Influence of Excess PbO Additions on {111} Single-Crystal Growth ofPb(Mg1/3Nb2/3)O3–35 mol% PbTiO3 by Seeded Polycrystal Conversion

Ajmal Khan,*,† Edward P. Gorzkowski,* Adam M. Scotch,* Edson R. Leite,*,‡ Tao Li,Helen M. Chan,* and Martin P. Harmer*

Materials Research Center, Lehigh University, Bethlehem, Pennsylvania 18015

The influence of additions of excess PbO to Pb(Mg1/3Nb2/3)O3–35 mol% PbTiO3 (PMN–35PT) on {111} single-crystal growthby seeded polycrystal conversion was studied in the range of0–5 vol% PbO. PbO volatilization and hence weight lossduring annealing was controlled effectively by a double-crucible type of arrangement. PbO additions increased bound-ary mobility significantly in PMN–35PT, thus facilitatingsingle-crystal growth by seeded polycrystal conversion (SPC).This is attributed to the formation of a boundary wettingPbO-based liquid phase. The growth process occurs veryrapidly initially, after which it slows down. This is presumablydue to both a decrease in the driving force for boundarymigration because of an increase in matrix grain size, and atransition to lower mobility facets. It is also shown that for agiven annealing time, the size of the grown crystal scales withthe lateral dimensions of the seed crystal.

I. Introduction

SINGLE crystals of Pb(Zn1/3Nb2/3)O3–PbTiO3 (PZN–PT) orPb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) exhibit exceptional pi-

ezoelectric properties with good dielectric properties as comparedwith the polycrystalline counterparts. For example, longitudinalcoupling coefficients k33 � 90%, effective piezoelectric coeffi-cients d33 � 1200 pC/N, maximum electric-field-induced strainlimits �0.7%, and dielectric constants of 1000–4000 with lossesof �1% have been reported for single crystals with nearmorphotropic-phase-boundary (MPB) compositions.1,2 The poly-crystalline forms of similar compositions have values of k33 �70%, d33 � 300–690 pC/N, maximum strain limits on the order of0.1–0.2%, and similar dielectric properties.1

Electromechanical devices fabricated out of PZN–PT and PM-N–PT single crystals are actively being pursued because thesuperior piezoelectric properties of these crystals are expected totranslate into exceptional device performance. For example, im-proved actuators,3 more powerful undersea transmitters for sonarapplications,4 and more sensitive ultrasonic transducers for med-ical imaging applications will be possible.5–8

These single crystals are primarily formed by melt techniquessuch as high-temperature solution growth from PbO-based fluxes9

and modified Bridgman growth.10 The seeded polycrystal conver-sion (SPC) process11 is an alternative single-crystal growth

method that offers some advantages over the melt methods. Thisprocess entails bonding a seed single crystal to a polycrystallineprecursor of the same composition and annealing to promotemigration of the single-crystal boundary through the polycrystal toform a large single crystal. The advantages of this method includeits applicability to incongruently melting systems, ease of integra-tion with the manufacture of current device geometries (such as1–3 composites4), and the fact that it does not require expensivecrystal growth furnaces.

The SPC process has been demonstrated as a viable means togrow single crystals of PMN–35 mol% PT (PMN–35PT), acomposition near the MPB, from single-crystal seeds of the samecomposition,12,13 and commercially available SrTiO3.14 Growth ofPMN–35PT single crystals via SPC has been shown to be criticallydependent on a grain boundary wetting PbO-based liquid secondphase within the polycrystalline PMN–35PT precursor.13 How-ever, the role of the PbO liquid phase on the seeded polycrystalconversion of PMN–35PT is currently not well understood. Theobjective of this work was to improve this understanding bysystematically studying the effect of excess PbO content, in therange of 0–5 vol%, on the PMN–35PT conversion process.

II. Experimental Procedure

Phase-pure PMN–35PT powder was prepared from high-purityMgO, TiO2, Nb2O5, and PbO starting powders by the Columbiteprocess15 as described in detail previously.13 This powder wasdivided into several batches to which excess PbO in nominalamounts of 0, 1, 1.5, 3, and 5 vol% were added. The final powderswere made by adding the appropriate amounts of PbO powder(99.9995%) (Puratronic powder from Alfa Aesar, Ward Hill, MA)to the PMN–35PT powder, ball-milling in ethanol for 24 h usingzirconia balls, drying the slurry, and finally calcining at 500°C for4 h.

