Synthesis and Characterization of a High-Purity AlN Powder
摘要:
High‐purity AIN powder was synthesized by preparing high‐purity (NH4)3 AIF6, decomposing the (NH4)3 AIF6 to AIF3, and reacting the AIF, at 800° to 1000°C with high‐purity NH3. AIN powders could be synthesized with a cation purity of 99.99% and an oxygen content <0.2 wt%. The specific surface area depended on the process conditions and varied from 0.2 to 2.6 m2/g. The thermodynamics of the process are evaluated and the influence of various process parameters on the resulting powder characteristics are described.
作者:Jasbinder S. Sanghera、Patricia Hart、Maria G. Sachon、Ken J. Ewing、Ishwar Aggarwal
DOI:10.1111/j.1151-2916.1990.tb05202.x
日期:1990.5
between ammonium bifluoride and specific anhydrous and hydrated metal fluoride salts. The products are defined as ammonium fluoride–metal fluoride complexes. The kinetics of their formation and subsequent dissociation were followed by thermogravimetric analysis. It was observed that these complexes decompose with the evolution of HF above temperatures at which ammonium bifluoride decomposes and where
diffraction and optical measurements. The structural relation between the low and high temperature phases has allowed to predict this transition to be a ferroelastic-prototype one. The observation of ferroelastic domains under polarizing microscope and their disappearance above Curie temperature are in good agreement with this assumption. The thermal dependence of the spontaneous strain has been determined
Polarisation remanente dans les varietes de basse temperature de (NH4) 3AlF6 ET (NH4) 3FeF6
作者:Maryvonne Lorient、Régnault Von der Mühll、Alain Tressaud、Jean Ravez
DOI:10.1016/0038-1098(81)90169-1
日期:1981.12
Abstract Dielectric and thermocurrent measurements have been carried out on (NH4) 3AlF6 and (NH4) 3FeF6 ceramic samples. A maximum of permittivity is observed close to the transition temperature (TT(NH4) 3AlF6 = 217K; TT(NH43FeF6 = 264K. In the low-temperature phase a polarization current of about 10-9A is obtained and can be reversed when the sign of the polarization field is changed, a property
A study of the structural phase transitions in AlF<sub>3</sub>: X-ray powder diffraction, differential scanning calorimetry (DSC) and Raman scattering investigations of the lattice dynamics and phonon spectrum
作者:P Daniel、A Bulou、M Rousseau、J Nouet、J L Fourquet、M Leblanc、R Burriel
DOI:10.1088/0953-8984/2/26/003
日期:1990.7.2
The cubic-rhombohedral phasetransition at 450 degrees C of AlF3 is studied by DSC, X-raypowderdiffraction and Ramanscattering. It is demonstrated that the transition is of first order with a hysteresis of about 6 degrees. It is established by X-raypowderdiffraction patterns that the room temperature space group is R3c. A temperature study of the Ramanscattering spectra (that confirms the above