Perovskite-type oxide materials are an important group of useful materials that have many interesting physical features, including being ferroelectric, piezoelectric, dielectric, ferromagnetic, magnetoresistant, and multiferroic. Over the past 100 years, these materials have been studied a lot, and many perovskite oxide combinations have been made. The structure of perovskite oxides is easy and adaptable, since they can be made from most metals by mixing different metal ions at the A and B sites in a sensible way. However, most perovskite oxides don’t have a cubic structure; instead, they have a twisted structure that makes room for the A- and B-cations.
Many perovskite oxide compounds made by solid-state reaction have a polycrystalline structure. However, this method has problems because the starting oxides can vaporise, which causes the chemicals to not be uniform and the particles to stick together in large groups. To get around these problems and make perovskite oxide powders that are uniform and the right amount of each ingredient, wet chemistry methods like the sol-gel process, hydrothermal synthesis, microwave-hydrothermal synthesis, and microemulsion synthesis have been created.
Using metal alkoxides as starting materials, the sol-gel process was used to make perovskite oxide nanopowders and thin films with controlled amounts of dopants. For perovskite oxide thin films, physical vapour deposition (PVD) or pulsed laser deposition (PLD) have also been used happily. Electronic devices based on perovskite-type 3D oxide nanoparticles, which were just recently created, are very important as microelectronic devices get smaller. For instance, 3D perovskite (La,Pr,Ca)MnO3 (LPCMO) nanoboxes have been made using nanoimprint and PLD together to make correlated perovskite oxide nanoelectronics that work very well.
The interesting nanofabrication and nanoscale features of perovskite-type 3D oxide nanostructures will open up new ways to study perovskite oxide nanoelectronics that change with size. In the last few decades, a lot of work has been made in making tiny perovskite oxide materials. This chapter is all about how to make perovskite-type oxide materials. It talks about bulk perovskite oxide ceramics, perovskite oxide nanopowders, and perovskite oxide nanoparticles in 1D, 2D, and 3D. The methods used to make perovskite oxide nanostructures (1D, 2D, and 3D) are emphasised because they have better chemistry and physical properties and can be used to study how size affects physical properties.
Preparation of Bulk Perovskite-Type Oxides
To make perovskite-type oxide ceramics, you need to prepare a powder, heat it, and then sinter it. Samples that have been cut, electroded, and poled are used to measure electrical qualities. A DC field is used to align ferroelectric domains and cause piezoelectricity. It is very important to get the poling voltage and temperature just right because they have a big effect on the electrical features of piezoelectric ceramics. There are several ways to measure the physical qualities of perovskite oxide ceramics, such as their ferroelectric, piezoelectric, and dielectric properties. You can find more information somewhere else.
Synthesis of Perovskite-Type Oxide Nanopowders
Solid-State Reaction Route
A common way to make perovskite oxide nanopowders, like BiFeO3 (BFO) and KNbO3, is through the solid-state reaction method. To make the perovskite phase, the starting materials must be weighed, mixed, milled, and then heated to very high temperatures. That being said, it is hard to make perovskite stoichiometric BFO nanoparticles this way without also making impurity phases like sillenite-type Bi25FeO39 and mullite-type Bi2Fe4O9.
In order to figure out how BFO nanoparticles are made, the reaction routes in the solid-state production of multiferroic BFO were studied. It was discovered that the process of impurity phases creation was controlled by the movement of Bi3+ ions into Fe2O3. The distance that Fe2O3 powder particles can move is controlled by their size. This is a key factor in determining the formation of unreacted phases in this system.
A similar situation happens when BT nanoparticles are made from a mix of BaCO3 and TiO2. The growth of BaTiO3 is controlled by the movement of Ba2+ ions through a perovskite layer. Along with the usual solid-state reaction method, other ready-made methods are being created, such as the liquid salt synthesis method, the mechanical milling method, the sol–gel process, and the hydrothermal synthesis method.
