Chapter Four · failure evidence
What Thermal Annealing & Calcination got wrong, from 71 dissertations
Thermal annealing and calcination across various material systems frequently result in unintended phase changes, morphological coarsening, and mechanical failure. Inappropriate thermal processing also degrades electrical performance, induces constituent desorption, or fails to activate desired structural transformations. These records come from PhD theses at 23 institutions, 2021 to 2026. Each links to its thesis. They were extracted by language models reading the full text, so treat each as a lead to read, not a verdict.
Unwanted phase transformations and elemental segregation degrade material structure
Thermal treatments frequently cause unintended transformations into non-target crystal polytypes, secondary brittle intermetallics, or decomposed phases instead of desired states. Heating also triggers elemental or halide phase segregation, solvent-induced clustering, and premature crystallization that compromise thin films and membranes.
Tried and failed
thermal annealing of vapor-deposited thin films applied to formamidinium lead iodide perovskite films. Reason: annealing caused transformation into mixed hexagonal polytypes rather than phase-pure cubic phase
Deposition of Metal Halide Perovskite Thin Films by Thermal Evaporation · Georgia Tech
Tried and failed
thermal annealing to remove polymer binder applied to printed transition metal dichalcogenide electrodes. Outcome: worse than baseline. Reason: annealing caused phase transition from conducting 1T' to semiconducting 2H phase via delithiation
Direct ink writing of two-dimensional materials for electrochemical energy storage devices · Imperial
Considered and rejected
Considered and rejected: Rejected post-growth thermal annealing of the completed heterostructure because it weakened both 2D and 3D crystal peaks and induced halide phase segregation.
Considered and rejected
Considered and rejected: Rejected annealing nano-K0.3MoO3 above 200 °C for sintering due to phase instability.
Tried and failed
thermal homogenization based on published phase diagrams applied to ternary metal alloy system. Reason: annealing at literature temperature precipitated unwanted brittle intermetallic secondary phases
Design of Superelastic Secondary-Phase-Toughened Alloys · MIT
Tried and failed
high-temperature annealing to homogenize multi-principal component alloys applied to equimolar refractory multi-element alloy. Reason: positive atomistic mixing energy causing persistent elemental segregation and multiphase retention despite extended annealing
Tried and failed
vacuum post-annealing of mechanochemically synthesized materials applied to halide solid electrolytes. Outcome: unstable. Reason: vacuum annealing induced thermal decomposition and unwanted phase transitions
Understanding ion transport in halide solid electrolytes with varying mobile species · Imperial
Considered and rejected
Considered and rejected: Rejected standard furnace annealing (220–240 °C) for amorphous synthesis because it formed crystalline spinel phases rather than amorphous oxides.
Tried and failed
thermal annealing to induce reverse phase transition applied to encapsulated layered chalcogenide thin films. Outcome: unstable. Reason: high temperatures caused sample degradation before triggering the reverse phase transition
Phase and defect control of 2D-material based memory devices by scanning tunneling microscopy · UT Austin
Tried and failed
high-temperature pre-annealing of sublayer coatings applied to optical interference multilayer coatings. Outcome: worse than baseline. Reason: phase separation within the sublayer increased mechanical loss and thermal noise
Tried and failed
solvent vapour annealing applied to conjugated polymer ionic liquid blends. Outcome: worse than baseline. Reason: induced phase segregation and fibril clustering, disrupting the interconnected conductive network and reducing current
Considered and rejected
Considered and rejected: Rejected post-deposition thermal annealing due to literature showing phase separation into Ge and C islands
Growth and characterization of polycrystalline Ge[subscript 1-x]C[subscript x] thin films · Iowa State
Considered and rejected
Considered and rejected: Rejected high-temperature PVDF annealing (90–150 °C) because elevated temperatures promoted thermodynamically stable α-phase over electroactive β-phase
Roll-to-Roll processable organic thin film transistor based circuits and their sensory application · Oxford
Considered and rejected
Considered and rejected: Rejected thermal annealing above 350 °C (specifically 350 °C and 400 °C) because it triggered phase transformation of SnS2 into orthorhombic SnS, collapsing the bandgap to ~1.3 eV and breaking exciton resonance.
