Borides crystal growth

The crystal chemistry of the borides is discussed in 6.7.2 according to this scheme. General methods of preparation, single-crystal growth and sintering of borides is considered, respectively, in 6.7.3, 6.7.4 and 6.7.5. 

Crystal growth is relatively difficult for borides because they have high melting points and sometimes low thermal stability, as indicated in 6.7.2. 

The crystal growth of metal borides by gas-phase methods permits preparation of products at moderate T (1000-1500°C). This is an important advantage since most borides melt at high T (ca. 3000°C), which makes their crystal growth from melts difficult. In addition, the gas-phase methods lead to the formation of single crystals and solid films of incongruently melting borides. 

The gas-phase methods usually applied to the crystal growth of borides are two chemical vapor deposition (CVD) and chemical vapor transport (CVT). 

Because of its stability and unusual properties, the crystal growth of TiB2 is the most studied process of boride preparation by CVD. It is interesting from both a scientific and an engineering viewpoint, and because of the availability, low cost and... 

Crystal Growth of Borides by Chemical Vapor Transport. 

Crystal Growth of Borides e.7.4.2. Liquid-Phase Methods 6.7.4.2.1. Crystal Pulling. 

Formation of Borides 6.7.4. Crystal Growth of Borides 6.7.4.S. Flux Methods... 

Low-temperature solvents are not readily available for many refractory compounds and semiconductors of interest. Molten salt electrolysis is utilized in many instances, as for the synthesis and deposition of elemental materials such as Al, Si, and also a wide variety of binary and ternary compounds such as borides, carbides, silicides, phosphides, arsenides, and sulfides, and the semiconductors SiC, GaAs, and GaP and InP [16], A few available reports regarding the metal chalcogenides examined in this chapter will be addressed in the respective sections. Let us note here that halide fluxes provide a good reaction medium for the crystal growth of refractory compounds. A wide spectrum of alkali and alkaline earth halides provides... 

This is a method solely used to obtain crystals of the borides. The raw materials of the borides are mixed into large amount of a low melting metal (e.g. Al, Cu, Sn) which will function in the role of the flux for the crystal growth, and then the mixture is heated. The flux is removed by an acid or alkali leaving the crystals as a solid residue. 

---