The powders were then hot-pressed into fully dense disks at880°C for 30 min and 20 MPa of pressure in air. All except the 3%PbO specimens were hot-pressed with a {111} PMN–35PT single-crystal seed plate embedded in the center. The seed plates weresliced from a flux-grown PMN–35PT crystal that had been firstoriented by Laue X-ray back-reflection. They were �0.5 mm thickwith a plate-face area of �10 mm2 and were polished on bothsurfaces down to 0.06 �m colloidal silica finish. The seed platestypically contained some through-thickness cracks that formedduring processing.

The disks were sectioned into several pieces of �1 g each forannealing treatments at 1150°C for times of 0.1–10 h using heatingand cooling rates of 5°C/min. The specimens were wrapped in Ptfoil to prevent the packing powder from sintering to them. Thecomposition of the packing powder was adjusted so as to result innegligible net specimen weight change during annealing. Theannealing was done using the double-alumina-crucible arrange-ment shown in Fig. 1. Specimen weight, before and after anneal-ing, was measured to ensure that weight loss, and hence PbO loss,was minimal during annealing. Bulk densities of the specimenswere measured by the Archimedes method using water as theimmersion medium.

G. S. Rohrer—contributing editor

Manuscript No. 186589. Received October 23, 2002; approved July 17, 2003.Presented in part at the 101st Annual Meeting of the American Ceramic Society,

Indianapolis, IN, April 26, 1999 (Dielectric Materials and Devices, Paper No.S-E-031-99).

Research Supported by DARPA/ONR under Contract No. N00014-96-I-0627 andAFOSR under Contract No. F49620-99-1-0340.

*Member, American Ceramic Society.†Now with Advanced Cerametrics Inc., Lambertville, New Jersey 08530.‡Visting Professor from Universidade Federal de Sao Carlos, Sao Carlos, SP,

13565-905, Brazil.

J. Am. Ceram. Soc., 86 [12] 2176–81 (2003)

2176

journal

Specimens were polished using standard techniques and thencharacterized using light optical microscopy (LOM) and scanningelectron microscopy (SEM). When necessary, they were chemi-cally etched with Kroll’s reagent (1 vol% HF � 4 vol% HNO3 �95 vol% H2O solution) to reveal grain boundaries. For SEManalysis the specimens were examined uncoated using a field-emission-gun instrument (JEOL JSM 6300F, Tokyo, Japan) oper-ated at 3.0 kV accelerating voltage.

The average grain size was determined by the feret method (theperpendicular distance between two parallel lines drawn tangent tothe boundaries of a given feature). This entailed using an auto-mated image analysis system (LECO 3001, St. Joseph, MI) toanalyze tracings of grains from SEM images. Eight ferets for eachgrain were measured at 22.5° increments in the range of 0 to157.5° and their mean was calculated to give a feret average. Thereported grain sizes are the feret average mean multiplied by aconversion factor of 1.56,16 to convert from a planar value to athree-dimensional value. The feret method was used to measuregrain size rather than the more conventional linear interceptmethod because it enabled pores and second phases to be readilyexcluded from the measurement.

III. Results

Figure 2 shows the microstructure of the as-hot-pressed 5%PbO material. This microstructure is etched and was typical of allthe as-hot-pressed materials studied. Note that what appears to be

pores in this specimen are interpreted as etched-out lead oxideparticles. The only difference between the as-hot-pressed micro-structures of the various excess-PbO compositions studied was thevolume fraction of second-phase PbO particles. The matrix grainsize and density of all the as-hot-pressed specimens were essen-tially the same, �0.7 �m and �8.15 g/cm3, respectively, regard-less of PbO content (see Table I).

Specimen weight change, �w, versus annealing time at 1150°Cis shown in Fig. 3. Included for comparison is the weight loss fora 0% specimen that was held for 10 h in an open crucible. Thisspecimen lost 6.6 wt%. Overall, the excess PbO specimensexhibited minimal weight change, �w � 0.5 wt%, for all compo-sitions and annealing times. Specimen density versus annealingtime at 1150°C is shown in Fig. 4. All the specimens exhibited adecrease in density on annealing, from an initial density of �8.2g/cm3 for the as-hot-pressed condition to �7.7 g/cm3 afterannealing for 10 h.

