Single-step sol-gel deposition and dielectric properties of 0.4 μm thick, (001) oriented Pb(Zr,Ti)O<Subscript>3</Subscript> thin films

Single-step sol–gel deposition was attempted for realizing submicron thick, (001) oriented Pb(Zr_0.53Ti_0.47)O₃ (PZT) thin films, using an alkoxide solution containing polyvinylpyrrolidone (PVP). A solution of molar composition, Pb(NO₃)₂:Zr(OC₃H₇ ⁿ)₄:Ti(OC₃H₇ ⁱ)₄:PVP:H₂O:CH₃COCH₂COCH₃:CH₃OC₂H₄OH:C₃H₇ ⁿOH = 1.1:0.53:0.47:0.5:5:0.5:22:0.98, was prepared as a coating solution. Gel films were prepared on Pt(111)/TiO₂/SiO₂/Si(100) substrates by spin-coating, and calcined at 350 °C and annealed at 650 °C either in an electric furnace or in a near-infrared (IR) furnace. When calcined in the near-IR furnace, the films became (001) oriented on annealing. When calcined in the electric furnace, on the other hand, the films became randomly oriented on annealing. These observations indicate that the heating the gel films from the substrate side in the calcination step at 350 °C induces crystallographic orientation in the annealing step at 650 °C. The effects of the heating methods on the thermal decomposition of the gel films, and the microstructure and dielectric properties of the fired films were studied. Finally 0.4 μm thick, (001) oriented PZT films could be successfully prepared by non-repetitive, single-step deposition. The oriented film thus obtained had the remnant polarization 2P _r of 39 μC/cm² and the dielectric constant ε′ of 960 ± 169.     

Atranes

Silatrane, in the presence of the corresponding sodium alkoxide of phenoxide readily reacts with alcohols and phenols with the liberation of hydrogen and the formation of 1-alkoxy- or 1-aryloxyatranes, . Depending on the nature of the alcohol or phenol, the rate of the reaction falls in the following sequence: p-CH₃OC₆H₄OH > p-(CH₃)₃CC₆H₄OH = n-C₄H₉OH = = n-C₅H₁₁OH > i-C₄H₉OH > s-C₄H₉OH > p-CH₃C₆H₄OH > C₆H₅OH > > p-ClC₆H₄OH > t-C₄H₉OH > p-O₂NC₆H₄OH > C₆F₅OH. The rate of the dehydrocondensation reaction of hydrosilanes with alcohols rises in the sequence . In the presence of ZnCl₂ as catalyst, the dehydrocondensation reaction of silatrane with alcohols takes place considerably more slowly and does not go to completion. The formation of 1-organyloxysilatranes from silatrane and alcohols does not take place in the presence of H₂PtCl₆ or in the absence of catalysts. Using the dehydrocondensation reaction, twelve 1-organyloxysilatranes have been synthesized, two of which were previously unknown.     

Schiff base derivatives of lanthanons

Bifunctional tridentate Schiff bases such as, $$\begin{gathered} HOC_6 H_4 C(CH_3 ) : NCH_2 CH_2 OH, \hfill \\ HOC_6 H_4 C(CH_3 ) : NCH_2 CH_2 (OH)CH_3 , \hfill \\ HOC_6 H_4 C(H) : NCH_2 CH_2 OH \hfill \\ \end{gathered} $$ and HOC₆H₄C(H)∶NCH₂CH(OH)CH₃ react with La(III), Pr(III) and Nd(III) isopropoxides to 1∶1 and 2∶3 derivatives of the type,Ln(O?i-C₃H₇)(OC₆H₄C[R]∶NR′O) andLn ₂(OC₆H₄C[R]∶ NR′O)₃ [where,Ln=La(III), Pr(III) or Nd(III); R=CH₃ or H and R′=CH₂?CH₂ or CH₂CHCH₃] in dry benzene. The labile nature of the isopropoxy groups in the 1∶1 derivatives has been shown by exchange reactions with an excess oft-butyl alcohol leading to the formation ofLn(O?t-C₄H₉)(OC₆H₄C[R]∶NR′O); (where R=CH₃ and R′=CH₂CHCH₃) type derivatives in almost quantitative yield. The IR spectra of the resulting derivatives have been recorded in the range of 4000–400 cm^?1, ν C=N frequency bands appear at ≈ 1620 cm^?1 and almost no change has been noted in their positions on complexation. Some new peaks are, however, observed in the range of 700–600 cm^?1 and these may be ascribed to the ring deformation coupled with both theLn?O stretching and C?CH₃ stretching modes.     

