reveal that the superior activity of Ru/Pr6O11 can be attributed to the enhanced interaction between the Ru NPs and Pr6O11, which can modulate the electronic structure of Ru NPs and trigger catalytic ammonia synthesis over Ru NPs on Pr6O11. Furthermore, nitrogen isotope exchange experiment reveals that superior nitrogen dissociation ability is essential for the excellent activity and intrinsic activity of Ru/Pr6O11 in ammonia synthesis. These findings demonstrate that Pr6O11 can be used as a new kind of support for preparation of efficient Ru-based catalysts for ammonia synthesis, and also open up opportunities for design of Pr6O11 supported metal catalysts for other catalytic reactions. Interaction between the Ru NPs and Pr6O11 can modulate the electronic structure of Ru NPs and trigger catalytic ammonia synthesis over Ru NPs on Pr6O11. [ABSTRACT FROM AUTHOR]

The work aims to explore the anisotropic etching of synthetic diamond single crystal by rare earth oxide. Under the protection of nitrogen, synthetic diamond single crystals were etched by Pr6O11 powder at 750-950℃. The surface morphology, phase composition and etching mechanism of different crystal surfaces of diamond single crystal after etching were characterized and analyzed by means of scanning electron microscopy, thermogravimetric analysis, X-ray diffraction and Raman spectroscopy, and the changes of diamond properties before and after etching were characterized by surface roughness, single particle compressive strength and impact toughness. The results show that the etching degree and morphology of {100} faces and {111} faces of diamond by Pr6O11 are different. When the temperature is 750℃, Pr6O11 etches slightly diamond crystals. The etching intensifies with the increase of etching temperature, moreover the etching degree of diamond {111} faces is more serious than that of {100} faces. The morphologies of the etching pits of diamond {111} faces change from triangular etching pits to layered triangular ones, and {100} faces change from slight quadrilateral to honeycomb-like etching pits. The maximum etching depth of {100} face increases from 1.12 μm to 12.54 μm, while the maximum etching depth of {111} face increases from 0.3 μm to 2.11 mm. The compressive strength of single diamond particle decreases from 576.25 N of unetched diamond to the smallest value of 530.06 N, and the impact toughness decreases from 92.94 J/cm2to 88.53 J/cm2. The etching mechanism of diamond single crystal by Pr6O11 is catalytic graphitization before 885℃, and the catalytic graphitization and oxidation after 885℃.

Praseodymium oxide (Pr6O11), hematite (Fe2O3), graphene oxide (GO), and polycaprolactone (PCL) based polymeric nanocomposites (NCs) are fabricated, aiming their usage as bio-scaffold for medical purposes. Because of their distinctive light absorption and stability, Fe2O3 and Pr6O11 have been introduced as potential optical elements. The structure and size examination of NCs were executed by XRD, Raman, and FESEM. Pr6O11/Fe2O3/GO@PCL polymeric NC is exhibited Pr6O11, and Fe2O3 average size of 1.4, 0.4 µm, while average pores size 2.1 µm. As well, the Uv–Vis shows an absorption edge shifting along the x-axis that it begins with 3.1 eV for pure PCL, after that it declined to 1.7 eV for Pr6O11@PCL NC. Also, Pr6O11 @PCL, and Pr6O11/ Fe2O3@PCL NCs show the lowest similar contact angle with 38°. Regarding cell attachment evaluation test, the Pr6O11/Fe2O3/GO@PCL NC healing valuation is touched ∼ 80%. As a result, the structure enabled 3-dimensional the division of normal cells, so promoting wound healing.

• Hollow Pr 12 O 22 nanospheres were applied to aromatic hydrocarbons detection. • The semiconductor presented a rare p-type behavior due to the Pr valence states. • The material showed higher selectivity to m-xylene than to benzene and toluene. • The sensor could detect low concentrations (5 ppm) of m-xylene. • Pr 12 O 22 showed long-term stability, which is fundamental for a reusable sensor. Praseodymium oxide has already been explored in several applications within materials science. Yet, its use as a chemoresistive gas sensor has rarely been reported. Herein, we present the aromatic hydrocarbon sensing performance of monoclinic Pr 12 O 22 nanospheres produced via a microwave-assisted solvothermal approach with a subsequent calcination step. Sensing tests were performed at temperatures ranging from 200 to 500 °C and under different relative humidity conditions, from 0 % to 93 %. At 400 °C and dry conditions, the sensor exhibits a response of ca. 50 % towards 200 ppm m-xylene, which is much higher than those to benzene and toluene. The sensor also reveals excellent sensitivity for concentrations as low as 5 ppm of m-xylene, even at high relative humidity, while maintaining stability and repeatability over several days. Furthermore, the Pr 12 O 22 -based sensor presents an unusual p-type behavior attributed to the mixed valence states of the rare earth metal. [Display omitted] [ABSTRACT FROM AUTHOR]

