Contactless density measurement of high-temperature BiFeO3 and BaTiO3

The density of liquid and undercooled BiFeO3 and high-temperature solid, liquid, and undercooled BaTiO3 was measured with an electrostatic levitation furnace. The density was obtained with an ultraviolet-based imaging technique that allowed excellent sample contrast throughout all phases of processing, including at elevated temperatures. Over the 1250- to 1490-K temperature range, the density of liquid BiFeO3 can be expressed as rho(L)(T)=6.70x10(3)-1.31 (T-T-m) (kg m(-3)) (+/-2 per cent) with T-m=1423 K, yielding a volume coefficient of thermal expansion alpha(L)(T)=1.9x10(-4) K-1. For BaTiO3, the density of the solid can be expressed as rho(S)(T)=5.04x10(3)-0.21 (T-T-m) (T=1893 K) over the 1220- to 1893-K range, yielding a volume coefficient of thermal expansion alpha(S) (T)=4.2x10(-5) K-1, whereas that of the liquid can be expressed as rho(L)(T)=4.04x10(3)-0.34 (T-T-m) over the 1300- to 2025-K range with alpha(L)(T)=8.4x10(-5) K-1.