Excess Volumetric and Spectroscopic Properties of Mixtures of Some <Emphasis Type="Italic">n</Emphasis>-Alkoxyethanols and of Some Polyethers with 2-Pyrrolidinone and <Emphasis Type="Italic">N</Emphasis>-Methyl-2-Pyrrolidinone at 298.15 K

Excess molar volumes V_m^E for binary liquid mixtures of n-alkoxyethanols or polyethers + 2-pyrrolidinone or N-methyl-2-pyrrolidinone have been measured with a continuous dilution dilatometer at 298.15 K and atmospheric pressure as a function of composition. The alkoxyethanols are diethylene glycol monomethylether, 2-(2-methoxyethoxy) ethanol, CH₃(OC₂H₄)₂OH; diethylene glycol monoethylether, 2-(2-ethoxyethoxy) ethanol, C₂H₅(OC₂H₄)₂OH; and diethylene glycol monobutylether, 2-(2-butoxyethoxy) ethanol, C₄H₉(OC₂H₄)₂OH; whereas the polyethers are diethylene glycol dimethylether, bis(2-methoxyethyl)ether, CH₃(OC₂H₄)₂OCH₃; diethylene glycol diethylether, bis(2-ethoxyethyl)ether, C₂H₅(OC₂H₄)₂OC₂H₅; and diethylene glycol dibutylether, bis(2-butoxyethyl)ether, C₄H₉(OC₂H₄)₂OC₄H₉. In all mixtures the excess molar volumes are negative and symmetric across the entire composition range. The excess volumes are fitted to the Redlich–Kister polynomial equation to obtain the binary coefficients and the standard errors. The experimental results have also been discussed on the basis of IR measurements.     

Bi4Ti3O12 Thin Films from Mixed Bismuth-Titanium Alkoxides

Bi₄Ti₃O₁₂ thin films were obtained by the sol-gel method. The precursor solution was prepared by allowing the two metallic alkoxides, Bi(OC₂H₄OCH₃)₃ and Ti(OC₂H₄OCH₃)₄, to react in 2-methoxy-ethanol to form the mixed alkoxide. This stable sol was deposited by spin-coating onto platinized silicon substrates. X-Ray diffraction patterns indicate that the perovskite initial crystallization temperature is 460°C for powder samples and it ranges between 400 and 500°C, for thin films, as a function of the number of coating layers. Dense, smooth and crack free thin films with grain sizes ranging from 20 nm to 500 nm are obtained, depending on the number of coating layers and on the post-deposition temperature annealing.     

Consecutive reactions of diethoxydimethylsilane and triethoxymethylsilane with methoxide ions in methanol solution

The consecutive reactions of (CH₃)₂Si(OC₂H₅)₂ and CH₃Si(OC₂H₅)₃ with methoxide ions were investigated in methanol solutions. The reverse transesterification reactions with ethoxide ions could be neglected in both cases since the concentration of ethoxide in methanol solution was assumed to be low due to the fast equilibrium reaction C₂H₅O^? + CH₃OH ? C₂H₅OH + CH₃O^?. The progress of the reactions was followed by monitoring the formation of ethanol with a Fourier-transform infrared spectrometer. All rate constants were determined at 295 K. The reactions between the dialkoxydimethylsilanes and methoxide ions were assumed to consist of two consecutive steps that can be represented by the net reaction; (CH₃)₂Si(OC₂H₅)₂ + 2CH₃O^? → (CH₃)₂Si(OCH₃)₂ + 2C₂H₅O^?. The two consecutive rate constants were established as 1.93 ± 0.12M^?1s^?1 and 1.00 ± 0.12M^?1s^?1, respectively. The consecutive rate constants for the reactions between the trialkoxymethylsilanes and methoxide ions can be written according to the total reaction; CH₃Si(OC₂H₅)₃ + 3CH₃O^? → CH₃Si(OCH₃)₃ + 3C₂H₅O^?. The three rate constants corresponding to each consecutive step were established as 1.12 ± 0.09 M^?1s^?1, 0.82 ± 0.10 M^?1s^?1, and 0.51 ± 0.06 M^?1s^?1, respectively. © 1995 John Wiley & Sons, Inc.     

