Wide-Temperature Tunable Phonon Thermal Switch Based on Ferroelectric Domain Walls of Tetragonal KTN Single Crystal.

Ferroelectric domain walls (DWs) of perovskite oxide materials, which can be written and erased by an external electric field, offer the possibility to dynamically manipulate phonon scattering and thermal flux behavior. Different from previous ferroelectric materials, such as BaTiO3, PbTiO3, etc., with an immutable and low Curie temperature. The Curie temperature of perovskite oxide KTa1-xNbxO3 (KTN) crystal can be tuned by altering the Ta/Nb ratio. In this work, the ferroelectric KTa0.6Nb0.4O3 (KTN) single crystal is obtained by the Czochralski method. To understand the role of ferroelectric domains in thermal transport behavior, we perform a nonequilibrium molecular dynamics (NEMD) calculation on monodomain and 90° DWs of KTN at room temperature. The calculated thermal conductivity of monodomain KTN is 9.84 W/(m·k), consistent with experimental results of 8.96 W/(m·k), and distinctly decreased with the number of DWs indicating the outstanding performance of the thermal switch. We further evaluate the thermal boundary resistance (TBR) of KTN DWs. An interfacial thermal resistance value of 2.29 × 10-9 K·m2/W and a large thermal switch ratio of 4.76 was obtained for a single DW of KTN. Our study shows that the ferroelectric KTN can provide great potential for the application of thermal switch at room temperature and over a broad temperature range.

Effect of prior drought and heat stress on Camellia sinensis transcriptome changes to Ectropis oblique (Lepidoptera: Geometridae) resistance.

Tea plants are continuously confronted with a wide range of biotic and abiotic stressors in the field, which can occur concurrently or sequentially. To elucidate the molecular mechanisms in responses to such individual and combined stresses, we used RNAseq to compare the temporal changes in the transcriptome of Camellia sinensis to Ectropis oblique Prout alone or in combination with exposure to drought and heat. Compared with the individual stress, tea plants exhibit significant differences in transcriptome profiles under the combined stresses. Additionally, many unique genes exhibited significant differences in expression in individual and combined stress conditions. Our research showed novel insights into the molecular mechanisms of E. oblique Prout resistance in tea plants and provided a valuable resource for developing tea varieties with broad spectrum stress tolerance.