najoNanosystems: Physics, Chemistry, MathematicsНаносистемы: физика, химия, математика2220-80542305-7971Университет ИТМО10.17586/2220-8054-2020-11-6-705-715najo-387Research ArticleCHEMISTRY AND MATERIALS SCIENCEХИМИЯ И НАУКА О МАТЕРИАЛАХFormation of nanocrystals based on equimolar mixture of lanthanum and yttrium orthophosphates under microwave-assisted hydrothermal synthesisEnikeevaM. O.

Moskovsky Pr., 26, Saint Petersburg, 190013

Politekhnicheskaya St. 26, Saint Petersburg, 194021

odin2tri45678@gmail.comProskurinaO. V.

Moskovsky Pr., 26, Saint Petersburg, 190013

Politekhnicheskaya St. 26, Saint Petersburg, 194021

proskurinaov@mail.ruDanilovichD. P.

Politekhnicheskaya St. 26, Saint Petersburg, 194021

dmitrydanilovich@gmail.comGusarovV. V.

Moskovsky Pr., 26, Saint Petersburg, 190013

victor.v.gusarov@gmail.comSaint Petersburg State Institute of Technology; Ioffe InstituteRussian FederationIoffe InstituteRussian FederationSaint Petersburg State Institute of TechnologyRussian Federation202029072025116705–715Copyright © Enikeeva M.O., Proskurina O.V., Danilovich D.P., Gusarov V.V., 20252025Enikeeva M.O., Proskurina O.V., Danilovich D.P., Gusarov V.V.Enikeeva M.O., Proskurina O.V., Danilovich D.P., Gusarov V.V.Данная работа распространяется под лицензией Creative Commons Attribution 4.0.This work is licensed under a Creative Commons Attribution 4.0 License.https://nanojournal.ifmo.ru/jour/article/view/387

The effect of hydrothermal-microwave treatment time at 180 ◦C on the phase composition, dimensional parameters of crystallites and nanoparticles of solid solutions of lanthanum and yttrium orthophosphates in the system 0.53LaPO4–0.47YPO4–(nH2O) has been determined. It has been proposed the mechanism for structural transition of lanthanum-yttrium orthophosphate solid solution with rhabdophane structure into monazite structure, which consists in the degeneration of nanocrystals having rhabdophane structure along certain edges into monazite structure. It is shown that phase nanoparticles of monazite structure having average crystallite size of 15–17 nm begin to form after 30 minutes of hydrothermalmicrowave treatment at 180 ◦C immediately after complete crystallization of amorphous phase in the system. The nanoparticle size increase (length of nanorods) with monazite structure after the stage of their formation occurs, mainly due to matter transfer from nanoparticles having rhabdophane structure to nanoparticles having monazite structure. In this case, the system considered conditions of hydrothermal treatment (temperature – 180 ◦C, pressure ∼1–1.5 MPa, duration – up to 120 min) remains two-phase.