Considered and rejected
Considered and rejected: Discarded high-temperature thermal annealing (~500 °C) of Si3N4 thin-film membranes because it relaxes material stress (by ~50% at 200 °C) and causes HfO2 crystallization, preventing wet-chemical removal.
Room-Temperature Quantum Optomechanics and Free-Electron Quantum Optics · EPFL
Excessive sintering and grain coarsening disrupt particle morphology and surface area
Prolonged or elevated thermal processing causes uncontrolled sintering and grain growth that dramatically diminish specific surface area. High temperatures also disrupt particle uniformity, enlarge interfacial defects and bubbles, and deform nanostructured geometries.
Tried and failed
low-temperature calcination to remove organic templates applied to mesoporous metal nanoparticle synthesis. Outcome: worse than baseline. Reason: lower temperature required excessively long annealing times and resulted in significantly reduced specific surface area
Exploring the Mechanisms of the Early Stages of the Formation of Silver Nanoparticles and the Role of Organic Additives · Leibniz Universität Hannover Repository
Considered and rejected
Considered and rejected: Rejected non-vacuum hotplate annealing for perovskite prints due to multi-nucleation forming core/satellite crystal structures.
Advancing Additive Nanomanufacturing of Quantum Optoelectronics · ResearchWorks
Considered and rejected
Considered and rejected: Rejected aqueous sol-gel and hydrothermal synthesis because required high-temperature annealing disrupts particle uniformity and morphology
Directed Synthesis and Doping of Wide Bandgap Semiconducting Oxide Nanocrystals · Penn
Tried and failed
extended thermal annealing duration applied to porous metal nanoparticle synthesis. Outcome: worse than baseline. Reason: prolonged heating caused excessive sintering, significantly reducing specific surface area
Exploring the Mechanisms of the Early Stages of the Formation of Silver Nanoparticles and the Role of Organic Additives · Leibniz Universität Hannover Repository
Tried and failed
thermal annealing at elevated temperatures applied to porous metal-organic precursor monoliths. Outcome: worse than baseline. Reason: excessive sintering reduced the specific surface area
Exploring the Mechanisms of the Early Stages of the Formation of Silver Nanoparticles and the Role of Organic Additives · Leibniz Universität Hannover Repository
Tried and failed
post-processing annealing heat treatment applied to extruded aluminium profiles. Outcome: worse than baseline. Reason: annealing caused grain growth, reducing both ultimate tensile strength and elongation compared to as-extruded condition
Tried and failed
post-fabrication thermal annealing to heal interface defects applied to 2D material van der Waals heterostructures. Outcome: worse than baseline. Reason: annealing caused interfacial bubbles and defects to aggregate and enlarge rather than heal
Interlayer Excitons in Atomically Thin van der Waals Semiconductor Heterostructures · Harvard
Lost to a baseline
Mass activity of dealloyed PdMn/C (0.30 mA/μgPd) was lower than dealloyed PdNi/C (0.37 mA/μgPd) due to large particle size from high-temperature annealing.
ELECTROCATALYSTS AND POLYMER ELECTROLYTES FOR ANION EXCHANGE MEMBRANE FUEL CELLS · Cornell
Considered and rejected
Considered and rejected: Rejected high-temperature annealing at 800 °C for AuAg nanostructures because it ruined the designed shape into an ill-defined blubbery geometry.
Fabrication and applications of AuAg alloy metasurfaces and hybrid metal dielectric nanoantennas · EPFL
Considered and rejected
Considered and rejected: Discarded 3-step solid-state reaction synthesis due to high processing temperatures, long annealing times, and excessive grain growth causing high thermal conductivity.
Development of Cu2SnS3 based thermoelectric materials and devices · IRIS - UNITN - prod
Considered and rejected
Considered and rejected: Direct single-step high-temperature reducing annealing (>600 °C) was rejected because it degraded NT morphology; a two-step double annealing (O2 at 500 °C then 2% H2/N2 at 600 °C) was used to form Magnéli phases.
