ZnO-doped lithium niobate crystals with a doped concentration of up to 8.3mol% were grown by the Czochralski technique. The effects of incorporating Zn2+ ions into LiNbO3 crystals were studied by powder x-ray diffraction and taking polarization hysteresis loop measurements. When the Li-site vacancy model is adopted, the coercive fields obtained from the polarization reversal measurement depend strongly on the number of NbLi4−+4VLi−. However, the coercive field of Zn-doped ions into LiNbO3 is insensitive to the ZnLi2++VLi−. Experimental results indicate that four distinct substitutions of Zn−2 ions incorporated into ions into LiNbO3 crystals for doping concentrations from 0to8.3mol%. The extent of Zn substitution is quantitatively determined for doping of below 7.5mol%.

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An investigation of the OH À absorption spectra of Zn-doped LiNbO 3 single crystals with doping concentrations from 0.0 to 8.3 mol % after proton exchange (PE) is carried out. Before PE treatment, the absorption bands are found centered at approximately 3485 cm À1 for the samples with Zn-doping concentrations below 7.5 mol %, whereas two distinct bands at 3505 and 3530 cm À1 are clearly observed for the samples with Zn-doping concentrations above 7.5 mol %. After PE treatment, an absorption band at 3505 cm À1 is predominant for all the samples, and this is attributed to the high concentration of H þ ions substituting Li atoms. However, for the highly Zn-doped samples, the lineshape and intensity of the 3530 cm À1 mode remain the same during PE. A theoretical investigation using the hybrid density functional B3LYP method with a simple cluster structure shows that the origins of the 3485 and 3530 cm À1 absorption modes correspond to the Li-and Nb-vacancy models, respectively.

The structures of TaO6 and NbO6 oxygen octahedra in xBa(Mg1∕3Ta2∕3)O3+(1−x)Ba(Mg1∕3Nb2∕3)O3 perovskite ceramics with x=0, 0.25, 0.50, 0.75, and 1.0 were investigated by the extended x-ray absorption fine structure method. The decline in the microwave dielectric constant as x increases is caused mainly by the decrease of the mean volume of the oxygen octahedra, regardless of the 1:2 ordered structure and the distortion of the oxygen octahedron. The low Qf values of the TaO6 and NbO6 mixed samples are caused by not only the degrading of the 1:2 ordered structure but also the distortion of oxygen octahedral cages.

Oxygen-octahedral A1g(O) phonons for both 1:2 ordered xBaTiO3+(1−x)Ba(Mg1∕3Ta2∕3)O3 (0≤x≤ 0.05) and 1:1 ordered xCa(Sc1∕2Nb1∕2)O3+(1−x)Ba(Sc1∕2Nb1∕2)O3 (0≤x≤ 0.25) ceramics were investigated using Raman scattering. Lineshapes of A1g(O) phonons directly reflect structural characteristic of TiO6, TaO6, ScO6, and NbO6 octahedral cages that are strongly correlated with microwave performance of the samples. The larger width of stretching A1g(O) phonon, implies poor crystalline structure and short phonon lifetime, giving us lower value of Q×f. The atomic polarizabilities of Ta5+, Ti4+, Ca2+, Sc3+, and Nb5+ have a strong influence on the structure of oxygen octahedron that dominates microwave performance of xBaTiO3+(1−x)Ba(Mg1∕3Ta2∕3)O3 and xCa(Sc1∕2Nb1∕2)O3+(1−x)Ba(Sc1∕2Nb1∕2)O3 ceramics.