ABSTRACT
The (NH 4 ) 3− x Rb x Ga 2 (PO 4 ) 3 solid solution (0 ≤ x ≤ 0.23), which crystallizes in the monoclinic structure with the lattice parameters a = 1,337.82 ± 0.13, b = 1,032.60 ± 0.06, c = 902.04 ± 0.07 pm and β = 111.366 ± 0.007° and a calculated density of 2.8149 ± 0.0004 g cm−3 for x = 0.23, is formed in the Ga–H–Rb–P–O–N system (Lesage et al. 2004). The crystals of this solid solution were obtained under hydrothermal conditions using 21-mL Teflon-lined stainless steel autoclaves. Ga2O3, (NH4)2HPO4, and RbNO3 were ground in an agate mortar in the molar ratio Ga/P = 2:3 and RbNO3/(NH4)2HPO4 = 1:1. Approximately, 0.4 mL of deionized water was then added to 0.8 g of the mixture, leading to a highly viscous solution. The obtained solution was heated in an autoclave at 180°C for 25 h and finally slowly cooled at room temperature for 18 h. The crystals of this solid solution were synthesized in the presence of Ga2O3 as secondary phase.
