Study Of The Structure And Luminescence Properties Of Zn-Al/Ti Bimetallic Oxides Semiconductor Materials

Red light component effectively improves the color rendering index of light emitting devices（LED）,and reduces the color temperature,and gives rise to better light-emitting properties,while its emission efficiency is improved.Due to temperature dependence of optical parameters,such as emission intensity,wavelength,fluorescence integral intensity ratio（FIR）and so on,they are suitable for optical thermometry.Compared with traditional thermometry,optical thermometry has more advantages,such as non-contact measurement,high sensitivity and short response time,so it can be applied in harsh environments.However,most of the related work are focused on expensive rare-earth element doping semiconductor materials.Transition metals replace suitably for rare earth elements due to their popular price and excellent optical properties,but there are few studies on transition metals in optical thermometry.In order to furtherly improve the luminescence properties and temperature sensitivity of fluorescent materials,the red luminescence of Mn²⁺,Cr³⁺,Eu³⁺doped Zn-Al/Ti bimetallic oxides are investigated by using some methods,such as energy transfer and charge compensation,in this work.The structure,optical properties and temperature sensing properties of Cr³⁺,Eu³⁺,Mn²⁺,Mn⁴⁺doped Zn-Al/Ti bimetallic oxides are studied as follows:1.The effects of energy transfer and crystal fields on improving nanoparticle photoluminescence and optical thermometer performance are investigated.Zn Al₂O₄:Cr³⁺,Mn²⁺nanophosphors with cubic phase are prepared.The energy transfer process between the Mn²⁺and Cr³⁺in Zn Al₂O₄:Cr³⁺,Mn²⁺crystals and the effect of the sensitizer on the crystal environment are investigated.The energy transfer type is investigated by Dexter theory as dipole-dipole interaction,and the energy transfer efficiency in the phosphor is as high as 97%.The color tunability from green emission to red emission can be realized by adjusting the impurities concentration.The doping of Mn²⁺changes the crystal field of zinc aluminate,causing the change of shape of the luminescence peak of Cr³⁺,and the emission intensity of Cr³⁺is enhanced about 60 times due to the energy transfer and improved crystallinity.After doping with Mn²⁺,the relative sensitivity of Zn Al₂O₄:Cr³⁺increases from0.1%K^-1 to 0.25%K^-1.2.The effect of Li⁺as charge compensator on the optical properties of Eu³⁺-doped zinc titanate is investigated.Zinc titanate has various structures,so the crystal phases of zinc titanate calcined at different temperatures are analyzed,Zn₂Ti₃O₈,Zn Ti O₃ and Zn₂Ti O₄phases could be formed at different temperatures.The charge compensator of Li⁺changes the asymmetric of the crystal field surrounding of Eu³⁺and enhances the luminescence properties of Eu³⁺.The temperature dependence of luminescence properties of Eu³⁺-doped zinc titanate is studied,and the optical thermometer of fluorescence intensity ratio type of Eu³⁺single-doped is designed.The effect of calcination temperature and lattice asymmetric on the thermometric performance of the fluorescence intensity ratio thermometer are discussed.After the charge compensator was doped,the lattice structure become more perfect,resulting in a decrease in temperature measurement performance of the optical thermometer.3.The effect of charge compensator on the structure and optical properties of Mn⁴⁺and Al³⁺co-doped Zn Ti O₃ phosphor is introduced in detail.An optical thermometer of dual excitation of rare earth element Eu³⁺and transition metal Mn⁴⁺is designed.Firstly,a series of Zn Ti O₃:Eu³⁺（2 mol%）,Mn⁴⁺（x mol%）samples are prepared by using solid-phase method.The prepared samples reveal mixture phases of cubic and hexagonal.The concentration of Mn⁴⁺has an obvious effect on the temperature sensitivity,and the maximum relative sensitivity of 2.6%K^-1 is obtained at the maximum Mn⁴⁺concentration of 4 mol%.Zn Ti O₃:Eu³⁺（2 mol%）,Mn⁴⁺（0.05 mol%）,Al³⁺（x mol%）samples with hexagonal perovskite structure are prepared by using water bath method.The uniform particle size and morphology of the samples and the element distribution are characterized by SEM（Scanning Electron Microscopy）and EDS（Energy dispersive X-ray spectrometer）,respectively.The luminescence intensity of Zn Ti O₃:Eu³⁺reveals double enhancement at the optimum concentration of Al³⁺charge compensator,but the addition of charge compensation reduces the sensitivity to temperature of photoluminescence properties of phosphor.The phosphor without charge compensator has better temperature measurement performance,and a relative sensitivity as high as 2.7%/K is obtained.