This work focuses on the synthesize of nanostructured (Fe65Co35)100-x (Pr6O11)x (x = 0, 5) powders using high energy ball milling. The influence of Pr6O11 on structural, morphological and magnetic properties of Fe65Co35 nanoparticles were carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) with a dispersive energy analyzer (EDS), vibratory sample magnetometer (VSM) and differential scanning calorimetry (DSC). Results show that the praseodymium oxide addition increased the decrement rate of the crystallite size with milling time of about 27 % and decreased the increment rate of the internal micro-strain of 50 %. Moreover, because of its high grain fragmentation tendency, Pr6O11 increases the hardness and brittleness of Fe-Co powders. Moreover, it minimized the cold welding between Fe-Co ductile particles leading to a significant decrease in the average particle size (~1�m). The magnetic measurements conducted at room temperature show that the saturation magnetisation (Ms) and the coercivity (Hc) increased with milling time in both compositions. A low Ms and high Hc values were detected in (Fe65Co35)95 (Pr6O11)5 nanoparticles. The results demonstrated a soft ferromagnetic nature in all of the synthesized nanoparticles with Ms in the range 207 � 216 emu/g and Hc is found to be 113 Oe.

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Sr-doped LaMnO 3 (LSM) is one of the state-of-the-art cathodes with outstanding chemical stability but suffers from poor electrochemical activity. It is promising that LSM can be used as good cathode for protonic ceramic fuel cells (PCFCs), provided that its catalytic activity can be improved. Herein, we have developed a high-performance and durable LSM-based cathode used for PCFCs with stable Y-doped BaZrO 3 electrolyte. In this work, commercial LSM cathode is mixed with high-performance BaZr 0.85 Y 0.15 O 3-δ particles. Pr 6 O 11 nano-catalysts are homogeneously dispersed into the composite cathode, resulting in a significant decrease in the cathode polarization resistance from 0.51 to 0.12 Ω·cm2 at 600 °C. The power output improves by ~96% at 600 °C. Distribution of relaxation time analysis indicates that the processes of oxygen adsorption/dissociation and oxygen species diffuse to triple phase boundary sites are significantly promoted by Pr 6 O 11. Furthermore, the 100 h stability tests show that the modified cathode is extremely stable. • The first-generation LSM cathode was optimized and used for BZY-based PCFCs. • The optimized cathode showed the lowest ever R p of traditional MIEC cathodes. • The optimized cathode exhibited outstanding durability. [ABSTRACT FROM AUTHOR]

The content of active lattice oxygen and oxygen vacancies is crucial for the catalytic oxidation of soot. Herein, we adjust the Pr-O bond strength in Pr 6 O 11 by doping several common transition metals (Mn, Fe, Co, Ni) to promote the formation of oxygen vacancies and the activation of lattice oxygen. This strategy does not compromise its crystal structure, allowing for improved catalytic performance while maintaining stability. The Mn-doped Pr 6 O 11 catalyst shows the best soot catalytic oxidation performance. Its T 50 (the temperature of soot conversion reaching 50 %) value is 396 °C under loose contact. Further characterizations and density functional theory (DFT) calculations demonstrate that PMO possesses a large specific surface area. Additionally, the weakening the strength of the Pr-O bond leaded to an increase in oxygen vacancies, which in turn enhanced the redox ability of catalyst. This work will provide a reference for the development of Pr-based catalysts for soot combustion. [Display omitted] • Transition metals doped Pr 6 O 11 catalysts were prepared by MOFs derivation method. • Transition metals doping effectively regulate the Pr-O bond strength. • Mn-doped Pr 6 O 11 catalyst has the weakest Pr-O bond strength and the best catalytic performance. • This study provides an idea for the development of Pr-based catalysts for soot combustion. [ABSTRACT FROM AUTHOR]

The advancement of functional nanomaterials has promoted the development of biomarker sensors underpinning promising analytical tools for a range of bioanalytes such as cholesterol. In this work, we established a light-on fluorescent probe for cholesterol in human serum by coordination of H2O2 on the surface of praseodymia nanorods (Pr6O11 NRs). The distinctive interactions of various nucleotides and H2O2 with praseodymia were examined, whereby good fluorescent quenching and recovery capability were observed. A highly sensitive and selective cholesterol detection was achieved in serum samples with a detection limit of 0.1 μM and recovery of 97.2–101.3%, respectively, due to the high oxygen mobility of praseodymia. The result suggests strong potential for work towards a key probe for a portable clinical test system for cholesterol as well as other H2O2-deriving biomarkers, potentially addressing the ever-increasing demand for the prevention of cardiovascular disease.

