As we learn more about the physics, chemistry and engineering of materials at the nanoscale, we find that the development of a complete understanding is not (in general) possible using one technique alone. Computer simulations provide a very valuable addition to our scientific repertoire, but it is not immediately intuitive which of the many methods available are right for a given problem. In this paper, various computational approaches are described as they apply to the study of the structure and formation of discrete inorganic nanoparticles. To illustrate how these methods are best used, results of studies from many research groups are reviewed, and informal case studies are constructed on carbon, titania and gold nanoparticles.

http://iopscience.iop.org/article/10.1088/0034-4885/73/8/086502/pdf

Modelling of nanoparticles: approaches to morphology and evolution

Controllable synthesis of metastable tetragonal zirconia nanocrystals using citric acid assisted sol–gel method

Mechanical, piezoelectric and dielectric properties of PZT ceramics (Pb 0.98 M 0.02 [(Zr 0.535 Ti 0.465 ) 0.995 ]O 3 , M=Er, Gd, Eu, Nd, La and Bi) have been studied. The fraction of A sites occupied by the different additives is estimated and is found to increase with the ionic radius of the additive ion. The density is high in Bi-, Gd- and Eu-PZT samples. Small amounts of the pyrochlore phase are present in Gd- and Eu-PZT. A maximum strength of 80–100 MPa and K IC of ∼1.5 MPa m 1/2 are obtained in Gd- and Eu-PZT. The R -curve behavior becomes more pronounced in Gd- and Eu-PZT, and it is observed that the strength and K IC increase with the slope of the K IC versus c 1/2 plot. Very good piezoelectric properties, i.e. d 33 of 410 PCN −1 , dielectric constant of 1005, κ p of 0.49 and the hydrophone figure of merit, d h g h , of 2760 are obtained for Nd-PZT. The piezoelectric properties in Bi-PZT are also higher than for the undoped composition, while for the Gd-PZT, these are slightly inferior. For all other compositions, the piezoelectric properties are not affected much.

Effect of rare earth (Er, Gd, Eu, Nd and La) and bismuth additives on the mechanical and piezoelectric properties of lead zirconate titanate ceramics

The feasibility of LiMgPO4 (LMP) ceramic for low-temperature cofired ceramic (LTCC) application was investigated. The ceramic was prepared by the conventional solid-state ceramic method. The ceramic sintered at 950°C showed a relative permittivity (ɛr) of 6.6 and high quality factor (Qu×f) of 79 100 GHz with a τf of −55 ppm/°C. The relatively large negative τf value was lowered by preparing LMP–TiO2 composite. The composite with 0.12 volume fraction TiO2 showed good microwave dielectric properties: ɛr=10, Qu×f=26 900 GHz, and τf=+1.2 ppm/°C. LMP–TiO2 composite did not react with the commonly used electrode material silver.

Temperature-Compensated LiMgPO4: A New Glass-Free Low-Temperature Cofired Ceramic

The nanocrystalline Gd-doped lead titanium zirconate (PGZT) with the composition Pb092Gd008(Zr053Ti047)098O3 has been synthesized by a combination of high-energy ball milling [mechanical alloying (MA)] and sintering PGZT prepared by MA followed by high-temperature sintering has a higher dielectric constant compared to that of the conventional technique PGZT shows a nonrelaxor ferroelectric behavior but has diffuse ferroelectric–paraelectric phase transition The activation energy of the material was found sensitive to its crystallite size

Ferroelectric phase transition in Pb0.92Gd0.08(Zr0.53Ti0.47)0.98O3 nanoceramic synthesized by high-energy ball milling

PZT powders of the composition Pb0.94Sr0.06 (Zr0.53Ti0.47)O3, prepared by spray drying and calcining techniques, were processed to sintered ceramics by conventional cold pressing and sintering at various temperatures and periods between 1000 to 1250°C for 0.5 to 12h. Sintered ceramics were evaluated for their microstructure and electromechanical properties. Highly dense ceramics having bulk density of the order of 97% of the theoretical value could be obtained after sintering at a considerably lower temperature of 1000°C in comparison to the 1300°C generally required for powders prepared by conventional ceramic processing. However, the increase in sintering temperature of reactive spray-dried powders causes the entrapment of closed pores as a result of exaggerated grain growth and subsequent pore coarsening thereby leading to a decrease in the bulk density of the ceramics. It has been observed that minor variations in the sintering parameters influence the porosity, grain size and electromechanical properties. Values of the dielectric constant, piezoelectric strain coefficient and electromechanic coupling factor increase with the increase in grain size and decrease with the increase in porosity of the sintered ceramic whereas the dielectric dissipation factor decreases with the increase in sintering temperature.

Effect of sintering parameters on the microstructure and properties of strontium modified pzt ceramics prepared using spray-dried powders

Transition between tetragonal and rhombohedral phases of PZT ceramics prepared from spray-dried powders

Preparation and characterization of submicron reactive PZT powders

Yttria-stabilized tetragonal zirconia (TZP) powders of composition ZrO 2 -xYO 1.5 with x = 0, 0.01, 0.02, 0.03, 0.04 and 0.05 were prepared by a sol-gel technique. These powders were calcined for 2 h in air at temperatures varying from 300°C to 1700°C. Characterisation of the powders for their phase composition and physical properties indicated that the content of metastable tetragonal phase in the material is dependent on the size of the crystallites and the concentration of yttria.

R. Krishnan

Papers

Effect of sintering parameters on the microstructure and properties of strontium modified pzt ceramics prepared using spray-dried powders

Transition between tetragonal and rhombohedral phases of PZT ceramics prepared from spray-dried powders

Preparation and characterization of submicron reactive PZT powders

Investigation of the metastable tetragonal phase in yttria-doped zirconia powders prepared by a sol-gel technique

Evolution of Microstructure in PZT Ceramics with Supervalent, Isovalent and Subvalent Cation Additions