The 0% PbO specimen exhibited negligible single-crystalboundary migration into the polycrystalline matrix even onannealing for up to 10 h at 1150°C (Fig. 5). Any migration ofthis boundary which may have occurred was indiscernible basedon before and after thickness measurements of the seed plate.Figure 6 shows the microstructure of the 1% PbO specimenafter annealing at 1150°C for 10 h. The single-crystal boundarymigrated a short distance through the polycrystal as evidencedby a thin single-crystal growth layer. The converted layercontained a combination of spherical pores and inclusions,clearly distinguishing it from the seed crystal. The growthdistance was 30 – 40 �m and was relatively uniform along thelength of the seed plate resulting in a macroscopically planargrowth front.

In contrast to the 0% and 1% PbO specimens, the 1.5% and5% PbO specimens exhibited substantial single-crystal bound-ary migration on annealing at 1150°C for times as short as 0.1 h,

Fig. 1. Schematic of double-crucible setup used for annealing treatments(drawn to scale).

Fig. 2. Microstructure of as-hot-pressed 5% PbO specimen (SEM). Fig. 3. Specimen weight change versus annealing time.

Table I. Matrix Grain Size and Density ofAs-Hot-Pressed Microstructures

PbO (vol%) Matrix grain size (�m) Density (g/cm3)

0 0.62 0.21 8.171 0.76 0.28 8.141.5 0.62 0.22 8.143 0.78 0.27 8.155 0.76 0.23 8.17

December 2003 {111} Single-Crystal Growth of Pb(Mg1/3Nb2/3)O3–35 mol% PbTiO3 2177

as shown in Figs. 7 and 8(A), respectively. The resultingconverted single crystals were characteristically facetted. Usu-ally, the facets were arranged such that the growth front in agiven specimen appeared saw-toothed. The majority of thesefacets are interpreted as {100}-type based on an earlier obser-vation that PMN–35PT crystals grown by SPC exhibit anequilibrium cube morphology with (100) cube faces.12 Consec-utive pairs of facets bounded triangular regions of convertedcrystal such as the one labeled a in Fig. 8(A). These triangularregions tended to correlate with discrete uncracked segments ofthe seed (see Figs. 7 and 8).

Growth distances, and hence the volume of converted singlecrystal, were comparable for both the 1.5% and 5% PbO speci-mens annealed for 0.1 h (cf. Figs. 7 and 8(A)). For the 5% PbOcomposition, growth distances increased somewhat as annealingtime increased from 0.1 to 10 h (Fig. 8). Growth distances in thedirection perpendicular to the seed plates (i.e., the 111� direction)ranged from a minimum of 0.1–0.3 mm, as taken from the initialseed boundary to the valleys between triangular growth regions, toa maximum of 0.3–0.7 mm measured to the furthest apexes alongthe growth front.

Figure 9 shows the mean matrix grain size with error bars of onestandard deviation, plotted for samples fired at 1150°C for 10 h

versus PbO content. The mean grain size increased progressivelywith increasing PbO content up to 3%, from 1.8 0.3 �m for the0% PbO composition to 19.5 3.4 �m for the 3% composition,after which it decreased to 10.7 0.8 �m with further increase ofPbO content to 5% (Fig. 9). This was accompanied by a progres-sive broadening of the grain size distribution with increasing PbOcontent up to 3%, after which it decreased somewhat with furtherincrease of the PbO content to 5% as reflected in the grain sizeerror bars (Fig. 9). The PMN–PT grain morphology transitionedfrom equiaxed for the 0% and 1% PbO composition, mixedequiaxed � cubic for the 1.5% and 3% compositions, and to cubicfor the 5% PbO composition.

IV. Discussion

(1) Packing Powder ConsiderationsThe 6.6 wt% loss observed for the 0% sample annealed in an

open crucible for 10 h clearly illustrates the need for someprecaution to prevent PbO loss and/or sample decompositionduring annealing. The double crucible with packing powder setupthat was used proved to be effective in this regard. For allannealing times considered, weight changes for the specimenscontaining excess PbO were negligible in comparison to their

Fig. 4. Specimen bulk density versus annealing time.

