Infrared (IR) absorption spectra of pyroehlore-type Ca2+-doped La2r2O7 proton conductors, i.e., (La2, Ca,)Zr2O7 .. δ and La2(Zr2, Ca,)O7 δ systems, were studied by the diffuse reflection method. The O-H stretching vibrations (vOH) due to the protons dissolved in the crystal with negligible effects of adhesion and/or adsorption water could be detected by improvement of the Sample preparation and the diffuse reflection technique. The vOH bands, due to protons dissolved in the crystal, were distinctly different between the (La2, Ca,)Zr2O7 δ systems; three vOH bands at 3517, 3401, and 3323 cm-1 for the (La2, Ca,)Zr2O7 δ system and six vOH bands at 3517, 3430, 3414, 3371, 3341, and 3289 cm1 for the La2(Zr2 Ca2)O7 - δ system were observed. The stable sites for dissolved protons were distinctly different between the two systems. The wave numbers and the widths of the vOH bands were higher and much sharper than those reported for the well-known perovskite-related-type proton conductors. It was concluded that the O-H bonds in Ca2+-doped La2Zr2O7 crystal are tight compared with perovskite-related-type proton conductors, and that definite stable sites for protons exist in Ca2+-doped La2Zr2O7 crystal, In the 1R spectra of (La2, Ca,)Zr2O7- δ samples with various water vapor pressures, PH2O, of proton dissolution treatment, the preferred dissolution of protons into the specific site was observed under low PH2O atmosphere. The details of the dissolution environment of protons are also discussed.
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