# High-Temperature Isostructural Phase Transition in Ce2(MoO4)3: A Rare Phenomenon Investigated through X‑ray Diffraction and Raman Scattering

## TL;DR

This paper investigates a rare high-temperature phase transition in a cerium molybdate compound using X-ray and Raman techniques.

## Contribution

The study identifies a rare isostructural phase transition in Ce2(MoO4)3 at high temperatures using in situ XRD and Raman spectroscopy.

## Key findings

- Ce2(MoO4)3 shows a stable low-temperature phase up to 303 K.
- An isostructural phase transition is observed at temperatures above 848 K.
- The phase transition is linked to anomalies in lattice parameters and Raman spectra.

## Abstract

The rare-earth compound cerium­(III) molybdate (Ce2(MoO4)3) has gained attention due to
its diverse industrial
applications, such as photocatalysis, corrosion inhibition, self-repair
of protective layers, as well as antiviral and antibacterial properties.
However, its response to extreme temperature conditions remains insufficiently
explored. This study employs ambient powder X-ray diffraction (PXRD),
UV–vis diffuse reflectance spectroscopy, scanning electron
microscopy (SEM), and Raman spectroscopy techniques to confirm the
successful hydrothermal synthesis of a crystalline sample of the Ce2(MoO4)3 compound. Subsequently, in situ
temperature-dependent (13–973 K) XRD and Raman scattering (293–998
K) studies were conducted. Rietveld analysis of diffraction patterns
reveals a stable low-temperature phase (13–303 K) and anomalies
in the high-temperature evolution (T > 583 K)
of
lattice parameters and the sample’s microstrain and crystallite
size. In the high-temperature (T > 848 K) Raman
spectra
of Ce2(MoO4)3, an additional band
emerges at 452 cm–1; the observed anomalies are
attributed to an isostructural phase transition (IPT). This type of
phase transition is among the rarest phenomena reported in the literature.
Our findings enhance the understanding of the physical properties
of Scheelite-type compounds and emphasize the importance of investigating
these uncommon phenomena. This knowledge can potentially drive the
development of novel materials and expand their applications in materials
science.