Thermal processing impairs electronic transport and photovoltaic device metrics
Annealing applied to semiconductor films and contact junctions often fails to improve contact resistance and causes exciton localization at structural defects. Furthermore, thermal steps can degrade open-circuit voltage, shunt resistance, surface passivation, and charge extraction across solar cells and photodetectors.
Tried and failed
post-deposition thermal annealing applied to vapor-deposited metal halide perovskite films. Outcome: unstable. Reason: annealing failed to stabilize the film against moisture-induced degradation and phase change
Tried and failed
slow cooling during post-annealing thermal processing applied to inorganic perovskite solar cells. Outcome: worse than baseline. Reason: oxygen-induced surface p-doping created a charge extraction barrier at the electron transport interface
Formation pathways and phase behaviour of CsPbI2Br: toward stable and reproducible solar sells · Imperial
Tried and failed
rapid thermal annealing for ohmic contact formation applied to p-doped 2D wide-bandgap semiconductors. Outcome: worse than baseline. Reason: annealing degraded electrical contact performance instead of improving ohmic behavior
Hexagonal boron nitride for deep UV applications · Georgia Tech
Tried and failed
post-deposition thermal annealing for contact resistance reduction applied to monolayer 2D semiconductor metal contacts. Outcome: worse than baseline. Reason: did not improve contact resistance and risked exciton localization around intrinsic structural defects
Exciton-Trion-Polaritons in Two-Dimensional Transition-Metal Dichalcogenides · Cornell
Lost to a baseline
Single-step air-annealed CsPbBr3 cells at 320 °C produced lower Voc and fill factor than two-step 320 °C/300 °C annealing.
Cesium based all inorganic perovskite solar cells · Iowa State
Lost to a baseline
Post-optimization thermal annealing of CZTS at 50 °C for 5 min decreased TAS charge transfer relative to unannealed washed films
Materials and deposition methods for the manufacture of low-cost solar cells · Imperial
Lost to a baseline
AuNPs/Gr/Si photodetectors fabricated by thin film annealing showed lower responsivity than bare Gr/Si photodetectors in the UV band (<400 nm) and IR band (>800 nm).
Research on graphene/silicon Schottky junction based photodetector · IRIS - POLITO - prod
Considered and rejected
Considered and rejected: Rejected post-deposition thermal annealing for PbI2-route MAPbI3 co-evaporated films because it degraded PV performance without morphology benefit.
Control of electronic properties of metal halide perovskites through vacuum co-deposition · Oxford
Considered and rejected
Considered and rejected: Thermal annealing (>70 °C) of PCE10:PC71BM layers was rejected because it degrades J-V characteristics by lowering shunt resistance and reducing EQE.
LOW-NOISE ORGANIC PHOTODIODES WITH NEAR-INFRARED SENSITIVITY · Georgia Tech
Considered and rejected
Considered and rejected: Pre-annealing the (i)a-Si:H layer above 250 °C (e.g., 260–275 °C) was rejected for standard fabrication because it inhomogeneously degrades baseline surface passivation.
Considered and rejected
Considered and rejected: Rejected post-metallization thermal contact annealing because metal-TMD junctions do not reliably improve and annealing causes exciton localization at defect sites.
Exciton-Trion-Polaritons in Two-Dimensional Transition-Metal Dichalcogenides · Cornell
Thermal activation fails to eliminate defects or drive intended phase transitions
Annealing in sub-optimal temperature regimes or non-dry environments fails to activate dopants, annihilate leakage-inducing defects, or fully restore oxidized nanocrystals. Additionally, slow kinetics, strain pinning, or improper heat dispersion can stall recrystallization and yield incomplete phase conversions.
