Standard X-ray Diffraction Powder Patterns

Terbium Arsenate, TbAsO4 (tetragonal)Powder data cards. None.Additional published patterns. None.NBS sample. The sample of terbium arsenatewas prepared at NBS from a water solution ofarsenic pentoxide and terbium trichloride. Itwas dried at 110 °C. Spectrographic analysisshowed the following major impurities: 0.01 to0.1 percent silicon; 0.001 to 0.1 percent each ofantimony, calcium, iron, magnesium, and lead.The sample was colorless. The indices of refraction could not be determined because thesample was too fine.The d-values of the three strongest lines are:3.550, 2.685, and 1.834 A.Structural data. No reference to the structureof terbium arsenate was found, but it is apparentlyisostructural with yttrium arsenate with the spacegroup DJ£-l4i/amd (No. 141) and 4(TbAsO4 ) perunit cell.Lattice constants1963 National Bureau ofStandards at 25 °C.aoA7. 1025cA6. 3536The density of terbium arsenate calculated fromthe NBS lattice constants is 6.172 g/cm3 at 25 °C.hkl101200112220202301103321312400420332204224512440600, 404532424116444316604624Internal Standard, 0Tungsten, a = 3.1648 ACo, 1.7889 A at 25 CdoA4. 7363. 5502. 6852. 5102. 3672. 2192.0291. 8821. 8341. 7751. 58781. 48091. 45001. 3423L 27551. 25531. 18381. 13731. 12301. 03640. 9849. 9577. 9495. 9168/81006922798653161514118134881245735Thallium Chromate, Tl 2CrO 4 (orthorhombic)Powder data cards. None.Additional published patterns. Abbad andRivoir [1] 1947.NBS sample. The sample of thallium chromatewas prepared at NBS from solutions of thalliumnitrate and sodium chromate. Spectrographicanalysis showed the following major impurities:0.1 to 1.0 percent lead; 0.01 to 0.1 percent eachof aluminum and silicon; and 0.001 to 0.01 percent each of barium, calcium, and antimony.The color of the sample was yellow. The refractive indices could not be determined becausethe sample was too fine.The rf-values of the three strongest lines are:3.145, 3.060, and 3.186 A.Structural data. Abbad and Rivoir [1] in 1947determined that thallium chromate has the potassium sulfate structure, the space group Dih-(No. 62), and 4(Tl 2CrO4 ) per unit cell.The lattice constants reported by Abbad andRivoir have been converted from kX to angstromunits for comparison with the NBS values.19471963Abbad and Rivoir[!]____________National Bureauof Standardsat 25 °C—_--.Lattice constantsaA7. 827.908±.001boA10. 7010. 730±. 001cA5. 925.913±. 001The density of thallium chromate calculatedfrom the NBS lattice constants is 6.946 g/cm3at 25 °C.54