This work focuses on the synthesize of nanostructured (Fe65Co35)100-x (Pr6O11)x (x = 0, 5) powders using high energy ball milling. The influence of Pr6O11 on structural, morphological and magnetic properties of Fe65Co35 nanoparticles were carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) with a dispersive energy analyzer (EDS), vibratory sample magnetometer (VSM) and differential scanning calorimetry (DSC). Results show that the praseodymium oxide addition increased the decrement rate of the crystallite size with milling time of about 27 % and decreased the increment rate of the internal micro-strain of 50 %. Moreover, because of its high grain fragmentation tendency, Pr6O11 increases the hardness and brittleness of Fe-Co powders. Moreover, it minimized the cold welding between Fe-Co ductile particles leading to a significant decrease in the average particle size (~1µm). The magnetic measurements conducted at room temperature show that the saturation magnetisation (Ms) and the coercivity (Hc) increased with milling time in both compositions. A low Ms and high Hc values were detected in (Fe65Co35)95 (Pr6O11)5 nanoparticles. The results demonstrated a soft ferromagnetic nature in all of the synthesized nanoparticles with Ms in the range 207 - 216 emu/g and Hc is found to be 113 Oe. [ABSTRACT FROM AUTHOR]

In this study, pure HfO 2 and Pr 6 O 11 -HfO 2 coatings were prepared by atmospheric plasma spraying. The chemical compositions, morphologies, infrared radiation performances and thermal resistances of the coatings were characterized. The results showed that doping Pr 6 O 11 could effectively improve the infrared emittance of the HfO 2 coating. The HfO 2 coating doping with 10 wt. % Pr 6 O 11 exhibited the highest infrared emittance, which was 0.859 at room temperature and 0.883 at 1600 °C, correspondingly. This was mainly attributed to the oxygen vacancies, which created by the substitution of Hf4+ by Pr3+, could introduce localized energy states within the HfO 2 band gap and increase the lattice distortion, producing lower symmetry vibrations. In addition, the Pr 6 O 11 -HfO 2 infrared radiation coating possessed high tensile adhesive strength and good thermal resistance, which could withstand a high temperature treatment at 1700 °C for at least 50 h without exfoliation, and there was only a slight reduction in emittance. [ABSTRACT FROM AUTHOR]

ZnO-Pr6O11-CoO-Cr2O3-based ceramic varistors doped with 0 - 2.0 mol.% ZrO2 were fabricated via conventional ceramic processing by sintering at 1300oC for 2 h. X-ray diffraction results indicate that the doped ZrO2 reacted with praseodymium oxides during sintering, resulting in Pr2Zr2O7 phase. Scanning electron microscopy analysis revealed that after the addition of ZrO2, the growth of ZnO grains was inhibited due to the formation of Pr2Zr2O7. When the amount was less than 0.5 mol.%, ZrO2 doping was beneficial for increasing the varistor nonlinear exponent. The varistor voltage increased with increasing ZrO2 contents in the ceramics, but the leakage current also increased with it. In this work, the sample doped with 0.5 mol.% ZrO2 presented the highest nonlinear exponent (17), and its varistor voltage was 623 V mm-1. The sample with 2.0 mol.% ZrO2 presented the highest varistor voltage (1490 V mm-1), and its nonlinear exponent was 10. The obtained varistor would be very promising in super-high-voltage power transmission systems.

Graphical abstract Highlights • A new combination of Pr 6 O 11 /g-C 3 N 4 photocatalyst is synthesized by simple solvent free solid state method. • The photocatalytic activity of Pr 6 O 11 /g-C 3 N 4 is investigated by degradation of AV7 dye under visible light. • Improved performance is attributed to enhanced visible light absorption and efficient charge separation as evidenced by photoelectrochemical study. • Pr 6 O 11 /g-C 3 N 4 also exhibit super capacitance behavior. Abstract A new Pr 6 O 11 /g-C 3 N 4 heterostructure material has been prepared by single step solvent free solid state method for photocatalytic environmental cleaning application using visible light. The Pr 6 O 11 /g-C 3 N 4 heterostructure exhibits enhanced visible light absorption, resulting in improved photoelectrochemical properties and photocatalytic performance. The optimized composition of Pr 6 O 11 /g-C 3 N 4 composite shows improved degradation kinetics and completely degrades AV7 dye within 20 min of visible light irradiation. Photoluminescence and electrochemical studies suggest better separation of photogenerated charge carriers in the composite compared to single phase materials. This is further substantiated by the improved photocurrent response of the composite. The notable increase of photocatalytic activity of Pr 6 O 11 /g-C 3 N 4 heterostructure is ascribed to the improved visible light absorption, reduced band gap and better separation of photogenerated electrons and holes. To the best of our knowledge, this new heterostructure photocatalyst is found to be more efficient for the degradation of AV7 dye compared to the systems reported so far. [ABSTRACT FROM AUTHOR]

