Dimorphic CeZnPO and PrZnPO

Well‐shaped single crystals of the phosphide oxides CeZnPO and PrZnPO were obtained from the rare earth metals, zinc oxide, and red phosphorous in an equimolar NaCl/KCl flux in sealed quartz ampoules. The high‐temperature (β) NdZnPO type modifications were obtained at 1170 K while the low‐temperature (α) ZrCuSiAs type modifications crystallized at 970 K. The four compounds were characterized by X‐ray diffraction on powders and single crystals: P 4/ nmm , a = 401.08(9), c = 882.0(4) pm, wR2 = 0.1277, 173 F 2 values, 9 variables for α–CeZnPO, a = 399.3(2), c = 877.2(7) pm, wR2 = 0.0583, 220 F 2 values, 12 variables for α–PrZnPO, and R 3 m , a = 401.2(4), c = 3121(3) pm, wR2 = 0.0221, 509 F 2 values, 14 variables for β–CeZnPO, a = 399.0(2), c = 3108(1) pm, wR2 = 0.0452, 291 F 2 values, 14 variables for β–PrZnPO. In both modifications we observe clear separation into rare earth–oxygen and zinc–phosphorous layers without any P–P and Zn–O interactions, leading to electron precise formulations Ce 3+ Zn 2+ P 3− O 2− and Pr 3+ Zn 2+ P 3− O 2− for these transparent compounds. The crystal chemical peculiarities are briefly discussed.