Whereas doping CaTiO3 or SrTiO3 with ∼0·05 formula units (f.u.) of trivalent rare earth ions substituted for Ca can yield majority positron annihilation lifetime τ1 increases of up to 30% due to the presence of cation vacancies, similar doping of BaTiO3 produces increases of only ∼10%. The difference is attributed to hole trapping around cation vacancies in BaTiO3. The absence of significant changes to τ1 for La doped CaTiO3 when oxidised samples are reduced by sintering in a hydrogenous atmosphere is attributed to the formation of oxygen vacancies that co-exist with the original cation vacancies. Solid state nuclear magnetic resonance showed that a significant fraction of the La ions in BaTiO3 containing 0·04 f.u. of La were in cubic coordination, irrespective of the charge compensation scheme employed. Doping of sintered SrTiO3 with La to produce up to 0·2 f.u. of Sr cation vacancies had no significant effect on Sr leaching in deionised water at 90°C.
TienT. Y. and HummelF. A.: ‘Solid solutions in the system SrTiO3–(La2O3∶3TiO2)’, Trans. J. Br. Ceram. Soc., 1967, 66, 233–245.
2.
VashookV., VasylechkoL., KnappM., UllmannH. and GuthU.: ‘Lanthanum doped calcium titanates: synthesis, crystal structure, thermal expansion and transport properties’, J. Alloys Compd, 2003, 354, 13–23.
3.
TsurY., DunbarT. D. and RandallC. A.: ‘Crystal and defect chemistry of rare earth cations in BaTiO3’, J. Electrochem. Soc., 2001, 7, 25–34.
4.
OhnumaK., OzakiN., MizunoY., HagiwaraT., KakimotoK. and OhsatoH.: ‘Occupational sites of Sm in BaTiO3 analyzed by Rietveld method and EXAFS’, Ferroelectrics, 2006, 332, 7–11.
5.
BuscagliaM. T., VivianiM., BuscagliaV. and BottinoC.: ‘Incorporation of Er3+ in BaTiO3’, J. Am. Ceram. Soc., 2002, 85, (6), 1569–1575.
6.
JonkerG. H. and HavingaE. E.: ‘The influence of foreign ions on the crystal lattice of barium titanate’, Mater. Res. Bull., 1982, 17, 345–350.
7.
DunbarT. D., WarrenW. L., TuttleB. A., RandallC. A. and TsurY.: ‘Electron paramagnetic resonance investigations of lanthanide-doped barium titanate: dopant site occupancy’, J. Phys. Chem. B, 2004, 108B, 908–917.
8.
MorrisonF. D., CoatsA. M., SinclairD. C. and WestA. R.: ‘Charge compensation mechanisms in La-doped BaTiO3’, J. Electroceram., 2001, 6, 219–232.
9.
KolodiazhnyiT. and PetricA.: ‘Analysis of point defects in polycrystalline BaTiO3 by electron paramagnetic resonance’, J. Phys. Chem. Solids, 2003, 64, 953–960.
10.
SmythD. M.: ‘The defect chemistry of donor-doped BaTiO3: a rebuttal’, J. Electroceram., 2002, 9, 179–186.
11.
TsudaN., ShirasakiS., AkahaneT., TroevT. and ChibaT.: ‘Lifetime spectra of positrons in (Ba1–1.5xGdx?0.5x)TiO3’, J. Phys. Soc. Jpn, 1978, 44, 914–918.
12.
TangC. Q.: ‘Nonmonotonic dependence of the positron lifetimes on the dopant content in La-doped BaTiO3’, Phys. Rev. B, 1994, 50B, 9774–9777.
13.
HsuF. H. and HouT. K.: ‘Positron annihilation studies of barium titanate ceramics’, Mater. Sci. Forum, 1992, 105–110, 655–658.
14.
MohsenM., Krause-RehbergR., MassoudA. M. and LanghammerH. T.: ‘Donor-doping effect in BaTiO3 ceramics using positron annihilation lifetime spectroscopy’, Radiat. Phys. Chem., 2003, 68, 549–552.
15.
ChangF., LiT., GeY., ChenZ., LiuZ. and JingX.: ‘Electrical properties and positron annihilation study of (Ba1–xHox)TiO3 ceramics’, J. Mater. Sci., 2007, 42, 7109–7115.
16.
HadleyJ. H., HsuF. H., YongHu, VanceE. R. and BeggB. D.: ‘Observation of vacancies by positron trapping in Ce-doped zirconolites’, J. Am. Ceram. Soc., 1999, 82, 203–205.
17.
KeebleD. J., McGuireS., SinghS., SuB., ButtonT. W. and PetzeltJ.: ‘Positron annihilation lifetime studies of SrTiO3 crystal and ceramic materials’, J. Phys. IV, 2005, 128, 111–114.
18.
VanceE. R., BakT., NowotnyJ., MansonN. B., FrenchS. E., HadleyJ. H.Jr, HsuF. H., YongHu and BellitoV.: ‘Rare earth incorporation in CaTiO3’, in ‘Ceramic interfaces, properties and applications’, (ed. SmartR St C and NowotnyJ.), 229–237; 1998, London, IOM Communications Ltd.
19.
HadleyJ. H.Jr, HsuF. H., VanceE. R. and BeggB. D.: ‘Positron annihilation lifetime spectroscopy of air-fired Ca(1–x)(La)xTiO3 perovskites’, J. Am. Ceram. Soc., 2005, 88, (1), 246–248.
20.
VanceE. R., BeggB. D., HannaJ. V., LucaV., HadleyJ. H. and HsuF. H.: ‘Charge compensation in Ca(La)TiO3 solid solutions’, in ‘Environmental issues and waste management technologies in the ceramic and nuclear industries X’, (ed. ViennaJ..), 199–206; 2005, Westerville, OH, American Ceramic Society.
21.
RingwoodA. E., KessonS. E., WareN. G., HibbersonW. and MajorA.: ‘Geological immobilisation of nuclear reactor wastes’, Nature, 1979, 278, 219–223.
22.
KunwarA. C., TurnerG. L. and OldfieldE.: ‘Solid-state spin echo Fourier transfer NMR of potassium-39 and zinc-67 salts at high field’, J. Magn. Reson., 1986, 69, 124–127.
23.
BodartP. R., AmoureuxJ. P., DumazyY. and LefortR.: ‘Theoretical and experimental study of quadrupolar echoes for half-integer spin in static solid-state NMR’, Mol. Phys., 2000, 98, 1545–1551.
24.
‘MCC-1 static test, nuclear waste materials handbook’, US report no. DOE/TIC-11400, Material Characterization Centre, Hanford, WA, USA, 1984
25.
GhoshV. J., NielsenB. and FriessneggT.: ‘Identifying open-volume defects in doped and undoped perovskite-type LaCoO3, PbTiO3 and BaTiO3’, Phys. Rev. B, 2000, 61B, 207–212.
26.
BalachandranU. and ErorG.: ‘Self compensation in lanthanum-doped calcium titanate’, J. Mater. Sci., 1982, 17, 1795–1800.
