Crystal structure, photocatalytic and dielectric property of ATiM2O8 (A: Mg, Zn; M: Nb, Ta)

Nobuhiro Kumada,Kohsuke Nakanome,Sayaka Yanagida,Takahiro Takei,Ichiro Fujii,Satoshi Wada,Chikako Moriyoshi,Yoshihiro Kuroiwa

doi:10.1080/21870764.2018.1504708

Nobuhiro Kumada, Kohsuke Nakanome + Show 6 more

Open Access

https://doi.org/10.1080/21870764.2018.1504708

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Abstract

ABSTRACTFour types of oxides, ATiM2O8 (A: Mg, Zn; M: Nb, Ta) were prepared by high-temperature solid-state reaction. MgTiNb2O8, ZnTiNb2O8 and ATiTa2O8 had rutile-type, α-PbO2-type and trirutile-type structures, respectively. The crystal structures of these compounds were refined based on the synchrotron X-ray powder diffraction data with the following R-factors: Rwp = 4.34% and Rp = 2.21% for MgTiNb2O8; Rwp = 2.19% and Rp = 1.52% for ZnTiNb2O8; Rwp = 9.03% and Rp = 6.31% for MgTiTa2O8; and Rwp = 5.70% and Rp = 4.16% for ZnTiTa2O8. Their lattice parameters were a = 4.69585(8) and c = 3.04260(6) Å for MgTiNb2O8; a = 4.67138(6), b = 5.65916(7) and c = 5.00745(6) Å for ZnTiNb2O8; a = 4.6876(2) and c = 9.1385(3) Å for MgTiNb2O8; and a = 4.6987(7) and c = 9.1296(1) Å for ZnTiTa2O8. The optical band gap for these compounds ranged from 2.98 to 3.15 eV and every compound exhibited a small amount of photocatalytic activity for phenol decomposition under UV light irradiation. However, no photocatalytic activity was observed under visible light irradiation. The dielectric constants for these compounds were between 25 and 125 at a temperature range of room temperature to 400°C.

Highlights

Transition-metal niobates and tantalates adopt mainly three types of crystal structures: rutile, trirutile- and columbite-types [1]
We reported the crystal structure and photocatalytic activity of the solid solution, Ni1-xCoxTi(Nb1-yTay)2O8 (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) [6], which had a rutile-type structure for y = 0, a trirutile-type structure for y = 1 and a trirutile-type structure appeared for y ≥ 0.4
The X-ray powder patterns of MgTiNb2O8 and ZnTiNb2O8 showed that these had a rutile- and an αPbO2-types structures, respectively

Summary

Introduction

Transition-metal niobates and tantalates adopt mainly three types of crystal structures: rutile-, trirutile- and columbite-types [1]. The addition of titanium in transition-metal niobates and tantalates is limited to the formation of rutile- and trirutile-type structures. We reported the crystal structure and photocatalytic activity of the solid solution, Ni1-xCoxTi(Nb1-yTay)2O8 (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) [6], which had a rutile-type structure for y = 0, a trirutile-type structure for y = 1 and a trirutile-type structure appeared for y ≥ 0.4. We describe the preparation, crystal structure refinement, photocatalytic activity and dielectric property of four types of niobates and tantalates (ATiM2O8; A: Mg, Zn; M: Nb, Ta)

Experimental

Results and discussion

Conclusions