nanocrystalslanthanum and yttrium orthophosphatesmonaziterhabdophanehydrothermal treatmentmicrowave heatingphase transitionX-ray diffraction studies and elemental analysis of the samples performed using devices of the Engineering Center of the St. Petersburg State Technological Institute (Technical University). Studies on transmission electron microscope were performed using equipment from the Federal Common Use Center “Materials Science and Diagnostics in Advanced Technologies” at the Ioffe Physical-Technical Institute of the Russian Academy of Sciences. These studies were financially supported by the Russian Fundamental Research Fund (Project No. 18-29-12119).ReferencesDu A., Wan C., Qu Z., Wu R., Pan W. Effects of texture on the thermal conductivity of the LaPO4 monazite. Journal of the American Ceramic Society, 2010, 93, P. 2822–2827.Du A., Wan C., Qu Z., Wu R., Pan W. Effects of texture on the thermal conductivity of the LaPO4 monazite. Journal of the American Ceramic Society, 2010, 93, P. 2822–2827.Hikichi Y., Ota T., Daimon K., Hattori T., Mizuno M. Thermal, Mechanical, and Chemical Properties of Sintered Xenotime-Type RPO4 (R = Y, Er, Yb, or Lu). Journal of the American Ceramic Society, 1998, 81, P. 2216–2218.Hikichi Y., Ota T., Daimon K., Hattori T., Mizuno M. Thermal, Mechanical, and Chemical Properties of Sintered Xenotime-Type RPO4 (R = Y, Er, Yb, or Lu). Journal of the American Ceramic Society, 1998, 81, P. 2216–2218.Ushakov S.V., Helean K.B., Navrotsky A., Boatner L.A. Thermochemistry of rare-earth orthophosphates. J. Mater. Res., 2001, 16(9), P. 2623– 2633.Ushakov S.V., Helean K.B., Navrotsky A., Boatner L.A. Thermochemistry of rare-earth orthophosphates. J. Mater. Res., 2001, 16(9), P. 2623– 2633.Schlenz H., Heuser J., Neumann A., Schmitz S., Bosbach D. Monazite as a suitable actinide waste form. Crystalline Materials, 2013, 228(3), P. 113–123.Schlenz H., Heuser J., Neumann A., Schmitz S., Bosbach D. Monazite as a suitable actinide waste form. Crystalline Materials, 2013, 228(3), P. 113–123.Mezentseva L., Osipov A., Ugolkov V., Akatov A., Doil’nitsyn V., Maslennikova T., Yakovlev A. Synthesis and Thermal Behavior of Nanopowders in LaPO4-YPO4(-H2O), LaPO4-LuPO4(-H2O) and YPO4-ScPO4(-H2O) Systems for Ceramic Matrices. J Nanomed. Res., 2017, 6(1), P. 00145.Mezentseva L., Osipov A., Ugolkov V., Akatov A., Doil’nitsyn V., Maslennikova T., Yakovlev A. Synthesis and Thermal Behavior of Nanopowders in LaPO4-YPO4(-H2O), LaPO4-LuPO4(-H2O) and YPO4-ScPO4(-H2O) Systems for Ceramic Matrices. J Nanomed. Res., 2017, 6(1), P. 00145.Gausse C., Szenknect S., Mesbah A., Clavier N., Neumeier S., Dacheux N. Dissolution kinetics of monazite LnPO4 (Ln = La to Gd): A multiparametric study. Applied Geochemistry, 2018, 93, P. 81–93.Gausse C., Szenknect S., Mesbah A., Clavier N., Neumeier S., Dacheux N. Dissolution kinetics of monazite LnPO4 (Ln = La to Gd): A multiparametric study. Applied Geochemistry, 2018, 93, P. 81–93.Toro-Gonzalez M., Dame A.N., Foster C. M., Millet L.J., Woodward J.D., Rojas J.V., Mirzadeh S., Davern S.M. Quantitative encapsulation´ and retention of 227Th and decay daughters in core–shell lanthanum phosphate nanoparticles. Nanoscale, 2020, 12, P. 9744–9755.Toro-Gonzalez M., Dame