najoNanosystems: Physics, Chemistry, MathematicsНаносистемы: физика, химия, математика2220-80542305-7971Университет ИТМО10.17586/2220-8054-2025-16-4-472-482najo-1447Research ArticleCHEMISTRY AND MATERIALS SCIENCEХИМИЯ И НАУКА О МАТЕРИАЛАХPhase formation in the BiPO4–YPO4–(H2O) systemФазообразование в системе BiPO4–YPO4–(H2O)https://orcid.org/0009-0008-8804-4732ОсмининаА. А.OsmininaA. A.

Alena A. Osminina 

St. Petersburg

alenaosminina3001@gmail.comhttps://orcid.org/0000-0003-4345-6086ЕловиковД. П.ElovikovD. P.

Dmitry P. Elovikov

St. Petersburg

syncdima@mail.ruhttps://orcid.org/0000-0002-2807-375XПроскуринаО. В.ProskurinaO. V.

Olga V. Proskurina 

St. Petersburg

proskurinaov@mail.ruBranch of Petersburg Nuclear Physics Institute named by B. P. Konstantinov of National Research Centre “Kurchatov Institute” – Institute of Silicate Chemistry; Ioffe Institute; St. Petersburg State Institute of TechnologyRussian FederationBranch of Petersburg Nuclear Physics Institute named by B. P. Konstantinov of National Research Centre “Kurchatov Institute” – Institute of Silicate Chemistry; St. Petersburg Electrotechnical University “LETI”Russian FederationIoffe Institute; St. Petersburg State Institute of TechnologyRussian Federation202503092025164472482Copyright © Osminina A.A., Elovikov D.P., Proskurina O.V., 20252025Осминина А.А., Еловиков Д.П., Проскурина О.В.Osminina A.A., Elovikov D.P., Proskurina O.V.This work is licensed under a Creative Commons Attribution 4.0 License.https://nanojournal.ifmo.ru/jour/article/view/1447

This work is devoted to the study of phase equilibria in the BiPO4–YPO4–(nH2O) system under mild conditions. It was shown that using the precipitation method leads to crystallization of the samples into the rhabdophane phase YPO4 · nH2O and the ximengite phase BiPO4. Hydrothermal treatment of the samples at 160◦C results in the gradual transformation of hexagonal yttrium phosphate with a rhabdophane-type structure into tetragonal xenotime YPO4, and hexagonal bismuth phosphate with a ximengite-type structure into monoclinic bismuth phosphate (space group P 21/n). The transformation into the stable phases of xenotime and monoclinic bismuth phosphate is almost complete after 28 days of isothermal holding under hydrothermal conditions at 160◦C. Moreover, the lower the content of the second component in samples containing both Bi and Y, the faster the structural transformation into the stable phase proceeds. A solid solution based on monoclinic bismuth phosphate with the composition Bi0.94Y0.06PO4 is formed in the system. Before disappearing, the rhabdophane-type phase represents a solid solution with the composition Y0.8Bi0.2PO4 · nH2O. The crystallite sizes of all phases increase with an increase in the bismuth content in the system.

Работа посвящена изучению фазовых равновесий в системе BiPO4-YPO4-(nH2O) в мягких условиях. Показано, что при использовании метода осаждения образцы кристаллизуются в фазах рабдофана YPO4·nH2O и ксименгита BiPO4. Гидротермальная обработка образцов при 160°C приводит к постепенной трансформации гексагонального фосфата иттрия со структурой рабдофана в тетрагональный ксенотим YPO4 и гексагонального фосфата висмута со структурой ксименгита в моноклинный фосфат висмута (P21/n). Трансформация в устойчивые фазы ксенотима и моноклинного фосфата висмута завершается практически полностью через 28 дней изотермической выдержки в гидротермальных условиях при 160°C. Причем, чем меньше второго компонента в образцах, содержащих как Bi, так и Y, тем быстрее идет процесс структурной трансформации в устойчивую фазу. В системе формируется твёрдый раствор на основе моноклинного фосфата висмута состава Bi0,94Y0,06PO4. Фаза со структурой рабдофана перед исчезновением представляет собой твердый раствор состава Y0,8Bi0,2PO4·nH2O. Размеры кристаллитов всех фаз возрастают с увеличением доли висмута в системенанокристаллыфазообразованиефосфат висмутаортофосфат иттриягидротермальный синтезnanocrystalsphase formationbismuth phosphateyttrium orthophosphatehydrothermal synthesisThe authors are grateful to Corresponding Member of the Russian Academy of Sciences V. V. Gusarov for his attention to the work and valuable comments, as well as D. P. Danilovich for his help in conducting the research. The work of A. A. O. and D. P. E. was carried out with the support of the Russian Science Foundation project No. 24-13-00445. Scanning electron microscopy and elemental analyses of samples were performed employing the equipment of the Engineering Center of the St. Petersburg State Institute of Technology. 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The authors declare that there are no conflicts of interest present.