Praseodymium oxide (Pr 6 O 11), hematite (Fe 2 O 3), graphene oxide (GO), and polycaprolactone (PCL) based polymeric nanocomposites (NCs) are fabricated, aiming their usage as bio-scaffold for medical purposes. Because of their distinctive light absorption and stability, Fe 2 O 3 and Pr 6 O 11 have been introduced as potential optical elements. The structure and size examination of NCs were executed by XRD, Raman, and FESEM. Pr 6 O 11 /Fe 2 O 3 /GO@PCL polymeric NC is exhibited Pr 6 O 11 , and Fe 2 O 3 average size of 1.4, 0.4 µm, while average pores size 2.1 µm. As well, the Uv–Vis shows an absorption edge shifting along the x-axis that it begins with 3.1 eV for pure PCL, after that it declined to 1.7 eV for Pr 6 O 11 @PCL NC. Also, Pr 6 O 11 @PCL, and Pr 6 O 11 / Fe 2 O 3 @PCL NCs show the lowest similar contact angle with 38°. Regarding cell attachment evaluation test, the Pr 6 O 11 /Fe 2 O 3 /GO@PCL NC healing valuation is touched ∼ 80%. As a result, the structure enabled 3-dimensional the division of normal cells, so promoting wound healing. [ABSTRACT FROM AUTHOR]

The simple, cost effective, highly efficient and self-protective siloxane coating was prepared by dispersing the praseodymium oxide in a hybrid sol-gel network. The embedded nanoparticles were varied from 0·25 to 1 wt-%, and an optimum percentage was carried for further studies. The corrosion resistance of the siloxane coatings was studied by salt spray technique and electrochemical impedance spectroscopy. Surface morphology was studied to explain the arrangement of nanoparticles on the surface of the coatings. The resulted SiO2@Pr6O11 core-shell was characterised by transmission electron microscopy. The above results revealed that the nanoparticles enriched silane could provide surpassing corrosion protection coatings compared to the unmodified silane films. This work presents an efficient anti-corrosive coating for the industrially significant stainless steel 304 (SS 304). This study had led to a better understanding factor influencing the anticorrosion performance and properties of anticorrosive coatings with embedded nanoparticles. [ABSTRACT FROM AUTHOR]

The electrical and microstructural properties of SnO2-based varistor ceramic sample were improved by addition of Pr6O11. It was found that the introduction of Pr6O11 can lead to a great improvement in the threshold voltage and the non-linear electrical properties of SnO2-based varistors. As the amount of Pr6O11 increased from 0.00 to 0.5 mol%, the mean grain size decreases from 16.64 to 7.58 μm, the relative dielectric constant (at 1 kHz) increases from 1243.2 to 4534.6, the non-linear coefficient increases from 15.44 to 18.25 and the break down electrical field increases from 275.3 to 880.5 V/mm. The structure-property relationship is discussed systematically. [ABSTRACT FROM AUTHOR]

It is important yet difficult to distinguish the specific roles of superficial O x n- and interfacial lattice oxygen in catalytic combustion, especially over catalysts consisting of reducible metal oxides. In this study, based on the comparison of two natural counterparts with similar structure — CeO 2 (an O x n- generator) and Pr 6 O 11 (a lattice oxygen contributor), it is suggested that the catalytic combustion of propane under lean-burn conditions followed a typical Mars-van Krevelen mechanism, in which catalyst lattice oxygen represented the dominant reactive phases while superficial O x n- played negligible roles. As for soot combustion, adsorbed O x n- represented more sustainable oxidants than lattice oxygen (drained easily at the beginning of the reactions). Such a comparison is readily achieved and widely applicable, which may shed light on the identification of dominant reactive phases for various oxidation reactions over oxide-based catalysts. [Display omitted] • Pr 6 O 11 with higher lattice oxygen mobility oxidized propane faster than did CeO 2. • The defects-induced O x n- worked as the key soot oxidizer over CeO 2. • Pr 6 O 11 deactivated with the draining of its lattice oxygen by soot. • The catalytic combustion of propane followed a typical Mars-van Krevelen mechanism. • Soot ignition followed a Mars-van Krevelen-like mechanism with open redox cycles. [ABSTRACT FROM AUTHOR]