Different substances are made depending on how deeply the Bi ions go into the Fe2O3 particles. At first, the 25:1 (Bi:Fe) sillenite phase forms on the outside, and the 1:1 BiFeO3 perovskite phase forms as it moves inside the structure. The spread will be better as the temperature rises, and more perovskite may be made. The full formation of BFO and the crystallisation of Bi2Fe4O9 mullite crystals are in competition with each other, which stops the formation of BFO. Eventually, all three phases appear at the same time.
Molten Salt Synthesis (MSS)
The MSS method is a flexible and inexpensive way to make perovskite oxide powders. It has been used to make multiferroic BFO nanoparticles and BFO nanoparticles doped with La in different molten salts. The ways that BFO forms have been studied, and it was found that boiling salts are very important for making BFO phase. The MSS method has also been used to make perovskite relaxors based on Pb, dielectric oxides based on Ba, and perovskite nanoparticles made of La1−xSrxMnO3 (LSMO). In conclusion, the MSS method is an easy, cheap, and eco-friendly way to get high-purity perovskite oxide nanopowders.
Mechanical Milling Method
Different mechanical milling techniques have been used to successfully make perovskite oxide nanoparticles such as BT, PT, PZ, and BST. Perovskite manganite Pr0.7Ca0.3MnO3 nanopowders with an average crystallite size of 29 nm are made by ball milling. The X-ray diffraction images show that at room temperature, these nanopowders crystallise into an orthorhombic perovskite structure with a Pnma space group. At 120 K, magnetic tests show that the phase changes from ferromagnetic to paramagnetic. But the vibro-mill method is more appealing because it can make smaller particles, have a tighter size distribution, use simple tools, start with low-cost materials, and make a lot of them.
If you pick the right milling time and heating conditions, you can make a lot of high-purity perovskite oxide nanopowders. Complex perovskite oxides, like (Bi,Na)TiO3, (K,Na)NbO3, and Pb(Zr, Ti)O3, have also been made from source powders that are only a few microns in size using a very powerful ball milling method and a mechanochemical reaction.
Just 30 to 40 minutes of milling is all it takes to get single-phase perovskite nanocrystalline BT powders. By using mechanochemical synthesis, multiferroic BFO nanopowders can be made right at room temperature. The mechanochemical method, on the other hand, can’t be used for large-scale industrial uses because it takes a long time and works best with small batches. Also, the crushing media may cause unwanted contaminations.
Wet Chemical Routes
Sol–Gel Processing
For making multicomponent perovskite oxide nanopowders with controlled stoichiometry, sol-gel processes are useful because they shorten the lengths over which particles can diffuse compared to regular solid-state reactions. The starting ingredients, content, pH value, and heat treatment plan all have a big impact on the physical features of perovskite nanopowders. For example, perovskite oxide BT nanopowders made from sol-gel are a common example. To change the size and spread of the grains, you need to find the best post-annealing temperature, time, atmosphere, and heating rate. The heating temperature is very important for controlling the size of BFO nanoparticles. As the temperature rises, the particle sizes get bigger, reaching over 100 nm. Some changed sol-gel methods, like the Pechini method, polymer complex solution, and glycol-gel reaction, have been created to make BFO nanoparticles with controlled grain size, shape, and crystallinity that don’t need any extra steps of sintering. You can now get these nanoparticles in sizes from nanometres to micrometres by carefully controlling steps in the processing, such as heat treatment and solid-state polymerisation.
Alkoxide-Hydroxide Sol–Precipitation Synthesis
Flaschen was the first person to suggest the alkoxide-hydroxide sol-precipitation process, which is now widely used to make solid perovskite oxide nanopowders at low temperatures without having to heat them up any further. This method, which is based on hydrolysis and condensation processes, has been used to make perovskite BT powders. But to control the size and shape of the particles, the water volume and its extra way need to be made better. Aqueous alkaline solution can be used as a starting material to make BT nanopowders at temperatures between 80 and 100°C. But the finished products have lumpy and uneven shapes, which means they can’t be used for powder processing or sintering. The hydrolysis-condensation process can be changed by starting with solid barium hydroxide octahydrate. The experiments show that BT nanoparticles smaller than 6 nm start to form at 50°C without making the TiO2 anatase in the middle. At 60°C, corner-sharing TiO6 octahedra form. At 80°C, the average size of BT powders gets bigger, up to about 7.5 nm. The BT nanopowders also have an odd lattice growth with a fairly high tetragonality.
