Ion Doping Modification And Properties Of LaAlO₃ Infrared Radiation Materials

With the increase of energy shortage,the application of high emissivity materials in the field of heating and energy saving has received more and more attention.At present,non-oxide infrared radiation materials have poor oxidation resistance and low emissivity in the near-infrared range during long-term use in a high-temperature oxidation environment.Therefore,it is necessary to develop a new ceramic material with high infrared emissivity and strong oxidation resistance.In this paper,lanthanum aluminate infrared radiation material with Al₂O₃ and La₂O₃ as raw materials,CaCO₃,Cr₂O₃ and MnCO₃ by solid state reaction.In this paper,the effects of Ca²⁺,Cr³⁺single doping and co-doping and different Ca²⁺-Cr³⁺doping concentrations on the infrared radiation properties of LaAlO₃ were investigated.The results show that Ca²⁺and Cr³⁺co-doping can effectively improve the infrared radiation performance of LaAlO₃.When the doping concentration of Ca²⁺is increased from 0.2 mol to 0.4 mol and the doping concentration of Cr³⁺is increased from 0.1 mol to 0.5 mol,the emissivity of LaAlO₃ increases from 0.706 to 0.919.When Ca²⁺=0.4 mol and Cr³⁺=0.5 mol,LaAlO₃ had the highest emissivity,which was0.919.The following are the main reasons for the increase of emissivity:?1?The increase of Ca²⁺doping concentration enhances the Cr⁴⁺content in LaAlO₃,increases the hole carrier concentration,and promotes the energy absorption of hole carriers;?2?The doping of Cr³⁺introduces the Cr impurity level in the energy gap of LaAlO₃,which reduces the forbidden band width of LaAlO₃.By adjusting the preparation process,the effects of sintering temperature and sintering aid B₂O₃ on the Ca²⁺-Cr³⁺co-doped LaAlO₃ infrared radiation properties were investigated.The results show that the increase of sintering temperature improves emissivity of LaAlO₃ from 0.782to 0.836.The addition of B₂O₃ reduced the near-infrared radiation performance of LaAlO₃,but increased the emissivity of LaAlO₃ in the mid-infrared region.Since Mn is a valence ion and Mn³⁺has a Jahn-Teller effect,it can cause lattice distortion and promote lattice vibration absorption.Therefore,the effects of different Ca²⁺-Mn²⁺doping concentration and sintering temperature on the infrared radiation properties of LaAlO₃ were studied.The results show that when the doping concentration of Ca²⁺is increased from 0.2 mol to 0.4 mol and the doping concentration of Mn²⁺is increased from 0.15 mol to 0.5 mol,the emissivity of LaAlO₃ increases from 0.706 to 0.900.When Ca²⁺=0.4 mol and Mn²⁺=0.5 mol,LaAlO₃ had the highest emissivity,which was 0.900.The following are the main reasons for the increase of emissivity:?1?The increase of Ca²⁺doping concentration enhances the Mn⁴⁺content in LaAlO₃,increases the hole carrier concentration,and promotes the energy absorption of hole carriersthe;?2?The increase of Mn²⁺doping concentration increases the Mn³⁺content,and increases the electronic transition in the impurity level,and the Jahn-Teller effect of Mn³⁺leads to lattice distortion,which increases the energy absorption of lattice vibration.As the sintering temperature increases,the emissivity of LaAlO₃ does not change significantly.