We fabricated electrolyte supported single cells with three types of cathodes that consisted of a Ce0.1Gd0.1O1.95 (GDC) buffer layer, a LaNi0.6Fe0.4O3 (LNF) cathode and an active layer. The only difference between the three cathodes was that each had a different active layer, namely a GDC–LNF composite active layer (our conventional cathode), a Pr x Ce1–x O2–δ (x = 0.1, 0.3, 1.0)–LNF composite active layer and a Pr6O11 (Pr x Ce1–x O2–δ (x = 1.0)) active layer. The interface resistance, R inf, and overvoltage, η c, of the cathodes were investigated. At 800 °C, the R inf of the cathode with the Pr6O11 active layer was reduced to 1/30 that of the cathode with the GDC–LNF composite active layer. The R inf at 800 °C for the cathode with the Pr6O11–LNF composite active layer was reduced to 1/8 that of the cathode with the GDC–LNF composite active layer. The R inf values of the cathode with an active layer between 650 and 750 °C were also much better than those of the cathode with the GDC–LNF composite active layer. By using the cathode with the Pr6O11 active layer, the operating temperature can be reduced to 700 °C while retaining the same performance (same overvoltage at 254 mA/cm2) as a cathode with a GDC–LNF composite active layer at 800 °C. We also investigated the reactions at the interfaces in the sintering process. X-ray diffraction (XRD) analysis revealed that the Pr6O11 reacted easily with zirconia, and Pr2Zr2O7 was produced at 1000 °C or above. It was suggested that the sintering temperature of the cathodes with the active layer could be increased to around 1000 °C without any reaction at the interface between Pr6O11 and other materials. [ABSTRACT FROM AUTHOR]

Pt-based alloy catalysts for oxygen reduction reaction (ORR) with outstanding performance have been well-studied in recent years. Among these, Pt-lanthanide alloy catalysts have been developed with quite a competitive ORR activity. However, to promote practical applications of a proton-exchange membrane fuel cell (PEMFC), catalysts with superior activity are still being explored. Herein, we present the Pr 6 O 11 -assisted Pt-Pr catalyst exhibiting further improved ORR activity than the state-of-the-art Pt/C. A simple annealing treatment is applied after the synthesis of the Pt-Pr alloy, obtaining Pr 6 O 11 nanoparticles attached to the surface of the Pt-Pr alloy to form a Pt-Pr/Pr 6 O 11 composite catalyst. Experimental and theoretical studies reveal that the electronic state of Pt in the Pt-Pr/Pr 6 O 11 system is modified. It was found that the strong oxophilicity of Pr adjusts the active site of Pt and promotes the adsorption and dissociation of O 2 . The preeminent intrinsic ORR activity on the Pt-Pr/Pr 6 O 11 catalyst reaches the promoted specific activity (2.01 mA cm -2 ) and mass activity (1.3 A mg Pt -1 ), which were 5.91- and 5.90-fold higher than those obtained by the state-of-the-art Pt/C catalyst (0.34 mA cm -2 and 0.22 A mg Pt -1 ). This study provides us with an idea that the ORR performance of Pt-based alloy could be enhanced with the assistance of the metal oxide phase.

A phenomenon of light emission by certain materials after exposure to an excitation source is called luminescence. Long persistent phosphors are those having very long afterglow emission or phosphorescence, in some cases even longer than a whole day, and a large application fields. Afterglow is caused by trapped electrons or holes produced during the excitation. The long persistent phosphorescence mechanism of the inorganic phosphors activated by rare earth ions have been attempted to be explained by many researchers. During the last decade, the researches on the development of new persistent phosphors and the improvement of their life time have been considerably conducted. In the present study, the effects of praseodymium oxide (Pr6O11) doping in SrAl2O4:Eu2+, Dy3+, Y3+phosphor on the luminescence efficiency and phosphorescence properties were investigated. Additionally, after the production, the possible application of the most suitable pigment developed during the study onto artistic glasses was searched. [ABSTRACT FROM AUTHOR]

Abstract: The microstructure and electrical properties of the ZPCMY varistor ceramics composed of ZnO–Pr6O11–Co3O4–MnCO3–Y2O3 systems sintered at temperature of 1200–1300°C were investigated. The addition of Y2O3 led to the decrease of the densification and the slight improvement of the electrical properties. The varistor voltage decreased over a wide range from 7100 to 2470V/cm with the increase of sintering temperature. The ZPCMY-based varistor ceramics sintered at 1275°C exhibited the best performance in terms of the densification and E–J characteristics. These varistors were characterized by 5.27 in bulk density, 55.3 in the nonlinear exponent and 1.53μA in the leakage current. [Copyright &y& Elsevier]

