Ab initio investigation of CaO-ZnO alloys under high pressure

Abstract

CaxZn1–xO alloys are potential candidates to achieve wide band-gap, which might significantly promote the band gap engineering and heterojunction design. We performed a crystal structure search for CaO-ZnO system under pressure, using an ab initio evolutionary algorithm implemented in the USPEX code. Four stable ordered CaxZn1–xO structures are found in the pressure range of 8.7–60 GPa. We further constructed the pressure vs. composition phase diagram of CaO-ZnO alloys based on the detailed enthalpy calculations. With the increase in Ca concentration, the CaO-ZnO alloy first undergoes a hexagonal to monoclinic transition, and then transforms back to a hexagonal phase. At Above 9 GPa, there is no cubic structure in the alloys, in contrast to the insostructural components (B1-B1). The band gap of the CaxZn1–xO alloy shows an almost linear increase as a function of the Ca concentration. We also investigated the variation regularity of the band gap under pressure.

Phase Equilibrium Study of the CaO–ZnO System

“…1 Calcium oxide (CaO) is also an important component for ceramics, advanced materials, and pyrometallurgical fluxing materials. [4][5][6][7][8][9] Ca x Zn 1Àx O solid solutions are potential candidates to achieve wide band gap, which might significantly promote the band gap engineering and heterojunction design. [4][5][6][7][8][9] Ca x Zn 1Àx O solid solutions are potential candidates to achieve wide band gap, which might significantly promote the band gap engineering and heterojunction design.…”

“…2,3 The CaO-ZnO system is widely used in advanced material fields. 4 CaO-ZnO containing glass and ceramics are suited for use as a reinforcement in a plastic, plaster, cement, or low-melting metal structure. 4 CaO-ZnO containing glass and ceramics are suited for use as a reinforcement in a plastic, plaster, cement, or low-melting metal structure.…”

“…There is no experimental work on the binary CaO-ZnO phase diagram. [4][5][6][7][8][9][10][11][12][13][14][15][16] This study aims at providing high-temperature information of the CaO-ZnO system by an experimental approach. But the work did not include any results on or near the CaO-ZnO system.…”

“…2,3 The CaO-ZnO system is widely used in advanced material fields. [4][5][6][7][8][9] Ca x Zn 1Àx O solid solutions are potential candidates to achieve wide band gap, which might significantly promote the band gap engineering and heterojunction design. 4 CaO-ZnO containing glass and ceramics are suited for use as a reinforcement in a plastic, plaster, cement, or low-melting metal structure.…”

“…[4][5][6][7][8][9] Ca x Zn 1Àx O solid solutions are potential candidates to achieve wide band gap, which might significantly promote the band gap engineering and heterojunction design. 4 CaO-ZnO containing glass and ceramics are suited for use as a reinforcement in a plastic, plaster, cement, or low-melting metal structure. [5][6][7] The calcined CaO-ZnO mixture can be used as catalyst in the selective conversion of CH 4 to C 2 hydrocarbons, 8 and can also be used in the transesterification of palm olefin, soybean, and sunflower oils.…”