Hexagonal Wurtzite Structure Of ZnO Research Articles

Synthesized zinc oxide nano rods and flowers studies for optical, di-electrical and photocatalytic applications

ZnO being most avid semiconductor metal oxide with a wide band gap of 3.37 eV. ZnO nanostructures were synthesized in the shape of nano rods and flowers to finds their proficiency in the field of photocatalysis and photovoltaics. ZnO nanostructures were investigated in the shape of nano rods and flowers by, X Ray Diffractometer (XRD) confirms pure hexagonal wurtzite structure of ZnO, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) images showed high crystalline morphology and the formation of nano rods and flowers. Ultraviolet and Photoluminescence (PL) study confirms the absorption at 375, 371 nm for ZnO rods and flower which leads to an increase in the band gap and the peak observed at the violet, blue and green emission. The peaks shift is due to increase in defect in flower nanostructures of ZnO, Dynamic Light Scattering (DLS) calculated the average particles size 617 and 823 nm for rods and flower respectively. Conductivity analysis prove that nano flowers are more conductive having more defects and large number of photocatalytic active sites and large number of electron-hole pairs make best suited for photocatalytic specie. Thus, ZnO nano flowers were observed ideal for photocatalysis and photovoltaic applications due its large number of active sites and defects.

Structural and Electrical Characterization of Ba/ZnO Nanoparticles Fabricated by Co-precipitation

Ba-doped ZnO nanostructures (0.8–4 mmol) were successfully fabricated by the co-precipitation method. X-ray diffraction analysis indicated that all samples exhibited a typical hexagonal wurtzite ZnO structure with the emergence of BaO phase. Moreover, the incorporation of Ba resulted in an increase of crystallite size and lattice parameter while microstrain decreases. The broadening of the Zn–O vibrational band and the redshift in Raman vibrational modes provided clear evidence of the incorporation of Ba within ZnO host lattice. Furthermore, Ba doping prompted an increase of the dielectric constant and ac conductivity (σac). Additionally, the subsequent decrease in tangent loss with increasing the applied field frequency was associated with the hopping frequency of electron that enhances the charge carriers’ mobility.

Effect of aluminum loading on structural and morphological characteristics of ZnO nanoparticles for heavy metal ion elimination.

The aim of this work consists on the synthesis of a nanomaterial for heavy metal ion removal from aqueous solutions. Al-doped ZnO (ZnO:Alx%) nanopowders with 0 to 5% Al content are prepared via an amended sol-gel method. The morphology and microstructure of the prepared ZnO:Alx% are probed by means of scanning electron microscopy (SEM), X-ray particles diffraction (XRD) analysis, energy dispersive X-ray spectroscopy (EDS) and elemental mapping. The findings reveal the prevalence of the hexagonal wurtzite ZnO structure with increasing crystallite size (45 to 60nm) as a result of Al doping. SEM images show nearly spherical nanoparticles with considerable aggregation. EDS and elemental mapping analysis confirm the incorporation of Al within ZnO host lattice. The relatively large surface area as estimated from N2 adsorption makes the nanopowders very favorable for the uptake Cd(II), Cr (IV), Co (II) and Ni(II) from aqueous solution. The ZnO:Alx% with 1wt% Al exhibits the highest uptake rate of heavy metal ions. The adsorption process has been found to be spontaneous and endothermic and obey Langmuir adsorption model. The high tendency of the prepared nanoparticles to eliminate heavy metal ions renders them suitable candidates for environmental remediation. Desorption studies with 0.1M NaOH indicate that ZnO:Alx% can be regenerated effectively.

Synthesis, Characterization, Photocatalytic and Sensing Properties of Mn-Doped ZnO Nanoparticles.

In this paper, Mn-doped ZnO nanoparticles (0 to 10 mol% Mn) were synthesized by facile low-temperature aqueous solution process and characterized by several techniques such as field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-visible and Raman-scattering spectroscopy. The SEM studies confirmed that the synthesized nanoparticles are grown in high density and increase in Mn content was found to have a significant effect on the morphologies of ZnO nanoparticles. The XPS studies established the structural variation of the samples with the change in dopant concentration and its oxidation state. XPS probe the existence of impurity phases in the as-synthesized samples. The results indicate further that hexagonal wurtzite structure of ZnO undergoes distortion with the increase in the dopant concentration. Also, with the increase in the dopant concentration, the blue-shift was observed in the UV-vis. spectra. Photocatalytic and chemicals sensing performances of these nanomaterials have been investigated by subjecting them to photocatalytic degradation of methyl orange (MO) under UV irradiation and for the detection of picric acid (PA) in aqueous solutions. Mn doped ZnO samples were found to be more efficient in catalyzing the MO degradation than pure ZnO. 5 mol% Mn doped ZnO nanomaterials were studied to use as fluorescence sensor for the detection of PA and the observed detection limit was found to be 2.5 μM.