Hydrothermal Routes
Hydrothermal Process
The geothermal method, which is also called the autoclave method, is a popular way to make perovskite nanoparticles because the liquid, temperature, and pressure work together to make the process more effective. This method makes sure that the end goods are steady and stops the formation of impurities. This method has been used to make perovskite BFO nanoparticles whose size and shape can be controlled. Han et al. wrote about how they made Bi12Fe0.63O18.945 nanocrystals, BFO nanoparticles and Bi2Fe4O9 nanoparticles of different shapes using special chemical conditions. Wang et al. also wrote about making bismuth ferrite compounds using geothermal methods. They said that alkali metal ions like K+, Na+, and Li+ ions helped.
Bi3+ and Fe3+ ions are changed into hydrogene Fe(OH)3 and Bi(OH)3 in precursors during the dissolution-crystallization process in the hydrothermal method. The precursors are then mixed with alkaline mineralisers like KOH, NaOH, and LiOH. The amounts of Bi3+ and Fe3+ ions in the alkaline solution are higher than their saturated levels. This causes the BFO phase to start to form and separate from the supersaturated hydrothermal fluid, which is followed by crystal growth. The degree of supersaturation has a big impact on the formation and crystal growth rate, which in turn has an impact on the particle size and shape of BFO particles.
Some mineralisers have cationic edges that change the shape and size of nanoparticles in a big way. Hojamberdiev et al. said that the average particle size of BFO powders made with LiOH, NaOH, and KOH mineralisers was 64 nm, 120 nm, and 200 nm, in that order. Most of the time, the hydrothermal reaction takes place at temperatures below 250 °C, sometimes as low as 130 °C. This is a lot cooler than the sol-gel process.
Perovskite oxide nanopowders, on the other hand, generally have very bad crystal structures. By way of example, the chemical method used to make BT nanopowders has structure flaws like lattice OH– ions and barium gaps (V00 Ba). These flaws can cause holes to form inside the grains and a strange growth known as “bloating phenomena” to happen during the last step of firing pottery.
Solvothermal Process
Solvothermal synthesis, which is usually done in nonaqueous solutions like NH3, methanol, ethanol, and n-propanol, is better than hydrothermal methods because the reaction conditions are cooler and nanometer-sized particles can be made in the cubic phase of perovskite powders. Using solvothermal synthesis, like using benzyl alcohol as a fluid, to make superfine BT nanopowder has been tried more than once. BT and BZ nanoparticles were made at temperatures between 200°C and 220°C, which are not very high.
The TEM pictures of the man-made BT nanoparticles show that the BT perovskite structure has changed into cubic and tetragonal shapes. The HRTEM pictures of two separate particles orientated in the [110] and [111] directions show that the particles have crystallised well and are free of any flaws. Alcohol-based liquids, such as ethanol, methanol, and n-propanol, were used to get BT powders that were nanosized and cubic in shape. But, tetragonal BT nanopowders with sizes between 50 and 100 nm were made using EtOH as a solvent.
Particle size was found to depend on the concentration of the material, like the content of the precursor. The tetragonal phase share in the powder went down from 85% to 57% as the particle size went from 89 nm to 58 nm. The cell parameter ratio also went down from 1.0080 to 1.0071.
Microwave-Hydrothermal Process
Microwaves are used to speed up the crystallisation process in the microwave-hydrothermal (M-H) process, which is an improved hydrothermal method. Komarneni et al. were the first to use it to make BaTiO3 nanoparticles in 1992. A study by W. Xia et al. looked into the M-H synthesis of solid materials in liquid phase and found that it has benefits over traditional hydrothermal synthesis, such as faster internal heating and lower costs. A lot of different perovskite oxide nanopowders, like BT, BST, and BFO, are quickly made using the M-H method. Microwave heating opens up a new way to make new inorganic nanoparticles faster, especially perovskite oxide nanopowders. It also lets you use liquids that are better for the environment, which results in cleaner and purer goods. This process works really well for perovskite oxide nanopowders.
