Abstract.
Experimental data are presented for the solubility of NaNbO3 in the ternary system CaCO3–Ca(OH)2–NaNbO3 (or calcite–portlandite–lueshite) over the temperature range 500–950 °C at 0.1 GPa pressure. Near-liquidus phase relationships are given for the pseudo-binary join ([CaCO3]45[Ca(OH)2]55)100– x –(NaNbO3) x ; (0 <x <70 wt%). These data show the presence of a large field of calcite plus liquid and the absence of NaNbO3 as a primary liquidus phase until the melts contain greater than 60 wt% NaNbO3. The primary crystallization fields of calcite and NaNbO3 are separated by a steep thermal valley located at about 55 wt% NaNbO3. Quenched liquids contain calcite, portlandite, sodium carbonates and perovskite-structured calcium niobates. The maximum solubility of Nb2O5 in this system is estimated to be on the order of 48 wt% at 650 °C at 0.1 GPa pressure. The experiments show that perovskite-structured compounds rather than pyrochlore crystallize from these fluorine-free, water-rich melts.
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Mitchell, R.H., Kjarsgaard, B.A. Solubility of niobium in the system CaCO3–Ca(OH)2–NaNbO3 at 0.1 GPa pressure. Contrib Mineral Petrol 144, 93–97 (2002). https://doi.org/10.1007/s00410-002-0384-3
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DOI: https://doi.org/10.1007/s00410-002-0384-3