Two-step continuous sintering schedules for β″ -Al2O3 ceramics

A method was developed for preparing ion-conductive membranes of Li₂O-stabilized β″ -Al₂O₃ with a fine-grained microstructure, density above 98% of the theoretical one and resistivity of 5–8 Ω cm. without additional thermal treatment. To this effect powders which contained about 90% β″ -Al₂O₃ were synthesized. A two-step continuous sintering schedule was applied with temperatures of the first step above, and of the second step around the melting point of the β″-A1₂O₃ - NaAlO₂ eutectic respectively. Under the conditions of this firing schedule grain growth is inhibited and a high degree of densification is attained with a minimum transient liquation of the eutectic. The contribution of each of the firing steps to the main characteristics of the membranes is assessed. The relationship between the resistivity, the phase composition and the microstructure is discussed.     

Additive prediction of thermodynamic functions of hydrofluorides

Summary The experimental data available on the thermodynamic functions ⁰ forMF·nHF hydrofluorides [M=Li, Na, K, Rb, Cs, NH₄, Ag(I) and Tl(I);n=1–3] have been evaluated additively. The unknown values of ⁰ forn=0÷7 are predicted.

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Additive Voraussagen der thermodynamischen Funktionen von Hydrogenfluoriden (Kurze Mitt.)

Zusammenfassung Die vorhandenen experimentellen Daten über die thermodynamischen Funktionen ⁰ von HydrogenfluoridenMF·nHF [M=Li, Na, K, Rb, Cs, NH₄, Ag(I) und Tl(I);n=1–3] werden linear ausgeglichen und die fehlendenden Werte für ⁰ mitn=0÷7 vorausgesagt.