Chemical or Physical Vapor Deposition
To make perovskite oxide nanopowders, you can use vapour deposition methods, which involve using physical or chemical methods to make gaseous precursor molecules in aersol reactors. In the vapour phase, these precursor molecules combine to make tiny nuclei of the desired phase. This causes primary particles to stick together and agglomerates to form, which are held together by van der Waals force. The gas phase condensation method lets the features of the gaseous starting materials be linked to the nanoparticles that are made. The way that different physical vapour formation methods, like heat evaporation, magnetic sputtering, and laser ablation, work with each other to make vapour and/or plasma is different. The kinds of atoms, molecules, groups, micro- and macroparticles, as well as their density, energy, and how excited they are in the plasma lead to different microstructures of nanocrystalline particles and thin films. Time, temperature, and the number of particles made per unit space are some of the most important factors in processing. Recently, gas phase deposition has been used to make PZT nanoparticles that are all the same size (4–20 nm). These nanoparticles are good for studying how size affects ferroelectric oxide nanoparticles and making ferroelectric nanodevices.
Preparation Methods of 1D Perovskite-Type Oxide
Nanostructures
In the past ten years, many 1D perovskite oxide nanoparticles have been made using a range of methods, such as chemical synthesis and template-based synthesis, which work from the bottom up, and focus ion beam milling and nanoimprint lithography, which work from the top down. Two groups can be made out of these methods: template-free synthesis and template-assisted synthesis. This part gives an overview of recent progress made in making these nanomaterials.
Template-Free Synthesis
A lot of template-free ways have been used to make nanoparticles of the perovskite type, like nanowires and nanotubes. The liquid salt method, the electrospinning process, and hydro/solvothermal synthesis are some of these ways. For making single-crystalline perovskite BT and ST nanowires, the solution-based template-free method has been used. For making monocrystalline BT nanowires, the molten salt method has been used.
The electrospinning method is also used to make tetragonal PT single-crystalline nanowires that look like necklaces. Sol–gel electrophoresis is used to make nanogenerators that can collect kinetic energy. Using the template-free chemical method, multiferroic BFO nanowires were made. Their widths ranged from 45 to 200 nm, and their lengths ranged from hundreds of nanometres to several microns.
Aside from perovskite ferroelectric oxide nanowires, chemical methods have also been used to make single-crystalline perovskite manganite nanowires with an orthorhombic perovskite structure. Using chemical methods, single-crystalline La0.5Sr0.5MnO3, La0.5Ba0.5MnO3, and Pr0.5Ca0.5MnO3 nanowires with a cubic perovskite structure have also been made.
Top-down methods, like the FIB milling process, let the user decide the shape of the nanoparticles that are made, even though they are slow and take a long time to do. You can also make perovskite oxide nanotubes (PONTs) without a template using techniques like alkaline synthesis. For instance, the chemical method was used to make BT and BST nanotube arrangements on titanium surfaces. BT and ST PONTs that are crystallised were made using low-temperature chemical methods and TiO2 nanotubes as a starting material.
Template-Assisted Methods
The template-assisted method is a very good way to make a lot of regular nanostructured groups. Common templates are colloidal monolayers, anodic aluminium oxide (AAO), block copolymers (BCPs), and nanoimprint moulds. This method has been used to create 1D perovskite oxide nanostructures like nanowires, nanotubes, nanorings, and nanobelts. It has benefits like creating high-density, regular nanostructured groups with a large surface-to-volume ratio and precise control over the sizes of the structures.
Many people like to use the sol–gel template method to make highly ordered perovskite oxide nanomaterials, like BT nanowires, PT nanotubes, and PZT nanowires. This method has also been used to make perovskite manganite nanowires, like La1−xCaxMnO3 nanowires, and ordered groups of La0.67Sr0.33MnO3 nanowires. Perovskite oxide La0.825Sr0.175MnO3 nanowires with a polycrystalline perovskite structure have also been made.
A sol–gel template-based method is also used to make perovskite oxide nanotubes. Anti-ferroelectric PZ PONTs are made by pulse laser deposition within AAO templates. The sol–gel electrodeposition process was also used to improve the AAO template’s filling effect. Magnetron sputtering and pulsed laser deposition are also used to make ferroelectric PZT nanotubes and metal-ferroelectric-metal hybrid nanotubes (Pt/PZT/Pt). Zinc oxide and silicon nanowires are used as positive templates.
