Ideal Transition Temperature Research Articles

Thermochromic Halide Perovskite Windows with Ideal Transition Temperatures

AbstractUrban centers across the globe are responsible for a significant fraction of energy consumption and CO2 emission. As urban centers continue to grow, the popularity of glass as cladding material in urban buildings is an alarming trend. Dynamic windows reduce heating and cooling loads in buildings by passive heating in cold seasons and mitigating solar heat gain in hot seasons. Here, reduced energy consumption in highly glazed buildings in a mesoscopic building energy model is demonstrated when thermochromic windows are employed. Savings are realized across eight disparate climate zones of the United States. The model is used to determine ideal critical transition temperatures of 20–27.5 °C for thermochromic windows based on metal halide perovskite materials. Ideal transition temperatures are realized experimentally in composite metal halide perovskite films composed of perovskite crystals and an adjacent reservoir phase. The transition temperature is controlled by cointercalating methanol, instead of water, with methylammonium iodide and tailoring the hydrogen‐bonding chemistry of the reservoir phase. Thermochromic windows based on metal halide perovskites represent a clear opportunity to mitigate the effects of energy‐hungry buildings.

Scaling concepts for the dynamics of viscous liquids near an ideal glassy state.

Motivated by recent mean-field theories of the structural glass transition and of the Potts glass model we formulate a scaling and droplet picture of an assumed ideal structural glass transition. The phase transition is a random first-order phase transition where the supercooled-liquid phase is composed of glassy clusters separated by interfaces or domain walls. Because of entropic driving forces the glassy clusters are continually being created and destroyed. As the ideal transition temperature is approached the entropic driving force vanishes and the size of the glassy clusters diverges with an exponent of \ensuremath{\nu}=2/d. All long-time dynamical processes are activated and the Vogel-Fulcher law is obtained for the liquid-state relaxation time.

Ferroelectric transition in Co-I-Boracite under pressure

The effect of hydrostatic pressure up to 103 atm has been measured on the ferroelectric phase transition temperature of Co3B7O13l. It was found that δTtr/δp = -11.1 × 10-3 deg/atm on cooling while δTtr/δp = -8.1 × 10-3 deg/atm on heating so that thermal hysteresis which reflects the 1st order nature of the transition increases with increasing pressure. Experimental data have been related to the thermodynamic theory developed by Dvorˆak which accounts for the fact that polarization is not the parameter of the transition in boracites. It is shown that the pressure dependence of the ideal transition temperature Ttr is governed by the interaction of stress with nonhomogeneous lattice modes and co-governed by the electrostrictive interaction. On the other hand, maximum thermal hysteresis. permittivity above Ttr and spontaneous polarization depend on pressure due to electrostriction only.