Nano-ZnO Sand Flowers and Rods: Hydrothermal Synthesis and Optical Properties

Nano-ZnO sand flowers and rods were prepared by hydrothermal process using the zinc sulfate (ZnSO4 · 7H2O) as inorganic precursor and hydroquinone (OH–C6H4–OH) or 4-aminophynol (H2N–C6H4–OH) as structure directing agents. The structural and morphology properties of the nano-ZnO were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD and SEM study demonstrated the existence of hexagonal wurtzite structure of ZnO and high degree of crystallinity with crystallite size of 10 to 12 nm with different morphologies. The optical properties of as-synthesized nano-ZnO were also studied. The result of this investigation showed that the band gap for ZnO nanorods and sand flowers have a value which amounted to 3.2 and 3.3 eV, respectively.

Al0.3Zn0.7O film UV detector and its laser sintering synthetic process

Al0.3Zn0.7O solid solution films were firstly synthesized by laser sintering method on quartz glass. The effects of laser sintering power density and sintering time on the properties of Al0.3Zn0.7O films were studied. The optimum laser sintering power density and sintering time were determined to be 44.7 W/cm2 and 25 s respectively. X-ray diffraction (XRD) analysis shows the Al0.3Zn0.7O solid solution films have better c-axis crystalline orientation and belong to hexagonal wurtzite ZnO structure. Ultraviolet absorption edge of the films blue shifts firstly and then red shifts with the laser sintering power density from 27 to 48.9 W/cm2 and sintering time from 10 to 30 s, respectively. Scan electron microscope (SEM) reveals that the film surface forms a rod shape structure. An UV detector with Au strip electrodes was fabricated by a mask method. The detector shows an ohm contact with a surface resistivity of 1.22 × 106 Ω/sq. The photo response has a broad spectrum from 250 to 400 nm peaking at 319 nm and the maximum responsivity is 0.019 A/W corresponding to the detectvity (D*) of 3.6 × 109 cm·Hz1/2·W−1 and signal-to-noise ratio (S/N) of 37.3.

Electrochemical growth and characterization of Cu2O:Na/ZnO heterojunctions for solar cells applications

Cu2O:Na/ZnO/FTO heterojunctions were successfully prepared by a simple two-step electrodeposition method. The effects of the doping concentration of Na on the electronic, morphological, microstructural, optical and electrical properties of the nanostructures were investigated. The deposition was carried out at various concentrations of Na ions and constant bath temperature (70 C°). Cyclic voltammetry was utilized for the determination of the selective potential for electrodeposition of pure Cu2O. Mott-Schottky electrochemical impedance analysis showed p-type conductivity for the Cu2O layers and n-type conductivity for the ZnO films. X-ray diffraction analysis indicated that all doped and undoped Cu2O nanostructures have a polycrystalline nature with a highly cubic Cu2O (111) oriented crystallites and a hexagonal wurtzite structure of ZnO having (002) preferential orientations. Scanning electron microscopy and atomic force microscopy measurements point out the decrease of the grain size and the roughness of Cu2O:Nax/ZnO heterojunctions with the formation of typical (111) textured feature, through the contribution of Na doping. From UV–Vis spectra, a red-shift of the bandgap from 2.223 to 2.008 eV with an increase in the optical conductivity range up to 9 × 1014 cm−1 was noted by increasing the Na content. The current-voltage characteristics of p-Cu2O:Na/n-ZnO heterojunctions showed excellent rectifying behavior, achieving a high rectifying ratio of 3133%. Na doping has been demonstrated by a huge drop in the series resistance of Cu2O/ZnO heterojunctions besides a great improvement in both of the ideality factor and the threshold voltages as well as photoelectric responses. The highlighted results are attractive and suitable for photovoltaic applications.