A.N., Foster C. M., Millet L.J., Woodward J.D., Rojas J.V., Mirzadeh S., Davern S.M. Quantitative encapsulation´ and retention of 227Th and decay daughters in core–shell lanthanum phosphate nanoparticles. Nanoscale, 2020, 12, P. 9744–9755.Lenz C., Thorogood G., Aughterson R., Ionescu M., J. Gregg D., Davis J., Lumpkin, G. The quantification of radiation damage in orthophosphates using confocal µ-luminescence spectroscopy of Nd3+. Frontiers in Chemistry, 2019, 7. Art.13.Lenz C., Thorogood G., Aughterson R., Ionescu M., J. Gregg D., Davis J., Lumpkin, G. The quantification of radiation damage in orthophosphates using confocal µ-luminescence spectroscopy of Nd3+. Frontiers in Chemistry, 2019, 7. Art.13.Osipov A.V., Mezentseva L.P., Drozdova I.A., Kuchaeva S.K., Ugolkov V.L., Gusarov V.V. Crystallization and thermal transformations in nanocrystals of the YPO4-LuPO4-H2O system. Glass. Phys. Chem., 2007, 33, P. 169–173.Osipov A.V., Mezentseva L.P., Drozdova I.A., Kuchaeva S.K., Ugolkov V.L., Gusarov V.V. Crystallization and thermal transformations in nanocrystals of the YPO4-LuPO4-H2O system. Glass. Phys. Chem., 2007, 33, P. 169–173.Osipov A.V., Mezentseva L.P., Drozdova I.A., Kuchaeva S.K., Ugolkov V.L., Gusarov V.V. Preparation and thermal transformations of nanocrystals in the LaPO4-LuPO4-H2O system. Glass. Phys. Chem, 2009, 35, P. 431–435.Osipov A.V., Mezentseva L.P., Drozdova I.A., Kuchaeva S.K., Ugolkov V.L., Gusarov V.V. Preparation and thermal transformations of nanocrystals in the LaPO4-LuPO4-H2O system. Glass. Phys. Chem, 2009, 35, P. 431–435.Ruigang W., Wei P., Jian C., Minghao F., Zhenzhu C., Yongming L. Synthesis and sintering of LaPO4 powder and its application. Mater. Chem. Phys, 2003, 79(1), P. 30–36.Ruigang W., Wei P., Jian C., Minghao F., Zhenzhu C., Yongming L. Synthesis and sintering of LaPO4 powder and its application. Mater. Chem. Phys, 2003, 79(1), P. 30–36.Ferhi M., Horchani-Naifer K., Ferid M. Combustion synthesis and luminescence properties of LaPO´ 4: Eu (5%). J. Rare Earths, 2009, 27(2), P. 182–186.Ferhi M., Horchani-Naifer K., Ferid M. Combustion synthesis and luminescence properties of LaPO´ 4: Eu (5%). J. Rare Earths, 2009, 27(2), P. 182–186.Lai H., Bao A., Yang Y., et al. UV luminescence property of YPO4:RE (RE = Ce3+, Tb3+). J. Phys. Chem. C, 2007, 112(1), P. 282–286.Lai H., Bao A., Yang Y., et al. UV luminescence property of YPO4:RE (RE = Ce3+, Tb3+). J. Phys. Chem. C, 2007, 112(1), P. 282–286.Pan W., Phillpot S.R., Wan C., Chernatynskiy A., Qu Z. Low thermal conductivity oxides. MRS Bull, 2012, 37(10), P. 917–922.Pan W., Phillpot S.R., Wan C., Chernatynskiy A., Qu Z. Low thermal conductivity oxides. MRS Bull, 2012, 37(10), P. 917–922.Grechanovsky A.E., Eremin N.N., Urusov V.S. Radiation resistance of LaPO4 (monazite structure) and YbPO4 (zircon structure) from data of computer simulation. Phys Solid State, 2013, 55, P. 1929–1935.Grechanovsky A.E., Eremin N.N., Urusov V.S. Radiation resistance of LaPO4 (monazite structure) and YbPO4 (zircon structure) from data of computer simulation. Phys Solid State, 2013, 55, P. 1929–1935.Terra O., Clavier N., Dacheux N., Podor R. Preparation and characterization of lanthanum–gadolinium monazites as ceramics for radioactive waste storage. New