Synthesis and structural characterization of the Zintl phases Na3Ca3TrPn4, Na3Sr3TrPn4, and Na3Eu3TrPn4 (Tr=Al, Ga, In; Pn=P, As, Sb)

The hexagonal, non-centrosymmetric structure of Na3E3TrPn4 (E=Ca, Sr, Eu; Tr=Al, Ga, In; Pn=P, As, Sb) features [TrPn4]9- tetrahedral units, surrounded by Na+ and Ca2+, Sr2+, Eu2+ cations.172