JOURNALOF MATERIALS SCIENCE: MATERIALS IN ELECTRONICS 12 (2001) 707±714 Effect of the addition of Y 2 O 3 on the structure, microstructure and piezoelectric properties of PZT(53/47) A. BEITOLLAHI, CH. KHEZRI Department of Metallurgy and Materials Science, Iran University of Science and Technology, Narmak, Tehran, Iran In this work, an attempt is made to study Pb 1x Y x (Zr 0:53 Ti 0:47 )O 3 system with x  0.0125, 0.025, 0.050, 0.075 and 0.1. It was shown that there is limited solid solubility (0.625mol%) of Y 2 O 3 or1.25mol%ofY 3 in PZT(53/47). For higher levels of dopant, mainly two other extra second phases were detected. The ®rst was a Zr-rich phase in which some Y 2 O 3 and small amountsofTiO 2 wasdissolved.ThesecondonewasaPbsolidsolution(PbO ss )composedof mainly PbO, Y 2 O 3 and ZrO 2 which was initially also seen in calcined samples. The formation of Zr-rich phase is thought possibly to originate due to the sublimation of Pb from PbO ss source during the sintering process. For higher x values, a structural shift towards Ti-rich region of PZT's phase diagram is seen. All piezoelectric parameters of the doped samples suchasd 33 ,g 33 areseentodeclinesharplycomparedtothatofundopedsamples.Increasing the level of dopant gave rise to the increase of conductivity and dielectric loss of sintered samples. The formation of non-ferroelectric extra phases, and the Zr/Ti change of the main formed phase is believed to be responsible for this behavior. # 2001 Kluwer Academic Publishers 1. Introduction Pb(Zr 1x Ti x )O 3 solid solution system near the morpho- tropic boundary in its phase diagram is well known for its very desirable piezoelectric parameters [1±4], making it a very suitable candidate for a wide range of sensor applications [5, 6]. The tailoring of the various piezo- electric parameters has been widely monitored by studying both the effects of different processing conditions [7±11] and the effects of the substitution of various dopants of different valences and ionic sizes, in this system [1, 10, 12±16]. In this respect, there is not much literature on the effect of the doping of PZT with Y 3 . In this work, we have tried to elucidate the effects of the addition of yttria on the structure, microstructure and piezoelectric properties of PZT(53/47). 2. Experimentals The conventional ceramic route was used for the fabrication of the studied samples in this work, and the purity of the chosen raw materials were all better than 99.5%. All of the raw materials used were in oxide form except that of the studied dopant YNO 3  3 ? 6H 2 O was used as the doping compound. This was chosen because it could have been added as a solution to the rest of materials, in order to have a better dispersion of small quantities of it throughout the whole mixture. The starting materials were accurately weighed according to the chosen stoichiometry and then were wet mixed for 6 h in a polyethylene jar with yttrium doped tetragonal zirconia (YTZ) balls in deionized water. Once the mixture was dried at 90  C for 2 h, the mixture was calcined at 850  C for 3 h in covered pure alumina boats. Then, the calcined powder were again wet ball milled for 8h. A 0.5% PVA binder solution was added before the last two hours of the second milling time. The obtained slurry was subsequently dried and disk-shaped samples were pressed at a pressure of 2 ton cm  2 . The pressed pellets were dried at 70  C for 12 h. In order to remove the organic materials, they were all then decarbonized at 500  C for 4 h in air. Then, these pellets were sintered at 1270  C for 2 h with a (PbZrO 3  2%PbO) buffer. Flat and polished samples were prepared before gold sputtering of the sample faces with a sputter coater. Poling of the samples before piezoelectric measurements were done at 30 kVcm  1 and at 100  C in silicone oil. For XRD characterization, a CuK a radiation was used with Ni ®lter. Si powder was used as internal angular calibrat. Microstructural and chemical analysis were carried out using a Leica Cambridge S360 model scanning electron microscope (SEM) with EDS system. For dielectric measurements at 1 kHz an automatic HP- 4270A capacitance bridge was utilized. For the evalua- tion of the d 33 parameter, a d 33 meter were used. Electrical resistivity were measured by using a 617 Keithley electrometer. Standard methods of density measurements were applied to measure the bulk density of the samples. 0957±4522 # 2001 Kluwer Academic Publishers 707