Fig. 5. Microstructure of 0% PbO specimen after 1150°C/10 h anneal(LOM).

Fig. 6. Microstructure of single-crystal/matrix boundary region in 1%PbO specimen after 1150°C/10 h anneal (SEM).

Fig. 7. Microstructure of 1.5% PbO specimen after 1150°C/0.1 h anneal(LOM).

2178 Journal of the American Ceramic Society—Khan et al. Vol. 86, No. 12

starting excess PbO contents (Fig. 3). This establishes that the PbOcontents of these samples were essentially invariant during theannealing treatments.

(2) Effect of Excess PbO on Boundary Mobilityand Microstructure

Consider that boundary migration velocity, v, is given as v � M� �F where M is boundary mobility and �F is the driving force.For the current case, �F for single-crystal boundary migration isdue to local boundary curvature as dictated by the matrix grainsize. Since the starting PMN–35PT grain sizes of all the compo-sitions studied were essentially the same, the starting driving forcefor boundary migration was the same. Thus, excess PbO clearlyenhances boundary mobility in PMN–35PT as evident fromsignificantly greater migration distances of the single-crystalboundary in the excess PbO compositions, in comparison to the0% PbO composition. Given that all of the samples that containedexcess PbO formed a boundary-wetting PbO-based liquid phase atthe annealing temperature of 1150°C, it is concluded that thisliquid phase increases grain boundary mobility significantly. Thisconclusion was also reached in a previous study of ours13 and bySabolsky et al.17 It is also consistent with the observed effect ofexcess PbO on the microstructure of PMN–PT and PMN ceramics,as reported by others. For example, Guha et al.18 observed thataddition of 0.5 to 5 wt% excess PbO to PMN–8PT results in aPbO-based liquid phase at 840°C that promotes densification andgrain growth during sintering above this temperature. Likewise,similar PbO additions to PMN have been reported by Yoon et al.19

to result in a PbO-based liquid phase that promotes densificationand grain growth during sintering at 900°C. The advantage of thecurrent study, however, is that no densification occurs duringannealing because the samples are fully dense after hot pressing.This allows for the observation of the grain growth behavior only.

Presumably, the PbO-based liquid phase facilitates boundarymigration by a solution-precipitation process. Considering that thisprocess requires solubility of PMN and PT in liquid PbO, it is thusconsistent with the PMN–PbO20 and TiO2–PbO21 phase diagramswhich predict solubility limits of �30 mol% PMN and �33 mol%PT in liquid PbO, respectively, at the annealing temperature of1150°C. To elucidate the mechanism of growth, further work willbe done studying the kinetics of this system. The mechanism willbe discerned by whether the matrix grain size follows parabolic(solution-precipitation) or cubic (diffusion) kinetics.

The dramatic increase in the single-crystal boundary migrationdistance observed on increasing the excess PbO content above 1%indicates that a critical PbO content exists at which acceleratedboundary migration kinetics occur. Based on single-crystal con-version results this critical content is somewhere between 1.5%and 3% excess PbO. We hypothesize that the critical PbO contentcorresponds to that at which enough PbO-based liquid phase isformed to “wet” the grain boundaries and, in particular, thesingle-crystal/polycrystalline-matrix boundary.

The microstructure of the converted crystals contains a combi-nation of pores � PbO-based inclusions. Both are trapped from the

Fig. 8. Microstructure of 5% PbO specimens after annealing at 1150°Cfor (A) 0.1, (B) 1, and (C) 10 h.

Fig. 9. Plot of matrix grain size versus volume percent excess PbO afterannealing.

December 2003 {111} Single-Crystal Growth of Pb(Mg1/3Nb2/3)O3–35 mol% PbTiO3 2179

matrix during growth. The pores first develop in the matrix duringannealing for reasons discussed elsewhere.22 This bloating phe-nomenon accounts for the density decrease of the excess PbOsamples (Fig. 4). Bloating also explains how density can decreasewhile observing negligible weight change. This is due to the factthat when density decreases either volume increases or the mass ofthe system decreases. The microstructure of the 1.5% convertedcrystal contained a somewhat lower volume fraction of theinclusions than that of the 5% PbO converted crystal (cf. Figs. 7and 8). This can be attributed to less pore formation and fewerPbO-based inclusions due to the lower overall excess PbO contentof the 1.5% specimen.