Wool roving textured reduced graphene oxide-HoVO4-ZnO nanocomposite for photocatalytic and supercapacitor performance

Reduced graphene oxide-HoVO4-ZnO nanocomposite was prepared via simple hydrothermal method and characterized by X-ray powder diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Energy-Dispersive Spectroscopy (EDX), High-Resolution Transmission Electron Microscopy (HR-TEM), X-Ray Photoelectron Spectroscopy (XPS), FT-Raman, UV–Visible Diffuse Reflectance Spectroscopy (DRS), Electrochemical impedance spectroscopy and Cyclic Voltammogram(CV). The XRD pattern confirmed the formation of hexagonal wurtzite structure of ZnO and monoclinic scheelite structure of HoVO4. FE-SEM images depicted the Wool roving textured reduced Graphene Oxide-HoVO4-ZnO catalyst. As prepared rGO-HoVO4-ZnO exhibits highest photodegradation efficiency achieving at 97.2% and 98% for ibuprofen (IBF)and ciprofloxacin (CIP) respectively in 60 min under UV light illumination. Superoxide radicals (O•-2) play an important role in the decomposition of IBF and CIP. Prepared catalysts were found to be stable and reusable even after six consecutive cycles without loss of catalyst. Also Besides, the electrochemical efficiency and galvanostatic charge-discharge of the rGO-HoVO4-ZnO and HoVO4-ZnO composites electrode materials were evaluated by cyclic voltammetry. rGO-HoVO4-ZnO composite showed higher specific capacitance of 322 Fg-1, compared to HoVO4-ZnO (252 Fg-1) in neutral aqueous electrolyte. The enhancement of specific capacitance of the composite electrode is mainly due to the interconnected conductive network as well as synergism of rGO. The experimental results reveal that rGO-HoVO4-ZnO material is an efficient electrode material for high-performance supercapacitors.

Structural and ESR studies of Cu‐doped ZnO nanostructures

AbstractSurface morphology, structural phases, and electron spin resonance (ESR) measurements were performed for Zn1‐xCuxO nanoparticles (x = 0.00, 0.01, 0.02, 0.03, 0.04, and 0.05) synthesized by sol‐gel method. The optimum annealing temperature (600°C) and weight loss was clarified using differential thermal analysis (DTA), and thermo gravimetric analysis (TG). By means of X‐ray diffraction (XRD) technique, the phase of the samples was defined as single with ZnO wurtzite hexagonal structure and proofed by Rietveld analysis for Zn0.98Cu0.02O sample with calculating c/a rate. Spherical shape random particle distributions were observed in all scanning electron microscope (SEM) measurements. ESR measurements were conducted for all samples and g‐value and ΔH (G) values were calculated and correlated from ESR measurements.

Durable Epoxy@ZnO Coating for Improvement of Hydrophobicity and Color Stability of Wood.

The hydrophobicity and color stability of wood are important properties that can be easily changed when wood is used as a raw material for outdoor products, reducing the service life of wood. Herein, an epoxy@ZnO coating was applied by a two-step simple spray coating method to improve the hydrophobicity and color stability of Styrax tonkinensis wood. The hydrophobicity, robustness of coating, as well as the color stability of uncoated wood samples and epoxy@ZnO coated wood samples were evaluated. The microstructure morphology and crystal structures of the coating were also characterized by a field-emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) analysis, respectively. Results showed that the obtained epoxy@ZnO coating was not only superhydrophobic with an average water contact angle of 154.1°, but also maintained superhydrophobicity with an average water contact angle of 149.6° after five water jetting tests. The color stability of the coated wood samples was improved by around 50% compared to that of uncoated wood samples. Additionally, a continuous epoxy@ZnO coating with hierarchical micro/nanoscale structures constructed by the wurtzite hexagonal structure of ZnO micro/nanoparticles on wood surfaces was confirmed.

Hydrothermal synthesis of C doped ZnO nanoparticles coupled with BiVO4 and their photocatalytic performance under the visible light irradiation

For the first time, C-ZnO/BiVO4 heterostructured nanocomposite has been synthesized from BiVO4 and carbon-doped ZnO nanoparticles. X-ray diffraction (XRD) study showed themonoclinic scheelite structure of BiVO4 and the hexagonal wurtzite structure of ZnO in the C-ZnO/BiVO4 composite. Field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) images revealed the spherical nanoparticles of size 20 to 30 nm for C-ZnO. The band gap of the ZnO has turned towards the visible region by doping with carbon as well as a composite formation with visible light active material BiVO4. The chemical states of Zn, O, C and Zn, O, C, Bi, V species in C-ZnO, and C-ZnO/BiVO4 composite respectively were confirmed by X-ray photoelectron microscopy (XPS) analysis. Also, the XPS spectra showed the significant peaks shift in the electronic states of Zn, O, and C for the heterojunction composite. The suppression of the electron-hole recombination rate was confirmed from the quenching of photoluminescence (PL) intensity for the composite. The adsorption study has performed, and the experimental results fit well with the Langmuir isotherm model for understanding the catalytic activity of the samples. The possible Z-scheme photocatalytic mechanism of the C-ZnO/BiVO4 nanocomposite photocatalyst has proposed. The nanocomposite exhibited the enhanced catalytic activity with the higher degradation rate constant of 0.050 min−1 for 50 min irradiation of visible light compared with their counterparts.

