Solidification characteristics of metastable and stable

Abstract

Solidification characteristics of metastable and stable from melts were systematically investigated by x-ray diffraction, differential thermal analysis and thermogravimetry. The experimental results show that the solidification either of metastable or of stable directly from melts appears to be dependent both on the melt temperature and on the cooling rate. In general, high melt temperatures and high cooling rates tend to solidify metastable . Otherwise, low melt temperatures and low cooling rates tend to solidify stable . To produce stable single-crystal , the melt temperature should be controlled to be less than and the cooling rate near the solidifying temperature should be less than .

Relaxor-like Dielectric Behavior in Stoichiometric Sillenite Bi12SiO20

“…DSC was performed on Bi 12 SiO 20 with a heating and cooling rate of 10 °C/min in the temperature range from ∼400 to 1123 K, Figure . Two pairs of reversible peaks with endothermic processes during heating and corresponding exothermic processes during cooling were observed at ∼920 and 1103 K, respectively, which indicates a plausible reversible γ → β → δ → β → γ phase transition sequence occurring in this sample as observed in other sillenites and doped Bi 2 O 3 compounds. XRPD confirmed the sample retained the same (γ) sillenite phase on post-DSC measurements.…”

“…heating and corresponding exothermic processes during cooling were observed at ∼920 and 1103 K, respectively, which indicates a plausible reversible γ → β → δ → β → γ phase transition sequence occurring in this sample as observed in other sillenites18 and doped Bi 2 O 3 compounds. XRPD confirmed the sample retained the same (γ) sillenite phase on post-DSC measurements.…”

Negative Refractive Index in Dielectric Crystals Containing Stoichiometric Rare‐Earth Ions

“…Although rare‐earth ions are a good candidate, the requirements of a negative index are still extreme. Theoretical studies predict negative indices in doped rare‐earth crystals for high doping concentrations (≳1%) with optical linewidths less than 1 MHz, [ 20,27–29 ] an unfeasible linewidth at such concentrations due to strain‐broadening of the line by the dopant itself. Other theoretical works propose using electromagnetically induced transparency techniques in a four‐level doped rare‐earth crystal, but also neglect inhomogeneous broadening.…”