## 5 Conclusions  
The ETMD model was used to investigate temperature changes and damage evolution in a coal sample (non-homogeneous coal matrix containing pyrite) under different microwave radiation modes, as well as the influence of the confining pressures on the damage effect. The main findings were the following:  
(1) The electric field distributions of the coal sample vary at different positions in the microwave cavity, leading to different dielectric loss power densities of pyrite, which causes significant differences in temperature distribution. The constant dielectric loss density of each pyrite in the static heating mode results in the temperature between them being significantly different. The coal sample moves and changes position in the rotating heating mode, causing perturbations in the electromagnetic wave, which enhances the uniformity of the pyrites' temperature and leads to a higher microwave-absorbed power. (2) The damage of the coal matrix is closely linked to the pyrite temperature. Under the expansion stress of high-temperature pyrite, the surrounding coal matrix experiences damage. The damaged area extending outwards is centered around the high-temperature pyrite and tends to connect to the boundary and other nearby damaged areas. In the rotational heating mode, more pyrites capable of damaging the coal matrix are developed compared to the static heating mode, resulting in more damage propagation paths. Some specific pyrites in the hot spot of the electric field can achieve higher localized damage efficiency under static heating. (3) The damage efficiency at different positions in the static heating mode is significantly different, and the damage area of S\({}_{180}\)M is 91 times that of S\({}_{90}\)M after 15 s of microwave heating. The rotational heating mode can achieve a higher damage efficiency and a wider damage coverage. The peak damage connectivity recorded under a higher electric field strength is faster than under other conditions, and the connectivity duration is shorter. (4) The occurrence and development of coal matrix damage under microwave radiation are inhibited by a uniform centripetal pressure, and greater inhibition is caused by a higher pressure. Under a certain pressure, static heating with hot spots with a high electric field can achieve more stable damage in local hot spots, while rotational heating can better ensure the occurrence of damage in vulnerable regions. (5) The intimidating pressure and heating time at which coal collapses are closely related to its heterogeneity. In addition, parallel pressure promotes damage paths parallel to the direction of pressure and inhibits damage paths perpendicular to the pressure direction. Compared to no confining pressure, the percentage of areas damaged in coal is lower under a low parallel pressure and higher under a high parallel pressure. Furthermore, under a non-uniform parallel pressure, the influence of high-pressure regions on the development of damage is more pronounced. (6) The use of the rotating microwave radiation mode can cause more damage to the coal sample than the static microwave radiation mode. This can increase the speed of the seepage of gas to a greater extent, making it more convenient for gas extraction. The rotating microwave-irradiated coal seam device is thus designed for field applications. This research provides an important reference for the future development of microwave devices for irradiating coal seams. Software, S.L. and X.S. ; Writing--review & editing, Y.H. All authors have read and agreed to the published version of the manuscript. The research was supported by the Natural Science Foundation of the Fujian Province (2022)01109) and the National Natural Science Foundation of China (51904285 and 52274181). * [PERSON] et al. (2021) [PERSON]; [PERSON]; [PERSON] Numerical modelling of microwave irradiated rock fracture. _Miner. Eng._**2021**, _203_, 108318. [CrossRef]
* [PERSON] et al.