journal of Chemistry, 2003, 27(6), P. 957–967.Terra O., Clavier N., Dacheux N., Podor R. Preparation and characterization of lanthanum–gadolinium monazites as ceramics for radioactive waste storage. New journal of Chemistry, 2003, 27(6), P. 957–967.Ohtaki K.K., Heravi N.J., Leadbetter J.W., Peter E.D. Morgan, Mecartney M.L. Extended solubility of Sr in LaPO4 monazite. Solid State Ionics, 2016, 293, P. 44–50.Ohtaki K.K., Heravi N.J., Leadbetter J.W., Peter E.D. Morgan, Mecartney M.L. Extended solubility of Sr in LaPO4 monazite. Solid State Ionics, 2016, 293, P. 44–50.Gallini S., Hansel M., Norby T. Impedance spectroscopy and proton transport number measurements on Sr-substituted LaPO¨ 4 prepared by combustion synthesis. Solid State Ionics, 2003, 162-163, P. 167–173.Gallini S., Hansel M., Norby T. Impedance spectroscopy and proton transport number measurements on Sr-substituted LaPO¨ 4 prepared by combustion synthesis. Solid State Ionics, 2003, 162-163, P. 167–173.Bryukhanova K.I., Nikiforova G.E., Gavrichev K.S. Synthesis and study of anhydrous lanthanide orthophosphate (Ln= La, Pr, Nd, Sm) nanowhiskers. Nanosystems: Physics, Chemistry, Mathematics, 2016, 7(3), P. 451–458.Bryukhanova K.I., Nikiforova G.E., Gavrichev K.S. Synthesis and study of anhydrous lanthanide orthophosphate (Ln= La, Pr, Nd, Sm) nanowhiskers. Nanosystems: Physics, Chemistry, Mathematics, 2016, 7(3), P. 451–458.Larina L.L., Alexeeva O.V., Almjasheva O.V., Gusarov V.V., Kozlov S.S., Nikolskaia A.B., Vildanova M.F., Shevaleevskiy O.I. Very widebandgap nanostructured metal oxide materials for perovskite solar cells. Nanosystems: Physics, Chemistry, Mathematics, 2019, 10(1), P. 70– 75.Larina L.L., Alexeeva O.V., Almjasheva O.V., Gusarov V.V., Kozlov S.S., Nikolskaia A.B., Vildanova M.F., Shevaleevskiy O.I. Very widebandgap nanostructured metal oxide materials for perovskite solar cells. Nanosystems: Physics, Chemistry, Mathematics, 2019, 10(1), P. 70– 75.Vildanova M.F., Nikolskaia A.B., Kozlov S.S., Karyagina O.K., Larina L.L., Shevaleevskiy O.I., Almjasheva O.V., Gusarov V.V. Nanostructured ZrO2-Y2O3-based system for perovskite solar cells. Doklady Physical Chemistry, 2019, 484(2), P. 36–38.Vildanova M.F., Nikolskaia A.B., Kozlov S.S., Karyagina O.K., Larina L.L., Shevaleevskiy O.I., Almjasheva O.V., Gusarov V.V. Nanostructured ZrO2-Y2O3-based system for perovskite solar cells. Doklady Physical Chemistry, 2019, 484(2), P. 36–38.Yorov Kh.E., Khodan A.N., Baranchikov A.E., Utochnikova V.V., Simonenko N.P., Beltiukov A.N., Petukhov D.I., Kanaev A., Ivanov V.K. Superhydrophobic and luminescent highly porous nanostructured alumina monoliths modified with tris(8-hydroxyquinolinato)aluminium. Microporous and Mesoporous Materials, 2020, 293, P. 109804.Yorov Kh.E., Khodan A.N., Baranchikov A.E., Utochnikova V.V., Simonenko N.P., Beltiukov A.N., Petukhov D.I., Kanaev A., Ivanov V.K. Superhydrophobic and luminescent highly porous nanostructured alumina monoliths modified with tris(8-hydroxyquinolinato)aluminium. Microporous and Mesoporous Materials, 2020, 293, P. 109804.Sklyarova A., Popkov V.I., Pleshakov I.V., Matveev V.V., Stepˇ ankov´ a P.H., Chlan V. Peculiarities of´ 57Fe NMR Spectrum in Micro- and Nanocrystalline Europium Orthoferrites. Applied