Praseodymium(III,IV) oxide is the inorganic compound with the formula Pr6O11 that is insoluble in water.[2] It has a cubic fluorite structure.[3] It is the most stable form of praseodymium oxide at ambient temperature and pressure.[4]
Pr6O11 adopts a cubic fluorite crystal structure, measured by XRD, TEM and SEM methods.[3][5] It can be considered an oxygen deficient form of praseodymium(IV) oxide (PrO2), with the Pr ions being in a mixed valency state Pr(III) and Pr(IV).[5] This characteristic is what gives the oxide its many useful properties for its catalytic activity.
Praseodymium oxide nanoparticles are generally produced via solid-state methods such as thermolysis, molten salt method, calcination or precipitation.[3][4][6] Practically all processes, however, contain a calcination step in order to obtain a crystalline Pr6O11 nanoparticles.
Typically, praseodymium nitrate Pr(NO3)3·6H2O[3][5] or praseodymium hydroxide Pr(OH)3[7] is heated at high temperatures (usually above 500 °C) under air to give praseodymium(III,IV) oxide. While less common, synthesis from other organic precursors such as praseodymium acetate, oxalate[8] and malonate[9] have also been reported in chemical literature.
The physical properties of the prepared nanoparticles such as particle shape or lattice parameter depend strongly on the conditions of calcination, such as the temperature or duration, as well as the different preparation methods (calcination, sol-gel, precipitation, for example). As a result, many synthesis routes have been explored to obtain the precise morphology desired.[3][4][5]
Praseodymium(III,IV) oxide has a number of potential applications in chemical catalysis, and is often used in conjunction with a promoter such as sodium or gold to improve its catalytic performance. It has a high-K dielectric constant of around 30 and very low leakage currents[10] which have also made it a promising material for many potential applications in nanodevices and microelectronics.[6]