Abstract:
The presented thesis deals with the synthesis and structural solution of new nitridoborates, furthermore with the phase transitions of the compounds M3(BN2)2 with
M = Ca, Sr, Ba or Eu and the clarification of their structural und experimental coherence.
The synthesis and structural solution of the previously unknown compound Ca3(BN2)N was successful, in the field of alkaline-earth nitridoborates. That can be described as the missing link between Ca2N3 and Ca3(BN2)2.
The synthesis of this compound yield to the question about further nitridoborate-nitrid-combinations such as Ca6(BN2)N3, Ca6(BN2)2N or Ca9(BN2)5N.
A comparison of the volumes of Ca3N2, Ca3(BN2)2 and Ca2(BN2)2 led to considerations about the high pressure behaviour of Ca3(BN2)2, which were examined by high pressure experiments.
In addition to that the crystal structure of beta-Ca3(BN2)2 was solved, which is the low-temperatur modification of alpha-Ca3(BN2)2. The structural relationship between both phases was derived by group-theory and matches with the experimental data.
The phase transition conditions were determined for the low- and high-temperature modification of Ca3(BN2)2 und Sr3(BN2)2. The different structures, occurring at the change to the low -temperature modifications, result from the different occupations in the high-temperature modifications.
Reactions to new nitridoborates of rare-earth metal elements with further anions led to the new compounds Nd6(BN3)O6 und Pr6(BN3)O6.