Magnetic Resonance, 2020.Sklyarova A., Popkov V.I., Pleshakov I.V., Matveev V.V., Stepˇ ankov´ a P.H., Chlan V. Peculiarities of´ 57Fe NMR Spectrum in Micro- and Nanocrystalline Europium Orthoferrites. Applied Magnetic Resonance, 2020.Popkov V.I., Bachina A.K., Valeeva A.A., Lobinsky A.A., Gerasimov E.Y., Rempel A.A. Synthesis, morphology and electrochemical properties of spherulite titania nanocrystals. Ceramics International, 2020, 46(15), P. 24483–24487.Popkov V.I., Bachina A.K., Valeeva A.A., Lobinsky A.A., Gerasimov E.Y., Rempel A.A. Synthesis, morphology and electrochemical properties of spherulite titania nanocrystals. Ceramics International, 2020, 46(15), P. 24483–24487.Kovalenko A.N., Tugova E.A. Thermodynamics and kinetics of non-autonomous phase formation in nanostructured materials with variable functional properties. Nanosystems: Physics, Chemistry, Mathematics, 2018, 9(5), P. 641–662.Kovalenko A.N., Tugova E.A. Thermodynamics and kinetics of non-autonomous phase formation in nanostructured materials with variable functional properties. Nanosystems: Physics, Chemistry, Mathematics, 2018, 9(5), P. 641–662.Roca A.G., Gutierrez L., Gavil´ an H., Fortes Brollo M.E., Veintemillas-Verdaguer S., Puerto Morales M. Design strategies for shape-controlled´ magnetic iron oxide nanoparticles. Advanced Drug Delivery Reviews, 2019, 138, P. 68–104.Roca A.G., Gutierrez L., Gavil´ an H., Fortes Brollo M.E., Veintemillas-Verdaguer S., Puerto Morales M. Design strategies for shape-controlled´ magnetic iron oxide nanoparticles. Advanced Drug Delivery Reviews, 2019, 138, P. 68–104.Davis J.B., Marshall D.B., Morgan P.E.D. Monazite-Containing Oxide/Oxide Composites. J. Eur. Ceram. Soc, 2000, 20(5), P. 583–587.Davis J.B., Marshall D.B., Morgan P.E.D. Monazite-Containing Oxide/Oxide Composites. J. Eur. Ceram. Soc, 2000, 20(5), P. 583–587.Arinicheva Y., Clavier N., Neumeier S., Podor R., Bukaemskiy A., Klinkenberg M., Roth G., Dacheux N., Bosbach D. Effect of powder morphology on sintering kinetics, microstructure and mechanical properties of monazite ceramics. J. Europ. Ceram. Soc., 2018, 38(1), P. 227– 234.Arinicheva Y., Clavier N., Neumeier S., Podor R., Bukaemskiy A., Klinkenberg M., Roth G., Dacheux N., Bosbach D. Effect of powder morphology on sintering kinetics, microstructure and mechanical properties of monazite ceramics. J. Europ. Ceram. Soc., 2018, 38(1), P. 227– 234.Kenges K.M., Proskurina O.V., Danilovich D.P., Aldabergenov M.K., Gusarov V.V. Influence of the Conditions for Preparing LaPO4-Based Materials with Inclusions of the LaP3O9 Phase on Their Thermal and Mechanical Properties. Russ. J. App. Chem., 2018, 91(9), P. 1539–1548.Kenges K.M., Proskurina O.V., Danilovich D.P., Aldabergenov M.K., Gusarov V.V. Influence of the Conditions for Preparing LaPO4-Based Materials with Inclusions of the LaP3O9 Phase on Their Thermal and Mechanical Properties. Russ. J. App. Chem., 2018, 91(9), P. 1539–1548.Shijina K., Sankar S., Midhun M., Firozkhan M., Nair B.N., Warrier K.G., Hareesh U.N.S. Very low thermal conductivity in lanthanum phosphate–zirconia ceramic nanocomposites processed using a precipitation–peptization synthetic approach. New J. Chem., 2016, 40(6), P. 5333–5337.Shijina K., Sankar