Calcium nitridoborates

Ca3(BN2)2 is readily formed when (distilled) calcium metal is melted in the presence of (layer-type) boron nitride. This reaction provides some insight on how alkaline-earth metals like calcium may act as a catalyst in the phase transformation of layered a-BN into its cubic modification. Instead of metals, nowadays alkaline-earth (Ca, Sr, Ba) nitridoborates can be used as a flux catalyst in high-pressure and high-temperature transformation reactions to produce cubic boron nitride [15]. 

Since a separation process for Ca3(BN2)2 and CaBg is unknown, Ca3N2 is better employed as a starting material for the synthesis of calcium nitridoborate nitride [16], and calcium nitridoborate  

Reactions suggest that Ca3(BN2)N can be viewed as an intermediate in the reaction (4). The substitutional effect of nitride by nitridoborate ions reflects that the linear [N=B=N] ion (with a typical B-N distance around 135 pm) can be viewed as a pseudo-nitride. 

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The chemistry of lanthanide nitridoborates was developed by the more flexible and more efficient solid-state metathesis route by using nitridoborate salts and a lanthanide trichloride, at reaction temperatures as low as 600 °C. This type of reaction has been previously established and studied in some detail for reactions, such as the synthesis of lanthanide nitrides (LnN). Following this concept, lanthanum nitridoborates are obtained from reactions of lanthanum trichloride and lithium nitridoborate (or calcium nitridoborate), performed in a salt-balanced manner with respect to the formation of the co-produced liCl ... 

A long time passed between the first discovery of AE3(BN2)2 phases [17] (AE = Ca, Sr) and their structural characterizations [18, 19]. Two distinct phases are known to exist for both calcium and strontium nitridoborate, denoted as low-temperature y9-AE3(BN2)2 and high-temperature a-AE3(BN2)2 [20]. Their phase transitions have been studied by temperature-dependent XRD, thermo-... 

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