Further methods to minimize pore and inclusion entrapmentmay be identified by studying slower moving boundaries. Slowermoving boundaries may allow the PbO liquid phase to move withthe boundary instead of being left behind. With this in mind,parallel studies are ongoing to use {100}-oriented seeds becausethe 100� has been shown to be the slowest moving direction.23

Another benefit to using the {100}-oriented seeds is that crosssections of these samples would always result in a macroscopicallyplanar growth front regardless of PbO content. This then leads tothe possibility of discerning the kinetics of the single crystal, as thegrowth distances will be much easier to measure.

(3) Factors Limiting Single-Crystal GrowthThe driving force for migration of the single-crystal boundary

migration is believed to be due to local boundary curvatureconsiderations as dictated by the matrix grain size. The single-crystal growth process occurs very rapidly initially and then slowsdown over the anneal times studied. This is indicated by the factthe converted crystal volume is substantial for the shortest annealtime of 0.1 h (see Figs. 7 and 8(A)), increasing somewhat onannealing for 1 h (Fig. 8(B)), but not much further for the longestanneal of 10 h (Fig. 8(C)). This can be attributed to the increase inmatrix grain size and hence decrease in the driving force forboundary migration. In other words, as the matrix coarsens duringannealing, the driving force for migration of the single-crystalboundary decreases.

Figure 8(B) provides evidence that the grown crystal size scaleswith size of the seed plate as follows. The macroscopicallytriangular faceted regions are actually discrete crystals that areslightly misoriented relative to each other by a few degrees, as hasbeen shown by electron backscatter diffraction analysis in ascanning electron microscope.24 They have been attributed togrowth having occurred from discrete uncracked seed plate seg-ments that are slightly misaligned relative to each other.24 Con-sider that the longest seed segment (labeled b in Fig. 8(B)) towardthe right of the micrograph resulted in a converted single crystalthat was considerably larger than those associated with the shorterseed segments to the left. This clearly demonstrates that the size ofthe grown crystal scales with the uncracked seed plate lateraldimension. We attribute this to a transition into lower energy facetsoccurring earlier in converted regions associated with smaller seedsegments. Once this occurs the lower mobility expected for thelower energy planes (facets), which are presumably {100} type,slows down the migration velocity. In other words, the transitionfrom a {111} growth front to a lower energy facet, such as {100}type, decreases boundary mobility and hence limits single-crystalgrowth. Thus, the faceting associated with single-crystal conver-sion also acts to limit the converted crystal size.

It is important to note that since the growth of the {111} singlecrystal scales with the lateral dimension of the seed, further studiesneed to be conducted with {100}-oriented seeds. Since {100}-oriented seeds have a planar growth front for all excess PbOcontents, there will be no growth differences for seeds of differentlateral length. This will aid in quantitatively measuring the growthdistance without needing to keep the seed single crystals the samelength.

Initially there is an increase in grain size with the addition ofexcess PbO to PMN–PT. Further additions of PbO result in adecrease in grain size (Fig. 9). This phenomenon can be explained

in terms of a decrease in boundary mobility as realized by anincrease in the boundary thickness. Assuming the process iscontrolled by diffusion through the liquid boundary layer, as thethickness of the liquid layer increases, the diffusion path lengthincreases, hence decreasing the growth rate (i.e., decreasingboundary mobility). This is the classical explanation given in theliterature for other ceramics containing a liquid phase. For exampleDrofenik et al.25 made analogous observations regarding theinfluence of mechanically admixed Bi2O3 additions to MnZnferrites on microstructure. Thus, the effect of the PbO-based liquidphase content on the mobility of the single-crystal boundary isexpected to exhibit the same trend as that seen for the matrix. Weinfer that the mobility of the single-crystal boundary is maximumat an intermediate liquid-phase content, �3% PbO based on thevalues tested, and that further increase in PbO content decreasesmobility. This observation is validated and discussed in a parallelstudy conducted by King et al.23

V. Conclusions

PbO additions increase boundary mobility significantly inPMN–35PT thus facilitating single-crystal growth by seededpolycrystal conversion. This is attributed to the formation of aboundary wetting PbO-based liquid phase. A critical amount ofexcess PbO is required, between 1 and 1.5 vol% over the rangetested. The growth process occurs rapidly initially, after which itslows down. This is believed to be due to both a decrease in thedriving force for boundary migration caused by an increase inmatrix grain size, and a transition to lower mobility facets. It isshown that the size of the grown crystal scales with the lateraldimensions of the seed crystal, for a given annealing time. Thus infuture studies seed crystals with a {100} orientation will be used aslateral dimension will have no effect on the growth distance. Also,PbO volatilization during annealing can be controlled by a double-crucible type of arrangement such as that used here.