S., Midhun M., Firozkhan M., Nair B.N., Warrier K.G., Hareesh U.N.S. Very low thermal conductivity in lanthanum phosphate–zirconia ceramic nanocomposites processed using a precipitation–peptization synthetic approach. New J. Chem., 2016, 40(6), P. 5333–5337.Zainurul A.Z., Rusop M., Abdullah S., Effect of annealing temperature on surface morphology of lanthanum phosphate (LaPO4) nanostructures thin films. Advanced Materials Research, 2012, 626, P. 302–305.Zainurul A.Z., Rusop M., Abdullah S., Effect of annealing temperature on surface morphology of lanthanum phosphate (LaPO4) nanostructures thin films. Advanced Materials Research, 2012, 626, P. 302–305.Ugolkov V.L., Mezentseva L.P., Osipov A.V., Popova V.F., Maslennikova T.P., Akatov A.A., Doil’nitsyn V.A. Synthesis of nanopowders and physicochemical properties of ceramic matrices of the LaPO4–YPO4–(H2O) and LaPO4–HoPO4–(H2O) systems. Rus. J. Appl. Chem., 2017, 90(1), P. 28–33.Ugolkov V.L., Mezentseva L.P., Osipov A.V., Popova V.F., Maslennikova T.P., Akatov A.A., Doil’nitsyn V.A. Synthesis of nanopowders and physicochemical properties of ceramic matrices of the LaPO4–YPO4–(H2O) and LaPO4–HoPO4–(H2O) systems. Rus. J. Appl. Chem., 2017, 90(1), P. 28–33.Maslennikova T.P., Osipov A.V., Mezentseva L.P., Drozdova I.A., Kuchaeva S.K., Ugolkov V.L., Gusarov V.V. Synthesis, Mutual Solubility, and Thermal Behavior of Nanocrystals in the LaPO4–YPO4–H2O System. Glass Physics and Chemistry, 2010, 36(3), P. 351–357.Maslennikova T.P., Osipov A.V., Mezentseva L.P., Drozdova I.A., Kuchaeva S.K., Ugolkov V.L., Gusarov V.V. Synthesis, Mutual Solubility, and Thermal Behavior of Nanocrystals in the LaPO4–YPO4–H2O System. Glass Physics and Chemistry, 2010, 36(3), P. 351–357.Mezentseva L., Osipov A., Ugolkov V., Kruchinina I., Popova V., Yakovlev A., Maslennikova T. Solid Solutions and Thermal Transformations in Nanosized LaPO4-YPO4-H2O and LaPO4-LuPO4-H2O Systems. J. Ceram. Sci. Tech., 2014, 05(03), P. 237–244.Mezentseva L., Osipov A., Ugolkov V., Kruchinina I., Popova V., Yakovlev A., Maslennikova T. Solid Solutions and Thermal Transformations in Nanosized LaPO4-YPO4-H2O and LaPO4-LuPO4-H2O Systems. J. Ceram. Sci. Tech., 2014, 05(03), P. 237–244.Mezentseva L.P., Kruchinina I.Yu., Osipov A.V., Kuchaeva S.K., Ugolkov V.L., Popova V.F., Pugachev K.E. Nanopowders of Orthophosphate LaPO4–YPO4–H2O System and Ceramics Based on Them. Glass Physics and Chemistry, 2014, 40(3), P. 356–361.Mezentseva L.P., Kruchinina I.Yu., Osipov A.V., Kuchaeva S.K., Ugolkov V.L., Popova V.F., Pugachev K.E. Nanopowders of Orthophosphate LaPO4–YPO4–H2O System and Ceramics Based on Them. Glass Physics and Chemistry, 2014, 40(3), P. 356–361.Wang R., Pan W., Chen J., Fang M., Meng J. Effect of LaPO4 content on the microstructure and machinability of Al2O3/LaPO4 composites. Mater Lett, 2002, 57(4), P. 822–827.Wang R., Pan W., Chen J., Fang M., Meng J. Effect of LaPO4 content on the microstructure and machinability of Al2O3/LaPO4 composites. Mater Lett, 2002, 57(4), P. 822–827.Sankar S., Raj A.N., Jyothi C.K., Warrier K.G.K., Padmanabhan P.V.A. Room temperature synthesis of high temperature stable lanthanum phosphate-yttria nano composite. Mater Res Bull, 2012, 47(7), P. 1835–1837.Sankar S., Raj A.N., Jyothi