Mono- and Bis-N-[3-(triorganylsilyl)propyl]guanidines and Their Derivatives

Organosilicon guanidine derivatives RNHC(=NH)NHCH₂CH₂CH₂Si(OC₂H5)_{3 - n} (OH)_n [R = H, n = 1; R = (CH₂)₃Si(OC₂H₅)₃, n = 0] were synthesized by condensation of guanidinium carbonate with (3-aminopropyl)triethoxysilane. The products were brought into ether interchange with thiethanolamine and hydrolytic polycondensation.     

Transition metal containing dendrimers based on cyclophosphazene units

The series of complexes [N₃P₃(OC₆H₅)₅OC₆H₄CH₂CN·MCl_n]PF₆, N₃P₃(OC₆H₄CH₂CN)₆·(MCl_n)₆](PF₆)₆, [N₃P₃(OC₆H₅)₅OC₆H₄CH₂CN·MCl_n−1]Cl and [N₃P₃(OC₆H₄CH₂CN)₆·(MCl_n−1)₆]Cl₆, MCl_n=MnCl₂, FeCl₃, CoCl₂, NiCl₂, CuCl₂ have been synthesized by reaction of the corresponding cyclophosphazene ligands: N₃P₃(OC₆H₅)₅OC₆H₄CH₂CN (L₁) and N₃P₃(OC₆H₄CH₂CN)₆ (L₂) with the respective salts MCl_n in CH₃OH as solvent and in presence or absence of NH₄PF₆. The new compounds were characterized by elemental analysis and IR, UV–Vis and EPR spectroscopy as well as electrochemical methods. The reaction of CuCl₂ with the ligand L₁ affords the copper (I) complex. [N₃P₃(OC₆H₅)₅OC₆H₄CH₂CN·Cu]PF₆ instead the expected Cu(II) complex, which was characterized by multinuclear NMR. For comparison, the complex [N₃P₃(OC₆H₅)₅OC₆H₄CH₂CN·ZnCl]PF₆ was also prepared. The hexametalladendrimers of iron exhibits a six-electron reduction while that the correspondent monometalladendrimers exhibit a single one-electron reduction. Upon coordination νCN increase in a similar way to crystal field effects dependence with the metal.     

Investigation of Polymerization and Cyclization of Dimethyldiethoxysilane by 29Si NMR and FTIR

Dimethyldiethoxysilane (DMDES) appears to be a very promising modifier to introduce functional groups to a silicate network. The polymerization and cyclization of DMDES under acid-catalyzed conditions (DMDES : Ethanol : water : HCl = 1:4:4:3.68 × 10^–4 in molar ratio) were investigated by high resolution liquid ²⁹Si nuclear magnetic resonance (NMR) and Fourier transform infrared spectrometry (FTIR). Time-dependent NMR and FTIR data illustrate that monomers of (CH₃)₂Si(OC₂H₅)₂, (CH₃)₂Si(OC₂H₅)(OH), and (CH₃)₂Si(OH)₂ reach meta-equilibrium in less than 4 minutes. 3-membered rings ((CH₃)₂SiO)₃ appear about half an hour later and 4-membered rings ((CH₃)₂SiO)₄ an hour later, which continue to be formed over 24 hours. The relative concentrations of monomers, linear structures and cyclic structures suggest a modified model for the kinetics of cyclization, where 4-membered rings are formed by dimer-dimer interactions, as opposed to monomer-trimer interactions previously proposed.     

