Transparent AIN ceramics

Theoretical predicted high-thermal-conductivity cubic Si3N4 and Ge3N4: promising substrate materials for high-power electronic devices

Ceramic substrates play key roles in power electronic device technology through dissipating heat, wherein both high thermal conductivity and mechanical strength are required. The increased power of new devices has led to the replacement of Al₂O₃ by high thermal conducting AlN and further β-Si₃N₄ based substrates. However, the low mechanical strength and/or anisotropic mechanical/thermal properties are still the bottlenecks for the practical applications of these materials in high power electronic devices. Herein, using a combination of density functional theory and modified Debye-Callaway model, two new promising substrate materials γ-Si₃N₄ and γ-Ge₃N₄ are predicted. Our results demonstrate for the first time that both compounds exhibit higher room temperature thermal conductivity but less anisotropy in expansion and heat conduction compared to β-Si₃N₄. The mechanism underpins the high RT κ is identified as relatively small anharmonicity, high phonon velocity and frequency. The suitability of these two nitrides as substrate materials was also discussed.

Electrophoretic Deposition of Aluminum Nitride from Its Suspension in Acetylacetone Using Iodine as an Additive

We have studied electrophoretic deposition of AlN from its suspension in acetylacetone with I2as an additive. AlN powder with particle size <10 μm is dispersed to produce a positive charge and deposited on the cathode by applying fields greater than 10 V/cm between the electrodes. X-ray diffraction and FTIR studies indicate that the AlN before and after deposition has the same composition and structure. An increase in the amount of AlN in the suspension, the deposition potential, and the deposition time results in a linear increase in the weight of the AlN deposited. Electrophoretic deposition from 10 g/L AlN suspension shows an initial increase in the weight of AlN deposited with the concentration of I2, and the weight of AlN decreases after reaching a maximum at 0.20 g/L I2.

Studies of Organometallic Precursors to Aluminum Nitride

The reaction of trialkylaluminum compounds with ammonia has been examined as a potential route to high purity AlN powder and to AlN thin films. This reaction proceeds in stages in which the initially formed Lewis acid/base adduct undergoes thermal decomposition to a series of intermediate alkylaluminum-amide and -imide species with increasing Al-N bonding, i.e.,

The structure and properties of several of these species have been studied using various physical and chemical methods, leading to a better understanding of the chemistry of this novel AlN precursor system. The structure of the intermediate organoaluminum amide, (CH3)2AlNH2, has been determined by single crystal X-ray diffraction methods and found to contain molecular trimer units with a six-membered Al-N ring structure similar to those which make up the wurzite structure of AlN. This compound is readily volatile and has been used to deposit AIN thin films on Si surfaces by a low-pressure CVD process. This approach has also been used to prepare AlN as a high surface area, high purity powder.

Synthesis of Ain and AlN/SiC Ceramics from Polymeric Molecular Precursors

Reactions of (Me3Si)3 AI·Et2O with NH3 in different stoichiometric ratios have been studied in search of useful precursors to AIN. Two molecular condensation-elimination compounds and an insoluble oligomer have been obtained from these reactions, and pyrolysis of the compounds leads to the convenient formation of AlN/SiC solid solutions.

Synthesis And Characterization Of Nine Metal Nitrides

We demonstrate a simple electrochemical method suitable for preparing precursors for nine different metal-nitride ceramics. These precursor powders were calcined in flowing NH3 or Ar to yield metal-nitride ceramic powders. This electrochemical synthetic technique was applied to Al, Ga, Mo, Nb, Ni, Ti, V, W, and Zr and resulted in a nitride of each of these metals. The calcination conditions determined the resulting phase, composition, and morphology of the product. The ceramic materials were characterized primarily by powder XRD.