Acknowledgments

We wish to thank Brian Gable for preparing the PMN–35PT powder as part of hissenior project, and Drs. Seung-Eek Park and Thomas R. Shrout of the MaterialsResearch Laboratory, Pennsylvania State University, for providing the Laue oriented,flux-grown PMN–35PT crystal from which the seed plates were sliced.

References

1S.-E. Park and T. R. Shrout, “Characteristics of Relaxor-Based PiezoelectricSingle Crystals for Ultrasonic Transducers,” IEEE Trans. Ultrason., Ferroelectr.Frequency Control, 44 [5] 1140–47 (1997).

2S.-E. Park and T. R. Shrout, “Ultrahigh Strain and Piezoelectric Behavior inRelaxor Based Ferroelectric Single Crystals,” J. Appl. Phys., 82 [4] 1804–11 (1997).

3S.-E. Park and T. R. Shrout, “Relaxor-Based Ferroelectric Single Crystals forElectromechanical Actuators,” Mater. Res. Innovations, 1, 20–25 (1997).

4K. McNeal, C. Near, R. Gentilman, M. Harmer, H. Chan, A. Scotch, V.Venkataraman, and C. Greskovich, “Processing and Application of Solid StateConverted High Strain Materials,” Proc. SPIE, 3675, 330–35 (1999).

5S. Saitoh, M. Izumi, S. Shimanuki, S. Hashimoto, and Y. Yamashita, “UltrasonicProbe,” U.S. Pat. No. 5 295 487, 1994.

6P. D. Lopath, S.-E. Park, K. K. Shung, and T. R. Shrout, “Single CrystalPb(Zn1/3Nb2/3)O3/PbTiO3 (PZN/PT) in Medical Ultrasonic Transducers,” Proc. IEEEUltrason. Symp., 2, 1643–46 (1997).

7S. Saitoh, T. Kobasyashi, K. Harada, S. Shimanuki, and Y. Yamashita, “Forty-Channel Phased Array Ultrasonic Probe Using 0.91Pb(Zn1/3Nb2/3)O3�0.09PbTiO3

Single Crystal,” IEEE Trans. Ultrason., Ferroelectr. Frequency Control, 46 [1]152–57 (1999).

8S. Saitoh, T. Takeuchi, T. Kobayashi, K. Harada, S. Shimanuki, and Y.Yamashita, “A 3.7 MHz Phased Array Ultrasonic Probe Using 0.91Pb(Zn1/3-Nb2/3)O3�0.09PbTiO3 Single Crystal,” IEEE Trans. Ultrason., Ferroelectr. Fre-quency Control, 46 [2] 414–21 (1999).

9T. R. Shrout, Z. P. Chang, N. Kim, and S. Markgraf, “Dielectric Behavior ofSingle Crystals Near the (1 x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 Morphotropic PhaseBoundary,” Ferroelectric, Lett. Sect., 12, 63–69 (1990).

10K. Harada, S. Shimanuki, T. Kobayashi, S. Saitoh, and Y. Yamashita, “CrystalGrowth and Electrical Properties of Pb((Zn1/3Nb2/3)0.91Ti0.09)O3 Single CrystalsProduced by Solution Bridgman Method,” J. Am. Ceram. Soc., 81 [11] 2785–88(1998).

11M. P. Harmer, H. M. Chan, H.-Y. Lee, A. M. Scotch, T. Li, F. Meschke, and A.Khan, U.S. Pat. No. 6 048 394, 2000.