Synthesis and mesomorphism of mixed ether-ester tail triphenylene discotic liquid crystals with long alkyloxy peripheral chains

Symmetrical and asymmetrical triphenylene discotic liquid crystals with two kinds of different peripheral chains, sym-TP(OC₁₁H₂₃)₃(O₂CR)₃ and asym-TP(OC₁₁H₂₃)₃(O₂CR)₃, (R=CH₂OC₂H₅, CH₂OC₃H₇, CH₂OC₄H₉, CH₂OC₅H₁₁, C₃H₇, C₄H₉, C₅H₁₁, C₆H₁₃, C₇H₁₅) were synthesized. Their thermotropic liquid crystalline properties were studied by polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). The results showed that the asymmetrical compounds had higher melting and clearing points than that of their corresponding symmetrical compounds. For the same series of compounds, TP(OC₁₁H₂₃)₃(O₂CR)₃, their melting points decrease and clearing points increase gradually with the lengthening of ester chains. Most of the β-oxygen containing esters of triphenylene derivatives, TP (OC₁₁H₂₃)₃(O₂CR)₃, (R=CH₂OC₂H₅, CH₂OC₃H₇, CH₂OC₄H₉, CH₂OC₅H₁₁), symmetrically or asymmetrically attached on triphenylene cores, have higher melting and clearing points than those of triphenylene derivatives, TP(OC₁₁H₂₃)₃(O₂CR)₃, (R=C₄H₉, C₅H₁₁, C₆H₁₃, C₇H₁₅), with the same length of peripheral chains. The triphenylene derivatives with longer peripheral chains have shown mesophase at room temperature. __________ Translated from Chemical Research and Application, 2007, 19(10) (in Chinese)     

Pervaporation of alcohols through highly permeable PIM-1 polymer films

Polycondensation material PIM-1 has attracted the attention of researchers owing to its high transport parameters in gas separation and a high free volume. The pervaporation characteristics of PIM-1 have been systematically studied. Lower aliphatic alcohols (CH₃OH, C₂H₅OH, and n-C₄H₉OH) and water were selected as objects of research. The rates of mass transfer for individual components at various temperatures have been estimated, and for the ethanol-water binary mixture, the process of separation has been examined. The films based on the polymer under study exhibit the properties of organophilic membranes and are characterized by high permeability with respect to alcohols. The apparent activation energy of permeability is low. This behavior is common for pervaporation membranes based on glassy polymers with a high free volume. The parameters of separation for the water-alcohol mixture surpass corresponding values for typical organophilic membranes based on PDMS. These parameters are commensurable with the values observed for membranes based on poly(trimethylsilylpropyne). At the same time, PIM-1 does not demonstrate a rapid decrease in permeability in the course of time.     

Encapsulation and Dynamic Behavior of Methanol and Formaldehyde inside Open‐Cage C60 Derivatives

Methanol (CH₃OH) and formaldehyde (H₂CO) molecules were inserted into an open‐cage C₆₀ derivative with a large opening, under high‐pressure and high‐temperature conditions in solution. Isolation of their molecular complexes in pure form was achieved by the use of recycling HPLC with Buckyprep columns. ¹H NMR spectroscopy, single‐crystal X‐ray diffraction studies, and DFT calculations revealed the orientation of the encapsulated CH₃OH and H₂CO, both in solution and in the solid state, and the results show that the CH₃ group of the CH₃OH and the carbonyl group of the H₂CO point to the bottom of the cages. Furthermore, the dynamic behavior of the CH₃OH and H₂CO were studied at the molecular level.     

Methanol als Ligand in Natriumphenolat: Darstellung und Struktur von [Na(CH3OH)4][OC6H5]

Methanol as a Ligand in Sodium Phenoxide: The Synthesis and Crystal Structure of [Na(CH₃OH)₄][OC₆H₅] By the reaction of sodium and phenol in N-methyl-?-caprolactam (NMC) sodium phenoxide has been yielded, which forms a complex with the furthermore obtained methanol of [Na(CH₃OH)₄][OC₆H₅]. The single crystals crystallize triclinic, space group P1 , with the lattice constants a = 6.613(3) Å, b = 10.537(4) Å, c = 10.656(4) Å, α = 108.27(2)°, β = 98.21(2) and γ = 95.26(2)°. Sodium is coordinated by six oxygen atoms of methanol in the form of an octahedron. These coordination polyhedrons are connected by sharing edges forming chain, whereas, the oxygen of phenoxide is not involved in the coordination of sodium. Although it is attached to the chain by hydrogen bonding.     