C.K., Warrier K.G.K., Padmanabhan P.V.A. Room temperature synthesis of high temperature stable lanthanum phosphate-yttria nano composite. Mater Res Bull, 2012, 47(7), P. 1835–1837.Mezentseva L., Osipov A., Ugolkov V., Kruchinina I., Maslennikova T., Koptelova L. Sol–gel synthesis of precursors and preparation of ceramic composites based on LaPO4 with Y2O3 and ZrO2 additions. J. Sol-Gel Sci Technol, 2019, 92(2), P. 427–441.Mezentseva L., Osipov A., Ugolkov V., Kruchinina I., Maslennikova T., Koptelova L. Sol–gel synthesis of precursors and preparation of ceramic composites based on LaPO4 with Y2O3 and ZrO2 additions. J. Sol-Gel Sci Technol, 2019, 92(2), P. 427–441.Proskurina O.V., Sivtsov E.V., Enikeeva M.O., Sirotkin A.A., Abiev R.S., Gusarov V.V. Formation of rhabdophane-structured lanthanum orthophosphate nanoparticles in an impinging-jets microreactor and rheological properties of sols based on them. Nanosyst Physics,Chem Math, 2019, 10(2), P. 206–214.Proskurina O.V., Sivtsov E.V., Enikeeva M.O., Sirotkin A.A., Abiev R.S., Gusarov V.V. Formation of rhabdophane-structured lanthanum orthophosphate nanoparticles in an impinging-jets microreactor and rheological properties of sols based on them. Nanosyst Physics,Chem Math, 2019, 10(2), P. 206–214.Wang S., Xu D., Guo Y., et al. Supercritical Hydrothermal Synthesis of Inorganic Nanomaterials. Supercritical Water Processing Technologies for Environment, Energy and Nanomaterial Applications, 2020, P. 117–147.Wang S., Xu D., Guo Y., et al. Supercritical Hydrothermal Synthesis of Inorganic Nanomaterials. Supercritical Water Processing Technologies for Environment, Energy and Nanomaterial Applications, 2020, P. 117–147.Darr J.A., Zhang J., Makwana N.M., Weng X. Continuous Hydrothermal Synthesis of Inorganic Nanoparticles: Applications and Future Directions. Chem. Rev., 2017, 117(17), P. 11125–11238.Darr J.A., Zhang J., Makwana N.M., Weng X. Continuous Hydrothermal Synthesis of Inorganic Nanoparticles: Applications and Future Directions. Chem. Rev., 2017, 117(17), P. 11125–11238.Kenges K., Aldabergenov M., Proskurina O., Gusarov V. Hydrothermal synthesis of monostructured LaPO4: morphology and structure. Chem Bull Kazakh Natl Univ., 2018, 3(90), P. 12–19.Kenges K., Aldabergenov M., Proskurina O., Gusarov V. Hydrothermal synthesis of monostructured LaPO4: morphology and structure. Chem Bull Kazakh Natl Univ., 2018, 3(90), P. 12–19.Enikeeva M.O., Kenges K.M., Proskurina O.V., Danilovich D.P., Gusarov V.V. Influence of Hydrothermal Treatment Conditions on the Formation of Lanthanum Orthophosphate Nanoparticles of Monazite Structure. Russ. J. Appl. Chem., 2020, 93(4), P. 540–548.Enikeeva M.O., Kenges K.M., Proskurina O.V., Danilovich D.P., Gusarov V.V. Influence of Hydrothermal Treatment Conditions on the Formation of Lanthanum Orthophosphate Nanoparticles of Monazite Structure. Russ. J. Appl. Chem., 2020, 93(4), P. 540–548.Patra C.R., Alexandra G., Patra S., et al. Microwave approach for the synthesis of rhabdophane-type lanthanide orthophosphate (Ln = La, Ce, Nd, Sm, Eu, Gd and Tb) nanorods under solvothermal conditions. New J. Chem., 2005, 29(5), P. 733–739.Patra C.R., Alexandra G., Patra S., et al. Microwave approach for the synthesis of rhabdophane-type