Features of Phase Formation of Pyrochlore-type Ceramics Bi2Mg(Zn)1- x Ni x Ta2O9

Nadezhda A Zhuk; Sofia Yu Kovalenko; Roman I Korolev; Boris A Makeev; Maria G Krzhizhanovskaya; Danil V Sivkov; Sergey V Nekipelov; Viktor N Sivkov; Maria V Yermolina

doi:10.1021/acsomega.3c00090

Features of Phase Formation of Pyrochlore-type Ceramics Bi₂Mg(Zn)_{1- x} Ni _x Ta₂O₉

ACS Omega. 2023 Mar 16;8(12):11351-11363. doi: 10.1021/acsomega.3c00090. eCollection 2023 Mar 28.

Authors

Nadezhda A Zhuk¹, Sofia Yu Kovalenko¹, Roman I Korolev¹, Boris A Makeev², Maria G Krzhizhanovskaya³, Danil V Sivkov⁴, Sergey V Nekipelov⁴, Viktor N Sivkov⁴, Maria V Yermolina⁵

Affiliations

¹ Syktyvkar State University, Oktyabrsky Prospect, 55, Syktyvkar 167001, Russia.
² Institute of Geology of the Komi Science Center UB RAS, Pervomaiskaya st. 48, Syktyvkar 167982, Russia.
³ Saint Petersburg State University, University Emb. 7/9, St. Petersburg 199034, Russia.
⁴ Institute of Physics and Mathematics of the Komi Science Center UB RAS, Oplesnina st. 4, Syktyvkar, Republic of Komi 167982, Russia.
⁵ University of Illinois Chicago, 845 W. Taylor St., MC 111, Chicago, Illinois 60607, United States.

Abstract

The phase formation of complex pyrochlores (space group Fd-3m) Bi₂Mg(Zn)_1-x Ni _x Ta₂O₉ was investigated during solid-phase synthesis. It was found that the pyrochlore phase precursor in all cases was α-BiTaO₄. The pyrochlore phase synthesis reaction proceeds mainly at temperatures above 850-900 °C and consists in the interaction of bismuth orthotantalate with a transition element oxide. The influence of magnesium and zinc on the course of pyrochlore synthesis was revealed. The reaction temperatures of magnesium and nickel (800 and 750 °C, respectively) were determined. The change in the pyrochlore unit cell parameter depending on the synthesis temperature was analyzed for both systems. Nickel-magnesium pyrochlores are characterized by a porous dendrite-like microstructure with a grain size of 0.5-1.0 microns, and the porosity of the samples reaches 20 percent. The calcination temperature does not significantly affect the microstructure of the samples. Prolonged calcination of the preparations leads to the coalescence of grains with the formation of larger particles. Nickel oxide has a sintering effect on ceramics. The studied nickel-zinc pyrochlores are characterized by a low-porous dense microstructure. The porosity of the samples does not exceed 10%. The optimal conditions for obtaining phase-pure pyrochlores (1050 °C and 15 h) were determined.