Tried and failed
thermal annealing to reverse ambient oxidation degradation applied to passivated semiconductor nanocrystal thin films. Reason: heating alone cannot fully restore electronic performance lost from atmospheric oxygen exposure
Engineering Nanocrystal Devices Through Cation Exchange And Surface Modifications · Penn
Tried and failed
low-temperature thermal annealing applied to defect complex formation in irradiated crystals. Outcome: worse than baseline. Reason: insufficient thermal energy for monovacancy diffusion to capture sites compared to higher-temperature anneals
High-Sensitivity Nitrogen-Vacancy Center Magnetometry: from DC to GHz · MIT
Tried and failed
thermal annealing to reduce defect-mediated leakage current applied to heteroepitaxial semiconductor photodetectors. Reason: point defect annihilation did not translate to lower dark current
Low temperature heterogeneous integration of germanium on silicon · MIT
Tried and failed
thermal annealing in non-ultra-dry ambient atmosphere applied to semiconductor ion-implantation dopant activation. Outcome: worse than baseline. Reason: trace water vapor above baseline levels causes dopant deactivation and increases sheet resistance
Lost to a baseline
EQE improvements from post-growth annealing in BGaInAs photodiodes (~10-30%) were significantly lower than the ~4x improvement observed in dilute nitrides.
III-V optoelectronic devices in the BGaInAs material system · UT Austin
Considered and rejected
Considered and rejected: Rejected post-synthesis next-day annealing in favor of single-step in-situ annealing because it yielded poor crystallinity and an XRD peak shift of +0.24 degrees.
Enhancing the Electron Transfer at Electrochemical Interfaces by Spinel Oxide-Nanostructures · IRIS - POLITO - prod
Tried and failed
thermal annealing to induce recrystallization from melt applied to metal-organic coordination polymer melts. Reason: extremely slow crystallization kinetics and high glass-forming ability cause permanent vitrification upon cooling
Tried and failed
transferring powder annealing parameters to monolith samples applied to metal aerogel monolith annealing. Outcome: did not generalise. Reason: heat dispersion differences led to insufficient heating and incomplete phase conversion in monolith cores
Tried and failed
strain-assisted displacive phase transformation via boundary pre-enrichment applied to heavily deformed maraging steel alloys. Outcome: worse than baseline. Reason: matrix strain hardening and defect accumulation pinned phase boundary mobility during low-temperature annealing
High-strength transformation-induced plasticity steels with reverted interlath austenite · MIT
Tried and failed
extended inert gas purging in vapor deposition applied to metal oxide thin film synthesis. Reason: produced rough films that failed to undergo phase transformation during post-deposition thermal annealing
Phase Transformations in Atomic Layer Deposited (ALD) Titanium Dioxide (TiO2) Thin Films · Georgia Tech
Tried and failed
thermal annealing below phase transition temperature applied to organic semiconductor thin films. Outcome: no signal. Reason: absence of phase transitions in that temperature range prevented morphological changes or photostability improvement
Thermal expansion mismatch and residual stress induce cracking and delamination
High temperatures generate severe thermal expansion coefficient mismatches across heterogeneous layers and bonded crystalline wafers. These thermal stresses routinely cause mechanical cracking, film rupture, delamination, and peeling from underlying substrates.
Tried and failed
direct wafer bonding with high-temperature annealing applied to heterogeneous materials with thermal mismatch. Outcome: unstable. Reason: thermal expansion coefficient mismatch caused mechanical cracking during annealing
A Novel Heterogeneously Integrated Photonic Platform for Optical Interconnects · Georgia Tech
Tried and failed
direct wafer bonding with thermal annealing applied to heterogeneous crystalline substrates. Outcome: unstable. Reason: thermal expansion mismatch between substrates caused cracking during post-bonding annealing
Tried and failed
thermal annealing of high-stress metallic thin films applied to deposited electrical contact test structures. Outcome: unstable. Reason: high as-deposited residual stress caused film rupture and delamination during heating
Effects of Crystalline Anisotropy on Solid-state Dewetting · MIT
Considered and rejected
Considered and rejected: Thermal annealing of samples post-laser scribing was rejected because repeated scribing and heating caused the glass substrates to crack reliably.
