TY - JOUR

T1 - The effect of CuO on the microstructure, spectral characteristics, thermal and electrical properties of BiNbO4 ceramics

AU - Zhuk, N. A.

AU - Shugurov, S. M.

AU - Krzhizhanovskaya, M. G.

AU - Belyy, V. A.

AU - Sekushin, N. A.

AU - Makeev, B. A.

AU - Nekipelov, S. V.

AU - Beznosikov, D. S.

AU - Busargina, Ya. A.

PY - 2020/5/5

Y1 - 2020/5/5

N2 - Thermal and electrical properties of copper oxide doped BiNbO4 ceramics as well as its spectral characteristics and microstructure were studied in this work. According to XRD, the samples calcined at 950 °C and 1100 °C had the structure of α-BiNbO4 in spite of the phase transition α→γ(β) at 1040 °C. The studied composite samples had the composition of BiNb1-хCuх-yO4-δ·yСuO (х≤0.04) and were characterized by the graphite color and visually pronounced grain microstructure. The DSC-curves of the samples revealed the reversible endo-effect near 900 °C associated with copper (II) oxide decomposition and the thermal effects caused by the chain of reconstructive phase transitions α→γ→β’→β in BiNb1-хCuх-yO4-δ. It was established that the presence of copper oxide additive in the samples increased the density of the ceramics, on average, by 8–10% and had a thermostatic effect on the compacted samples manifested in the increase in the α→γ(β) phase transformation temperature by ∼ 100 °C. The mass spectrum of vapor over the BiNb1-хCuх-yO4-δ·yСuO samples in vacuum has shown the ionic currents of Bi+ and O2+. The absence of Cu+ ions in the mass spectrum of vapor was due to low partial pressure of copper vapor. The comparison of the Cu2p-NEXAFS spectra of copper oxides (I) and (II) and BiNb1-хCuх-yO4-δ·yСuO, synthesized at 950 °C and 1100 °C allowed to conclude that copper atoms were in the Cu(II) state in the studied ceramics. The impedance spectroscopy showed that an increase in the copper content reduced the conductivity of the samples synthesized at 950 °C and increased the conductivity of the samples synthesized at 1100 °C. A threefold increase in the copper content led to an increase in low-frequency dielectric losses by 20% in the samples synthesized at 1100 °C. The growth of the capacity of the samples with decreasing frequency indicated the ion-migration nature of polarization.

AB - Thermal and electrical properties of copper oxide doped BiNbO4 ceramics as well as its spectral characteristics and microstructure were studied in this work. According to XRD, the samples calcined at 950 °C and 1100 °C had the structure of α-BiNbO4 in spite of the phase transition α→γ(β) at 1040 °C. The studied composite samples had the composition of BiNb1-хCuх-yO4-δ·yСuO (х≤0.04) and were characterized by the graphite color and visually pronounced grain microstructure. The DSC-curves of the samples revealed the reversible endo-effect near 900 °C associated with copper (II) oxide decomposition and the thermal effects caused by the chain of reconstructive phase transitions α→γ→β’→β in BiNb1-хCuх-yO4-δ. It was established that the presence of copper oxide additive in the samples increased the density of the ceramics, on average, by 8–10% and had a thermostatic effect on the compacted samples manifested in the increase in the α→γ(β) phase transformation temperature by ∼ 100 °C. The mass spectrum of vapor over the BiNb1-хCuх-yO4-δ·yСuO samples in vacuum has shown the ionic currents of Bi+ and O2+. The absence of Cu+ ions in the mass spectrum of vapor was due to low partial pressure of copper vapor. The comparison of the Cu2p-NEXAFS spectra of copper oxides (I) and (II) and BiNb1-хCuх-yO4-δ·yСuO, synthesized at 950 °C and 1100 °C allowed to conclude that copper atoms were in the Cu(II) state in the studied ceramics. The impedance spectroscopy showed that an increase in the copper content reduced the conductivity of the samples synthesized at 950 °C and increased the conductivity of the samples synthesized at 1100 °C. A threefold increase in the copper content led to an increase in low-frequency dielectric losses by 20% in the samples synthesized at 1100 °C. The growth of the capacity of the samples with decreasing frequency indicated the ion-migration nature of polarization.

KW - Ceramics

KW - Copper

KW - Dielectrics

KW - Phase transformations

UR - http://www.scopus.com/inward/record.url?scp=85077342818&partnerID=8YFLogxK

U2 - 10.1016/j.jallcom.2019.153619

DO - 10.1016/j.jallcom.2019.153619

M3 - Article

AN - SCOPUS:85077342818

VL - 822

JO - Journal of Alloys and Compounds

JF - Journal of Alloys and Compounds

SN - 0925-8388

M1 - 153619

ER -