Structure and Mechanical Properties of Magnesium Aluminum Spinel Ceramics Strengthened by Manganese Ion Diffusion

doi:10.16552/j.cnki.issn1001-1625.2026.0124

Abstract

Abstract:

To prepare high-performance magnesium aluminum spinel structural ceramics， this study used bauxite and magnesite as raw materials and pyrolusite as an additive to prepare MgAl₂O₄ ceramics via a solid-state sintering method. The effect of the additive on the spinel structure was analyzed， the role of manganese ions in modifying impurity phases was elucidated， and the mechanism by which manganese ion diffusion enhanced the densification and mechanical properties of MgAl₂O₄ was revealed. The results show that adding pyrolusite to the natural raw materials allow Mn²⁺ to dissolve into the MgAl₂O₄ lattice， forming a （Mn _x Mg_1-_x ）Al₂O₄ solid solution. This process weakens the Kirkendall effect， reduces porosity on the MgO side during spinel formation， enhances the diffusion and mass transfer rate of Mg²⁺， and improves the densification and flexural strength of the samples. Meanwhile， the reaction between Mn²⁺ and anorthite generates johannsenite and Al₂O₃， which induces lattice distortion in the pyroxene， increases the concentration of lattice defects， and further promotes the ions diffusion rate. When the pyrolusite addition reaches 3% （mass fraction）， the bulk density of the material reaches 3.29 g/cm³， the apparent porosity decreases to 0.24%， and the flexural strength increases to 140.2 MPa.

Key words: magnesium aluminum spinel, pyrolusite, solid-phase sintering, ion diffusion, densification, mechanical property

CLC Number:

TQ175

XUAN Songtong, KONG Xiangchen, WANG Kaiyue, TIAN Yuming. Structure and Mechanical Properties of Magnesium Aluminum Spinel Ceramics Strengthened by Manganese Ion Diffusion[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2026, 45(9): 3280-3288.

Figures/Tables 12

Table 1 Chemical composition of raw material

Raw material	Mass fraction/%
Raw material	Al₂O₃	MgO	SiO₂	Fe₂O₃	TiO₂	CaO	MnO₂	LOI
Bauxite	74.30	—	6.00	2.00	2.60	—	—	15.10
Magnesite	0.43	41.25	7.37	0.58	—	5.00	—	45.37
Pyrolusite	1.11	—	10.94	9.21	—	—	35.61	43.13

Table 2 Mix ratio of raw materials in different samples

Sample	Mass fraction/%
Sample	Bauxite	Magnesite	Pyrolusite
MA-Mn0	58.60	41.40	—
MA-Mn1	58.01	40.99	1
MA-Mn3	56.84	40.16	3
MA-Mn5	55.67	39.33	5

Fig.1 Schematic diagram of preparation process

Fig.2 Bulk density， apparent porosity and flexural strength of MA-Mn0 sample at different sintering temperatures

Fig.3 Bulk density， apparent porosity and flexural strength of MA-Mnx samples sintered at 1 400 ℃

Fig.4 XRD patterns of MA-Mnx samples sintered at 1 400 ℃ and XRD enlarged patterns of MA（311） crystal plane

Table 3 Lattice constants of MA phase in MA-Mnx samples （x=0， 1， 3， 5）

Sample	MA-Mn0	MA-Mn1	MA-Mn3	MA-Mn5
Lattice constant/Å	8.085 44	8.085 87	8.086 55	8.086 71

Fig.5 SEM images of surface of MA-Mnx samples sintered at 1 400 ℃

Table 4 EDS analysis of MA grains in MA-Mnx samples sintered at 1 400 ℃

Sample	Atomic fraction/%
Sample	Mg	Al	O	Si	Fe	Ca	Mn
MA-Mn0	13.19	28.40	54.30	2.58	0	1.53	0
MA-Mn1	15.24	29.38	53.43	2.58	0.87	0	0.69
MA-Mn3	14.14	27.27	53.02	2.24	0.35	1.04	1.30
MA-Mn5	14.49	29.31	53.50	0.58	0.07	0.25	1.45

Fig.6 XPS spectra of Mn element in MA-Mn3 sample

Fig.7 Distribution maps of Mn element in MA-Mnx samples （x=1， 3， 5） sintered at 1 400 °C

Fig.8 Schematic diagram of Mn2+ solid solution into MA forming solid solution

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