Abstract: Sintering and grain growth of Pr6O11-based ZnO varistors were investigated in detail over a range of temperature and holding time. The grain growth kinetics in the Zn–Pr–Co–Mn–O system was studied using the simplified phenomenological grain growth kinetics equation: = K 0 t exp(−Q/RT) together with the physical properties of the sintered samples. From 1050°C to 1300°C, the grain growth exponent value (n) and the apparent activation energy for this system were found to be approximately 3.7 and 306±61kJ/mol respectively. Highly densified ceramics sintered at 1300°C for 4h were obtained, reaching about 96% of theoretical density (TD=5.78g/cm3). These values are compared with those obtained for Bi2O3-based ZnO varistors. The maximum nonlinear exponent (α =54.7) was obtained at a sintering temperature of 1275°C. [Copyright &y& Elsevier]

Abstract: ZnO–Pr6O11 based varistor ceramics doped with 0–2.0mol% SnO2 were fabricated by sintering samples at 1300°C for 2h with conventional ceramic processing method. X-ray diffraction analysis indicated that the doped SnO2 reacted with praseodymium oxides during sintering, generating Pr2Sn2O7 phase. Through scanning electron microscopy, it was found that the doping of SnO2 played a role against the growth of ZnO grains. Capacitance–voltage analysis revealed that the doped SnO2 acted as a donor in the varistor. The measured electric-field/current-density characteristics of the samples showed that the varistor voltage increased with the increase of SnO2 doping content, when the SnO2 content was no more than 1.0mol%; with the SnO2 content up to no more than 0.5mol%, the doping of SnO2 could increase the nonlinear coefficient; but, when the SnO2 doping content was further increased, the nonlinear coefficient and varistor voltage of the samples decreased, and the leakage current increased. [Copyright &y& Elsevier]

Abstract: The effect of the addition of various amounts of Pr6O11 on the grain growth and densification process, microstructure, formation and distribution of secondary phases, and electrical properties of SnO2-based varistors containing cobalt and niobium oxides has been investigated. It has been observed that in the presence of as low as 0.1mol% of Pr6O11, the formation of Pr2Sn2O7 can be detected using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The kinetics of grain growth in samples without and with praseodymium oxide has shown that increasing Pr6O11 from 0 to 0.5mol%, changes the grain growth exponent from 2 to 6 and the activation energy from 350kJ/mol to around 700kJ/mol. This may be due to the cooperative effect of the secondary phases. The largest nonlinear coefficient, α, and the lowest leakage current, IL, has been observed for the sample containing 0.05mol% Pr6O11 whereas the highest breakdown voltage has been recorded for the sample with 0.5mol% Pr6O11. [Copyright &y& Elsevier]

High voltage zinc varistors were synthesized by high-energy milling with Pr6O11 and Y2O3 doped ZnO-Bi2O3 system as raw materials. The effects of high-energy milling on the microstructures, electrical properties and densities of samples were investigated in detail. The results show that high-energy milling make the as-prepared varistors have refined and homogeneous microstructures, which result in improving their electrical properties. The optimal prepared samples were obtained by milling for 7.5 hours and sintering at 1100°C, which exhibited varistor voltage (V1mA) of about 533 V/mm, non linear coefficient (α) reaching 36 and leakage current (IL) of 2.96 μA. [ABSTRACT FROM AUTHOR]

Abstract: The doping effect of Fe2O3 on the microstructural and electrical properties of ZnO–Pr6O11 based varistor ceramic materials was investigated. Fe2O3 doping would inhibit the growth of ZnO grains, whose average sizes were found to decrease from 3.0 to 2.7μm with the doping level of Fe2O3 increased from 0 to 1mol%. When the doping level of Fe2O3 was 0.005mol%, the varistors exhibited the optimum nonlinear electrical characteristics with nonlinear coefficient of about 26, breakdown voltage of approximately 571V/mm and leakage current of less than 65μA. With higher doping level of Fe2O3, more Fe atoms would segregate at grain boundaries, providing more extra electrical carriers, decreasing the resistances of the grain boundaries, and PrFeO3 would be formed, destroying the construction of grain boundaries. Therefore, the nonlinear electrical properties of the resultant varistor materials were deteriorated. [ABSTRACT FROM AUTHOR]

Abstract: The effect of CuO doping on the microstructure and electrical properties of Pr6O11 varistors was investigated. Samples were prepared by conventional ceramic techniques, and were sintered at 1150°C in air for 2h. The microstructure was investigated by scanning electron microscopy (SEM). The phases and chemical composition were analyzed by X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The results indicated that CuO can promote the densification of the Pr6O11-based varistors to 95.8% of the theoretical density. CuO forms a solid solution with Pr6O11 up to 0.5mol%, above which Pr2CuO4 precipitates in the grain boundary. From the I–V measurements, minor CuO doping can improve the nonlinear electrical properties. A further increase in CuO content induces a reduction in the nonlinear electrical properties due to the consumption of absorbed oxygen on the grain surfaces. [Copyright &y& Elsevier]