Unraveling the Reconfiguration Dynamics of Silver Nanowire Networks under Electrothermal Stress · MIT
Tried and failed
high-temperature thermal annealing applied to heterogeneous thin film on substrate. Outcome: unstable. Reason: thermal expansion mismatch causes film cracking, delamination, ion out-diffusion, and surface degradation
Integrated lithium niobate photonics and applications · Harvard
Tried and failed
sequential thin film deposition and high-temperature annealing applied to oxide coatings on silicon substrates. Reason: severe thermal expansion coefficient mismatch caused substrate cracking during high-temperature annealing
Fluorescent Materials and Thin Film Coatings for Temperature Sensing Applications · Georgia Tech
Considered and rejected
Considered and rejected: Rejected using polysilicon contacts/dopant sources due to peeling and flaking of PECVD amorphous silicon upon annealing.
Design, fabrication and testing of lateral double diffused MOS transistors · Iowa State
High temperatures cause substrate thermal damage and volatile component desorption
Elevated annealing temperatures cause outgassing, evaporation of absorber layers, and significant desorption of volatile lattice constituents. In addition, exceeding thermal tolerance thresholds causes substrate degradation, oxygen diffusion, and deformation of polymer or metallic microheater supports.
Considered and rejected
Considered and rejected: Rejected silver (Ag) resistive microheaters due to low melting temperature causing deformation of plasmonic meta-atoms during repeated annealing.
Dynamic Nanophotonic Structures Leveraging Chalcogenide Phase-Change Materials · Georgia Tech
Considered and rejected
Considered and rejected: Rejected post-growth high-temperature annealing (>250 °C) because it leads to significant desorption of Zn from the Zn3P2 lattice and degrades thin-film composition.
Zn3P2 as an earth-abundant photovoltaic material: from growth to device · EPFL
Considered and rejected
Considered and rejected: Discarded thermal annealing (>450°C to 900°C) for forming Cu/Zn nanoparticles due to substrate thermal degradation constraints.
Innovative smart composite coatings endowing antimicrobial properties to several materials · IRIS - POLITO - prod
Considered and rejected
Considered and rejected: Rejected direct high-temperature annealing (>500 °C) on glass/flexible substrates due to thermal degradation and substrate-induced oxygen diffusion.
Progress on 2D-MoS2: development of a scalable fabrication method and demonstration of an X-ray detector · IRIS - UNITN - prod
Considered and rejected
Considered and rejected: Rejected annealing AgNP above 140 °C due to the 78 °C glass transition temperature and deformation of donor PET substrates.
Tried and failed
intermediate annealing before chemical conversion applied to two-step thin-film semiconductor synthesis. Outcome: worse than baseline. Reason: premature volatilization and loss of crystalline modifier additive degraded device open-circuit voltage and fill factor
Considered and rejected
Considered and rejected: Discontinued further development of Cu2SnS3 (CTS) spray-pyrolysis absorber solar cells due to layer evaporation during post-deposition annealing and insufficient film thickness (200-400 nm).
Estudio y desarrollo de películas de Cu2ZnSnS4 obtenidas por sputtering para su posible aplicación en dispositivos fotovoltaicos · Repositorio Institucional BUAP
Post-processing heat treatments degrade mechanical strength and structural integrity
Annealing can reduce material yield strength and promote excessive malleability, leading to unintended structural deformation during handling. Extended heating cycles also cause significant reductions in tensile strength, biaxial strength, stiffness, or lattice strut ductility.
Tried and failed
thermal annealing before hydrophobic coating deposition applied to porous gas-diffusion electrodes. Outcome: worse than baseline. Reason: pre-treatment heat application degraded the electrode structure and reduced overall electrochemical performance
Electrocatalyst performance at the gas/Electrolyte interface under high mass transport conditions · Imperial
Lost to a baseline
PEEK Young's modulus under direct annealing (DA) was inferior compared to traditional post-oven annealing (PA).
