Preparation And Properties Of LaMO₃(M=Ga,Al) Based Amorphous Spheres With High Refractive Index

With the development of optical technology,optical components are required to have high refractive index(nd?2.1),high transmittance(more than 70%in the range of ultraviolet to visible light),miniaturization and versatility.Traditional oxide amorphous materials which contain glass network formations such as SiO2,B2O3 and P2O5 would directly affect refractive index and other optical properties of glasses.When heavy metal elements such as Pb,Bi,Sb or Te are added,the transmittance of transparent materials in visible light will be reduced obviously and the development and application of these materials will be restricted,However,the amorphous materials without glass network and heavy metal elements have very high requirements for the preparation technology,and the traditional amorphous preparation technology can not meet the requirements,so it is urgent to develop a new amorphous material system by using new amorphous preparation technology.In order to solve the above problems,the preparation of LaMO3(M=Ga?Al)amorphous materials was studied in this paper,and(1-x)LaGaO3-xTiO2,(1-x)LaGaO3-xNb2O5 and(1-x)LaAlO3-xNb2O5 binary series amorphous materials,as well as 0.3LaGaO3-(0.7-x)Tio2-xNb2O5 ternary series amorphous materials were synthesized by a new O2 levitation containerless solidification technology.An air levitation furnace was used to investigate the amorphous formation region of the synthetic materials.The glass transition temperature(tg)and the crystallization onset temperature(tx),were determined via differential scanning thermal analyzer.The characteristics of the refractive indexes of the amorphous samples were evaluated by using an ellipsometer.An UV-vis spectrometer and a Fourier infrared spectrometer were used to record the transmittance spectra of the amorphous samples in the UV-vis spectral and near-infrared spectral.A radio frequency impedance analyzer was used to investigate the dielectric constant and dielectric loss of the amorphous samples.The amorphous forming ability,optical properties,electrical properties and interaction of synthetic materials were explored.(1)A series of(1-x)LaGaO3-xTiO2 amorphous materials were synthesized using O2 levitation containerless solidification technology by TiO2 with high refractive energy coefficient and LaGaO3 with strong amorphous formation ability.The experimental results show that transparent amorphous spheres with the diameters of about 2?4 mm can be obtained in the range of x=0 and 0.625?x?0.74.The maximum ?t of(1-x)LaGaO3-xTiO2 amorphous samples is about 82? for x=0.625.The refractive index can be tuned by adjusting the molar percentage content of TiO2.The highest refractive index at 587.6 nm is 2.49 for x=0.74 and the as-prepared amorphous materials exhibit a transmittance exceeding 70%in the visible light range.The leakage current is very low of 10-11?10-12 A/cm2 for the amorphous samples.With the increase of the molar percentage of TiO2,the dielectric constant shows a certain upward trend,and the dielectric loss shows a certain downward trend.(2)In order to further broaden the formation range of amorphous materials,in this paper,Nb2O5 with high refractive energy coefficient is combined with LaGaO3 to prepare amorphous(1-x)LaGaO3-xNb2O5 system with high refractive index.The results show that the amorphous formation region of(1-x)LaGaO3-xNb2O5 is very wide and transparent amorphous spheres with the diameters of about 2?4 mm can be obtained in the range of 0?x?0.675.The maximum ?t is about 108? for x=0.6.With the increase of the molar percentage content of Nb2O5,the refractive index increases gradually.The highest refractive index at 587.6 nm is 2.45 for x=0.675.The transmittance of these amorphous samples is over 70%in the visible range.With the increase of the molar percentage content of Nb2O5,the band gap Eopt of amorphous samples decreases linearly,the density of amorphous samples decreases gradually,the dielectric constant increases gradually and the dielectric loss decreases gradually.(3)In order to further reduce the cost of preparing high refractive index amorphous materials,the more expensive Ga in LaGaO3 raw materials was replaced by relatively cheap Al,LaAlO3 and LaGaO3 belong to perovskite system and LaAlO3 is also a strong amorphous forming agent.The amorphous(1-x)LaAlO3-xNb2O5 system was prepared from LaAlO3 and Nb2O5.The results show that,transparent amorphous spheres with diameters of about 2?4 mm can be obtained in the range of 0?x?0.2 and 0.6?x?0.7.The maximum ?t is about 75?for x=0.65,and the maximum refractive index at 587.6 nm is 2.26 for x=0.7 and the as-prepared amorphous samples exhibit a transmittance exceeding 70%in the visible light range.With the increase of the molar percentage content of Nb2O5 the dielectric constant shows a certain upward trend,and the dielectric loss shows a certain downward trend.(4)In order to further broaden the formation range of amorphous nd?2.2(nd is the refractive index of amorphous sample at 587.6 nm),using TiO2,Nb2O5 and LaGaO3 as raw materials to prepare 0.3LaGaO3-(0.7-x)TiO2-xNb2O5 series amorphous.The results show that,the amorphous formation region of 0.3LaGaO3-(0.7-x)TiO2-xNb2O5 system is very wide,transparent amorphous spheres with diameters of approximately 2?4 mm can be obtained in the range of 0?x?0.65.At x=0.65,the maximum ?t is about 75?,and the highest refractive index at 587.6 nm is 2.26 for x=0.7 and all these amorphous samples exhibit a transmittance exceeding 70%in the visible light range.The dielectric constant and dielectric loss not change significantly while the total molar percentage of TiO2 and Nb2O5 remain unchanged.