Abstract: The microstructural and electrical properties of ZnO–Pr6O11 based varistors, which are composed of ZnO–Pr6O11–Co3O4–TiO2 with different doping amounts of TiO2, were investigated. Through X-ray diffraction and scanning electron microscopy analyses, it was found that TiO2 acted as an inhibitor of ZnO grain growth in varistor ceramics, resulting in the decrease of ZnO grain size with more TiO2 doped, due to the formation of more second phases such as PrTiO3, Zn2TiO4 and even Pr2Ti2O7 at the grain boundaries, which would exert more intensive pinning effects on the ZnO grain growth. Doping with appropriate amount of TiO2 can improve the nonlinear property, and decrease the leakage current of the as-prepared ZnO–Pr6O11 based varistors. The samples’ varistor voltage and nonlinear exponents can be enhanced till no more than 1.0mol% TiO2 doped. The maximal values of varistor voltage and nonlinear exponents acquired in this work were 90.2V/mm and 15, respectively. The obtained materials might be much promising in application of varistors for devices working under low voltages. [Copyright &y& Elsevier]

Abstract: The characteristics of an HC sensor consisting of a gas-detection cell and an oxygen pump cell have been investigated. A Pt active electrode and a Pr6O11 inactive electrode were formed on YSZ in the gas-detection cell using a sputtering technique, and the concentration of hydrocarbon gases was determined from the electromotive force generated between these two electrodes. The pump cell was assembled such that the oxygen concentration in the gas-detection space was decreased. At 800°C, the gas-detection cell showed high output sensitivity for hydrocarbon gases such as CH4 and C3H8. However, the sensitivity was low for H2 and CO. The sensor output increased when the pump cell was operated in C3H8/O2/N2. This result shows that decreasing the oxygen concentration in the gas-detection space by using the pump cell is an effective technique for improving the detection sensitivity of the sensor. [Copyright &y& Elsevier]

The microstructure and electrical properties of varistor ceramics, in the ZnO–Pr6O11–CoO–Cr2O3–Dy2O3 (ZPCCD) system, were investigated in the range of 0.0–2.0 mol% Dy2O3. The Dy2O3 microstructurally played the role of inhibition in the densification and grain growth. As Dy2O3 content is increased, the density was decreased in the range of 5.49–4.64 g/cm3, and the average ZnO grain size was decreased in the range of 18.2–4.6 μm. The incorporation of Dy2O3 significantly improved the nonlinear properties of ZPCCD-based varistor ceramics, above 45 in the nonlinear exponent compared with that without Dy2O3. The varistor ceramics with Dy2O3 content of 0.5 mol% exhibited the best performance, with 5.49 g/cm3 in density, 55.3 in nonlinear exponent, and 0.1 μA in leakage current. [Copyright &y& Elsevier]

The microstructure and electrical properties of varistors, which are composed of ZnO-Pr6O11-CoO-Cr2O3-Dy2O3 (ZPCCD)-based ceramics, were investigated in the range of 0.0–2.0 mol% Dy2O3. As Dy2O3 content is increased, the density was decreased in the range of 5.53–4.43 g/cm3 and the average ZnO grain size was decreased in the range of 18.6–4.7 μm. The varistors with Dy2O3 exhibited a high nonlinear exponent above 30, compared with that without Dy2O3. The incorporation of Dy2O3 significantly improved the nonlinear properties of ZPCCD-based varistors. The varistor with Dy2O3 content of 0.5 mol% exhibited the highest nonlinearity, in which a nonlinear exponent is 66.6 and a leakage current is 1.2 μA. The donor concentration and the density of interface states were decreased in the range of 4.19×1018–0.33×1018/cm3 and 5.38×1012–1.74×1012/cm2, respectively, with increasing Dy2O3 content. [Copyright &y& Elsevier]

The nonlinear properties and stability of ZnO–Pr6O11–CoO–Cr2O3–Er2O3 (ZPCCE)-based varistors, which are composed of ZnO–Pr6O11–CoO–Cr2O3–Er2O3-based ceramics, were investigated with sintering temperature and time in the range of 1325–1345 °C for 1–2 h. Among all ZPCCE-based varistors, the varistors sintered at 1335 °C for 1 h exhibited the highest nonlinearity, with a nonlinear exponent of 70.53 and a leakage current of 1.92 μA. While, the varistors sintered at 1340 °C for 2 h, with a nonlinear exponent of 43.37, exhibited the highest stability under continuous DC stress, such as (0.80 V1 mA/90 °C/12 h)+(0.85 V1 mA/115 °C/12 h)+(0.90 V1 mA/120 °C/12 h)+(0.95 V1 mA/125 °C/12 h)+(0.95 V1 mA/150 °C/12 h). Then, they showed that the variation rates of the varistor voltage and nonlinear exponent were −1.54% and −2.49%, respectively. It was found that the nonlinear properties and stability of ZPCCE-based varistors are strongly affected by the sintering temperature and time. [Copyright &y& Elsevier]

