| Compared to the glass and single crystal, transparent ceramics not only havehigh transparency and corrosion resistance, but also can work in extreme environment(high temperature and pressure). Transparent ceramics are gradually applied invarious fields such as optical, lighting, high temperature and wireless electronictechnology due to their high thermal conductivity, resistance against high strength andexcellent dielectric properties. In this paper, M4+doped Ba(Mg1/3Nb2/3)O3(M=Sn, Zr)transparent ceramics were synthesized by a solid state reaction. The influences ofsintering techniques as well as the doping amount of M4+ion on crystal structure,microstructure and optical properties were studied. The factors influencing thetransmittance of transparent ceramics were analyzed and the correlation ofmicrostructures and macroscopic properties was discussed as well. Moreover, thephotoluminescence properties of Sm3+doped Ba(Sn, Mg,Nb)O3transparent ceramicswere investigated.(1) The influence of preparation process on crystal structure of Sn4+:Ba(Mg1/3Nb2/3)O3transparent ceramics was analyzed by TG-DTA, XRD, particle sizeanalysis and SEM. The results showed that when the additive amount of Sn4+ion wasabove10mol%, the ceramics had cubic structure without birefringence. However,there appeared second crystalling phases when the additive amount of Sn4+ionreached15mol%. Moreover, the densities of ceramics increased to a maximum, andthen decreased with the increasing sintering time and temperature. As a result, theoptimal sintering processing of Sn4+: Ba(Mg1/3Nb2/3)O3transparent ceramics whohave high density and excellent microstructure with homogeneous grain size and asmall number of grain boundary was1550℃for48h.(2) The influences of sintering techniques as well as the doping amount of Sn4+ion on optical properties were studied. When the ceramic was sintered at1550℃for48h, the transmittance and refractive index of the Sn4+: Ba(Mg1/3Nb2/3)O3transparentcaramic in the visible range were high to53%and2.09-2.22, respectively. Thetransmittance of transparent ceramics is mainly influenced by crystal structure andmicrostructure. Sn4+: Ba(Mg1/3Nb2/3)O3transparent ceramics who belonged to isotropy had high transmittance when its porosity was below0.5%and it hadexcellent microstructure with homogeneous grain size (25μm) and a small number ofgrain boundary. Meanwhile, Sn4+: Ba(Mg1/3Nb2/3)O3transparent ceramics had goodmicrowave dielectric properties: r=31.74，Q×f=25,499GHz， f=+17.73ppm/℃.(3) The influences of preparation process on crystal structure as well as opticalproperties were studied. The of Zr4+:Ba(Mg1/3Nb2/3)O3transparent ceramics wasexplored and determined. When the additive amount of Zr4+ion is above15mol%,ceramics have cubic structure. However, there appeared second crystalling phaseswhen the additive amount of Zr4+ion reached20mol%. The optimal sinteringprocessing of Zr4+: Ba(Mg1/3Nb2/3)O3transparent ceramics was1550℃for48h.The relative density and transmittance of ceramics sintered at1550℃for48h were99.74%and50%, respectively. Moreover, the influences of microstructure such asporosity, grain size and the morphology of grain boundary on optical properties werestudied. The results showed that the samples who have high density,5μm-size crystalparticle and blurred grain boundary obtain high transmittance.(4) The photoluminescence properties of Sm3+doped Ba(Sn, Mg, Nb)O3transparent ceramics were also studied. UV-Vis absorption spectrum revealed that thepeaks located at407nm and468nm when the doped amount of Sm3+ion was1mol%. The most notable excitation line was located at407nm. Strong yellow (562nm), orange (597nm) and red (643and703nm) emission lines were observed in theemission spectrum. And when emited at597nm, excitation lines located at346,363,379,407,419,437,462,480,498and527nm were observed in the excitationspectrum. All the fluorescence peaks belong to4f-4f radiative transition of Sm3+ion.Therefore, Sm3+doped Ba(Sn, Mg, Nb)O3transparent ceramics are candidates fornear ultraviolet LED excitation. |
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