Thermal expansion of boron subnitrides

Thermal expansion of α-boron and some boron-rich pnictides

“…The retrieved volume TECs of α-B12, B12P2 and B12As2 (see Table I ) were found to be of the same order of magnitude as those of other boron-rich solids [8,9,[23][24][25][26][27][28]. The αv value of B12As2 (15.3(1)×10 -6 K -1 ) is in excellent agreement with the literature data (15(2)×10 -6 K -1 ) [9].…”

“…Unlike cubic boron pnictides, the tetrahedra (with central X atom) in B13N2, B12P2 and B12As2 are significantly distorted (see Table II). Employing the explanation that has been already used in the case of B50N2 thermal expansion [8] we assume that thermal vibrations lead to the reduction of the distorted tetrahedra towards the ideal ones i.e. at high temperatures the X-X bonds in B12P2 and B12As2 tend to shrink (see Table II for corresponding diatomic equilibrium bonds), whereas N-B-N chains in B13N2 tend to expand.…”

“…The unit cell parameters of α-B12, B13N2 [8], B12P2 and B12As2 in hexagonal (a hex , c hex ) and rhombohedral (a rh , α rh ) settings are presented in Table I. Further we will consider the thermal expansion in hexagonal unit cell only, so the "hex" indexes of lattice parameters will not be used.…”

“…Very recently thermal expansion of two boron-rich nitrides synthesized under extreme conditions has been studied by synchrotron X-ray diffraction [8]. In the present paper we report the results on thermal expansion of α-rhombohedral boron (α-B12) and two boron-rich pnictides, B12P2 and B12As2.…”

“…In the present paper we report the results on thermal expansion of α-rhombohedral boron (α-B12) and two boron-rich pnictides, B12P2 and B12As2. The retrieved thermal expansion coefficients compared with those reported earlier [8,9] allowed us to analyze the thermal expansion variation in the family of boron-rich pnictides.…”