• Thin YSZ (∼40 μm) self-supporting SSOFC with Sr 2 Fe 1.5 Mo 0.5 O 6-δ electrodes were prepared. • Symmetrical Pr 6 O 11 infiltration increased the power output from 301 mW/cm2 to 455 mW/cm2 (H 2 , 800 °C). • Pr 6 O 11 simultaneously boosted H 2 oxidation (HOR) and O 2 reduction (ORR). Symmetrical solid oxide fuel cells based on yttrium-stabilized zirconia (YSZ) electrolyte and Sr 2 Fe 1.5 Mo 0.5 O 6-δ (SFM) electrode are prepared via phase-inversion and impregnation processes. The YSZ symmetrical electrolyte support is constructed using two porous frameworks and one thin-dense-membrane via phase-inversion combined with drip-coating techniques. SFM is infiltrated into the porous frameworks of the symmetric YSZ support to work as electrodes. Nanoscale Pr 6 O 11 catalysts are further infiltrated into the electrodes to promote electrochemical performance. The optimal loading of SFM and Pr 6 O 11 are systematically investigated. At 800 °C, with the optimal loading of SFM (12 wt%), the polarization resistance (R p) for anode and cathode of the cell decrease to 0.19 and 0.10 Ω cm2, respectively. The maximum power density (MPD) achieves 301 mW•cm−2 in H 2 at 800 °C. After loading Pr 6 O 11 , the R p for anode and cathode further decrease by 47% to 0.10 Ω•cm2 and by 80% to 0.021 Ω•cm2, respectively. And the MPD improves by 51% to 455 mW•cm−2 (at 800 °C). These results and analysis of distribution of relaxation times demonstrate that the introduction of Pr 6 O 11 as bifunctional catalysts is a promising approach for simultaneously improving H 2 fuel oxidation and O 2 reduction activities. Symmetric solid oxide fuel cells based on thin YSZ self-supporting "porous | dense | porous" electrolyte backbone and Sr 2 Fe 1.5 Mo 0.5 O 6-δ electrodes were prepared. Then symmetrical Pr 6 O 11 infiltration simultaneously boosted H 2 oxidation (anode) and O 2 reduction (cathode). [Display omitted] [ABSTRACT FROM AUTHOR]

This paper investigated the effects of Pr6O11 and Co3O4 on the electrical properties of ZnO-BaTiO3 varistor ceramics. The Pr6O11 doping has a notable influence on the characteristics of the nonlinear coefficient, varistor voltage, and leakage current where the values varied from 2.29 to 2.69, 12.36 to 68.36 V/mm and 599.33 to 548.16 µA/cm2, respectively. The nonlinear varistor coefficient of 5.50 to 7.15 and the varistor voltage of 7.38 to 8.10 V/mm was also influenced by the use of Co3O4 as a dopant. When the amount of Co3O4 was above 0.5 wt.%, the leakage current increased from 202.41 to 302.71 μA/cm2. The varistor ceramics with 1.5 wt.% Pr6O11 shows good nonlinear electrical performance at higher breakdown voltage and reduced the leakage current of the ceramic materials. Besides, the varistor sample that was doped with 0.5 wt.% Co3O4 was able to enhance the nonlinear electrical properties at low breakdown voltage with a smaller value of leakage current. [ABSTRACT FROM AUTHOR]

In this work, we successfully developed a novel and sensitive gas sensor for the determination of trace acetophenone based on its cataluminescence (CTL) emission on the surface of nano-praseodymium oxide (nano-Pr6O11). The effects of working conditions such as temperature, flow rate, and detecting wavelength on the CTL sensing were investigated in detail. Under the optimized conditions, the sensor exhibited linear response to the acetophenone in the range of 15–280 mg/m3 (2.8–52 ppm), with a correlation coefficient (R2) of 0.9968 and a limit of detection (S/N = 3) of 4 mg/m3 (0.7 ppm). The selectivity of the sensor was also investigated, no or weak response to other compounds, such as alcohols (methanol, ethanol, n-propanol, iso-propanol, n-butanol), aldehyde (formaldehyde and acetaldehyde), benzenes (toluene, o-xylene, m-xylene, p-xylene), n-pentane, ethyl acetate, ammonia, carbon monoxide, carbon dioxide. Finally, the present sensor was applied to the determination of acetophenone in human exhaled breath samples. The results showed that the sensor has promising application in clinical breath analysis. [ABSTRACT FROM AUTHOR]