2180 Journal of the American Ceramic Society—Khan et al. Vol. 86, No. 12

12T. Li, A. M. Scotch, H. M. Chan, M. P. Harmer, S.-E. Park, T. R. Shrout, andJ. R. Michael, “Single Crystals of Pb(Mg1/3Nb2/3)O3–35 mol% PbTiO3 fromPolycrystalline Precursors,” J. Am. Ceram. Soc., 81 [2] 244–48 (1998).

13A. Khan, F. A. Meschke, T. Li, A. M. Scotch, H. M. Chan, and M. P. Harmer,“Growth of Pb(Mg1/3Nb2/3)O3–35 mol% PbTiO3 Single Crystals from (111) Sub-strates by Seeded Polycrystal Conversion,” J. Am. Ceram. Soc., 82 [12] 2958–62(1999).

14T. Li, S. Wu, A. Khan, A. M. Scotch, H. M. Chan, and M. P. Harmer,“Hetero-Epitaxial Growth of Bulk Single Crystal Pb(Mg1/3Nb2/3)O3–35 mol%PbTiO3 from (111) SrTiO3,” J. Mater. Res., 14 [8] 3189–91 (1999).

15S. L. Swartz and T. R. Shrout, “Fabrication of Perovskite Lead MagnesiumNiobate,” Mater. Res. Bull., 17, 1245–50 (1982).

16M. I. Mendelson, “Average Grain Size in Polycrystalline Ceramics,” J. Am.Ceram. Soc., 52 [8] 443–46 (1969).

17E. M. Sabolsky, G. L. Messing, and S. Trolier-McKinstry, “Kinetics ofTemplated Grain Growth of 0.65Pb(Mg1/3Nb2/3)�0.35PbTiO3,” J. Am. Ceram. Soc.,84 [1] 2507–13 (2001).

18J. P. Guha, D. J. Hong, and H. U. Anderson, “Effect of Excess PbO on theSintering Characteristics and Dielectric Properties of Pb(Mg1/3Nb2/3)O3–PbTiO3-Based Ceramics,” J. Am. Ceram. Soc., 71 [3] C-152–C-154 (1988).

19K. H. Yoon, Y. S. Cho, D. H. Lee, and D. H. Kang, “Interfacial Phenomena andDielectric Properties of Pb(Mg1/3Nb2/3)O3 Ceramics with Excess PbO”; pp. 371–78

in Ceramic Transactions, Vol. 41, Grain Boundaries and Interfacial Phenomena inElectronic Ceramics. Edited by L. M. Levinson and S.-I. Hirano. American CeramicSociety, Westerville, OH, 1994.

20Z-G. Ye, P. Tissot, and H. Schmid, “Pseudo-Binary Pb(Mg1/3Nb2/3)O3–PbOPhase Diagram and Crystal Growth of Pb(Mg1/3Nb2/3)O3 [PMN],” Mater. Res. Bull.,25, 739–48 (1990).

21B. Jaffe, W. R. Cook Jr., and H. Jaffe, Piezoelectric Ceramics; p. 117. AcademicPress, London, U.K., 1971.

22A. M. Scotch, E. P. Gorzkowski, H. M. Chan, and M. P. Harmer, “Swelling inPMN–PT with Excess PbO,” unpublished work.

23P. T. King, E. P. Gorzkowski, A. M. Scotch, D. J. Rockosi, H. M. Chan, andM. P. Harmer, “Kinetics of {001} Pb(Mg1/3Nb2/3)O3–35 mol% PbTiO3 SingleCrystals Grown by Seeded Polycrystal Conversion,” J. Am. Ceram. Soc., 86 [12]2182–87 (2003).

24A. Khan, D. T. Carpenter, A. M. Scotch, H. M. Chan, and M. P. Harmer,“Electron Backscatter Diffraction Analysis of Pb(Mg1/3Nb2/3)O3–35 mol% PbTiO3

Single CrystalsGrown by Seeded Polycrystal Conversion,” J. Mater. Res., 16 [3]694–700 (2001).

25M. Drofenik, A. Znidarsic, and D. Makovec, “Influence of the Addition of Bi2O3

on the Grain Growth and Magnetic Permeability of MnZn Ferrites,” J. Am. Ceram.Soc., 81 [11] 2841–48 (1998). �

December 2003 {111} Single-Crystal Growth of Pb(Mg1/3Nb2/3)O3–35 mol% PbTiO3 2181