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 ϱL(T)=6.70×103–1.31 (T-Tm) (kg m-3) (±2 per cent) with Tm=1423 K, yielding a volume coefficient of thermal expansion αL(T)=1.9×10-4 K-1. For BaTiO3, the density of the solid can be expressed as ϱS(T)=5.04×103–0.21(T-Tm) (Tm=1893 K) over the 1220- to 1893-K range, yielding a volume coefficient of thermal expansion αS(T)=4.2×10-5 K-1, whereas that of the liquid can be expressed as ϱL(T)=4.04×103-0.34 (T-Tm) over the 1300- to 2025-K range with αL(T)=8.4×10-5 K-1.