Physicochemical behavior of M doped Zn0.95Cu0.05O nanocomposites synthesized by facile sol–gel method

In the present work, the synthesis of Zn0.94Cu0.05M0.01O (M=Ag; Ni; Fe) nanocomposites by a simple sol-gel method is illustrated. XRD, SEM, EDX and FTIR were utilized to characterize the prepared nanocomposites structure; additionally, their porosity and surface area were investigated via N2 adsorption. The XRD data asserted the pertinence of the ZnO hexagonal wurtzite structure with the evolution of a CuO monoclinic phase. The FTIR analysis emphasized the bonding of the metal ions to the ZnO host as dictated by a shift in the Zn–O vibration mode. The dielectric properties variations with frequencies as a consequence of the incorporation of M-ions in the Zn0.95Cu0.05O nanocomposite showed that the dielectric constant, dielectric loss tangent and conductivity values were found to change inversely with the applied frequencies. On the other hand a direct dependence of impedance was observed. Hopping of charge carriers between ions such as Fe2+ → Fe3+ and Cu2+ + M+n → Cu+ + M+n+1 may be the cause for the electrical and dielectric dispersion in the samples. The above mentioned findings make these materials promising candidates for optoelectronic and photocatalytic applications.

Synthesis and characterization of undoped and Er-doped ZnO nano-structure thin films deposited by sol-gel spin coating technique

Pure and Erbium (Er3+)-doped ZnO (Er3+ = 0.0, 1.0 and 1.5 mol%) nano-structure thin films were prepared by modified sol-gel spin coating technique. The influence of Er doping on the composition, structure, morphology, optical was examined by energy dispersive x-ray analysis (EDS), x-ray diffraction (XRD), transmission electron microscope (TEM), Raman spectroscopy, field emission scanning electron microscopy (FESEM). The XRD measurement and selected area electron diffraction pattern (SEDA) confirmed the hexagonal wurtzite structure of ZnO for all samples and average crystallite size is about 9.7 nm. Moreover, Both XRD and Raman spectroscopy show that the incorporation of Er3+ in ZnO matrix resulted in improved crystallinity. FESEM plane images indicated that the ZnO thin film has interconnected spherical particles with the presence of pore, whilst Er-doped ZnO films have compact and uniform morphology. Analyses of optical data point out that value of band gap of Er doped ZnO have lower values than pure film, consistent with earlier works prepared by different methods. The absorption edge shifts towards lower photon energies with increasing Erbium content.

Fabrication of n-MgZnO/p-Si heterojunction diode: Role of magnesium doping

Transparent conducting undoped and magnesium doped zinc oxide (MgZnO) thin films were deposited on glass and p-Si(100) substrates via atmospheric pressure chemical vapor deposition method. Influence of varied Mg content (0, 2, 4 and 6 wt%) on the morphology, structure, optical and electrical behavior of the fabricated n-MgZnO/p-Si heterojunction diodes were evaluated. AFM images of the film containing 6 wt% of Mg revealed dense columns-like morphology and fewer voids on the film's surface. Both the average surface roughness (from 91 ± 5 to 32 ± 2 nm) and the grain size (from 63.5 ± 3.2 to 29.0 ± 1.5 nm) of films were decreased with the increase in Mg content from 0 to 6 wt%. XRD patterns of the studied films showed the polycrystalline hexagonal wurtzite structure of ZnO with preferred lattice orientation along the c-axis at x = 6 wt%. With increasing Mg content, the transmittance of the film was enhanced up to ∼85% accompanied by a blue-shift at the UV absorption edge and the band gap was widened from 3.22 to 3.46 eV. All the n-MgZnO/p-Si heterojunction diodes exhibited clear rectification behavior (a real signature of the p-n junction diode) wherein the electrical parameters were sensitive to the doping concentration. Furthermore, the electrical traits of the diodes were significantly improved due to the inclusion of Mg2+ into the ZnO films. In terms of rectification performance, the diodes prepared at x ≥ 4 wt% were the best. The proposed controlled growth strategy may constitute a basis to realize high-performance nano-optoelectronic heterojunction devices.