OXYPHOSPHORANE MODELS FOR NUCLEOPHILIC DISPLACEMENTS AT Pα AND Pγ OF ADENOSINE-5′ TRIPHOSPHATE

Abstract

The reaction of dimethylphosphorous triethylpyrophosphoric anhydride, (CH₃O)₂POP(O)(OC₂H₅)OP(O)(OC₂H₅)₂, with hexafluorobiacetyl, CF₃COCOCF₃, yields 4,5-bis(trifluoromethyl)2,2-dimethoxy-2-triethylpyrophosphato-2,2-dihydro-1,3,2-dioxaphospholene. This oxyphosphorane, with a pyrophosphate group at the apical position of trigonal bipyramidal phosphorus, simulates the pentacovalent intermediate in the addition-elimination mechanism of nucleophilic displacements at the Px and Py centers of adenosine-5′ tri-phosphate. The oxyphosphorane is remarkably stable in solution, although the pyrophosphate group is easily displaced by an alkoxy group in base-catalyzed reactions with alcohols.     

Preparation and Optical Properties of Gold-Dispersed BaTiO3, PGO (Pb5Ge3O11) and PLT (Pb1-1.5xLaxTiO3) Thin Films by Sol-Gel Process

Gold-dispersed BaTiO₃, PGO and PLT thin films, which will be used for third-order nonlinear optical devices, were prepared by sol-gel process with spin-coating using HAuCl₄4H₂O, Ba(CH₃COO)₂, Ti[O(CH₂)₃CH₃]₄, Pb(CH₃COO)₂3H₂O, Ge[O-n-C₄H₉]₄, La(CH₃COO)₃1.5 H₂O as starting materials. The thin films were heat-treated in air at temperatures ranging from 400 to 800 for 1 h. The nonlinear optical property of these thin films was measured by the degenerate four-wave mixing (DFWM) method using a frequency-doubled Nd: YAG laser with 20 ps pulse duration. Third-order nonlinear susceptibility χ⁽³⁾ of gold-dispersed BaTiO₃, PGO and PLT thin films with 5 vol% of gold were 1.410⁻⁶ esu, 3.510⁻⁷ esu respectively. The large χ⁽³⁾ may be ascribed to the high dielectric constant of the films.     

Secondary isotope effects in the mass spectra of C2D5OC2H5 and CD3CH2OC2H5

Secondary isotope effects were examined in the loss of methyl from the molecular ions of C₂D₅OC₂H₅ and CD₃CH₂OC₂H₅ for ion source processes and collisional activation (CA) processes. In the ion source loss of CH₃ was slightly favored over loss of CD₃, but in CA the CH₃ loss was favored to a much larger extent than expected. A possible explanation is given which invokes an energy distribution function peaked near the appearance energy for the methyl loss process.     

Complexes carbeniques des ferroporphyrines: Preparation de complexes carbeniques comportant deux substituants electrodonneurs par alcoolyse ou thionolyse des complexes halogenocarbeniques correspondants

α-Halocarbeneporphyriniron complexes, Fe(P)(C(Cl)R) react with alcohols or thiols with substitution of the chlorine atom by OR′ or SR′ groups. This reaction has been used to obtain new carbeneporphyriniron complexes in which the carbene ligand is substituted by two electrodonating groups. The complexes Fe(P)(C(XR′)R) with XR′ = OCH₃ or OC₂H₅, R = CH₃ or (CH₃)₂CH and P = TPP (tetraphenylporphyrin) or TTP (tetratolylporphyrin) and with XR′ = SCH₂C₆H₅, R = CH₃ and P = TPP or TTP, have been isolated and fully characterized.     