Using AAO template-assisted synthesis along with microwave treatment makes it easy to make perovskite manganite nanotube arrays, like highly ordered La2/3Ca1/3MnO3 nanotubes. This makes it possible to make nanotube arrays at relatively low temperatures. Rare-earth manganese oxide nanotubes made of La0.325Pr0.30Ca0.375MnO3 are created by filling the tubes with a liquid precursor, heating them in a microwave, and then heating them again at 800 °C. A sol–gel template method is also used to make perovskite La0.59Ca0.41CoO3 nanotubes.
It is also possible to make ferroelectric PZT nanorings and their periodic groups, and their microstructures are well understood. The PZT nanorings’ sizes rely on the AAO template’s channel size, but rings with the smallest pores can be made in the shape shown in Fig. 6c. The SAED test proved that the PZT nanoring is a perovskite diffraction type, and direct imaging of the lattice edges showed this.
It looks at how to make perovskite-type oxide materials, in particular Pb(Zr0.2Ti0.8)O3 (PZT) nanodiscs and nanorings. The laser interference lithography (LIL) process and the PLD method were used to successfully make these nanomaterials on a single-crystal SrTiO3 substrate with SrRuO3 as the bottom electrode. The shapes of these nanorings were shown by AFM and TEM pictures.
One way to tell that PZT is in the perovskite form is to look at d101 perovskite PZT, which has a lattice spacing that is unique to that form. The PFM tests show that the ferroelectricity is still present in the PZT nanodiscs and nanorings.
A precursor-template method is used to make NaNbO3 nanobelt bands with variable aspect ratios. The SEM pictures of the Na7(H3O)Nb6O19–14H2O nanobelt are shown in Fig. 11a. These were heated in air at 500–550 °C for 1–4 hours to make single-crystalline monoclinic NaNbO3 nanobelt arrays. Also shown was the PZT nanoring array made from nanospheres with a diameter of 100 nm and a wall thickness of 10 nm.
A large BFO nanoring array was made using a precursor-template method. The SEM topography and flat TEM pictures of the large BFO nanoring array are shown below. The shape and size of the PZT nanorings were found by studying how the atoms moved around in the crystal structure of Na7(H3O)Nb6O19–14H2O after it was heated to a high temperature for a long time.
Amorphous PZT nanodiscs and NaNbO3 nanobelts were made by heating the amorphous PZT nanodiscs at 650 °C for 1 hour and 700 °C for 1 hour after baking them. The TEM pictures of a Na7(H3O)Nb6O19–14H2O nanobelt and b NaNbO3 nanobelts were made by changing the order of atoms in the crystal structure of Na7(H3O)Nb6O19–14H2O after it was heated to a high temperature.
In conclusion, the work shows that perovskite-type oxide materials could be used to make nanomaterials and nanobelts. Laser interference printing and ion beam etching were used to make these nanomaterials, which shows that they could be useful in the field of nanoscale ferroelectric materials.
Preparation Methods of 2D Perovskite-Type Oxide
Nanostructures
Nanostructures made of perovskite oxide, like thin films, nanodot clusters, lamellae patterns, nanosheets, nanoplates, and nanowalls, are very important in today’s microelectronics. More recently, ways to make these shapes have been found. Making thin strips of perovskite oxide, 2D perovskite ferroelectric oxide nanoparticles, and perovskite oxide nanosheets is talked about in this section.
Perovskite Oxide Thin Films or Multilayers
As starting materials are changed into films or multilayers on a base, perovskite oxide thin films or multilayers are made. Many methods are used, such as molecular beam epitaxy (MBE), chemical solution deposition (CSD), physical vapour deposition (PVD), and metalorganic chemical vapour deposition (MOCVD). This book talks about techniques such as MBE, PLD, CSD, CVD, MOCVD, and CVD.