Microwave-assisted synthesis of FexZn1−xO nanoparticles for use in MEH-PPV nanocomposites and their application in polymer light-emitting diodes

A one-step microwave-assisted polyol method was used to fabricate FexZn1−xO (x = 0.01, 0.05, 0.10) nanoparticles. Zinc acetate dihydrate, iron (III) acetylacetonate, oleic acid and diethylene glycol were placed in a Teflon-lined reaction vessel. The reaction mixture was heated up to 250 °C for 15 min in a microwave reactor. The surface modification with oleic acid prevented agglomeration of the nanoparticles. The X-ray diffraction analysis revealed characteristics wurtzite hexagonal structure of ZnO and successful incorporation of the Fe dopant into the host crystal lattice. Doping of ZnO by Fe led to bandgap modification as estimated by Tauc plot. The as-prepared nanopowders were dispersed in toluene and mixed with a poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) polymer to make stable homogenous dispersions. Then, the FexZn1−xO/MEH-PPV nanocomposite thin films were prepared by spin coating and used as thin active layers in polymer light-emitting diodes. The thickness of deposited FexZn1−xO/MEH-PPV film was ca. 30 nm and that of reference neat MEH-PPV film was ca. 25 nm. The electroluminescent spectroscopy study showed that direct blending of MEH-PPV with Fe-doped ZnO nanoparticles is a simple and effective approach to significantly increase the luminance intensity of the diode in comparison to the diode fabricated by neat MEH-PPV.

Structural and electrical properties of zno varistor with different particle size for initial oxides materials


 
 
 We report here structural, electrical and dielectric properties of ZnO varistors prepared with two different particle sizes for initial starting oxides materials (5 µm and 200 nm). It is found that the particle size of ZnO does not influence the hexagonal wurtzite structure of ZnO, while the lattice parameters, crystalline diameter, grain size and Zn-O bond length are affected. The nonlinear coefficient, breakdown field and barrier height are decreased from 18.6, 1580 V/cm and 1.153 eV for ZnO micro to 410 V/cm, 7.26 and 0.692 eV for ZnO nano. While, residual voltage and electrical conductivity of upturn region are increased from 2.08 and 2.38x10-5 (Ω.cm)-1 to 4.55 and 3.03x10-5 (Ω.cm)-1. The electrical conductivity increases by increasing temperature for both varistors, and it is higher for ZnO nano than that of ZnO micro. The character of electrical conductivity against temperature is divided into three different regions over the temperature intervals as follows; (300 K ≤ T ≤ 420 K), (420 K ≤ T ≤ 580 K) and (580 K ≤ T ≤ 620 K), respectively. The activation energy is increased in the first region from 0.141 eV for ZnO micro to 0.183 eV for ZnO nano and it is kept nearly constant in the other two regions. On the other hand, the average conductivity deduced through dielectric measurements is increased from 2.54x10-7 (Ω.cm)-1 for ZnO micro to 49x10-7 (Ω.cm)-1. Similar behavior is obtained for the conductivities of grains and grain boundaries. The dielectric constant decreases as the frequency increases for both varistors, and it is higher for ZnO nano than that of ZnO micro. These results are discussed in terms of free excited energy and strength of link between grains of these varistors.
 
 

Gas sensing properties of ZnO nanostructures (flowers/rods) synthesized by hydrothermal method

Here, we report the hydrothermal synthesis of flower-shaped ZnO nanostructures and investigated their morphology-dependent gas sensing properties. Scanning electron microscope (SEM) study confirmed the formation of two kinds of floral structures. At short reaction time, flower-like structures (2–3 μm in size) composed of nanoparticles are formed, whereas floral assemblies (˜ 5 μm) of nanorods are formed at long reaction time. X-ray diffraction (XRD) confirmed the formation of the hexagonal wurtzite structure of ZnO. The average crystallite size of prepared nanoflowers and nanorods were found to be 21 nm and 43 nm, respectively. These results are supported by transmission electron microscopy (TEM). The band gap of ZnO nanostructures was calculated from the UV–vis absorption spectrum and found to be 3.0 eV and 3.19 eV for ZnO nanoflowers and nanorods, respectively. Broad absorption peak in the visible region of photoluminescence (PL) spectra confirmed the presence of oxygen vacancies in both specimens. Furthermore, morphology dependent gas sensing property was investigated for ethanol, benzene, carbon monoxide, and nitrogen dioxide at different operating temperatures and concentrations. Although both morphologies have shown good sensitivity and selectivity towards NO2 at ppb, the response of nanoflower was higher than that of nanorods, which was attributed to its relatively higher surface area and amount of surface defects.