Synthese d'ethers et de thioethers allyliques fluores par catalyse par transfert de phase

Several fluorinated allylic ethers, thioethers and diethers have been prepared in excellent yields by phase transfer catalysis (CTP). The used halogenated compounds are allyl chloride and bromide, p-chloromethylstyrene. The used fluorinated alcohols are aromatic pentafluorophenol and various aliphatics: CF₃CH₂OH, CF₂HCF₂CH₂OH ClCF₂CF₂CH₂OH,C₆F₁₃C₂H₄OH, HOCH₂CF₂CFClCF₂CH₂OH and HOC₆H₄C(CF₃)₂C₆H₄OH. All these new compounds have been characterized by ¹H and ¹³C NMR. We conclude that CTP is the best method to obtain allylic and diallylic compounds.     

Kinetics and mechanism associated with the reactions of hydroxyl radicals and of chlorine atoms with 1‐propanol under near‐tropospheric conditions between 273 and 343 K

Rate constants for the reactions of OH radicals and Cl atoms with 1‐propanol (1‐C₃H₇OH) have been determined over the temperature range 273–343 K by the use of a relative rate technique. The value of k(Cl + 1‐C₃H₇OH) = (1.69 ± 0.19) × 10^?12 cm³ molecule^?1 s^?1 at 298 K and shows a small increase of 10% between 273 and 342 K. The value of k(OH + 1‐C₃H₇OH) increases by 14% between 273 and 343 K with a value of (5.50 ± 0.55) × 10^?12 cm³ molecule^?1 s^?1 at 298 K, and further when combined with a single independent experimentally determined value at 753 K gives k(OH + 1‐C₃H₇OH) = 4.69 × 10^?17T^1.8 exp(422/T) cm³ molecule^?1 s^?1, which fits each data point to better than 2%. Two well‐established structure–activity relationships for H abstraction by OH radicals give accurate predictions of the rate constant for OH + 1‐C₃H₇OH, provided the β‐CH₂ group is given an increased reactivity of a factor of about 2 over that for the structurally equivalent CH₂ group in alkanes at 298 K. A quantitative product analysis was carried out at 298 K for the Cl‐initiated photooxidation of 1‐C₃H₇OH, using both FTIR and gas chromatography. HCHO, CH₃CHO, and C₂H₅CHO were the only major organic primary products observed, although HCOOH was found in much smaller amounts as a secondary product. A key characteristic of the analysis was that the initial values of the product ratio [CH₃CHO]/[C₂H₅CHO] were effectively constant for NO pressures between 0.15 and 0.3 Torr, but fell by about 35% as the pressure fell to 0.0375 Torr. From a detailed consideration of the mechanism for the oxidation, it is suggested that C₂H₅CHO, CH₃CHO (+HCHO), and 3 molecules of HCHO are formed uniquely from CH₃CH₂CHOH, CH₃CHCH₂OH, and CH₂CH₂CH₂OH radicals, respectively. On this basis, use of the product yields gives the branching ratios of 56, 30, and 14% for Cl atom reaction at the α‐, β‐, and γ‐C? H positions in 1‐C₃H₇OH at 298 K. Given the very low temperature coefficients involved, little change will occur over tropospheric temperature ranges. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 110–121, 2002     

Allylstannation III. Synthesis of homoallylic alcohols and 4-chloro-2,6-dialkyl-3-methyltetrahydropyrans by reactions between (E/Z)-2-butenyldichloro-n-butyltin and aldehydes

2-Butenyldichloro-n-butyltin (in various cis/trans isomer ratios) reacts readily with neat RCHO (R = CH₃, C₂H₅, (CH₃)₂CH, and C₆H₅) at 25°C to give (a) linear alcohols, RCH(OH)CH₂CHCHCH₃ in the E and Z forms, (b) branched alcohols, RCH(OH)CH(CH₃)CHCH₂ in the threo and erythro forms, and (c) 2,3,4,6-tetra-substituted tetrahydropyrans (A) as a mixture of cis/trans isomers arising from the CH(CH₃)CHCl bond. The maximum yields of these tetrahydropyrans were obtained

by the use of 3–3.5 molar ratios RCHO/tin compound in the absence of solvent, whereas work-up after reactions in CH₂Cl₂ gave linear, alcohols as the main products. The formation of linear alcohols appears to be stereospecific, as the ratio of _E/_Z isomers obtained is the same as that in the organotin compound. Tetrahydropyrans are formed preferentially as the _trans isomers.