Synthesis of rare earth phosphate single crystals from controlled phase separation at high temperature using glasses as reaction media

• Grant number: 25/21838-0
• Support Opportunities: Scholarships in Brazil - Master
• Start date: December 01, 2025
• End date: November 30, 2027
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Inorganic Chemistry
• Principal Investigator: Marcelo Nalin
• Grantee: Maria Eduarda Aguiar Mariano
• Host Institution: Instituto de Química (IQ). Universidade Estadual Paulista (UNESP). Campus de Araraquara. Araraquara , SP, Brazil
• Associated research grant: 25/04339-0 - New synthesis method for single crystals containing rare-earth ions from supercooled liquids for photonics, AP.R

Abstract

Single crystals containing rare earth ions have numerous applications, including optical and magnetic devices. Although glasses are highly versatile materials and offer good solubility for these ions, some more specific applications require rare earths to occupy more defined crystallographic sites. This leads to more efficient emission processes, as well as narrower emission lines. Among the most emerging applications are those in magnetic, optical, and magneto-optical materials. Despite being known for a long time, single crystal preparation techniques are still expensive and time-consuming. Most synthesis methodologies for rare earth phosphates of the TRPO4 type (where TR = rare earths, including Y and Sc) produce powders, either at the nano or micrometer scale, but these materials are typically polycrystalline. This presents some disadvantages from an application standpoint. We recently developed a system containing GeO2-SbPO4-Al2O3-TR2O3 that exhibits phase separation, leading to the formation of single crystals during the controlled cooling process. Initial tests with some rare earth elements demonstrated the possibility of obtaining crystals up to 70 mm in length. However, despite demonstrating the feasibility of the synthesis, no further in-depth studies have been conducted to understand the mechanisms responsible for crystal formation, nor whether it is possible to vary the synthesis parameters to control size. The development of this methodology could help provide scalability for obtaining hundreds of crystals per batch, helping to promote the use of these materials in applications. Thus, the overall objective of this master's project will focus on the synthesis and characterization of at least three sets of samples within the GeO2-SbPO4-Al2O3-TR2O3 system (TR = Er3+, Tb3+, and Eu3+). (AU)