Dielectric and magnetic properties of nanoporous nickel doped zinc oxide for spintronic applications

Abstract Nanoporous Ni doped ZnO is prepared in the configuration NiO(x)·ZnO(1−x) (x = 0, 0.02, 0.04, 0.06, 0.08 and 0.10) using sol-gel combustion technique. The crystal structure, morphology, elemental composition, magnetic and dielectric properties of NiO(x)·ZnO(1−x) are determined from XRD, FE-SEM with EDX, VSM and LCRQ meter, respectively. XRD investigation confirms the presence of wurtzite hexagonal structure of ZnO in all the prepared samples. At low doping level of Ni, the crystal structure remains identical to ZnO meanwhile some structural imperfection is observed on increasing the doping concentration. FESEM images indicate the occurrence of nanopores distributed uniformly in the NiO(x)·ZnO(1−x). Magnetic characteristics of the samples found enhanced with increasing dopant concentration till x = 0.06. The possible explanation for the origin of the dielectric and magnetic behaviours of NiO(x)·ZnO(1−x) are discussed. Based on the obtained results, NiO(0.06)·ZnO(0.94) is a suitable candidate for Diluted Magnetic Semiconductors for spintronic applications.

Fabrication of Al and Ga Co‐Doped ZnO Films on Flexible Substrates and Control Charts Monitor Deposition Process

Al and Ga co‐doped zinc oxide (AGZO) films are deposited onto flexible poly(ethylene terephthalate) (PET) substrates by radio frequency magnetron sputtering. Before the AGZO film coating, oxygen plasma etching is used to modify the surface of the PET substrate. The results show that the substrate is very hydrophilic. This study determines the effect of the deposition parameters on the structural, morphological, and optoelectronic performances of AGZO films. Based on the gray Taguchi analysis for the AGZO film coatings show that the electrical resistivity is decreased to 6.30 × 10−3 Ω cm and the optical transmittance is increased to 81.0%. The XRD diffraction and TEM images show that the AGZO films exhibit a hexagonal ZnO wurtzite structure. A comparison of the PET substrates that do or do not undergo plasma pretreatment, shows that the AGZO films coating there is a 4.7% improvement in elastic recovery, a 13.65% improvement in hardness H, a 1.69% improvement in the elastic modulus E, a 12.15% improvement in in H/E, and a 42.06% improvement in H3/E2. Shewhart control charts are used to monitor the deposition processes for the AGZO films. Finding shown that the deposition parameters for the films and process performance are in control and stable.

Dehydration of 1,5‐Pentanediol over ZrO2‐ZnO Mixed Oxides

AbstractZn addition was found to affect both activity and selectivity of ZrO2 for dehydration of 1,5‐pentanediol. ZrO2 tends to produce more or less equimolar mixture of tetrahydropyran (THP) derivatives and 4‐penten‐1‐ol from 1,5‐pentanediol. The conversion of 1,5‐pentanediol on ZrO2 increases with increasing Zn content up to 30–50 mole percent; however, catalyst containing Zn beyond 50 mole percent had an adverse effect on both conversion of diol and the selectivity for unsaturated alcohol (i. e., 4‐penten‐1‐ol). XRD and Raman analysis infer that the presence of tetragonal ZrO2, the amorphous phase (ZrO2, ZrZnOx, ZnO), and hexagonal wurtzite structure of ZnO in the catalysts. The interplanar spacing of ZrO2 (111) and ZnO (100) planes for catalysts indicate that Zn incorporates into ZrO2 lattice and vice‐versa. Basicity assessed from CO2‐TPD and acidity from FTIR‐pyridine adsorption techniques indicate that both basicity and Lewis acid sites density increases with increasing Zn proportion on ZrO2 up to 50:50 molar ratios of Zn to Zr. An optimum Zn:Zr mole ratio is required to achieve higher density of oxygen vacant metal sites (i. e., Lewis acidity) and balanced acid‐base strength which improves the diol conversion.