lanthanide orthophosphate (Ln = La, Ce, Nd, Sm, Eu, Gd and Tb) nanorods under solvothermal conditions. New J. Chem., 2005, 29(5), P. 733–739.Ekthammathat N., Thongtem T., Phuruangrat A., Thongtem S. Microwave-assisted synthesis and characterisation of uniform LaPO4 nanorods. J. Exp Nanosci, 2012, 7(6), P. 616–623.Ekthammathat N., Thongtem T., Phuruangrat A., Thongtem S. Microwave-assisted synthesis and characterisation of uniform LaPO4 nanorods. J. Exp Nanosci, 2012, 7(6), P. 616–623.Zhang F.X., Wang J.W., Lang M., Zhang J.M., Ewing R.C., Boatner L.A. High-pressure phase transitions of ScPO4 and YPO4. Phys. Rev. B - Condens Matter Mater Phys., Published online 2009, 80, P. 184114.Zhang F.X., Wang J.W., Lang M., Zhang J.M., Ewing R.C., Boatner L.A. High-pressure phase transitions of ScPO4 and YPO4. Phys. Rev. B - Condens Matter Mater Phys., Published online 2009, 80, P. 184114.Ochiai A., Utsunomiya S. Crystal chemistry and stability of hydrated rare-earth phosphates formed at room temperature. Minerals, 2017, 7(5), P. 84.Ochiai A., Utsunomiya S. Crystal chemistry and stability of hydrated rare-earth phosphates formed at room temperature. Minerals, 2017, 7(5), P. 84.Mogilevsky P., Boakye E.E., HayAldered R.S. Solid Solubility and Thermal Expansion in a LaPO4–YPO4 System. Journal of the American Ceramic Society, 2007, 90(6), P. 1899–1907.Mogilevsky P., Boakye E.E., HayAldered R.S. Solid Solubility and Thermal Expansion in a LaPO4–YPO4 System. Journal of the American Ceramic Society, 2007, 90(6), P. 1899–1907.Aldred A.T. Cell volumes of APO4, AVO4, and ANbO4 compounds, where A = Sc, Y, La-Lu. Acta Cryst., 1984, B40, P. 569–574.Aldred A.T. Cell volumes of APO4, AVO4, and ANbO4 compounds, where A = Sc, Y, La-Lu. Acta Cryst., 1984, B40, P. 569–574.de Biasi R.S., Fernandes A.A.R., Oliveira J.C.S. Cell volumes of LaPO4-CePO4 solid solutions. J. Appl. Cryst., 1987, 20, P. 319–320.de Biasi R.S., Fernandes A.A.R., Oliveira J.C.S. Cell volumes of LaPO4-CePO4 solid solutions. J. Appl. Cryst., 1987, 20, P. 319–320.Dumler F.L., Skornyakova K.P., Shul’ga G.G. Lanthanum rhabdophane in the weathered mantle on limestones—a new type of rare earth mineralization. International Geology Review, 12(9), P. 1140–1145.Dumler F.L., Skornyakova K.P., Shul’ga G.G. Lanthanum rhabdophane in the weathered mantle on limestones—a new type of rare earth mineralization. International Geology Review, 12(9), P. 1140–1145.Mooney R.C.L. Crystal structures of a series of rare earth phosphates. The Journal of Chemical Physics, 1948, 16, P. 1003–1004.Mooney R.C.L. Crystal structures of a series of rare earth phosphates. The Journal of Chemical Physics, 1948, 16, P. 1003–1004.Bowles J., Morgan D.J. The composition of rhabdophane. Mineralogical Magazine, 48(1), P. 146–148.Bowles J., Morgan D.J. The composition of rhabdophane. Mineralogical Magazine, 48(1), P. 146–148.Almjasheva O.V., Gusarov V.V. Metastable Clusters and Aggregative Nucleation Mechanism. Nanosystems: Physics, Chemistry, Mathematics, 2014, 5(3), P. 404–416.Almjasheva O.V., Gusarov V.V. Metastable Clusters and Aggregative Nucleation Mechanism. Nanosystems: Physics, Chemistry, Mathematics, 2014, 5(3), P. 404–416.

The authors declare that there are no conflicts of interest present.