摘要:

Transparent ferroelectric ceramic materials suitable for a variety of electrooptic applications were found in the quaternary (Pb,La)(Zr,Ti)O3system. These PLZT materials are prepared from mixed oxides and hot‐pressed typically at 1100°C for 16 h at 2000 psi. Modifying the lead zirconate‐titanate system with lanthana linearly reduces the Curie point with increasing lanthana. Transmission measurements in the visible and infrared show that these materials exhibit a nearly constant response from the absorption edge of 0.37 μ to ∼6 μm. The highest transmission values, essentially 100% (neglecting reflection losses of ∼18%) for thin polished plates, were noted for compositions containing 8 at.% La or more. Specific compositions within the system display electrooptic memory or conventional linear or quadratic electrooptic effects; on the basis of the magnitude of the electrooptic effects, they compare quite favorably with singl

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12105.x-i1

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Freezing and eutectic temperatures were determined for the NaF‐KF‐K2NbF7ternary system and the NaF‐K2NbF7, KFK2NbF7, and NaF‐KF binary systems. The compound KF‐K2NbF7freezes congruently at 770°C; eutectics occur at 708° and 724°C for high‐ and low‐K2NbF7mixtures, respectively. The NaF‐K2NbF7eutectic freezes at 658°C. The ternary system has two eutectics, a high‐KF mixture and a high‐K2NbF7mixture, which occur at 663°

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12156.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The compositions of anion‐deficient zirconia and thoria in equilibrium with O2were measured from 1 to 10−6atm and 1400° to 1900°C; for ZrO2‐x(po2in atm, and T in °K), log x∼−0.890‐[(0.400×104)/T]‐[(logp)/6]; for ThO2‐x, log x∼−1.870‐[(0.340×104)/T]‐[(logp)/6]. The ZrO2‐x‐Zr boundary was located at x=0.014 at 1800°C; thoria was single‐phase over the entire range. Consistent results were obtained when O2/inert gas mixtures were used, but use of H2/H2O and CO/CO2at 1000° to 1200°C gave abnormal and, in the latter case, erratic data; side reactions in these atmospheres are inferred. The monoclinic‐tetragonal phase change of ZrO2and the lattice thermal expansion, room‐temperature Young's modulus, and strength properties of ZrO2and ThO2bodies were not appreciably altered by oxygen deficiency. The lattice dimensions decreased s

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12157.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The initial sintering kinetics of uranium dioxide powder compacts were determined as a function of temperature and stoichiometry (800°

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12158.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The study of the oxidation of Cu and Fe by continuous recording of weight gain is described. Equations are given for the rates of oxidation at several temperatures of the metals, both uncoated and enamel‐coated. Uncoated Cu was less strongly oxidized than uncoated Fe, but coated Cu was more strongly oxidized than coated Fe. The presence of CoO in the coating caused no significant difference in the action of the enamels on the metal

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12159.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The Knoop hardness anisotropy and plastic deformation markings around the DPH indentation were investigated for an Mn‐Zn ferrite single crystal. Knoop hardness values, which depended primarily on the crystallographic direction, were represented on a standard stereographic triangle. The hardness was maximum in thedirection and minimum in theanddirections. The patterns of the plastic deformation markings show that the ferrite deforms plastically at room temperature by {110}and {111}sli

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12160.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The oxidation‐reduction kinetics of MnO in CO/CO2atmospheres at 1230°C were measured by gravimetric and electrical conductivity techniques. The dependence of the kinetics on time, inert gas dilution, total pressure, and specimen thickness indicates that the kinetics are controlled by a slow surface reaction step. Attempts to analyze the data quantitatively using equations for linear heat flow in a solid with a radiation boundary condition were unsuccessf

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12161.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Solid‐state reactions of equimolar mixtures of Bi2O3and Fe2O3from 625° to 830°C and their kinetics were investigated. The reaction rates were determined from the integrated X‐ray diffraction intensities of the strongest peaks of the reactants and products. The activation energy for the formation of BiFeO3was 96.6±9.0 kcal/mol; that for a second‐phase compound, Bi2Fe4O9, which formed above 675°C, was 99.4±9.0 kcal/mol. Specific rate constants for these simultaneous reactions were obtained. The preparation of single‐phase BiFeO3from the stoichiometric mixture of Bi2O3and Fe2O3

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12162.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The grain growth and densification rates of Mn‐Zn ferrites during sintering are closely linked to the characteristics of the calcined and milled powders used. Long milling times enlarge powder particle size distributions and tend to promote discontinuous grain growth during sintering. For fixed sintering conditions, an optimum milling time, which corresponds to minimal eddy current and hysteresis losses, exists. The electrical properties of overmilled powders deteriorate greatly because duplex structure occurs. Theoretical analysis of the probability of discontinuous grain growth occurring during sintering in relation to powder particle size distribution agrees with the experimental result

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12163.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The thermal conductivities, λ, of single‐crystal and polycrystalline UO2were measured from 80° to 420°K. The results indicate no observable difference in λ between single‐crystal and polycrystalline UO2, and both materials have broad peaks in λ at ∼220°K. The results were used with literature values to determine the effect of closed porosity on λ. The thermal conductivity of theoretically dense UO2is described phenomenologically from 80° to 1400°K, where conduction is dominated by the phonon component. The phonon conduction is analyzed by comparison with ThO2. This analysis indicates that the high‐temperature λ is limited by 3‐phonon Umklapp scattering processes. Scattering by the disordered spins associated with the paramagnetic U ions contributes a large temperature‐independent phonon scattering term. This mechanism has a mean free path of about 51 Å, which implies that grain boundaries and impurities have a relatively insignificant effect on the phonon conduction far above the antiferromagnetic‐para‐magnetic transition at ∼ 30°K. This implication agrees

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12164.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY