No abstract

Co mpositional proximity to a morphotropic t ransformation between two ferroelectric solid-s olution phases seems to yie ld ceramic transducers having desirable properties over a wide range of te mperature. Examples of t his phenomenon were observed in the systems PbTi03-PbZr03, PbTi03-PbO:Sn02, PbTi03-PbZr03-PbO:SnO" and PbTi03-PbHf03. The dielectric and piezoelectric properties of ceramics having compos itions in these syste ms and in t he system PbZr03-PbO:Sn02 are described .The composition Pb (Ti .. 5Zr .5,) 0 3 ex hibits a high radial coupli ng coefficient, greater than 0.3, for temperatures a s high as 275 0 C and has t he highest g31 constant, 1l .7 X 10-3 volt -meters per ne\\·toll. For the ser ies of compos itions containing 30 perce nt PbO:SnO, in the ternary system PbTi03-PbZr03-PbO:Sn02 the tetragonal composition nearest the morphotropic boundary has the highes t d31 value, 74 X 10-12 coul ombs per newton . The rhombohedral composition nea rest. the morphotropic boundary sho\\'s the least change of fr equenc y co nstant with temperature, a 2 perce nt variat io n over t he ra nge of 25 0 to 225 0 C.

A study has been made of solid-state reactions in t he qu ate rnary system M gO-CaO-Sn0 2" Ti02 a nd in its subordinate binary and ternary systems. Compatibility relations have been d etermined for· each. Extensive solid-solut ion fo rmation has bee n noted in the Sn02-TiO" MgO-SnO,-Ti O" CaO-Sn02-Ti02, a nd MgO-CaO-Sn02-Ti02 systems. Lit tle or no solid solu t ion was observed in t he other syste ms in vo lved. One te rna r.v compound, having t he probable formula 2:vI:gO·SnOz· TiO" has been observed . ~o quaternary co mpounds we re detected.A survey ha s been co ndu cted of t he eff ect of composit ion a nd te m.perat ure variat ions on t he d ielectri c properties of spec imens in some of t hese syste ms. Data are given for t he valu es of K and () at 50 kilocycles per seco nd, a nd at 1 and 20 megacycles per second. The changes in t hese values wi t h changes in te mperature have been s t udied at 1 megacycle per seco nd.Indexed X-ray po \\"der pattern s are listed fo r t he co mpo unds CaO· TiOz, CaO·SnO" a nd 2MgO ·Sn02· TiO,.' An un indexed pattern is given for the compo und 2CaO·S nO,.

A st ud y of solid-state r eact ion s and dielectric properties was made for t h e ternary systems MgO-ZrOz-Ti0 2 and CaO-Zr02-TiOz. The co mpat ibility r elations were d etermin ed for each , and an est imate of t he extent of t he solid-solution areas was obtain ed . One tern ary co mpound having the formula CaO·ZrOz· 2Ti02 was discover ed . An X-ray diffraction powd er p attern of t his co mpound is in cluded.Ce ra mic dielectric-test pieces were prepared from co mpositions within these sys tems. Data are given for the valu es of J{ an d Q at 50 ki locycles per second, a nd at 1 a nd 20 m egacycles pel' e cond . The variat ion s of t hese valu cs with chan ges i n temperat ure were observed at a rreq uency of 1 m cgacycle per second.

Three independen t velocitics of sound can be measured along a ny direction of propagat ion in a cubic crystal except t he [100] and [Ill] directions. These three velocities suffi ce to determine the three clastic constants and for the [110] direction, the calculation of t hese constan ts is easy. For aU other direction s, t he calculation is more di fficul t; the only existing m e thod appears to be a pertUl'bation tec hnique developed by Keighbours.The prese nt paper prese nts a method usin g exact equations a nd an itrrati\'c procedure to solve t hese eq uat ion s and to calculate bo t h t he elastic co nstants and the ir standard deviations fr om l he soupd \'elocities a nd t heir stand a rd deviations. The mcthod is illustrated with new d ata on SrTi03 which g i\'e C' 11= 3.156 ± 0.027, cI2= 1.027 ± 0.027 , c,,= 1.215 ± 0.006X 10 12 dynes/cm 2 at 25°C. The importance of includ ing co\'ariance terms in calculations of the standard deviatio ns is e mphas ized.