High-entropy structures in layered compounds,especially transitional metal dichalcogenides(TMDCs),have powered the field with disordered and versatile chemical compositions,showing great potential in various functiona...High-entropy structures in layered compounds,especially transitional metal dichalcogenides(TMDCs),have powered the field with disordered and versatile chemical compositions,showing great potential in various functional applications,including energy storage and catalysis.However,the reported high-entropy phases are mainly 1T phases,2H phases are rare,and approximately 3R phases are still lacking.Here,phase engineering of high-entropy TMDCs is achieved by tuning the chemical composition of(Mo_(0.5)W_(0.5))_(1−x)(Nb_(0.5)Ta_(0.5))_(x)Se_(2+δ),0≤x<1,and−0.1≤δ≤0.3.A phase diagram is constructed to guide the synthesis of pure 2H/3R phases over a wide composition/entropy range.The increase in VB-group element content and Se overdose facilitated the formation of 3R phases,whereas the opposite occurred for 2H phases.Thermodynamic first-principles calculations evaluate the stability of phases in different polytypes and compositions,matching well with the composition-dependent crystalline habits.Moreover,the optimized thermoelectric performance,with a figure of merit(zT=0.36@723 K)in 2H phase of x=0.2,is attributed to the low thermal conductivity(κ)caused by the high-entropy effect,which is one of the highest among(Mo/W)Se_(2)-based materials.Our work enriches high-entropy TMDCs with versatile polytypes,expanding their potential uses for various fields.展开更多
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB0470303)the National Nature Science Foundation of China(No.52473295)+1 种基金the Young Elite Scientists Sponsorship Program by CAST(No.2024QNRC001)the State Key Laboratory of Structural Chemistry(No.20230020).
文摘High-entropy structures in layered compounds,especially transitional metal dichalcogenides(TMDCs),have powered the field with disordered and versatile chemical compositions,showing great potential in various functional applications,including energy storage and catalysis.However,the reported high-entropy phases are mainly 1T phases,2H phases are rare,and approximately 3R phases are still lacking.Here,phase engineering of high-entropy TMDCs is achieved by tuning the chemical composition of(Mo_(0.5)W_(0.5))_(1−x)(Nb_(0.5)Ta_(0.5))_(x)Se_(2+δ),0≤x<1,and−0.1≤δ≤0.3.A phase diagram is constructed to guide the synthesis of pure 2H/3R phases over a wide composition/entropy range.The increase in VB-group element content and Se overdose facilitated the formation of 3R phases,whereas the opposite occurred for 2H phases.Thermodynamic first-principles calculations evaluate the stability of phases in different polytypes and compositions,matching well with the composition-dependent crystalline habits.Moreover,the optimized thermoelectric performance,with a figure of merit(zT=0.36@723 K)in 2H phase of x=0.2,is attributed to the low thermal conductivity(κ)caused by the high-entropy effect,which is one of the highest among(Mo/W)Se_(2)-based materials.Our work enriches high-entropy TMDCs with versatile polytypes,expanding their potential uses for various fields.
