New ternary phosphides and arsenides. Syntheses, crystal structures, physical properties of Eu2ZnP2, Eu2Zn2P3 and Eu2Cd2As3

Three new europium pnictides Eu2ZnP2, Eu2Zn2P3 and Eu2Cd2As3 have been synthesized and their structures were determined by single-crystal X-ray diffraction. Eu2ZnP2 is isotypic with Yb2CdSb2 (Cmc21 (No. 36); cell parameters a=4.1777(7) Å, b=15.925(3) Å, c=7.3008(12) Å), while the latter two compounds crystallize with the Ba2Cd2Sb3 structure type (C2/m (No. 12); cell parameters a=15.653(5)/16.402(1) Å, b=4.127(1)/4.445(4) Å, c=11.552(4)/12.311(1) Å and β=126.647(4)/126.515(7)° for Eu2Zn2P3 and Eu2Cd2As3, respectively). Magnetic susceptibility measurements in the interval 5–300 K confirm paramagnetic behavior and effective magnetic moments characteristic of Eu2+ ([Xe] 4f7) ground states. Temperature-dependent electrical conductivity measurements also prove that Eu2Cd2As3 is a semiconducting compound with a narrow band gap of 0.059 eV below 100 K. According to TG/DSC analyses, Eu2Cd2As3 starts to decompose at about 950 K. - Graphical abstract: A polyhedral view of the crystal structure of new pnictides Eu2T2Pn3 (T=Zn or Cd; Pn=P or As). Display Omitted - Highlights: • Three new ternary pnictide Zintl compounds, Eu2ZnP2, Eu2Zn2P3 and Eu2Cd2As3, have been synthesized and characterized. • The europium cations are divalent and ferromagnetically coupled in both Eu2Zn2P3 and Eu2Cd2As3. • Eu2Cd2As3 has a very small band gap of 0.06 eV and starts to decompose over 950 K