The Sesquioxide and Hydroxides of Gallium

Synthesis of Gallium Oxide Hydroxide Crystals in Aqueous Solutions with or without Urea and Their Calcination Behavior

“…The formation of these nanosized pores is due to the elimination of water from constitutional OH groups, and this process starts at temperatures above 300°C. 7 Finally, as seen from the micrograph of Fig. 3(f), after calcination as a loose powder compact at 1200°C for 6 h, the rodlike crystals fused to each other at their mutual point of contact.…”

“…Roy et al 8 also confirmed that the Ga(OH) 3 precipitates, which are likely to be metastable compared with gallium oxide hydroxide, would only be converted into ␣-GaO(OH) with time at ambient temperature. However, the transformation of ␣-GaO(OH) to ␤-Ga 2 O 3 was observed by Laubengayer et al 7 at temperatures higher than 300°C.…”

“…4 The high-temperature structure 4,5 of Ga 2 O 3 (␤ form) is monoclinic (space group C2/m), with the lattice parameters a ϭ 12.214, b ϭ 3.037, c ϭ 5.798 Å, ␤ ϭ 103.83°. 6 ␤-Ga 2 O 3 is only one of five well-known forms [7][8][9] of gallium oxide: ␣-, -, ␦-, and ε-Ga 2 O 3 , and all of these polymorphs are converted to ␤-Ga 2 O 3 at T Ͼ 870°C. 10 Growth of the single crystals 11 of ␤-Ga 2 O 3 has been studied by Okada et al, 12 using the tin-flux method, and Ga 2 O 3 nanowires were prepared by Zhang et al 13 and Choi et al 14 Manufacture of n-type semiconducting Ga 2 O 3 thin films on electrically insulating substrates has been studied by Meixner et al, 15 which are considered and developed for the detection of reducing gases.…”

“…We have encountered the incidental formation of gallium oxide hydroxide (GaO(OH)) in aqueous solutions throughout the course of our recent studies, which were mainly focused on the wet-chemical synthesis of powders of doped LaGaO 3 fuel cell ceramics. 24,25 The first experimental study on the transformation of gallium oxide polymorphs and hydroxides was performed by Laubengayer et al 7 in 1939 over the temperature range of 110°to 1000°C. These authors synthesized ␣-GaO(OH) from a gel obtained through the hydrolysis of gallium nitrate or gallium chloride, after calcination at temperatures between 110°and 300°C.…”

“…These authors synthesized ␣-GaO(OH) from a gel obtained through the hydrolysis of gallium nitrate or gallium chloride, after calcination at temperatures between 110°and 300°C. It was claimed 7 that, in this temperature range, Ga(OH) 3 transforms in a sluggish manner to ␣-GaO(OH) in aqueous solution. Roy et al 8 also confirmed that the Ga(OH) 3 precipitates, which are likely to be metastable compared with gallium oxide hydroxide, would only be converted into ␣-GaO(OH) with time at ambient temperature.…”