Integrating Science and Education in a Scientific Research Training Experiment： Thermochromism of Yttrium Iron Garnet under the Framework of Crystal Field Theory

doi:10.19894/j.issn.1000-0518.250289

Chinese Journal of Applied Chemistry ›› 2025, Vol. 42 ›› Issue (11): 1550-1558.DOI: 10.19894/j.issn.1000-0518.250289

• Chemistry Teaching and Experiment Innovation • Previous Articles Next Articles

Integrating Science and Education in a Scientific Research Training Experiment： Thermochromism of Yttrium Iron Garnet under the Framework of Crystal Field Theory

Xiao-Feng WU¹, Shan WANG², Long YUAN²^,³(), Chang-Min HOU¹

^1.State Key Laboratory of Inorganic Synthesis & Preparative Chemistry，Jilin University，Changchun 130012，China
^2.Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education，Jilin Normal University，Changchun 130103，China
^3.Jilin Provincial Key Laboratory of Wide Bandgap Semiconductor Material Growth and Device Applications，Jilin Normal University，Changchun 130103，China

Received:2025-07-17 Accepted:2025-10-09 Published:2025-11-01 Online:2025-12-05
Contact: Long YUAN
About author:Email： yuanlong@jlnu.edu.cn
Supported by:
Jilin University 2024 Graduate Education Reform Research Project(2024JGY017);Jilin Province Higher Education Teaching Reform Research Project(JLJY202329642179)

Abstract

Abstract:

Crystal field theory serves as an important foundation for understanding and investigating the rich physicochemical properties of transition metal compounds. Its teaching content often focuses on the explanation of coordination structures and atomic orbitals， which tends to be highly abstract. Here， a scientific research training experimental integrating science and education is proposed， it combines the heat induced lattice changes and intuitive visual impact， guiding students to analyze the crystal field from the thermochromic phenomenon of inorganic materials， deepening their understanding of the theoretical essence and promoting the construction of their inorganic chemistry knowledge framework. Y₃Fe₅O₁₂ nanopowder with a garnet structure was synthesized via the sol-gel method， and then characterized by using scanning electron microscopy （SEM）， variable-temperature X-ray powder diffraction （XRD）， X-ray photoelectron spectroscopy （XPS） and ultraviolet-visible absorption spectroscopy （UV-Vis）. Combined with the interesting observation and quantitative analysis of reversible thermochromic phenomena in pre-patterned ceramic plate， the temperature dependence of the unit cell parameters was established and further elucidated how structural modulation affects d-d transitions and charge transfer， thereby summarizing the generation mechanism of the specific colors presented at different temperatures. This process fosters a more systematic and concrete understanding of crystal field theory and related concepts， ultimately enabling students to deeply internalize the core chemical principle of “structure determines properties”. Compared with existing color-display experiments， the innovation lies in dynamically presenting the reversible thermochromism through lattice expansion， the selected garnet model has both tetrahedral and octahedral structural units， and its color-changing mechanism involves both d-d transitions and charge transfer. Moreover， embedding the thermochromic pigment in ceramics has application prospects such as temperature measurement and indication. This approach of “applying learning to practice” aims to enhance teaching and learning enjoyment， potentially stimulating students' innovative potential and enthusiasm for exploration.

Key words: Crystal field theory, Thermochromism, Charge transfer, d-d transitions, Garnet structure

CLC Number:

O614.8

Xiao-Feng WU, Shan WANG, Long YUAN, Chang-Min HOU. Integrating Science and Education in a Scientific Research Training Experiment： Thermochromism of Yttrium Iron Garnet under the Framework of Crystal Field Theory[J]. Chinese Journal of Applied Chemistry, 2025, 42(11): 1550-1558.

Figures/Tables 8

Fig.1 Schematic diagram of synthesizing yttrium iron garnet Y3Fe5O12 by the sol-gel method

Fig.2 SEM image of Y3Fe5O12 powder sample （A） and its selected area X-ray energy dispersive spectrum （B）， quantitative result of elements as an inset in top right

Fig.3 （A） The XRD patterns of Y3Fe5O12 obtained under variable temperatureand （B） the enlarged diffraction peak of （420） plane

Fig.4 （A） The unit cell structure of cubic phase garnet Y3Fe5O12 and its subunits centered on octahedrons and tetrahedrons；（B） The refined cell lattice parameters change with temperature and shows lattice expansion due to heating.

Fig.5 XPS survey （A） and core level spectra of Y3d （B）， Fe2p （C） and O1s （D） for the Y3Fe5O12 powder

Fig.6 The color of the emblem pattern filled with Y3Fe5O12 powder changes with temperature increasing （A） and the L， a and b chromaticity coordinate parameters of those colors， the inset is the standard CIE-Lab color space （B）

Fig.7 Temperature dependent UV-Vis spectra of Y3Fe5O12 powder （A） and its microscopic mechanism of thermochromism caused by charge transfer and d-d transition （B）

Fig.8 The content arrangement of each module for the experimental course on garnet thermochromic effect

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Integrating Science and Education in a Scientific Research Training Experiment： Thermochromism of Yttrium Iron Garnet under the Framework of Crystal Field Theory

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