Pulsed Laser Deposition (PLD)
Many people like to use the PLD approach for thin film growing. Smith and Turner were the first people to use it in 1965. It makes it possible for pictures to have compositions that are very close to the goal, even when the stoichiometry is complicated. A lot of different perovskite oxide thin films or multilayers can be made by changing things like the laser’s effect, frequency, pulse time, repeat rate, target to substrate distance, substrate temperature, and chamber pressure. There are good studies of the literature on epitaxial formation of thin films and superlattices of perovskite oxide.
Chemical Solution Deposition (CSD)
Cost-effectively making thin films, CSD has benefits like being cheap, simple to set up, and able to fill big areas. It was in the mid-1980s that perovskite oxide thin films were first made. The CSD method has been used to make many perovskite oxide thin films. There are four main steps in the process: making the precursor solution, covering it with a spin or dip, breaking it down at low temperatures, and crystallising it at high temperatures. The size of the films and how quickly they grow crystallise depend on the temperature of the fluid. The steps of deposition, pyrolysis, and crystallisation are done more than once to get the thickness that is wanted. Processing elements such as the percentage of the precursor solution, the substrate and bottom electrode stack, and the heating temperature have a big impact on the start and growth of the film.
CVD and MOCVD
People often use CVD to make high-quality perovskite oxide thin films that work well. To speed up the formation reaction and adatom movement, the process needs a high vapour pressure and a heated base. The temperature of the substrate, the amount of precursor transport, and the temperature of the vaporiser affect the structure and make-up of the film. To get a better handle on film quality, modified CVD technologies have been created, such as liquid pumping and cloud creation.
With metal-organic chemical vapour deposition (MOCVD), perovskite oxide thin films and superlattices can be made. This method is better than other physical deposition methods because it allows for better control of film stoichiometry, high crystallisation quality, and the ability to cover large areas and complex shapes. Low-pressure MOCVD, atmosphere pressure MOCVD, direct liquid injection MOCVD, and plasma-enhanced MOCVD are some of the different types of MOCVD that are being made to meet different needs.
By Injection By inserting a fast-moving electrical valve into the evaporator system, MOCVD manages the creation of tiny drops of the precursor solution. The time and frequency of the input change the growth rates that work best for each material. By changing the amounts of each precursor in the precursor liquid source, it is possible to finetune the end film’s stoichiometry.
A lot of people use injection MOCVD to make ferroelectric perovskite oxide thin films, perovskite oxide superlattices, and ferroelectric perovskite oxide thin films right now.
Molecular Beam Epitaxy (MBE)
The MBE method is like atomic spray painting in that it is used to make thin films of perovskite oxide. It involves controlling the cation stoichiometry very exactly by using elemental sources that are stopped alternately. This makes high-quality perovskite oxide thin films. Controlling oxide substrates at well-defined ionic planes and keeping an eye on the formation of individual molecule or atomic layers are important steps. For in situ tracking, reflection high-energy electron diffraction (RHEED) is often used. It has been possible to make perovskite oxide thin films and epitaxial heterostructures with MBE.
2D Perovskite Oxide Nanostructures Based on Planar
Structures
Top-Down Methods
Nanoimprint lithography (NIL) and electron beam lithography (EBL) have been used to make 2D perovskite oxide nanoparticles from flat structures. Alexe et al. did groundbreaking work on how to order perovskite ferroelectric oxide nanoparticles in two dimensions for high-density ferroelectric memories. EBL method was used to successfully make regular arrays of SrBi2Ta2O9 and PZT nanoisland capacitors with horizontal dimensions of 100 nm. FIB technique was also used to make BT nanodots.
Bottom-up Methods
Template-assisted synthesis and top-down methods have both been used to make 2D perovskite oxide nanostructures from groups of nanodots on the sides. For example, template-assisted “bottom-up” synthetic methods like nanosphere lithography (NSL) are used to make 2D ordered ferroelectric oxide nanodots of BT, PZT, and SrBi2Ta2O9. People have used AAO membranes, gold nanotube membranes, and silicon nanonitride shadow masks as nanostencil masks to put down many layers of materials and improve the crystallisation quality of perovskite oxide ferroelectrics. As an example, PZT nanodot patterns were made on Pt/MgO surfaces using PLD and very thin AAO membranes as a stencil mask.
