Synthesis, crystal structure, and thermal stability of double borate Na 3 ErB 2 O 6

Double borate Na 3 ErB 2 O 6 was synthesized by the solid-state reaction. The crystal structure of Na 3 ErB 2 O 6 was refined by the Rietveld method: P 2 1 /c , a  = 6.49775(14) A, b  = 8.50424(17) A, c  = 12.0067(3) A, β = 118.4797(9)°, Z  = 4. The crystal structure of Na 3 ErB 2 O 6 consists of –[ErO 6 ] ∞ -chains along the " b " axis, which are linked by BO 3 triangles in a three-dimensional framework. Sodium atoms occupy empty positions inside the channels. The thermal behavior of Na 3 ErB 2 O 6 was studied in detail in the range of 25–1150 °C range by DSC and TG methods. Na 3 ErB 2 O 6 congruently melts at 1116 °C. Based on the results of DSC measurements, three reversible phase transitions were found for Na 3 ErB 2 O 6 .