3D printing of semi-crystalline high-performance polymers for localized production · IRIS - POLITO - prod
Tried and failed
thermal annealing to relieve residual mechanical stress applied to metallic substrate formers. Reason: annealing reduced material yield strength, causing excessive malleability and unintended deformation during subsequent handling
Characterizing and using defects in high-temperature superconductor cables and magnets · MIT
Tried and failed
post-fabrication annealing heat treatment applied to micrometer-scale additively manufactured titanium lattice structures. Reason: microstructural phase transformation failed to provide sufficient ductility to prevent brittle layer-by-layer strut crumbling
Hierarchical Strengthening of Polycrystal-Inspired Lattice Materials · Imperial
Lost to a baseline
Annealing the milled TNM bulk material for 100 h at 850 °C in ambient air caused a biaxial strength reduction from 1984 ± 190 MPa to 1209 ± 71 MPa (loss of ~775 MPa)
High-temperature oxidation resistant coatings concepts for γ-TiAl based alloys · DSpace-CRIS at TU Wien
Left open by the authors
Problems the authors named and did not get to.
Left open
Determine whether reduced total NV center concentration after 1250 °C annealing stems from mobile detrimental species or thermochromic charge-transfer effects. Blocker: Requires diamond sample fabrication, high-temperature annealing furnace, and photoluminescence spectroscopy equipment.
High-Sensitivity Nitrogen-Vacancy Center Magnetometry: from DC to GHz · MIT
Left open
Implement a post-annealing step to reduce amorphous regions and improve discharge capacity in MnO thin films. Blocker: Requires a physical materials synthesis and characterization laboratory with annealing equipment and electrochemical testing apparatus.
Left open
Determine activation energy and mechanisms for dopant deactivation and reactivation under controlled PO2 using calibrated heating rates and staged anneals to saturation. Blocker: Requires a physical materials synthesis/annealing furnace with controlled PO2 environment and experimental characterization equipment.
Left open
Optimize post-process thermal annealing cycles for SLM soda-lime silica glass structures to enhance optical translucency while retaining geometric accuracy. Blocker: Requires physical SLM hardware, high-temperature annealing furnaces, and optical/dimensional measurement equipment.
Investigations into glass additive manufacturing by selective laser melting and directed energy deposition · University of Nottingham Repository
Left open
Optimize annealing parameters for Inconel 600 to prevent abnormal grain growth. Blocker: Requires materials laboratory equipment for metallurgical heat treatment, annealing, and microstructure characterization
Bromide induced corrosion of stainless steels and Ni-based alloys · Imperial
Left open
Design thin layer-like precipitation phases that nucleate at mechanical stacking faults during low-temperature annealing in metastable FCC alloys. Blocker: Requires materials synthesis, heat treatment equipment, and experimental metallography characterization facilities.
Left open
Systematically vary furnace annealing temperatures and soak times to increase the CuAg alloy fraction beyond 2%. Blocker: Requires a physical materials synthesis laboratory and furnace annealing apparatus
Gas hydrates and Metal Nanoparticles for the Energy Transition and Environmental Applications · IRIS - UNICAM - prod
Left open
Systematically decouple particle size, misfit strain, and transformation temperature effects by adjusting annealing protocols, vanadium matrix content, and nickel-to-titanium ratios. Blocker: Requires a physical metallurgy lab, alloy synthesis equipment, heat treatment furnaces, and in-situ characterization tools
Design of Superelastic Secondary-Phase-Toughened Alloys · MIT
Left open
Anneal synthesized Zr-based MAX phases at intermediate temperatures to experimentally test predicted decomposition into intermetallics and carbides. Blocker: Requires a physical materials synthesis and high-temperature annealing laboratory.
A theoretical study of the stability of Zr-Al-C and Ti-Al-C MAX phases · Imperial
Left open
Optimize the flash lamp annealing process using sub-second multi-flash annealing to synthesize phase-pure cubic FeGe thin films. Blocker: Requires a physical materials synthesis and annealing laboratory (sputtering, flash lamp annealing system, XRD/magnetometry characterization).
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