Perovskite Oxide Nanosheets
Wet chemistry methods, like hydrothermal processes, can be used to make perovskite oxide nanosheets. Gao et al. used a one-step chemical process to make 2D single-crystal perovskite ZnSnO3 nanoplates with (111) facets on the plate sides that were uncovered. The nanoplates that were synthesised have the shape of hexagonal plates made of ZnSnO3 with lattice edges that are spaced 0.26 nm apart. The matching SAED proves that the nanoplate is made of a single crystal. A melted salt method can also be used to make rectangular perovskite La2Ti2O7 platelets. The process of making perovskite oxide 2D nanoparticles is still in its early stages, and using them in oxide microelectronic devices is very difficult. A lot of work needs to be done in this area.
Preparation Methods of 3D Perovskite-Type Oxide
Nanostructures
Bottom-up and top-down methods can both be used to make 3D nanostructures. Bottom-up methods use solution-based methods, like sol–gel-based CSD, template-making, and hydro/solvothermal synthesis, to make nanowires, rods, or tubes that are lined up vertically. Top-down methods, like FIB milling and some lithographical methods, involve cutting away the main ferroelectric material and making nanoscale shapes that are ordered in a way that makes sense.
Top-down methods for making 3D perovskite oxide nanomaterials with FIB milling have many benefits, such as accurate positioning and full control over shapes and sizes. But the FIB milling method has some problems, like slow milling and patterning speeds, especially for bigger structures. It also can’t be used to form nanoparticles in volume. On top of that, problems happen at the nanoscale because ions hitting the sides of the samples cause damage.
A number of methods, such as photolithography, electron beam lithography, and scanning probe lithography, have been used to make big nanostructure groups whose shape and structure can be precisely controlled. Not long ago, 3D perovskite ferroelectric nanoparticles were made using PLD and the AAO template together. We made ferroelectric PZT nanocapacitor stacks with Pt top electrodes. The density was very high, at *Tb/inch2.
Other than AAO template-assisted manufacturing, 3D nanotemplate PLD and other methods have also been used to create 3D perovskite oxide nanostructures. In this method, a substrate is deposited on the side walls of a 3D nanopatterned substrate at an angle. The deposition time can be changed to control the thickness between 30 and 160 nm. At higher temperatures than the equivalent film, these LPCMO nanoboxes show an insulator-to-metal shift, which could be useful in oxide spintronics. The 3D nanotemplate PLD method is a new way to make 3D shapes out of perovskite oxide nanostructures.
Conclusions and Outlook
This chapter talks about the improvements in how to make perovskite-type oxide materials, such as bulk perovskite oxide ceramics, perovskite oxide nanopowders, and perovskite oxide nanoparticles in 1D, 2D, and 3D. Usually, standard solid-state processes are used to make perovskite oxide ceramics, but the microstructures that are made have a lot of chemical heterogeneity, particle clumping, and big, rough grains. Nanoscale oxide electronics progress has made people interested in these materials, which is why controlled particle size, shape, and stoichiometry production methods had to be created.
Over the past few decades, many different ways to make high-purity, ultra-fine, and agglomerate-free perovskite oxide nanopowders have been created using solid, liquid, or gas phase precursors. 1D perovskite oxide nanoparticles, like perovskite oxide nanowires and nanotubes, are important building blocks for making tiny electronic devices. These devices can be used in new ways in computing, data storage, and energy gathering.
Direct printing techniques that work from the top down and chemical bottom-up methods that work from the top down have both been used to make 1D and 2D perovskite oxide crystals. The 3D nanotemplate PLD method was created to make 3D perovskite oxide nanostructures that can be controlled in size and shape. This lets the physical properties of CMR oxide nanostructures be tuned and could be used in oxide nanoelectronics.
New methods, such as laser-MBE and reactive molecular beam epitaxy, have been created to make it possible to grow perovskite oxide thin films with a thickness as low as one molecular layer. This is because growth methods for these films are still in their early stages for use in nanoelectronic devices. These 2D perovskite ultrathin films can be used to look into unusual 2D correlated quantum phases and find useful uses in multipurpose electronic nanodevices.
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